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Effect of physicochemical and empirical rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough
Accepted Manuscript Effect of physicochemical and rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough Johannes Frauenlob, Maria Moriano, Ute Innerkofler, Stefano D'Amico, Mara Lucisano, Regine Schoenlechner PII:
S0733-5210(17)30104-2
DOI:
10.1016/j.jcs.2017.06.021
Reference:
YJCRS 2394
To appear in:
Journal of Cereal Science
Received Date: 31 January 2017 Revised Date:
28 June 2017
Accepted Date: 29 June 2017
Please cite this article as: Frauenlob, J., Moriano, M., Innerkofler, U., D'Amico, S., Lucisano, M., Schoenlechner, R., Effect of physicochemical and rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough, Journal of Cereal Science (2017), doi: 10.1016/j.jcs.2017.06.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Effect of physicochemical and rheological wheat flour properties on
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quality parameters of bread made from pre-fermented frozen dough
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Johannes Frauenlob1, Maria Moriano2, Ute Innerkofler1, Stefano D’Amico1, Mara Lucisano2,
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Regine Schoenlechner1*
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Technology, Institute of Food Technology, Muthgasse 18, 1190 Vienna, Austria
BOKU - University of Natural Resources and Life Sciences, Department of Food Sciences and
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Sciences (DeFENS), Via Mangiagalli 25, 20133 Milan, Italy
SC
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Università degli Studi di Milano, Department of Food, Environmental and Nutritional
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*Corresponding author (phone +43 1 47654 75240; e-mail:
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[email protected])
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Keywords:
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frozen dough, frozen storage, flour quality, RVA;
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Abbreviations:
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dm, dry matter;
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RP-HPLC, reversed phase high-performance liquid chromatography;
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RVA, rapid visco analyser;
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HE, haubelt units;
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GS, glutenin subunits;
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HMW, high-molecular-weight;
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LMW, low-molecular-weight;
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Abstract
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The objective of this study was to examine the influence of flour quality on the properties of
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bread made from pre-fermented frozen dough. The physicochemical parameters of 8
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different wheat flours were determined in detail. A standardized baking experiment was
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performed with frozen storage periods from 1 to 168 days. Baked bread was characterised
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for specific loaf volume, crumb firmness and elasticity. Duration of frozen storage
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significantly affected loaf volume and crumb firmness. The reduction of loaf volume was
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different among the used flours and its behaviour and intensity was highly influenced by
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flour properties. For control (none frozen) breads wet gluten, flourgraph E7 maximum
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resistance and RVA peak viscosity were positively correlated with loaf volume. However,
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after 1 to 28 days of frozen storage, wet gluten content did not significantly influence loaf
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volume, while other parameters were still significantly correlated with bread properties.
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After 168 days of frozen storage all breads showed low quality, thus no significant
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correlations between flour properties und bread quality were found. Findings suggest that
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flours with strong gluten networks, which show high resistance to extension, are most
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suitable for frozen dough production, but starch pasting characteristics also affected bread
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quality in pre-fermented frozen dough.
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1. Introduction
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Cereals and cereal products like bread are the largest energy source for human nutrition
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(Goesaert et al., 2005). Bread making is one of the oldest food production technologies,
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which underlies a permanent fluctuation due to the changes in social habits and consumer
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demands (Asghar et al., 2011; Rosell and Gómez, 2007). One of the key advances in the last
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decades was the use of frozen storage for preservation of bread and dough (Asghar et al.,
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2011). Freezing technology can be applied at different processing steps of bread production.
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Commonly, fully baked bread, partially baked bread, pre-fermented dough or even
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unfermented dough are frozen (Rosell, 2010). The use of pre-fermented frozen dough offers
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an opportunity to meet both, product quality and economical production of bread (Curic et
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al., 2008).
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Since the first implementation, the quality of frozen dough has increased markedly, yet,
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there is still a huge potential for process improvement (Rosell and Gómez, 2007). Possible
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drawbacks associated with this process to be solved are a decreased bread volume, lack of
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texture, crust fissures, worsened crumb structure, and even splitting of the crust (Rosell,
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2010). In addition, Ribotta et al. (2001) reported faster staling for breads prepared from
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frozen dough due to a higher degree of amylopectin retrogradation. Factors that do have
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enormous influence on frozen dough quality are the dough preparation conditions, freezing
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and thawing, use of additives, and of course the quality of the raw materials (Rosell and
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Gómez, 2007). As the production parameters (e.g. thawing time, baking program) in bake-off
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stations cannot be adapted constantly, the possible impact of processing conditions can be
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restricted to dough production in a centralized plant. Additionally, food industry attempts to
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keep the use of additives to a minimum, due to the steadily growing consumer concerns
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(Smith et al., 2004). Therefore, a comprehensive knowledge about the role of the raw
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material, in particular flour quality, is beneficial to further improve the quality of frozen
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dough.
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Currently, an elevated number of studies exist, describing significant correlations between
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standardized flour analysis and specific loaf volume of fresh bread, which was determined by
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baking tests (Stojceska and Butler, 2012; Thanhaeuser et al., 2014). However, only few
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researcher groups studied the influence on quality of bread made from frozen dough
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(Bhattacharya et al., 2003; Kenny et al., 1999).
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ACCEPTED MANUSCRIPT Wolt and D’Appolonia (1984) studied the effect of flour quality on frozen dough and
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indicated that the crude protein content is not a reliable indicator for frozen dough quality.
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The findings of Neyreneuf and Van der Plaat (1991) indicated that overly strong wheat
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flours, with high values for Extensograph maximum resistance can increase loaf volumes of
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bread from frozen dough. However gluten network can also appear to be too strong, which
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is reflected in poor loaf volume due to limited CO2 expansion (Lu and Grant, 1999a). Flour
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reconstitution experiments conducted by Lu and Grant (1999b) showed that the glutenin
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protein fraction had the highest impact on frozen dough quality. A further aspect to be
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mentioned is the role of starch in frozen dough. Lu and Grant (1999a) indicated that
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repeated freeze-thaw cycles induce a modification in the physicochemical properties of
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starch, which consequently does have a substantial effect on the resulting dough. A high
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amount of damaged starch is not desirable in frozen dough production, as it shows adverse
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effects on loaf volume (Ma et al., 2016). Besides protein and starch, alpha-amylase activity
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could also have an influence on bread quality, because of their remaining activity at low
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temperatures (Neyreneuf and Van der Plaat, 1991).
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The objective of this study was to define chemical, physical or rheological parameters that
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are possibly able to predict the baking quality of flours for production of breads from pre-
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fermented frozen dough. For this aim an extensive frozen dough baking experiment was
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performed using 8 commercial wheat flours. Detailed flour characterisation included not
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only the typical parameters provided by millers like the content of ash, protein, wet gluten
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and rheological properties, but also additional parameters like pasting properties (RVA) and
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glutenin subunit composition. Baking quality was followed by determination of specific
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bread volume and texture (crumb firmness and relative elasticity). Pre-fermented doughs
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were frozen over a storage period of up to 24 weeks. Selected measuring points (day 0, 1, 3,
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7, 14, 21, 28 and 168) of bread quality were condensed in the first period of storage, as it is
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known that the severest quality changes occur during the first week of frozen storage. In
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order to evaluate the influence of the flour parameters on bread quality of frozen doughs, a
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thorough correlation analysis of all parameters was performed. All baking experiments were
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performed in triplicate.
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2. Materials and methods
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2.1 Materials
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Eight different wheat flours (6 conventional, 2 organically produced) were provided from
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GoodMills Austria GmbH (Schwechat, Austria) and Pfahnl Backmittel GmbH (Pregarten,
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Austria). All of them were stored at 4°C in paper bags. Salt (iodised), dry yeast (saf-instant,
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Lesaffre Austria AG, Wiener Neudorf, Austria) and sucrose were obtained locally.
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2.2 Flour quality
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ICC Standard methods were used to determine flour moisture (110/1), crude protein
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(105/2), a conversion factor of 5.7 was used, ash (104/1) and fat (136). Wet gluten content
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(ICC 155) was determined using the Glutomatic 2200 (Perten Instruments AB, Hägersten,
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Sweden). Total Starch was determined enzymatically (Megazyme International, Bray,
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Ireland) according to AACC 76-13.01. Rheological properties of flours were analysed by
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flourgraph E6 (Haubelt Laborgeräte GmbH, Berlin, Germany) according to ICC standard
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method No. 179 and flourgraph E7 (Haubelt Laborgeräte GmbH, Berlin, Germany) according
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to ICC standard method No. 180.
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2.3 Pasting properties (RVA)
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Pasting profiles of flours were determined using the RVA 4500 (Perten Instruments AB,
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Hägersten, Sweden). Flour (3.5 g, 14% dm) was dispersed with 25.0 ± 0.1 ml of distilled
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water. The suspensions were subjected to RVA General Pasting Method 1: holding time at
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50°C for 1 min, then heating to 95°C over 3 min 42 s, holding at 95°C for 2 min 30 s, cooling
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to 50°C over 3 min 48 s, holding at 50°C for 2 min. Stirring speed was 160 rpm. The starch
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viscosity parameters measured were peak viscosity, trough viscosity, breakdown, setback
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and final viscosity. All measurements were replicated three times; the results are presented
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as means of the measurements.
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2.4 Determination of glutenin subunits
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Glutenin extracts were prepared according to Wieser et al. (1998) and analysed as previously
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reported by Mansberger et al. (2014), applying a gradient of 25 to 55% acetonitrile with
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0.05% TFA for 50 min. RP-HPLC was conducted on Shimadzu HPLC system (Shimadzu
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Cooperation, Kyoto, Japan) equipped with DAD at 210 nm. Various glutenin-subunits (ωb GS,
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HMW GS, LMW GS) were quantified using LabSolutions Software (Shimadzu Cooperation,
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ACCEPTED MANUSCRIPT Kyoto, Japan) as relative amounts of total chromatogram area. The characteristic patterns
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shown by Wieser et al. (1998) were used to identify the subunits in the chromatograms. The
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ratio between LMW GS and HMW GS was calculated, as it is a commonly used quality index
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in other studies (Wieser and Kieffer, 2001).
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2.5 Dough formulation and preparation of frozen doughs
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The bread recipe was following ICC standard method 131 and is summarised in Figure 1. The
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amount of water used was determined by flourgraph E6. The baking formula was: 2500 g
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flour (14% moisture basis), 2% sugar, 1.8% salt, 1.8% dry yeast and 1500 g water (60% water
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absorption). First dry yeast was rehydrated with part of the water for 10 min (30 °C/85% RH).
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Then flour, water, salt, sugar and yeast solution were mixed with a standard hook (Baer
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Varimixer RN10 VL-2, Wodschow & Co., Broendby, Denmark) for 1 min at 110 rpm and 5 min
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at 212 rpm. Final dough temperature was 27±1 °C. Pieces of 200±1 g were prepared and
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placed in a multiple baking pan (MULTISIZE Cake Pan, Alan Silverwood LTD, Birmingham, UK)
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with 9 separate compartments (10 x 10 cm), the central one was not used. After a first
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fermentation for 30 min (30 °C/85% RH) dough pieces were round by hand for 20 s. Fresh
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control breads were fermented for further 30 min (30°C/85% RH) then baked for 22 min
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(Model 60/3 W, MANZ Backtechnik GmbH, Creglingen, Germany). Frozen doughs were
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fermented for 10 min and frozen in a blast freezer (IF101L, Sagi S.p.a., Ascoli Piceno, Italy) to
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a core temperature of -15 °C. Subsequently the dough pieces were packaged in air-tight
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plastic bags, sealed and frozen according the defined storage period at -18°C. After frozen
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storage doughs were placed into baking pans and thawed in the fermentation chamber for
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45 min (30 °C/85% RH). Baking process differed from fresh bread and lasted 28 min. Dough
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was prepared 3 times for each flour.
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2.6 Bread quality evaluation
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After baking, breads were cooled for 45 min at room temperature and stored in a climate
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chamber (20°C/50% RH) for 135 min. Bread volume was measured twice for each loaf by
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rapeseed displacement, specific loaf volume was expressed as cm³/100 g bread. Relative
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volume reduction after 1, 28 and 168 days of storage was calculated according to (equ. 1),
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where
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volume of the fresh control bread, produced with the same flour.
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is the specific loaf volume after n storage days and
the specific loaf
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(equ. 1)
= 100% −
Crumb firmness was measured by TA-XT2i texture analyser (Stable Micro Systems™ Co.,
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Godalming, UK) using the SMS P/100 probe and 5 kg load cell. Data were evaluated using the
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Texture Expert Software (Stable Micro Systems™ Co., Godalming, UK). Two crumb samples
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were cut out from every loaf of bread (3 x 3 x 3 cm) with a tailor-made cutting device and
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analysed with following conditions: pre-test speed 5.0 mm/s, test speed 0.5 mm/s, post-test
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speed 10 mm/s and test distance 9 mm (corresponding to 30% deformation, holding time
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120 s). The resulting peak force of compression was reported as maximum crumb firmness
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(Fmax). Relative crumb elasticity (FREL, %) was calculated as ratio of Fmax to F120 (force after 120
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s test time) multiplied by 100.
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2.7 Statistical analysis
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One-way ANOVA was performed by using SPSS 21 for Windows (SPSS Inc., Chicago, IL, USA)
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to analyse the significance of flour type on standard quality parameters, pasting properties,
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glutenin subunits and bread properties. To determine individual differences between groups
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the Tukey test was used at p > 0.05. Relationships within flour quality characteristics and
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between flour quality and bread properties were estimated by Pearson correlation
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coefficients.
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3. Results and discussion
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3.1 Analytical and rheological properties of flours
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Significant differences in chemical and rheological properties within the eight flours were
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found. The results of the basic flour characterisations are shown in Table 1. The ash contents
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ranged from 0.54 in flour 1 to 1.43% in flour 3, which was a flour with high aleurone content
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that is used in some typical Austrian loaf breads. Flour protein contents between 10.89 and
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15.00% were found. For wet gluten content, values between 24.94 and 33.02% were
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obtained, flour 3 was not analysed, because through its high aleurone content an analysis
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with standard methodology was not possible. In flours 2, 4 and 6 a wet gluten content lower
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than 30% was found, which was suggested as a minimum value for frozen dough production
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by Olivera (2011). Regarding the fat content, typical values for wheat flour where found
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(1.03 – 2.16%) which were highly significant correlated with ash content (r = 0.861, p < 0.01).
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Total starch content of these 8 flours was varying from 72.04 to 80.95%.
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ACCEPTED MANUSCRIPT Basic rheological parameters such as dough development time and the maximum resistance
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to extension are also shown in Table 1. Great differences in Flourgraph E6 values were
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found; for example water absorption at 500 HE varied from 57.3 to 67.9%. The increased
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value of flour 3 can be contributed to its lower endosperm quantity as a result of the high
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ash content (Goesaert et al., 2005). Maximum resistance measured by Flourgraph E7 varied
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between 235 and 784 HE. The organic flours 2 and 3 showed the lowest values, this was the
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same for energy, an explanation for that could be the influence of growing conditions on
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protein composition (Pechanek et al., 1997). Also for Flourgraph E7 ratio, a very broad
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spectrum of properties was found within the eight wheat flours. These data must be
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interpreted with caution, because flourgraph E7 values are correlated but not directly
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comparable with the Brabender Extensograph; data of Iancu and Ognean (2015) has shown
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that values for maximum resistance and ratio are higher and extensibility is lower in the
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Flourgraph E7.
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3.2 Wheat flour pasting properties
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As presented in Table 1 RVA viscosities show high variation and due to the low standard
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deviations, significant differences between the flour have been detected for all parameters.
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RVA pasting parameters are influenced by amylose content, α-amylase activity, proteins,
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lipids and also by particle size distribution as well as milling technology (Sahlstrøm et al.,
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2003). As flour components are underlying some changes during flour storage, pasting
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properties are also influenced by flour storage duration (Brandolini et al., 2010). The RVA-
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analysis was conducted only a few days prior to the baking experiment to eliminate this
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influencing factor. Over all samples, peak viscosity ranged from 1280 to 2330 cP, trough
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viscosity from 607 to 1263 cP and final viscosity from 1601 to 2667 cP. Flour 3 had the
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lowest viscosities, therefore its high ash content could be responsible for. Hareland (2003)
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found a significant negative correlation between ash content and RVA viscosities, also in our
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study a significant correlation with peak viscosity was found (r = -0.831, p < 0.05) but none
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with trough viscosity or final viscosity. From the three basic parameters, breakdown and
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setback viscosities were also calculated. Breakdown was lowest for flour 3 (673 cP) and
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highest for flour 1 (1065 cP). For setback the highest viscosities were found with flour 8
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(1602 cP) and the lowest with flour 3 (993cP). Remarkable high values were found for flours
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7 and 8, a possible explanation remains unclear. For peak time also significant differences
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(2010) who showed an increase in peak time when fat content of flour was lowered.
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3.3 Glutenin subunit composition of wheat flours
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Table 2 provides the results obtained from the RP-HPLC of the glutenin fraction. Glutenins
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contained ωb GS in a range of 0.91 to 3.02%. Values for flours 3 and 4 were significantly
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lower and for flours 7 and 8 significantly higher than for the others. Big differences for this
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minor fraction were also reported in other studies (Wieser, 2000), furthermore there is only
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very little information about the functionality of ωb GS. Relative amount of HMW GS was
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significantly correlated (r = 0,733, p > 0.05) with flour protein content. This correlation is in
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agreement with findings of Pechanek et al. (1997) who found a higher amount of HMW GS
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and flour protein, due to increased fertilization levels. The LMW/HMW-ratios are consistent
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with data from other authors (Pechanek et al., 1997; Thanhaeuser et al., 2014), but rather
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high. The reason for that might be that in our study ωb GS were quantified separately.
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3.4 Effects of freezing and storage
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The results of the bread quality evaluation are summarised in Table 3. A two-way ANOVA
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revealed that both, storage time and flour type had significant influences on all bread
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parameters (specific loaf volume, Fmax, Frel). With every flour, the highest specific volume and
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lowest crumb firmness (Fmax) was obtained by the fresh control bread. A direct comparison
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between frozen dough and the fresh control bread should be made with caution, because
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different baking procedures were applied. During increasing frozen storage time (1 to 168
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days), loaf volume was decreasing significantly for all flours, expect for flour 2 and 3. This
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volume decrease has been shown in most research papers on frozen dough stability and is
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mainly attributed to reducing substance as a consequence of yeast damage and also to ice
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crystal growth during storage (Rosell and Gómez, 2007). After 168 days of storage, very low
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bread volume occurred and bread quality was not satisfactorily, irrespective of flour type.
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Figure 2 illustrates the different relative volume reductions attributed to the freezing
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process itself (1 day), to normal storage (28 days) and to prolonged storage (168 days) in
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comparison to the fresh control breads. Roughly, four different behaviours of volume
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changes during frozen storage can be categorized. Flour 5 which had no significant volume
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decrease after one day frozen storage had also the highest flourgraph E7 ratio. This flour
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shows a great stability during the freezing process itself, nevertheless with ongoing storage
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ACCEPTED MANUSCRIPT the volume is decreasing markedly. Flour with similar properties showed superior quality in
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an experiment by Inoue and Bushuk (1992). A possible explanation for that could be that this
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flour has too strong properties for conventional bread making. Only with an additional
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freezing process the dough network is weakened enough to be able to expand optimally.
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Since flour 1 showed similar behaviour in the extension test, but not for bread volume,
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another influencing factor could be the high proportion of HMW GS found in flour 5. For
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HMW GS a positive correlation with loaf volume was described by Wieser and Kieffer (2001).
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The volume loss of the two organic flours 2 and 3 remains constant throughout the storage,
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only a slight reduction was obtained for the longtime storage. This unusual volume stability
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is contributed to the fact that very low loaf volumes of breads were already measured after
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1 day of frozen storage. With flour 8 also a constant reduction was found, but at a very high
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percentage. The loaf volume was dramatically reduced already after one day; in this case the
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freezing process itself had a huge impact on the loaf volume in comparison to the fresh
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bread, irrespective of storage duration. Interestingly, the highest volume for fresh bread was
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observed with this flour, this data highlights that flour requirements for fresh bread and for
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bread made from pre-fermented frozen dough are different. For flours 1, 4, 6 and 7 a typical
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reduction of bread volume with increasing frozen storage duration, as previously described
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(Bhattacharya et al., 2003; Inoue and Bushuk, 1992), was found. Relative volume reduction
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of these flours was quite similar at the same storage duration, after one day (12.4 ± 1.4 %),
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28 days (22.3 ± 4.5 %) and after 168 days (38.3 ± 5.7 %).
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Regarding crumb firmness similar behaviour as for loaf volume was found, as a result of its
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relation through bread density. A steady increase occurred with all flours, expect for flour 2.
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In comparison to the results of Bhattacharya et al. (2003), the increase of crumb firmness
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was substantial, it should be noted that in their study the final proofing time was variated to
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decrease the quality loss. For flours 4, 5 and 6 it was not possible to cut a representative test
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cube after 168 days storage, because of their very low loaf volume and uneven crumb
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structure. Therefore, Fmax and Frel were not analysed. Breads made from flour 1, 2 and
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especially 7, obtained desirable soft crumb structures after frozen storage up to 28 days.
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In Table 3 it is demonstrated that only slight changes in Frel were determined. The lowest
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values were found with flour 3. A tendentious decrease with increasing storage time can be
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attributed to the loss of moisture during frozen storage (Selomulyo and Zhou, 2007).
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3.5 Correlation analysis
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The results of the correlation analyses are summarised in Table 4, only flour parameters with
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significant correlations were listed, therefore different parameters were listed for specific
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loaf volume and Fmax. Considering the data above, wheat flours with a wide spectrum of
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properties were used in this study, also several different behaviours for bread volume loss
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during frozen storage were found. Thus, some significant correlations were identified
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between flour properties and bread quality parameters. Significance of correlations was
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changing with storage time for some parameters. After 168 days of frozen storage no
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significant correlations were found. This indicates that the pre-fermented frozen dough is
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not suitable for such long storage times. Possible solutions for this problem could be the use
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of additives, modified packaging or freezing of pre-baked frozen bread or non-fermented
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dough.
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A significant negative correlation of ash content was found with bread volume at most
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storage times. This influence can be attributed to the decreasing effect of aleurone particles
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on bread volume (Stojceska and Butler, 2012). Within the RVA pasting properties, peak
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viscosity was positively correlated with specific loaf volume. These results are likely to be
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related to alpha-amylase activity, which is preferred to be low for frozen dough production
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according to the theory of Neyreneuf and Van der Plaat (1991). There are, however, other
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possible explanations, because RVA pasting profiles are also affected by other flour
309
constituents (Sahlstrøm et al., 2003). The physicochemical characteristics of starch are also
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influencing RVA parameters and these have substantial effects on frozen dough quality (Ma
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et al., 2016). However, in this study, peak viscosity had the potential to predict the specific
312
loaf volume of pre-fermented frozen dough up to storage periods of 28 days.
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Wet gluten content, which is a widely used quality indicator for bread making quality in
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Europe, was significantly correlated only with bread volume of fresh bread. Furthermore, the
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composition of the gluten proteins is only poorly represented with wet gluten content, a
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better view can be obtained by extensibility tests which are highly significant correlated with
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the gliadin/glutenin ratio (Horvat et al., 2006). In this study the highest correlation
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coefficients were found between specific loaf volume and Flourgraph E7 ratio. They were
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ACCEPTED MANUSCRIPT correlated positively at a level of p > 0.01. Dough resistance was also positively correlated
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with loaf volume, this is in agreement with the correlation obtained by Kenny et al. (1999)
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who did a non-fermented frozen dough experiment. Contrasting effects for fresh bread were
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found by Thanhaeuser et al. (2014), where dough resistance was negatively correlated with
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loaf volume of breads produced by micro-Rapid-Mix-Test. Nevertheless, in the same study it
324
has been noted that a suitable baking test is essential for a representative performance test
325
of wheat flour, because with the applied microbaking test different correlation coefficients
326
were found.
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Observing the correlation matrix for Fmax (also shown in Table 4) it must be noted that RSD
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for specific loaf volume (5.07%) was much lower than for Fmax (18,74%). Similar to loaf
329
volume, significant negative correlations were found with ash content, maximum resistance,
330
ratio and peak viscosity. Different to loaf volume other significant correlations were found
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for Fmax. Flourgraph E6 stability was negatively and degree of softening positively correlated
332
to Fmax at some storage durations. As stability was highly positively correlated with dough
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development time (r = 0.898, p < 0.01) a possible explanation might be, that for some flours
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the applied kneading time (which was set constant in this baking experiment) was too short
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and were thus producing breads with increased crumb firmness. Individual variation of
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kneading time in baking experiments is not a common practice, but it could offer more
337
information about the breadmaking potential of wheat flours (Thanhaeuser et al., 2014).
338
Furthermore a positive correlation was found between HMW GS content and Fmax after 21
339
and 28 days of frozen storage.
340
Taken together, these results suggest that RVA peak viscosity and especially resistance to
341
extension and ratio (maximum resistance divided by extensibility) have great potential to
342
predict bread quality made from pre-fermented frozen dough. The intensity of this
343
correlation was not changing considerably during 28 days of frozen storage. A note of
344
caution is due here since a relatively low number of 8 wheat flours were used for the
345
calculation of correlation coefficients.
346
4. Conclusions
347
The main aim of the current study was to identify flour quality parameters, which can help to
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predict final quality of bread made from frozen dough within a bakery orientated baking test
349
setup. The results after long-term storage highlighted that pre-fermented frozen dough
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ACCEPTED MANUSCRIPT without any modifications is not suitable for storage times up to 168 days, but after storage
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times of 28 days most breads still showed acceptable quality, dependent on flour type. The
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most significant influence on loaf volume was Flourgraph E7 maximum resistance to
353
extension and ratio and also RVA pasting parameters. It can therefore be assumed that
354
flours with high resistance to extension and high pasting viscosities should be used in
355
production of pre-fermented frozen dough. The results of this study indicate that loaf
356
volume is decreasing with increasing storage duration, but the intensity of this decrease is
357
following different behaviours and was highly dependent on flour properties. Another
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finding was that wet gluten content was no reliable quality indicator for frozen dough
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quality.
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Acknowledgment
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This work was financially supported by the Austrian Research Promotion Agency (FFG Project
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No. 844234).
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Curic, D., Novotni, D., Skevin, D., Rosell, C.M., Collar, C., Le Bail, A., Gabric, D., 2008. Design of a quality index for the objective evaluation of bread quality: Application to wheat breads using selected bake off technology for bread making. Food Research International 41, 714– 719. Goesaert, H., Brijs, K., Veraverbeke, W., Courtin, C., Gebruers, K., Delcour, J., 2005. Wheat flour constituents: how they impact bread quality, and how to impact their functionality. Trends in Food Science & Technology 16, 12–30. Hareland, G.A., 2003. Effects of pearling on falling number and α-amylase activity of preharvest sprouted spring wheat. Cereal Chemistry 80, 232–237.
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Inoue, Y., Bushuk, W., 1992. Studies on frozen doughs. II. Flour quality requirements for bread production from frozen dough. Cereal Chemistry 69, 423–428. Kenny, S., Wehrle, K., Dennehy, T., Arendt, E., 1999. Correlations between empirical and fundamental rheology measurements and baking performance of frozen bread dough. Cereal Chemistry 76, 421–425. Lu, W., Grant, L., 1999a. Effects of prolonged storage at freezing temperatures on starch and baking quality of frozen doughs. Cereal Chemistry 76, 656–662. Lu, W., Grant, L., 1999b. Role of flour fractions in breadmaking quality of frozen dough. Cereal Chemistry 76, 663–667.
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Sahlstrøm, S., Bævre, A., Bråthen, E., 2003. Impact of starch properties on hearth bread characteristics. I. Starch in wheat flour. Journal of Cereal Science 37, 275–284. Selomulyo, V.O., Zhou, W., 2007. Frozen bread dough: Effects of freezing storage and dough improvers. Journal of Cereal Science 45, 1–17.
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ACCEPTED MANUSCRIPT Wieser, H., 2000. Comparative investigations of gluten proteins from different wheat species I. Qualitative and quantitative composition of gluten protein types. European Food Research and Technology 211, 262–268.
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Wieser, H., Antes, S., Seilmeier, W., 1998. Quantitative determination of gluten protein types in wheat flour by reversed-phase high-performance liquid chromatography. Cereal Chemistry 75, 644–650. Wieser, H., Kieffer, R., 2001. Correlations of the amount of gluten protein types to the technological properties of wheat flours determined on a micro-scale. Journal of Cereal Science 34, 19–27.
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Wolt, M., D’Appolonia, B., 1984. Factors involved in the stability of frozen dough. II. The effects of yeast type, flour type, and dough additives on frozen-dough stability. Cereal Chemistry 61, 213–221.
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Figure Captions
Figure 1. Pre-fermented frozen dough breadmaking procedure (WA = water absorption; mb
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= moisture basis)
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Figure 2. Relative volume reduction after 1, 28 and 168 days of frozen storage in comparison
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to fresh control breads
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Table 1. Flour characteristics of the eight used flours Quality Testsa
1
2
3
4
5
6
7
8
0.54 ± 0.01a
0.76 ± 0.01b
1.43 ± 0.03e
0.64 ± 0.03c
0.68 ± 0.03c
0.72 ± 0.02bc
0.84 ± 0.05d
0.72 ± 0.01bc
Protein (N x 5.7), %
11.90 ± 0.20b
11.10 ± 0.50a 12.71 ± 0.37bc 12.12 ± 0.16b
13.14 ± 0.02c
10.89 ± 0.37a
14.56 ± 0.06d
15.00 ± 0.22d
Wet gluten (ICC 155),c %
31.89 ± 0.51cd 25.63 ± 0.77a
b
Gluten Index (ICC 155) b
Fat, % b
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24.94 ± 0.29a
31.46 ± 0.02c
27.88 ± 0.54b
31.02 ± 0.36c
33.02 ± 0.22d
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Ash,b %
96 ± 1ab
98 ± 1b
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94 ± 3a
97 ± 2ab
97 ± 1ab
96 ± 0ab
96 ± 2ab
1.03 ± 0.09a
1.37 ± 0.08c
2.16 ± 0.01f
1.23 ± 0.01b
1.58 ± 0.00d
1.71 ± 0.10e
1.48 ± 0.03d
1.21 ± 0.03b
80.95 ± 0.40d 78.75 ± 1.19cd 74.59 ± 0.63ab 75.12 ± 0.97ab 72.04 ± 0.65a 76.03 ± 1.17bc 73.48 ± 1.33ab 76.98 ± 2.41bc
Flourgraph E6 (ICC 179) Water absorption 500HE, % Dough development time, min Stability, min Degree of softening, HE Quality number, HE
60.7 ± 0.3cd 9.4 ± 0.7d 16.6 ± 1.7e 41 ± 6a 148 ± 25c
58.1 ± 0.4ab 6.6 ± 0.1bc 9.2 ± 0.7bc 51 ± 6ab 91 ± 15b
67.9 ± 0.3e 5.4 ± 0.4b 7.1 ± 0.5ab 70 ± 12c 85 ± 8b
Flourgraph E7 (ICC 180) - 90 min Maximum resistance (R), HE Extensibility (E), mm Energy, cm² Ratio (R/E)
784 ± 31f 158 ± 8abc 161 ± 9d 5.0 ± 0.4cd
504 ± 50b 138 ± 9ab 99 ± 5b 3.7 ± 0.6b
235 ± 6a 141 ± 10ab 53 ± 5a 1.7 ± 0.1a
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58.5 ± 0.6b 6.9 ± 0.6bc 10.6 ± 0.5cd 70 ± 5bc 105 ± 9b
57.3 ± 0.1a 6.8 ± 0.4bc 10.4 ± 0.8cd 52 ± 4abc 101 ± 15b
61.2 ± 0.1d 7.8 ± 1.0cd 12.8 ± 0.5d 55 ± 8abc 114 ± 6bc
59.9 ± 0.0c 7.0 ± 0.7cd 9.6 ± 1.6cd 56 ± 10abc 108 ± 13b
747 ± 47def 146 ± 18ab 141 ± 31cd 5.2 ± 0.3d
649 ± 14cd 132 ± 1a 118 ± 1bc 4.9 ± 0.1cd
760 ± 6ef 163 ± 8bc 159 ± 10d 4.7 ± 0.3bcd
675 ± 44de 184 ± 8c 165 ± 13d 3.7 ± 0.3b
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58.2 ± 0.3ab 1.9 ± 0.3a 5.7 ± 0.2a 70 ± 3c 41 ± 21a
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Starch, %
563 ± 47bc 141 ± 3ab 107 ± 6bc 4.0 ± 0.4bc
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RVA (ICC 162, STD1 profile) Peak viscosity, cP 2330 ± 45a 1686 ± 48b 1280 ± 23c 1885 ± 28de 1928 ± 8eg 1793 ± 30d Trough viscosity, cP 1263 ± 25a 819 ± 24b 607 ± 3c 1094 ± 18de 1078 ± 8de 1066 ± 22de Breakdown, cP 1065 ± 27a 867 ± 25b 673 ± 23c 791 ± 12d 851 ± 0bd 726 ± 14c Setback, cP 1296 ± 24a 1094 ± 20b 993 ± 3c 1179 ± 16d 1324 ± 5a 1172 ± 6d Final viscosity, cP 2561 ± 43a 1913 ± 44b 1601 ± 3c 2273 ± 34d 2401 ± 11e 2238 ± 28d Peak time, min 5.98 ± 0.08abc 5.85 ± 0.03ad 5.75 ± 0.03d 6.11 ± 0.03c 5.91 ± 0.08abd 5.93 ± 0.00ab a Mean and standard deviation of three replicates. b water-free basis c 14% moisture basis Within row, values with the same following letter do not differ significantly from each other (p > 0.05)
2081 ± 14f 2026 ± 14fg 1123 ± 7e 1066 ± 3d 958 ± 9e 960 ± 16e 1460 ± 18e 1602 ± 5f 2583 ± 23af 2667 ± 4f 6.05 ± 0.03bc 5.98 ± 0.03abc
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Table 2. Proportionsa (%) of glutenin proteins in wheat flours determined by RP-HPLC
a
1 1.62 ± 0.15a 23.84 ± 0.12a 74.51 ± 0.14a 3.13 ± 0.02a
2 1.46 ± 0.09a 21.82 ± 0.11b 76.72 ± 0.05b 3.52 ± 0.02b
3 1.02 ± 0.12b 25.10 ± 0.16c 73.88 ± 0.28ad 2.94 ± 0.03c
4 0.91 ± 0.05b 25.11 ± 0.43c 73.98 ± 0.49a 2.95 ± 0.07c
Calculated as percent (%) of total glutenins area
b
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Mean and standard deviation of three replicates. Within row, values with the same following letter do not differ significantly from each other (p > 0.05)
5 1.47 ± 0.08a 26.61 ± 0.65d 71.92 ± 0.59c 2.70 ± 0.09d
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reversed-phase HPLCb ωb GS HMW GS LMW GS LMW/HMW Ratio
6 1.72 ± 0.12a 25.32 ± 0.68c 72.97 ± 0.64d 2.88 ± 0.10c
7 3.02 ± 0.19c 21.17 ± 0.25b 75.81 ± 0.21b 3.58 ± 0.05b
8 2.87 ± 0.13c 21.28 ± 0.27b 75.85 ± 0.26b 3.57 ± 0.06b
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1
2
3
4
5
6
7
8
Specific loaf volume, cm³/100g 315 ± 52abA
283 ± 28aA
192 ± 21cA
314 ± 10abA
331 ± 23abA
322 ± 14abA
335 ± 7bA
342 ± 8bA
1
267 ± 5abB
220 ± 23cB
163 ± 5eB
281 ± 13bB
330 ± 18dA
279 ± 13bB
294 ± 16bB
241 ± 11caB
3
252 ± 9abB
207 ± 2cB
168 ± 10dAB
263 ± 10abeBC
284 ± 9fB
278 ± 10efBC
270 ± 4befCDE
248 ± 5aB
7
261 ± 6abB
215 ± 10cB
154 ± 3dB
246 ± 15aC
296 ± 22eB
258 ± 7abCD
275 ± 9beBCD
212 ± 7cCDE
14
276 ± 5aAB
205 ± 11bB
162 ± 5cB
242 ± 11dC
275 ± 7aBC
243 ± 15dDE
290 ± 11aBC
195 ± 9bDE
21
255 ± 4aB
204 ± 11bB
173 ± 3cAB
249 ± 14aC
247 ± 11aD
248 ± 12aDE
248 ± 5aE
191 ± 4bcE
28
256 ± 15abB
201 ± 19cB
163 ± 15dB
241 ± 21abeC
253 ± 9abCD
231 ± 3beE
267 ± 7aDE
215 ± 13ceCD
168
196 ± 16abC
226 ± 27bcB
176 ± 15aAB
212 ± 19abcD
202 ± 9abcE
201 ± 17abcF
180 ± 15aF
233 ± 15cBC
1.7 ± 0.1aA
1.6 ± 0.3aA
3.3 ± 0.6bA
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0 (control)
0 (control)
a
1.3 ± 0.1aA
1.8 ± 0.4abA
4.5 ± 0.3cA
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1.7 ± 0.0aA
1.4 ± 0.3aA
1
2.2 ± 0.8aAB
3.2 ± 0.5abcB
7.2 ± 0.8dAB
4.6 ± 0.6bcB
3.3 ± 0.4abB
3.8 ± 0.6abAB
2.5 ± 0.4abAB
4.9 ± 1.3cC
3
2.9 ± 0.7abAB
3.9 ± 0.6abcB
7.8 ± 0.5eBC
5.0 ± 0.8cdBC
4.5 ± 1.1bcB
5.0 ± 1.2cdABC
2.5 ± 0.5aAB
5.3 ± 0.7dC
7
3.3 ± 0.4aAB
4.5 ± 0.4abB
7.5 ± 0.5cAB
5.9 ± 1.5bcBC
4.4 ± 1.3abB
5.5 ± 1.0bBCD
3.3 ± 0.5aB
4.9 ± 0.4abBC
14
4.3 ± 0.5abBC
4.4 ± 0.8abB
8.5 ± 1.5cdBC
7.0 ± 2.1bcdCD
6.0 ± 0.8bcC
9.2 ± 3.6dE
2.6 ± 0.2aAB
6.2 ± 0.8bcdCD
6.8 ± 0.7cdBCD
3.4 ± 0.4aAB
3.7 ± 0.4abB
8.2 ± 0.2dBC
8.3 ± 0.8dD
7.6 ± 1.8dCDE
3.1 ± 0.9aB
5.6 ± 1.3bcCD
3.7 ± 1.4abB
4.1 ± 1.2abB
10.0 ± 0.6cC
8.4 ± 0.8cD
7.7 ± 1.5cD
7.9 ± 1.7cDE
2.4 ± 1.2aAB
5.2 ± 1.5bC
168
6.5 ± 3.5aC
3.8 ± 0.3aB
8.0 ± 1.9aBC
-
-
-
6.5 ± 2.1aC
7.6 ± 1.6aD
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FREL, %
71.3 ± 1.3aA
69.0 ± 0.5bcAB
67.3 ± 0.4cdA
70.2 ± 1.9abA
71.0 ± 0.7abA
70.2 ± 0.9abAB
69.3 ± 0.7bcAB
66.4 ± 0.6dA
1
72.0 ± 0.2aA
69.5 ± 0.6cdAB
65.6 ± 0.4eA
69.9 ± 1.3bcdA
71.3 ± 1.0abcA
70.2 ± 1.2abcA
72.4 ± 0.7abB
67.9 ± 1.4deABC
3
72.1 ± 0.8aA
69.5 ± 0.9cdAB
66.2 ± 0.4eA
69.7 ± 0.9bcdAB
71.5 ± 1.5abA
69.5 ± 1.4cdABC
71.3 ± 0.3abcB
68.3 ± 0.8dBC
7
71.4 ± 0.7abA
69.9 ± 0.4bcAB
64.5 ± 1.2eAB
69.1 ± 1.5cAB
72.1 ± 0.1aA
68.6 ± 0.9dABCD
69.5 ± 0.4cAB
67.5 ± 0.6dAB
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69.6 ± 0.8abAB
68.7 ± 1.0abcB
66.4 ± 1.4bcA
68.5 ± 3.1abcAB
69.8 ± 1.3abA
64.7 ± 4.4cD
71.6 ± 3.3aB
66.9 ± 0.7bcAB
21
71.2 ± 0.6aA
71.1 ± 1.0aA
65.0 ± 2.0dAB
68.3 ± 1.3bcAB
66.4 ± 1.1cdB
66.0 ± 2.8cdBCD
69.4 ± 0.9abAB
67.6 ± 0.5bcdABC
28
70.3 ± 1.6aA
68.8 ± 1.0abcB
66.1 ± 0.6bcA
66.2 ± 2.1bcB
67.0 ± 1.8abcB
65.3 ± 3.8cCD
70.0 ± 2.1abAB
69.0 ± 0.9abcC
168
66.8 ± 4.1aB
65.6 ± 2.6aC
62.6 ± 2.1aB
-
-
-
67.3 ± 1.1aA
67.3 ± 1.1aAB
Mean and standard deviation of three replicates.
Values with same capital letter, in the same column and lower cases, in the same row are not significant different (p > 0.05)
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Table 4. Pearson correlation coefficients between flour characteristics and bread properties after different frozen storage durations (1-168 days) Specific loaf volume, cm³/100g Storage time (Days) fresh 1 3 7 14 21 28 168 Ash content –0.868** –0.735* –0.774* –0.754* –0.654 –0.717* –0.766* –0.542 Wet gluten 0.833* 0.288 0.435 0.212 0.262 0.056 0.471 –0.152 Maximum resistance - 90min 0.920** 0.847** 0.872** 0.882** 0.849** 0.752* 0.921** 0.178 Ratio - 90min 0.855** 0.914** 0.912** 0.962** 0.894** 0.882** 0.913** 0.132 RVA - Peak viscosity 0.830* 0.676 0.717* 0.724* 0.764* 0.682 0.860** 0.202 RVA - Setback 0.772* 0.484 0.569 0.433 0.393 0.196 0.558 0.301
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Fmax, N 7 14 0.703 0.356 –0.874** –0.522 –0.776* –0.366 –0.810* –0.571 0.640 0.436 –0.866** –0.596 –0.884** –0.806* 0.443 0.646
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3 0.728* –0.821* –0.788* –0.715* 0.628 –0.818* –0.781* 0.421
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** Correlation is significant at the 0.01 level (2-tailed). * Correlation is significant at the 0.05 level (2-tailed).
1 0.780* –0.842** –0.876** –0.733* 0.625 –0.788* –0.701 0.242
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fresh 0.834* –0.762* –0.905** –0.477 0.379 –0.677 –0.442 –0.061
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Storage time (Days) Ash content Maximum resistance - 90min Ratio - 90min Stability Degree of softening RVA - Peak viscosity RVA - Breakdown HMW content
21 0.360 –0.406 –0.251 –0.592 0.748* –0.567 –0.782* 0.808*
28 0.465 –0.615 –0.448 –0.693 0.741* –0.681 –0.855** 0.793*
168 0.442 –0.141 –0.357 –0.109 0.507 –0.085 –0.195 0.382
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Highlights: •
Pre-fermented frozen dough baking trials were performed with 8 wheat flours
3
•
Frozen storage periods were 1, 3 ,7 ,14 ,21 ,28 and 168 days
4
•
Wet gluten content was not correlated with loaf volume of frozen dough breads
5
•
Flourgraph E7 ratio was positively correlated with loaf volume
6
•
High RVA peak viscosities had a positive effect on loaf volume
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S0733-5210(17)30104-2
DOI:
10.1016/j.jcs.2017.06.021
Reference:
YJCRS 2394
To appear in:
Journal of Cereal Science
Received Date: 31 January 2017 Revised Date:
28 June 2017
Accepted Date: 29 June 2017
Please cite this article as: Frauenlob, J., Moriano, M., Innerkofler, U., D'Amico, S., Lucisano, M., Schoenlechner, R., Effect of physicochemical and rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough, Journal of Cereal Science (2017), doi: 10.1016/j.jcs.2017.06.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Effect of physicochemical and rheological wheat flour properties on
2
quality parameters of bread made from pre-fermented frozen dough
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Johannes Frauenlob1, Maria Moriano2, Ute Innerkofler1, Stefano D’Amico1, Mara Lucisano2,
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Regine Schoenlechner1*
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6 7
1
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Technology, Institute of Food Technology, Muthgasse 18, 1190 Vienna, Austria
BOKU - University of Natural Resources and Life Sciences, Department of Food Sciences and
9 2
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Sciences (DeFENS), Via Mangiagalli 25, 20133 Milan, Italy
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Università degli Studi di Milano, Department of Food, Environmental and Nutritional
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*Corresponding author (phone +43 1 47654 75240; e-mail:
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[email protected])
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Keywords:
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frozen dough, frozen storage, flour quality, RVA;
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Abbreviations:
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dm, dry matter;
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RP-HPLC, reversed phase high-performance liquid chromatography;
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RVA, rapid visco analyser;
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HE, haubelt units;
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GS, glutenin subunits;
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HMW, high-molecular-weight;
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LMW, low-molecular-weight;
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Abstract
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The objective of this study was to examine the influence of flour quality on the properties of
30
bread made from pre-fermented frozen dough. The physicochemical parameters of 8
31
different wheat flours were determined in detail. A standardized baking experiment was
32
performed with frozen storage periods from 1 to 168 days. Baked bread was characterised
33
for specific loaf volume, crumb firmness and elasticity. Duration of frozen storage
34
significantly affected loaf volume and crumb firmness. The reduction of loaf volume was
35
different among the used flours and its behaviour and intensity was highly influenced by
36
flour properties. For control (none frozen) breads wet gluten, flourgraph E7 maximum
37
resistance and RVA peak viscosity were positively correlated with loaf volume. However,
38
after 1 to 28 days of frozen storage, wet gluten content did not significantly influence loaf
39
volume, while other parameters were still significantly correlated with bread properties.
40
After 168 days of frozen storage all breads showed low quality, thus no significant
41
correlations between flour properties und bread quality were found. Findings suggest that
42
flours with strong gluten networks, which show high resistance to extension, are most
43
suitable for frozen dough production, but starch pasting characteristics also affected bread
44
quality in pre-fermented frozen dough.
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1. Introduction
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Cereals and cereal products like bread are the largest energy source for human nutrition
48
(Goesaert et al., 2005). Bread making is one of the oldest food production technologies,
49
which underlies a permanent fluctuation due to the changes in social habits and consumer
50
demands (Asghar et al., 2011; Rosell and Gómez, 2007). One of the key advances in the last
51
decades was the use of frozen storage for preservation of bread and dough (Asghar et al.,
52
2011). Freezing technology can be applied at different processing steps of bread production.
53
Commonly, fully baked bread, partially baked bread, pre-fermented dough or even
54
unfermented dough are frozen (Rosell, 2010). The use of pre-fermented frozen dough offers
55
an opportunity to meet both, product quality and economical production of bread (Curic et
56
al., 2008).
57
Since the first implementation, the quality of frozen dough has increased markedly, yet,
58
there is still a huge potential for process improvement (Rosell and Gómez, 2007). Possible
59
drawbacks associated with this process to be solved are a decreased bread volume, lack of
60
texture, crust fissures, worsened crumb structure, and even splitting of the crust (Rosell,
61
2010). In addition, Ribotta et al. (2001) reported faster staling for breads prepared from
62
frozen dough due to a higher degree of amylopectin retrogradation. Factors that do have
63
enormous influence on frozen dough quality are the dough preparation conditions, freezing
64
and thawing, use of additives, and of course the quality of the raw materials (Rosell and
65
Gómez, 2007). As the production parameters (e.g. thawing time, baking program) in bake-off
66
stations cannot be adapted constantly, the possible impact of processing conditions can be
67
restricted to dough production in a centralized plant. Additionally, food industry attempts to
68
keep the use of additives to a minimum, due to the steadily growing consumer concerns
69
(Smith et al., 2004). Therefore, a comprehensive knowledge about the role of the raw
70
material, in particular flour quality, is beneficial to further improve the quality of frozen
71
dough.
72
Currently, an elevated number of studies exist, describing significant correlations between
73
standardized flour analysis and specific loaf volume of fresh bread, which was determined by
74
baking tests (Stojceska and Butler, 2012; Thanhaeuser et al., 2014). However, only few
75
researcher groups studied the influence on quality of bread made from frozen dough
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(Bhattacharya et al., 2003; Kenny et al., 1999).
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ACCEPTED MANUSCRIPT Wolt and D’Appolonia (1984) studied the effect of flour quality on frozen dough and
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indicated that the crude protein content is not a reliable indicator for frozen dough quality.
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The findings of Neyreneuf and Van der Plaat (1991) indicated that overly strong wheat
80
flours, with high values for Extensograph maximum resistance can increase loaf volumes of
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bread from frozen dough. However gluten network can also appear to be too strong, which
82
is reflected in poor loaf volume due to limited CO2 expansion (Lu and Grant, 1999a). Flour
83
reconstitution experiments conducted by Lu and Grant (1999b) showed that the glutenin
84
protein fraction had the highest impact on frozen dough quality. A further aspect to be
85
mentioned is the role of starch in frozen dough. Lu and Grant (1999a) indicated that
86
repeated freeze-thaw cycles induce a modification in the physicochemical properties of
87
starch, which consequently does have a substantial effect on the resulting dough. A high
88
amount of damaged starch is not desirable in frozen dough production, as it shows adverse
89
effects on loaf volume (Ma et al., 2016). Besides protein and starch, alpha-amylase activity
90
could also have an influence on bread quality, because of their remaining activity at low
91
temperatures (Neyreneuf and Van der Plaat, 1991).
92
The objective of this study was to define chemical, physical or rheological parameters that
93
are possibly able to predict the baking quality of flours for production of breads from pre-
94
fermented frozen dough. For this aim an extensive frozen dough baking experiment was
95
performed using 8 commercial wheat flours. Detailed flour characterisation included not
96
only the typical parameters provided by millers like the content of ash, protein, wet gluten
97
and rheological properties, but also additional parameters like pasting properties (RVA) and
98
glutenin subunit composition. Baking quality was followed by determination of specific
99
bread volume and texture (crumb firmness and relative elasticity). Pre-fermented doughs
100
were frozen over a storage period of up to 24 weeks. Selected measuring points (day 0, 1, 3,
101
7, 14, 21, 28 and 168) of bread quality were condensed in the first period of storage, as it is
102
known that the severest quality changes occur during the first week of frozen storage. In
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order to evaluate the influence of the flour parameters on bread quality of frozen doughs, a
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thorough correlation analysis of all parameters was performed. All baking experiments were
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performed in triplicate.
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2. Materials and methods
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2.1 Materials
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Eight different wheat flours (6 conventional, 2 organically produced) were provided from
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GoodMills Austria GmbH (Schwechat, Austria) and Pfahnl Backmittel GmbH (Pregarten,
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Austria). All of them were stored at 4°C in paper bags. Salt (iodised), dry yeast (saf-instant,
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Lesaffre Austria AG, Wiener Neudorf, Austria) and sucrose were obtained locally.
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2.2 Flour quality
113
ICC Standard methods were used to determine flour moisture (110/1), crude protein
114
(105/2), a conversion factor of 5.7 was used, ash (104/1) and fat (136). Wet gluten content
115
(ICC 155) was determined using the Glutomatic 2200 (Perten Instruments AB, Hägersten,
116
Sweden). Total Starch was determined enzymatically (Megazyme International, Bray,
117
Ireland) according to AACC 76-13.01. Rheological properties of flours were analysed by
118
flourgraph E6 (Haubelt Laborgeräte GmbH, Berlin, Germany) according to ICC standard
119
method No. 179 and flourgraph E7 (Haubelt Laborgeräte GmbH, Berlin, Germany) according
120
to ICC standard method No. 180.
121
2.3 Pasting properties (RVA)
122
Pasting profiles of flours were determined using the RVA 4500 (Perten Instruments AB,
123
Hägersten, Sweden). Flour (3.5 g, 14% dm) was dispersed with 25.0 ± 0.1 ml of distilled
124
water. The suspensions were subjected to RVA General Pasting Method 1: holding time at
125
50°C for 1 min, then heating to 95°C over 3 min 42 s, holding at 95°C for 2 min 30 s, cooling
126
to 50°C over 3 min 48 s, holding at 50°C for 2 min. Stirring speed was 160 rpm. The starch
127
viscosity parameters measured were peak viscosity, trough viscosity, breakdown, setback
128
and final viscosity. All measurements were replicated three times; the results are presented
129
as means of the measurements.
130
2.4 Determination of glutenin subunits
131
Glutenin extracts were prepared according to Wieser et al. (1998) and analysed as previously
132
reported by Mansberger et al. (2014), applying a gradient of 25 to 55% acetonitrile with
133
0.05% TFA for 50 min. RP-HPLC was conducted on Shimadzu HPLC system (Shimadzu
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Cooperation, Kyoto, Japan) equipped with DAD at 210 nm. Various glutenin-subunits (ωb GS,
135
HMW GS, LMW GS) were quantified using LabSolutions Software (Shimadzu Cooperation,
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ACCEPTED MANUSCRIPT Kyoto, Japan) as relative amounts of total chromatogram area. The characteristic patterns
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shown by Wieser et al. (1998) were used to identify the subunits in the chromatograms. The
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ratio between LMW GS and HMW GS was calculated, as it is a commonly used quality index
139
in other studies (Wieser and Kieffer, 2001).
140
2.5 Dough formulation and preparation of frozen doughs
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The bread recipe was following ICC standard method 131 and is summarised in Figure 1. The
142
amount of water used was determined by flourgraph E6. The baking formula was: 2500 g
143
flour (14% moisture basis), 2% sugar, 1.8% salt, 1.8% dry yeast and 1500 g water (60% water
144
absorption). First dry yeast was rehydrated with part of the water for 10 min (30 °C/85% RH).
145
Then flour, water, salt, sugar and yeast solution were mixed with a standard hook (Baer
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Varimixer RN10 VL-2, Wodschow & Co., Broendby, Denmark) for 1 min at 110 rpm and 5 min
147
at 212 rpm. Final dough temperature was 27±1 °C. Pieces of 200±1 g were prepared and
148
placed in a multiple baking pan (MULTISIZE Cake Pan, Alan Silverwood LTD, Birmingham, UK)
149
with 9 separate compartments (10 x 10 cm), the central one was not used. After a first
150
fermentation for 30 min (30 °C/85% RH) dough pieces were round by hand for 20 s. Fresh
151
control breads were fermented for further 30 min (30°C/85% RH) then baked for 22 min
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(Model 60/3 W, MANZ Backtechnik GmbH, Creglingen, Germany). Frozen doughs were
153
fermented for 10 min and frozen in a blast freezer (IF101L, Sagi S.p.a., Ascoli Piceno, Italy) to
154
a core temperature of -15 °C. Subsequently the dough pieces were packaged in air-tight
155
plastic bags, sealed and frozen according the defined storage period at -18°C. After frozen
156
storage doughs were placed into baking pans and thawed in the fermentation chamber for
157
45 min (30 °C/85% RH). Baking process differed from fresh bread and lasted 28 min. Dough
158
was prepared 3 times for each flour.
159
2.6 Bread quality evaluation
160
After baking, breads were cooled for 45 min at room temperature and stored in a climate
161
chamber (20°C/50% RH) for 135 min. Bread volume was measured twice for each loaf by
162
rapeseed displacement, specific loaf volume was expressed as cm³/100 g bread. Relative
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volume reduction after 1, 28 and 168 days of storage was calculated according to (equ. 1),
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where
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volume of the fresh control bread, produced with the same flour.
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is the specific loaf volume after n storage days and
the specific loaf
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(equ. 1)
= 100% −
Crumb firmness was measured by TA-XT2i texture analyser (Stable Micro Systems™ Co.,
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Godalming, UK) using the SMS P/100 probe and 5 kg load cell. Data were evaluated using the
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Texture Expert Software (Stable Micro Systems™ Co., Godalming, UK). Two crumb samples
169
were cut out from every loaf of bread (3 x 3 x 3 cm) with a tailor-made cutting device and
170
analysed with following conditions: pre-test speed 5.0 mm/s, test speed 0.5 mm/s, post-test
171
speed 10 mm/s and test distance 9 mm (corresponding to 30% deformation, holding time
172
120 s). The resulting peak force of compression was reported as maximum crumb firmness
173
(Fmax). Relative crumb elasticity (FREL, %) was calculated as ratio of Fmax to F120 (force after 120
174
s test time) multiplied by 100.
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2.7 Statistical analysis
176
One-way ANOVA was performed by using SPSS 21 for Windows (SPSS Inc., Chicago, IL, USA)
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to analyse the significance of flour type on standard quality parameters, pasting properties,
178
glutenin subunits and bread properties. To determine individual differences between groups
179
the Tukey test was used at p > 0.05. Relationships within flour quality characteristics and
180
between flour quality and bread properties were estimated by Pearson correlation
181
coefficients.
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3. Results and discussion
183
3.1 Analytical and rheological properties of flours
184
Significant differences in chemical and rheological properties within the eight flours were
185
found. The results of the basic flour characterisations are shown in Table 1. The ash contents
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ranged from 0.54 in flour 1 to 1.43% in flour 3, which was a flour with high aleurone content
187
that is used in some typical Austrian loaf breads. Flour protein contents between 10.89 and
188
15.00% were found. For wet gluten content, values between 24.94 and 33.02% were
189
obtained, flour 3 was not analysed, because through its high aleurone content an analysis
190
with standard methodology was not possible. In flours 2, 4 and 6 a wet gluten content lower
191
than 30% was found, which was suggested as a minimum value for frozen dough production
192
by Olivera (2011). Regarding the fat content, typical values for wheat flour where found
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(1.03 – 2.16%) which were highly significant correlated with ash content (r = 0.861, p < 0.01).
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Total starch content of these 8 flours was varying from 72.04 to 80.95%.
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ACCEPTED MANUSCRIPT Basic rheological parameters such as dough development time and the maximum resistance
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to extension are also shown in Table 1. Great differences in Flourgraph E6 values were
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found; for example water absorption at 500 HE varied from 57.3 to 67.9%. The increased
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value of flour 3 can be contributed to its lower endosperm quantity as a result of the high
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ash content (Goesaert et al., 2005). Maximum resistance measured by Flourgraph E7 varied
200
between 235 and 784 HE. The organic flours 2 and 3 showed the lowest values, this was the
201
same for energy, an explanation for that could be the influence of growing conditions on
202
protein composition (Pechanek et al., 1997). Also for Flourgraph E7 ratio, a very broad
203
spectrum of properties was found within the eight wheat flours. These data must be
204
interpreted with caution, because flourgraph E7 values are correlated but not directly
205
comparable with the Brabender Extensograph; data of Iancu and Ognean (2015) has shown
206
that values for maximum resistance and ratio are higher and extensibility is lower in the
207
Flourgraph E7.
208
3.2 Wheat flour pasting properties
209
As presented in Table 1 RVA viscosities show high variation and due to the low standard
210
deviations, significant differences between the flour have been detected for all parameters.
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RVA pasting parameters are influenced by amylose content, α-amylase activity, proteins,
212
lipids and also by particle size distribution as well as milling technology (Sahlstrøm et al.,
213
2003). As flour components are underlying some changes during flour storage, pasting
214
properties are also influenced by flour storage duration (Brandolini et al., 2010). The RVA-
215
analysis was conducted only a few days prior to the baking experiment to eliminate this
216
influencing factor. Over all samples, peak viscosity ranged from 1280 to 2330 cP, trough
217
viscosity from 607 to 1263 cP and final viscosity from 1601 to 2667 cP. Flour 3 had the
218
lowest viscosities, therefore its high ash content could be responsible for. Hareland (2003)
219
found a significant negative correlation between ash content and RVA viscosities, also in our
220
study a significant correlation with peak viscosity was found (r = -0.831, p < 0.05) but none
221
with trough viscosity or final viscosity. From the three basic parameters, breakdown and
222
setback viscosities were also calculated. Breakdown was lowest for flour 3 (673 cP) and
223
highest for flour 1 (1065 cP). For setback the highest viscosities were found with flour 8
224
(1602 cP) and the lowest with flour 3 (993cP). Remarkable high values were found for flours
225
7 and 8, a possible explanation remains unclear. For peak time also significant differences
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(2010) who showed an increase in peak time when fat content of flour was lowered.
228
3.3 Glutenin subunit composition of wheat flours
229
Table 2 provides the results obtained from the RP-HPLC of the glutenin fraction. Glutenins
230
contained ωb GS in a range of 0.91 to 3.02%. Values for flours 3 and 4 were significantly
231
lower and for flours 7 and 8 significantly higher than for the others. Big differences for this
232
minor fraction were also reported in other studies (Wieser, 2000), furthermore there is only
233
very little information about the functionality of ωb GS. Relative amount of HMW GS was
234
significantly correlated (r = 0,733, p > 0.05) with flour protein content. This correlation is in
235
agreement with findings of Pechanek et al. (1997) who found a higher amount of HMW GS
236
and flour protein, due to increased fertilization levels. The LMW/HMW-ratios are consistent
237
with data from other authors (Pechanek et al., 1997; Thanhaeuser et al., 2014), but rather
238
high. The reason for that might be that in our study ωb GS were quantified separately.
239
3.4 Effects of freezing and storage
240
The results of the bread quality evaluation are summarised in Table 3. A two-way ANOVA
241
revealed that both, storage time and flour type had significant influences on all bread
242
parameters (specific loaf volume, Fmax, Frel). With every flour, the highest specific volume and
243
lowest crumb firmness (Fmax) was obtained by the fresh control bread. A direct comparison
244
between frozen dough and the fresh control bread should be made with caution, because
245
different baking procedures were applied. During increasing frozen storage time (1 to 168
246
days), loaf volume was decreasing significantly for all flours, expect for flour 2 and 3. This
247
volume decrease has been shown in most research papers on frozen dough stability and is
248
mainly attributed to reducing substance as a consequence of yeast damage and also to ice
249
crystal growth during storage (Rosell and Gómez, 2007). After 168 days of storage, very low
250
bread volume occurred and bread quality was not satisfactorily, irrespective of flour type.
251
Figure 2 illustrates the different relative volume reductions attributed to the freezing
252
process itself (1 day), to normal storage (28 days) and to prolonged storage (168 days) in
253
comparison to the fresh control breads. Roughly, four different behaviours of volume
254
changes during frozen storage can be categorized. Flour 5 which had no significant volume
255
decrease after one day frozen storage had also the highest flourgraph E7 ratio. This flour
256
shows a great stability during the freezing process itself, nevertheless with ongoing storage
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ACCEPTED MANUSCRIPT the volume is decreasing markedly. Flour with similar properties showed superior quality in
258
an experiment by Inoue and Bushuk (1992). A possible explanation for that could be that this
259
flour has too strong properties for conventional bread making. Only with an additional
260
freezing process the dough network is weakened enough to be able to expand optimally.
261
Since flour 1 showed similar behaviour in the extension test, but not for bread volume,
262
another influencing factor could be the high proportion of HMW GS found in flour 5. For
263
HMW GS a positive correlation with loaf volume was described by Wieser and Kieffer (2001).
264
The volume loss of the two organic flours 2 and 3 remains constant throughout the storage,
265
only a slight reduction was obtained for the longtime storage. This unusual volume stability
266
is contributed to the fact that very low loaf volumes of breads were already measured after
267
1 day of frozen storage. With flour 8 also a constant reduction was found, but at a very high
268
percentage. The loaf volume was dramatically reduced already after one day; in this case the
269
freezing process itself had a huge impact on the loaf volume in comparison to the fresh
270
bread, irrespective of storage duration. Interestingly, the highest volume for fresh bread was
271
observed with this flour, this data highlights that flour requirements for fresh bread and for
272
bread made from pre-fermented frozen dough are different. For flours 1, 4, 6 and 7 a typical
273
reduction of bread volume with increasing frozen storage duration, as previously described
274
(Bhattacharya et al., 2003; Inoue and Bushuk, 1992), was found. Relative volume reduction
275
of these flours was quite similar at the same storage duration, after one day (12.4 ± 1.4 %),
276
28 days (22.3 ± 4.5 %) and after 168 days (38.3 ± 5.7 %).
277
Regarding crumb firmness similar behaviour as for loaf volume was found, as a result of its
278
relation through bread density. A steady increase occurred with all flours, expect for flour 2.
279
In comparison to the results of Bhattacharya et al. (2003), the increase of crumb firmness
280
was substantial, it should be noted that in their study the final proofing time was variated to
281
decrease the quality loss. For flours 4, 5 and 6 it was not possible to cut a representative test
282
cube after 168 days storage, because of their very low loaf volume and uneven crumb
283
structure. Therefore, Fmax and Frel were not analysed. Breads made from flour 1, 2 and
284
especially 7, obtained desirable soft crumb structures after frozen storage up to 28 days.
285
In Table 3 it is demonstrated that only slight changes in Frel were determined. The lowest
286
values were found with flour 3. A tendentious decrease with increasing storage time can be
287
attributed to the loss of moisture during frozen storage (Selomulyo and Zhou, 2007).
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3.5 Correlation analysis
291
The results of the correlation analyses are summarised in Table 4, only flour parameters with
292
significant correlations were listed, therefore different parameters were listed for specific
293
loaf volume and Fmax. Considering the data above, wheat flours with a wide spectrum of
294
properties were used in this study, also several different behaviours for bread volume loss
295
during frozen storage were found. Thus, some significant correlations were identified
296
between flour properties and bread quality parameters. Significance of correlations was
297
changing with storage time for some parameters. After 168 days of frozen storage no
298
significant correlations were found. This indicates that the pre-fermented frozen dough is
299
not suitable for such long storage times. Possible solutions for this problem could be the use
300
of additives, modified packaging or freezing of pre-baked frozen bread or non-fermented
301
dough.
302
A significant negative correlation of ash content was found with bread volume at most
303
storage times. This influence can be attributed to the decreasing effect of aleurone particles
304
on bread volume (Stojceska and Butler, 2012). Within the RVA pasting properties, peak
305
viscosity was positively correlated with specific loaf volume. These results are likely to be
306
related to alpha-amylase activity, which is preferred to be low for frozen dough production
307
according to the theory of Neyreneuf and Van der Plaat (1991). There are, however, other
308
possible explanations, because RVA pasting profiles are also affected by other flour
309
constituents (Sahlstrøm et al., 2003). The physicochemical characteristics of starch are also
310
influencing RVA parameters and these have substantial effects on frozen dough quality (Ma
311
et al., 2016). However, in this study, peak viscosity had the potential to predict the specific
312
loaf volume of pre-fermented frozen dough up to storage periods of 28 days.
313
Wet gluten content, which is a widely used quality indicator for bread making quality in
314
Europe, was significantly correlated only with bread volume of fresh bread. Furthermore, the
315
composition of the gluten proteins is only poorly represented with wet gluten content, a
316
better view can be obtained by extensibility tests which are highly significant correlated with
317
the gliadin/glutenin ratio (Horvat et al., 2006). In this study the highest correlation
318
coefficients were found between specific loaf volume and Flourgraph E7 ratio. They were
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ACCEPTED MANUSCRIPT correlated positively at a level of p > 0.01. Dough resistance was also positively correlated
320
with loaf volume, this is in agreement with the correlation obtained by Kenny et al. (1999)
321
who did a non-fermented frozen dough experiment. Contrasting effects for fresh bread were
322
found by Thanhaeuser et al. (2014), where dough resistance was negatively correlated with
323
loaf volume of breads produced by micro-Rapid-Mix-Test. Nevertheless, in the same study it
324
has been noted that a suitable baking test is essential for a representative performance test
325
of wheat flour, because with the applied microbaking test different correlation coefficients
326
were found.
327
Observing the correlation matrix for Fmax (also shown in Table 4) it must be noted that RSD
328
for specific loaf volume (5.07%) was much lower than for Fmax (18,74%). Similar to loaf
329
volume, significant negative correlations were found with ash content, maximum resistance,
330
ratio and peak viscosity. Different to loaf volume other significant correlations were found
331
for Fmax. Flourgraph E6 stability was negatively and degree of softening positively correlated
332
to Fmax at some storage durations. As stability was highly positively correlated with dough
333
development time (r = 0.898, p < 0.01) a possible explanation might be, that for some flours
334
the applied kneading time (which was set constant in this baking experiment) was too short
335
and were thus producing breads with increased crumb firmness. Individual variation of
336
kneading time in baking experiments is not a common practice, but it could offer more
337
information about the breadmaking potential of wheat flours (Thanhaeuser et al., 2014).
338
Furthermore a positive correlation was found between HMW GS content and Fmax after 21
339
and 28 days of frozen storage.
340
Taken together, these results suggest that RVA peak viscosity and especially resistance to
341
extension and ratio (maximum resistance divided by extensibility) have great potential to
342
predict bread quality made from pre-fermented frozen dough. The intensity of this
343
correlation was not changing considerably during 28 days of frozen storage. A note of
344
caution is due here since a relatively low number of 8 wheat flours were used for the
345
calculation of correlation coefficients.
346
4. Conclusions
347
The main aim of the current study was to identify flour quality parameters, which can help to
348
predict final quality of bread made from frozen dough within a bakery orientated baking test
349
setup. The results after long-term storage highlighted that pre-fermented frozen dough
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ACCEPTED MANUSCRIPT without any modifications is not suitable for storage times up to 168 days, but after storage
351
times of 28 days most breads still showed acceptable quality, dependent on flour type. The
352
most significant influence on loaf volume was Flourgraph E7 maximum resistance to
353
extension and ratio and also RVA pasting parameters. It can therefore be assumed that
354
flours with high resistance to extension and high pasting viscosities should be used in
355
production of pre-fermented frozen dough. The results of this study indicate that loaf
356
volume is decreasing with increasing storage duration, but the intensity of this decrease is
357
following different behaviours and was highly dependent on flour properties. Another
358
finding was that wet gluten content was no reliable quality indicator for frozen dough
359
quality.
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Acknowledgment
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This work was financially supported by the Austrian Research Promotion Agency (FFG Project
363
No. 844234).
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Iancu, M.L., Ognean, M., 2015. Use of flour-graphics technique in the compatibility parameter extensograph brabender and flourgraph E7. The Journal of Microbiology, Biotechnology and Food Sciences 5, 277–281.
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Inoue, Y., Bushuk, W., 1992. Studies on frozen doughs. II. Flour quality requirements for bread production from frozen dough. Cereal Chemistry 69, 423–428. Kenny, S., Wehrle, K., Dennehy, T., Arendt, E., 1999. Correlations between empirical and fundamental rheology measurements and baking performance of frozen bread dough. Cereal Chemistry 76, 421–425. Lu, W., Grant, L., 1999a. Effects of prolonged storage at freezing temperatures on starch and baking quality of frozen doughs. Cereal Chemistry 76, 656–662. Lu, W., Grant, L., 1999b. Role of flour fractions in breadmaking quality of frozen dough. Cereal Chemistry 76, 663–667.
ACCEPTED MANUSCRIPT Ma, S., Li, L., Wang, X., Zheng, X., Bian, K., Bao, Q., 2016. Effect of mechanically damaged starch from wheat flour on the quality of frozen dough and steamed bread. Food Chemistry 202, 120–124. Mansberger, A., D’Amico, S., Novalin, S., Schmidt, J., Tӧmӧskӧzi, S., Berghofer, E., Schoenlechner, R., 2014. Pentosan extraction from rye bran on pilot scale for application in gluten-free products. Food Hydrocolloids 35, 606–612.
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Neyreneuf, O., Van der Plaat, J., 1991. Preparation of frozen French bread dough with improved stability. Cereal Chemistry 68, 60–66.
Olivera, S.D., 2011. The effect of basic raw materials in the process of wheat dough freezing. Food and Feed Research 38, 9–19.
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Pechanek, U., Karger, A., Grӧger, S., Charvat, B., Schӧggl, G., Lelley, T., 1997. Effect of nitrogen fertilization on quantity of flour protein components, dough properties, and breadmaking quality of wheat. Cereal Chemistry 74, 800–805. Ribotta, P.D., León, A.E., Añón, M.C., 2001. Effect of freezing and frozen storage of doughs on bread quality. Journal of Agricultural and Food Chemistry 49, 913–918. Rosell, C.M., 2010. Trends in Breadmaking: Low and Subzero Temperatures. In: Passos, M.L., Ribeiro, C.P. (Eds.), Innovation in food engineering: New techniques and products. CRC Press. Boca Raton, pp. 59–79
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Rosell, C.M., Gómez, M., 2007. Frozen dough and partially baked bread: an update. Food Reviews International 23, 303–319.
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Sahlstrøm, S., Bævre, A., Bråthen, E., 2003. Impact of starch properties on hearth bread characteristics. I. Starch in wheat flour. Journal of Cereal Science 37, 275–284. Selomulyo, V.O., Zhou, W., 2007. Frozen bread dough: Effects of freezing storage and dough improvers. Journal of Cereal Science 45, 1–17.
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ACCEPTED MANUSCRIPT Wieser, H., 2000. Comparative investigations of gluten proteins from different wheat species I. Qualitative and quantitative composition of gluten protein types. European Food Research and Technology 211, 262–268.
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Wieser, H., Antes, S., Seilmeier, W., 1998. Quantitative determination of gluten protein types in wheat flour by reversed-phase high-performance liquid chromatography. Cereal Chemistry 75, 644–650. Wieser, H., Kieffer, R., 2001. Correlations of the amount of gluten protein types to the technological properties of wheat flours determined on a micro-scale. Journal of Cereal Science 34, 19–27.
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Wolt, M., D’Appolonia, B., 1984. Factors involved in the stability of frozen dough. II. The effects of yeast type, flour type, and dough additives on frozen-dough stability. Cereal Chemistry 61, 213–221.
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Figure Captions
Figure 1. Pre-fermented frozen dough breadmaking procedure (WA = water absorption; mb
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= moisture basis)
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Figure 2. Relative volume reduction after 1, 28 and 168 days of frozen storage in comparison
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Table 1. Flour characteristics of the eight used flours Quality Testsa
1
2
3
4
5
6
7
8
0.54 ± 0.01a
0.76 ± 0.01b
1.43 ± 0.03e
0.64 ± 0.03c
0.68 ± 0.03c
0.72 ± 0.02bc
0.84 ± 0.05d
0.72 ± 0.01bc
Protein (N x 5.7), %
11.90 ± 0.20b
11.10 ± 0.50a 12.71 ± 0.37bc 12.12 ± 0.16b
13.14 ± 0.02c
10.89 ± 0.37a
14.56 ± 0.06d
15.00 ± 0.22d
Wet gluten (ICC 155),c %
31.89 ± 0.51cd 25.63 ± 0.77a
b
Gluten Index (ICC 155) b
Fat, % b
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24.94 ± 0.29a
31.46 ± 0.02c
27.88 ± 0.54b
31.02 ± 0.36c
33.02 ± 0.22d
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Ash,b %
96 ± 1ab
98 ± 1b
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94 ± 3a
97 ± 2ab
97 ± 1ab
96 ± 0ab
96 ± 2ab
1.03 ± 0.09a
1.37 ± 0.08c
2.16 ± 0.01f
1.23 ± 0.01b
1.58 ± 0.00d
1.71 ± 0.10e
1.48 ± 0.03d
1.21 ± 0.03b
80.95 ± 0.40d 78.75 ± 1.19cd 74.59 ± 0.63ab 75.12 ± 0.97ab 72.04 ± 0.65a 76.03 ± 1.17bc 73.48 ± 1.33ab 76.98 ± 2.41bc
Flourgraph E6 (ICC 179) Water absorption 500HE, % Dough development time, min Stability, min Degree of softening, HE Quality number, HE
60.7 ± 0.3cd 9.4 ± 0.7d 16.6 ± 1.7e 41 ± 6a 148 ± 25c
58.1 ± 0.4ab 6.6 ± 0.1bc 9.2 ± 0.7bc 51 ± 6ab 91 ± 15b
67.9 ± 0.3e 5.4 ± 0.4b 7.1 ± 0.5ab 70 ± 12c 85 ± 8b
Flourgraph E7 (ICC 180) - 90 min Maximum resistance (R), HE Extensibility (E), mm Energy, cm² Ratio (R/E)
784 ± 31f 158 ± 8abc 161 ± 9d 5.0 ± 0.4cd
504 ± 50b 138 ± 9ab 99 ± 5b 3.7 ± 0.6b
235 ± 6a 141 ± 10ab 53 ± 5a 1.7 ± 0.1a
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58.5 ± 0.6b 6.9 ± 0.6bc 10.6 ± 0.5cd 70 ± 5bc 105 ± 9b
57.3 ± 0.1a 6.8 ± 0.4bc 10.4 ± 0.8cd 52 ± 4abc 101 ± 15b
61.2 ± 0.1d 7.8 ± 1.0cd 12.8 ± 0.5d 55 ± 8abc 114 ± 6bc
59.9 ± 0.0c 7.0 ± 0.7cd 9.6 ± 1.6cd 56 ± 10abc 108 ± 13b
747 ± 47def 146 ± 18ab 141 ± 31cd 5.2 ± 0.3d
649 ± 14cd 132 ± 1a 118 ± 1bc 4.9 ± 0.1cd
760 ± 6ef 163 ± 8bc 159 ± 10d 4.7 ± 0.3bcd
675 ± 44de 184 ± 8c 165 ± 13d 3.7 ± 0.3b
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58.2 ± 0.3ab 1.9 ± 0.3a 5.7 ± 0.2a 70 ± 3c 41 ± 21a
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563 ± 47bc 141 ± 3ab 107 ± 6bc 4.0 ± 0.4bc
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RVA (ICC 162, STD1 profile) Peak viscosity, cP 2330 ± 45a 1686 ± 48b 1280 ± 23c 1885 ± 28de 1928 ± 8eg 1793 ± 30d Trough viscosity, cP 1263 ± 25a 819 ± 24b 607 ± 3c 1094 ± 18de 1078 ± 8de 1066 ± 22de Breakdown, cP 1065 ± 27a 867 ± 25b 673 ± 23c 791 ± 12d 851 ± 0bd 726 ± 14c Setback, cP 1296 ± 24a 1094 ± 20b 993 ± 3c 1179 ± 16d 1324 ± 5a 1172 ± 6d Final viscosity, cP 2561 ± 43a 1913 ± 44b 1601 ± 3c 2273 ± 34d 2401 ± 11e 2238 ± 28d Peak time, min 5.98 ± 0.08abc 5.85 ± 0.03ad 5.75 ± 0.03d 6.11 ± 0.03c 5.91 ± 0.08abd 5.93 ± 0.00ab a Mean and standard deviation of three replicates. b water-free basis c 14% moisture basis Within row, values with the same following letter do not differ significantly from each other (p > 0.05)
2081 ± 14f 2026 ± 14fg 1123 ± 7e 1066 ± 3d 958 ± 9e 960 ± 16e 1460 ± 18e 1602 ± 5f 2583 ± 23af 2667 ± 4f 6.05 ± 0.03bc 5.98 ± 0.03abc
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Table 2. Proportionsa (%) of glutenin proteins in wheat flours determined by RP-HPLC
a
1 1.62 ± 0.15a 23.84 ± 0.12a 74.51 ± 0.14a 3.13 ± 0.02a
2 1.46 ± 0.09a 21.82 ± 0.11b 76.72 ± 0.05b 3.52 ± 0.02b
3 1.02 ± 0.12b 25.10 ± 0.16c 73.88 ± 0.28ad 2.94 ± 0.03c
4 0.91 ± 0.05b 25.11 ± 0.43c 73.98 ± 0.49a 2.95 ± 0.07c
Calculated as percent (%) of total glutenins area
b
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Mean and standard deviation of three replicates. Within row, values with the same following letter do not differ significantly from each other (p > 0.05)
5 1.47 ± 0.08a 26.61 ± 0.65d 71.92 ± 0.59c 2.70 ± 0.09d
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reversed-phase HPLCb ωb GS HMW GS LMW GS LMW/HMW Ratio
6 1.72 ± 0.12a 25.32 ± 0.68c 72.97 ± 0.64d 2.88 ± 0.10c
7 3.02 ± 0.19c 21.17 ± 0.25b 75.81 ± 0.21b 3.58 ± 0.05b
8 2.87 ± 0.13c 21.28 ± 0.27b 75.85 ± 0.26b 3.57 ± 0.06b
ACCEPTED MANUSCRIPT Table 3. Effect of frozen dough storage time and wheat flour type on bread characteristics Flour Storage Time (Days)
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2
3
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Specific loaf volume, cm³/100g 315 ± 52abA
283 ± 28aA
192 ± 21cA
314 ± 10abA
331 ± 23abA
322 ± 14abA
335 ± 7bA
342 ± 8bA
1
267 ± 5abB
220 ± 23cB
163 ± 5eB
281 ± 13bB
330 ± 18dA
279 ± 13bB
294 ± 16bB
241 ± 11caB
3
252 ± 9abB
207 ± 2cB
168 ± 10dAB
263 ± 10abeBC
284 ± 9fB
278 ± 10efBC
270 ± 4befCDE
248 ± 5aB
7
261 ± 6abB
215 ± 10cB
154 ± 3dB
246 ± 15aC
296 ± 22eB
258 ± 7abCD
275 ± 9beBCD
212 ± 7cCDE
14
276 ± 5aAB
205 ± 11bB
162 ± 5cB
242 ± 11dC
275 ± 7aBC
243 ± 15dDE
290 ± 11aBC
195 ± 9bDE
21
255 ± 4aB
204 ± 11bB
173 ± 3cAB
249 ± 14aC
247 ± 11aD
248 ± 12aDE
248 ± 5aE
191 ± 4bcE
28
256 ± 15abB
201 ± 19cB
163 ± 15dB
241 ± 21abeC
253 ± 9abCD
231 ± 3beE
267 ± 7aDE
215 ± 13ceCD
168
196 ± 16abC
226 ± 27bcB
176 ± 15aAB
212 ± 19abcD
202 ± 9abcE
201 ± 17abcF
180 ± 15aF
233 ± 15cBC
1.7 ± 0.1aA
1.6 ± 0.3aA
3.3 ± 0.6bA
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1.3 ± 0.1aA
1.8 ± 0.4abA
4.5 ± 0.3cA
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1.7 ± 0.0aA
1.4 ± 0.3aA
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2.2 ± 0.8aAB
3.2 ± 0.5abcB
7.2 ± 0.8dAB
4.6 ± 0.6bcB
3.3 ± 0.4abB
3.8 ± 0.6abAB
2.5 ± 0.4abAB
4.9 ± 1.3cC
3
2.9 ± 0.7abAB
3.9 ± 0.6abcB
7.8 ± 0.5eBC
5.0 ± 0.8cdBC
4.5 ± 1.1bcB
5.0 ± 1.2cdABC
2.5 ± 0.5aAB
5.3 ± 0.7dC
7
3.3 ± 0.4aAB
4.5 ± 0.4abB
7.5 ± 0.5cAB
5.9 ± 1.5bcBC
4.4 ± 1.3abB
5.5 ± 1.0bBCD
3.3 ± 0.5aB
4.9 ± 0.4abBC
14
4.3 ± 0.5abBC
4.4 ± 0.8abB
8.5 ± 1.5cdBC
7.0 ± 2.1bcdCD
6.0 ± 0.8bcC
9.2 ± 3.6dE
2.6 ± 0.2aAB
6.2 ± 0.8bcdCD
6.8 ± 0.7cdBCD
3.4 ± 0.4aAB
3.7 ± 0.4abB
8.2 ± 0.2dBC
8.3 ± 0.8dD
7.6 ± 1.8dCDE
3.1 ± 0.9aB
5.6 ± 1.3bcCD
3.7 ± 1.4abB
4.1 ± 1.2abB
10.0 ± 0.6cC
8.4 ± 0.8cD
7.7 ± 1.5cD
7.9 ± 1.7cDE
2.4 ± 1.2aAB
5.2 ± 1.5bC
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6.5 ± 3.5aC
3.8 ± 0.3aB
8.0 ± 1.9aBC
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6.5 ± 2.1aC
7.6 ± 1.6aD
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FREL, %
71.3 ± 1.3aA
69.0 ± 0.5bcAB
67.3 ± 0.4cdA
70.2 ± 1.9abA
71.0 ± 0.7abA
70.2 ± 0.9abAB
69.3 ± 0.7bcAB
66.4 ± 0.6dA
1
72.0 ± 0.2aA
69.5 ± 0.6cdAB
65.6 ± 0.4eA
69.9 ± 1.3bcdA
71.3 ± 1.0abcA
70.2 ± 1.2abcA
72.4 ± 0.7abB
67.9 ± 1.4deABC
3
72.1 ± 0.8aA
69.5 ± 0.9cdAB
66.2 ± 0.4eA
69.7 ± 0.9bcdAB
71.5 ± 1.5abA
69.5 ± 1.4cdABC
71.3 ± 0.3abcB
68.3 ± 0.8dBC
7
71.4 ± 0.7abA
69.9 ± 0.4bcAB
64.5 ± 1.2eAB
69.1 ± 1.5cAB
72.1 ± 0.1aA
68.6 ± 0.9dABCD
69.5 ± 0.4cAB
67.5 ± 0.6dAB
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69.6 ± 0.8abAB
68.7 ± 1.0abcB
66.4 ± 1.4bcA
68.5 ± 3.1abcAB
69.8 ± 1.3abA
64.7 ± 4.4cD
71.6 ± 3.3aB
66.9 ± 0.7bcAB
21
71.2 ± 0.6aA
71.1 ± 1.0aA
65.0 ± 2.0dAB
68.3 ± 1.3bcAB
66.4 ± 1.1cdB
66.0 ± 2.8cdBCD
69.4 ± 0.9abAB
67.6 ± 0.5bcdABC
28
70.3 ± 1.6aA
68.8 ± 1.0abcB
66.1 ± 0.6bcA
66.2 ± 2.1bcB
67.0 ± 1.8abcB
65.3 ± 3.8cCD
70.0 ± 2.1abAB
69.0 ± 0.9abcC
168
66.8 ± 4.1aB
65.6 ± 2.6aC
62.6 ± 2.1aB
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-
-
67.3 ± 1.1aA
67.3 ± 1.1aAB
Mean and standard deviation of three replicates.
Values with same capital letter, in the same column and lower cases, in the same row are not significant different (p > 0.05)
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Table 4. Pearson correlation coefficients between flour characteristics and bread properties after different frozen storage durations (1-168 days) Specific loaf volume, cm³/100g Storage time (Days) fresh 1 3 7 14 21 28 168 Ash content –0.868** –0.735* –0.774* –0.754* –0.654 –0.717* –0.766* –0.542 Wet gluten 0.833* 0.288 0.435 0.212 0.262 0.056 0.471 –0.152 Maximum resistance - 90min 0.920** 0.847** 0.872** 0.882** 0.849** 0.752* 0.921** 0.178 Ratio - 90min 0.855** 0.914** 0.912** 0.962** 0.894** 0.882** 0.913** 0.132 RVA - Peak viscosity 0.830* 0.676 0.717* 0.724* 0.764* 0.682 0.860** 0.202 RVA - Setback 0.772* 0.484 0.569 0.433 0.393 0.196 0.558 0.301
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Fmax, N 7 14 0.703 0.356 –0.874** –0.522 –0.776* –0.366 –0.810* –0.571 0.640 0.436 –0.866** –0.596 –0.884** –0.806* 0.443 0.646
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3 0.728* –0.821* –0.788* –0.715* 0.628 –0.818* –0.781* 0.421
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** Correlation is significant at the 0.01 level (2-tailed). * Correlation is significant at the 0.05 level (2-tailed).
1 0.780* –0.842** –0.876** –0.733* 0.625 –0.788* –0.701 0.242
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fresh 0.834* –0.762* –0.905** –0.477 0.379 –0.677 –0.442 –0.061
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Storage time (Days) Ash content Maximum resistance - 90min Ratio - 90min Stability Degree of softening RVA - Peak viscosity RVA - Breakdown HMW content
21 0.360 –0.406 –0.251 –0.592 0.748* –0.567 –0.782* 0.808*
28 0.465 –0.615 –0.448 –0.693 0.741* –0.681 –0.855** 0.793*
168 0.442 –0.141 –0.357 –0.109 0.507 –0.085 –0.195 0.382
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Highlights: •
Pre-fermented frozen dough baking trials were performed with 8 wheat flours
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Frozen storage periods were 1, 3 ,7 ,14 ,21 ,28 and 168 days
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Wet gluten content was not correlated with loaf volume of frozen dough breads
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Flourgraph E7 ratio was positively correlated with loaf volume
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High RVA peak viscosities had a positive effect on loaf volume
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