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Selection and incorporation of hydrocolloid for gluten-free leavened millet breads and optimization of the baking process thereof
Journal Pre-proof Selection and incorporation of hydrocolloid for gluten-free leavened millet breads and optimization of the baking process thereof Subir Kumar Chakraborty, Nachiket Kotwaliwale, Surekha Ashok Navale PII:
S0023-6438(19)31220-4
DOI:
https://doi.org/10.1016/j.lwt.2019.108878
Reference:
YFSTL 108878
To appear in:
LWT - Food Science and Technology
Received Date: 2 April 2019 Revised Date:
2 October 2019
Accepted Date: 22 November 2019
Please cite this article as: Chakraborty, S.K., Kotwaliwale, N., Navale, S.A., Selection and incorporation of hydrocolloid for gluten-free leavened millet breads and optimization of the baking process thereof, LWT - Food Science and Technology (2019), doi: https://doi.org/10.1016/j.lwt.2019.108878. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier Ltd.
Leavened gluten-free millet bread
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Selection and incorporation of hydrocolloid for gluten-free leavened millet breads and optimization of the
2
baking process thereof 1a
3
1
2
Subir Kumar Chakraborty , Nachiket Kotwaliwale , Surekha Ashok Navale 1
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Agro Produce Processing Division, ICAR - Central Institute of Agricultural Engineering, Bhopal, India
2
5
College of Agricultural Engineering and Technology, DBS Konkan Agricultural University, Dapoli, India
6
a
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Senior Scientist, Agro Produce Processing Division, ICAR – Central Institute of Agricultural Engineering,
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Nabibagh, Berasia Road, Bhopal, India. email - [email protected], Orchid: 0000-0002-1560-1728
Corresponding author
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Abstract
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Suitability amongst the hydrocolloids, - tragacanth gum, gum arabic, guar gum and xanthan gum to be used as
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an ingredient for mimicking the action of gluten was carried out based on gluten-free millet (pearl, little and
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kodo) bread quality in terms of expansion (cm), specific volume (mL/g) and textural characteristics. Xanthan
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gum was found to be the most suitable hydrocolloid for rendering an acceptable structure to the bread.
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Gluten-free leavened breads were made using central composite rotatable experimental design of response
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surface methodology with proofing time (Pt, 1.3 - 4.7 h), baking time (Bt, 32 - 48 min) and baking temperature
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(BT, 158 – 192 C) as input variables. Statistically significant (p<0.01) second order models were used to
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understand effect of variables upon the responses. Textural property of little millet flour bread was observed
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to be better amongst all the millet breads. Optimum conditions for little millet bread in terms of Pt, Bt and BT
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was 3.5 h, 48 min and 190 C, respectively; under these conditions this bread exhibited best expansion,
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springiness and hardness. 2-tailed paired t-test revealed that quality characteristics of bread prepared at
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model predicted values did not significantly (p<0.01) differ from that actually prepared under optimum
22
condition.
o
o
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Keywords: Bread quality; Gluten-free; Hydrocolloids; Kodo millet; Pearl millet; Little millet
1
Leavened gluten-free millet bread
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1. Introduction
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The world is witnessing an upsurge of consciousness among the consumers for nutritional and safety aspect of
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food like never before. Across the world, consumption of baked goods is common and widespread. Refined
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wheat flour (RWF) is the key ingredient in all such culinary preparations. RWF provides carbohydrate, protein
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and some minerals (magnesium, phosphorus, iron) but, it is failing the consumers on two counts, one - RWF is
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deficient in fibre and has high glycemic index (GI); two - RWF contains gluten, incidence of gluten intolerance
31
causing allergic reaction for individuals resulting in inflammation of the small intestine leading to mal
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absorption of several important nutrients and intestinal mucosal damage. This is called coeliac disease, which
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does not have a pharmaceutical cure; initiation of clinical recovery is possible only by a strict adherence to
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gluten-free diet throughout the lifetime of the patient (Gallagher, Gormley, & Arendt, 2004).
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Millets are gluten free, high in fibre content and rich in minerals (Chakraborty, Singh, & Kumbhar, 2014). Fibre
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rich foods have low GI and can reduce the risk of postprandial oxidative stress (a factor for onset of several
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chronic diseases) (Jenkins, Josse, Wong, Nguyen, Kendall, 2007). Consumption of millets lessens the chance of
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cardio vascular diseases, certain forms of cancer, abnormal blood pressure, obesity and results in a healthy
39
gastrointestinal tract (Jones and Larzelere, 2008). Also, bolstering gluten-free baked products with dietary
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fibres is helpful for coeliac patients as they have a low intake of fibres attributed to their gluten-free diet
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(Thompson, 2000).
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Gluten provides a plastic structure that entraps gases generated during proofing and temporarily binds water
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required to gelatinize starch. Hydration of proteins of gluten during dough formation and gelatinization of
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starch ensures the desirable structure of bread crumb. Millets do not contain gluten and bread made from
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gluten free dough pose a big challenge to any baker. Gluten-free bread suffers from structural and textural
46
defects (Renzetti and Arendt, 2009). Millet doughs are liquid and similar to a batter because of an unstable
47
starch and the existence of mutually repulsive forces between the starch granules (Onyango, Mutungi,
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Unbehend, & Lindhauer, 2010). The resultant incoherent structure is unsuitable for entrapping gases
49
generated during batter mixing and proofing. Thus, the batter does not rise resulting in a bread with rigid and
50
crumbly texture.
51
Gluten-free doughs must show appropriate viscoelastic characteristics to enhance the acceptance of the final
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product by the consumer. Hydration during dough formation define the rheological properties of the gluten-
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free dough (Crockett et al., 2011). Adding the right volume of water can control quality aspects of gluten-free
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bread such as, - loaf specific volume and crumb hardness (Rozylo et al., 2015). Water-starch system relies on
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fragile intermolecular bonds for structural stability or the lack of it, hence the gluten-free dough has a low
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mixing tolerance and poor extensional property (Lazaridou, Duta, Papageorgiou, Belc, & Biliaderis, 2007).
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Adding an extra source of starch as an ingredient to gluten free bread formulation is widespread and well
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researched. It has been reported that tapioca starch inherits the polymeric substances that makes it a suitable
59
gluten-free ingredient (Milde, Ramallo, & Puppo, 2012). It can reproduce the viscoelastic properties of gluten
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and can provide the structure to retain gases produced during proofing (McCarthy, Gallagher, Gormley,
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Schober, & Arendt, 2005).
2
Leavened gluten-free millet bread
62
Characteristic properties of gluten-free dough, say millet dough, can be improved with the presence of
63
hydrocolloids (Meza et al., 2011). Hydrocolloids exhibit a special function in gluten-free dough in order to help
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to mimic the gluten properties (Moreira, Chenlo, Torres, & Rama, 2014). The gel network structure of the
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hydrocolloids serves to stabilization of the gluten-free dough system by increasing the dough intermolecular
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viscosity (Houben, Höchstötter, & Becker, 2012) resulting in a higher gas retention during leavening and
67
specific volume of breads (Mancebo, San Miguel, Martínez, & Gómez, 2015)
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A variety of hydrocolloids have been investigated for making good quality gluten-free bread, these include
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guar gum, xanthan, hydroxyl propyl methyl cellulose, methylcellulose, carboxy methyl cellulose, locust bean
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gum, and psyllium gum (Houben et al., 2012; Lazaridou et al., 2007). However, their utility and suitability is
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based on the objective purpose.
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This study envisages to develop leavened bread using a suitable hydrocolloid amongst tragacanth gum, gum
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arabic, guar gum and xanthum gum as an ingredient for mimicking the action of gluten. The bread made
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thereof has been evaluated on quality (expansion, specific volume and textural characteristics) aspects based
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on the varying baking conditions in terms of proofing time (Pt), baking time (Bt) and baking temperature (BT).
76
2. Materials and methods
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2.1 Materials
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Based on the rheological studies conducted by Chakraborty, Kotwaliwale, & Navale (2018), the following
79
millets were used for preparing gluten-free breads, - pearl millet (Pennisetum glaucum), little millet (Penicum
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milliare) and Kodo millet (Paspalum scrobiculatum). Kodo and little millet were donated by M.P. Vigyan Sabha,
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Bhopal, India (a non-government organization working in the tribal areas of Central India since 1985) as whole
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grain, dehusking was carried out by ICAR - CIAE millet mill. Pearl millet and other miscellaneous ingredients
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were purchased from the local market of Bhopal. Cleaned and dehusked millets were pulverized in an attrition
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mill. Hydrocolloids (Thomas Baker Pvt. Ltd., Mumbai, India) used for the present study were tragacanth gum,
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gum arabic, guar gum, xanthum gum.
86
2.2 Hydrocolloids
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The hydrocolloids tragacanth gum, gum arabic, guar gum and xanthan gum were used in the present study.
88
Separate series of experiments were conducted to select a hydrocolloid and its level (g), to be included as
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bread ingredient by comparing specific volume and texture profile of the millet bread developed using each
90
hydrocolloid.
91
2.3 Particle size distribution
92
The results of rheological studies are affected by particle size of flour used for dough making (Servais, Jones, &
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Roberts, 2002). Availability of particle size allows comparison of rheological data across various researches
94
(Fraiha, Biagi, & Ferraz, 2011). Particle size analysis (Mastersizer, Malvern Inc., Worcestershire, United
95
Kingdom) of all the flours has been reported in terms of D[4,3] or the volume or mass moment mean or the De
96
Broucker mean and as D[3,2] surface area moment mean or Sauter Mean Diameter (SMD). 4,3 =
∑ ∑
(1)
3
Leavened gluten-free millet bread
3,2 =
∑ ∑
(2)
97
Where, d is diameter of sphere (µm) best representing the particle
98
2.4 Bread making
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Bread made from RWF was considered as a control sample to set target for the quality parameters of the
100
gluten-free millet breads. Several preliminary experiments were conducted to set limit of input variables, -
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proofing time (Pt, h), baking time (Bt, min), baking temperature (BT, C) and a fixed quantity of a particular
102
hydrocolloid ranging from 2 to 5 per cent (Crockett et al., 2011). Finally, bread was made with Pt, Bt and BT as
103
input variables and responses were expansion, specific volume and instrumental textural profile.
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Millet bread was made by straight dough method (Moore, Schober, Dockery, Arendt, 2004). The volume and
105
temperature of water used for dough making was 100ml (for 40g millet flour along with all the other
106
ingredients) and 40 C, respectively. Temperature of water was given a consideration because, traditionally
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non-wheat-based dough preparation is carried out by using warm water; this initiates the gelatinization of the
108
starch which acts as the only resort for assisting the dough formation in the absence of gluten (Hoseney,
109
Finney, Pmeranz, & Shogren, (1971)
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Compressed yeast used in bread making process was kept under refrigerated conditions before being used for
111
experiments. The yeast was thawed in lukewarm water at 30±2˚C, as recommended by Thiessen (1942). All the
112
ingredients were mixed before any water was added. Mixing is normally designed to achieve a target energy
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input into dough or a target final dough temperature. Over mixing can retard the metabolism of yeast.
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Kneading of the dough was carried out by heel of the hand to push and finger tips were used to lift and fold it
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before repeating the same process again and again for 8 -10 min. After mixing and kneading, the round shaped
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dough with all its ingredients (Table 1) was kept in a lightly oiled pan (Schober, Bean, Boyle, & Park, 2008).
117
Improved viscoelastic zein-starch doughs for leavened gluten-free breads: Their rheology and microstructure.
118
Journal of Cereal Science, 48, 755-767.
119
). A damp cotton towel was used as a wrap to prevent a skin formation on dough whilst resting in a draught-
120
free place to allow the dough to rise/proof. Thus, the proofing took place at 100 per cent relative humidity (Rh)
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and at ambient temperature of 35±2 C. The Pt (h), Bt (min) and BT ( C) were as per the experimental design.
122
The baked bread was allowed to cool down before recording the quality parameters.
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2.5 Bread quality
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The quality of the bread was assessed in terms of expansion, cm; specific volume, mL/g; and texture profile
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analysis (TPA). Expansion: Vertical rise in shape of dough measured as the difference of height (cm) before (L)
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and after (L’) baking (Fig. 1).
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Specific volume (Sv, mL/g): The volume (V, mL) of the bread was measured by mustard displacement method
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(AACC, 1998) and then weighing (W, g) the baked dough (Morreale, Garzón, & Rosell, 2017). Three replicates
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were obtained for each experiment. Specific volume was expressed as,
o
o
o
o
(3)
=
130
Texture profile analysis: Instrumental texture was measured in terms of,- hardness, resilience, springiness and
131
cohesiveness of bread (Fig. 2) as these properties are considered to be appropriate indicators of textural 4
Leavened gluten-free millet bread
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quality of a bread (Matos and Rossel, 2013; Morreale et al., 2017). The texture analysis was carried out by TA-
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XT Texture Analyser of Stable Micro Systems, UK using the 75 mm diameter plate (P-75 probe). The
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compression mode texture profile analysis was carried out with pre-test speed of 10.0 mm/s, test speed of 2.0
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mm/s, post-test speed of 2.0 mm/s target strain of 40 per cent (Matos and Rosell, 2012) and a trigger force of
136
5 g.
137
2.6 Experimental design
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Central composite rotatable design (CCRD) of response surface methodology (RSM) for three variables, -
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proofing time (Pt, h), baking time (Bt, min), and baking temperature (BT, C) was obtained by using Design
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Expert (ver. 10). There were six experiments conducted at centre point and two each for every variable at the
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augmented points and 2 (where, n is the number of variables) experiments across all variables for factorial
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points. In all twenty experiments were conducted (Table 2). Determination of coded values and augmented
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point values for input variables were obtained by methods as described in Chakraborty et al. (2014). A perfect
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solution for a multi response matrix can be obtained with Design Expert (ver. 10) by combining the goals into a
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composite function D(x) called the desirability function (Myers and Montogomery, 2002), it is defined as:
o
n
=
146
×
×
× … … . .×
⁄
(4)
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where, d1, d2, d3 .......dn are the responses and n is the total number of responses in the measure. Numerical
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optimization solution is obtained as a point with maximum desirability.
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2.7 Statistical analysis
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The experimental data comprised responses from twenty experiments in terms of bread quality parameters.
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Effect of input variables on the responses was understood by conducting regression analysis and analysis of
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variance (ANOVA) by means of a second order polynomial model (eq. 5). n
P= βo +
n
βi Xi + i=1
n-1
βii X2i i=1
n
+
(5) βij Xi Xj
i=1 j=i+1
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where, P is response, n is number of variables, X’s are the variables, βo, βi, βii and βij are the regression
154
coefficients.
155
3. Results and discussion
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Selection of a particular hydrocolloid and its level was based on the ability of the hydrocolloid to impart
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acceptable textural features to gluten-free bread. Bread was prepared using the selected hydrocolloid and the
158
processing variables were optimised.
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3.1 Hydrocolloid selection
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The amount of hydrocolloid to be used as an ingredient was finalized after a series of preliminary experiments.
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All the four hydrocolloids, - gum arabic, guar gum, tragacanth gum and xanthum gum were used for preparing
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leavened breads. The quality of breads was assessed on the basis of expansion, specific volume and textural
163
properties in terms of hardness, springiness, resilience and cohesiveness. The responses for the blends made
164
from non-gluten dough were compared with that of RWF dough (Fig. 3). Xanthum gum at a higher amount (2.5
165
g) exhibited a slight decrease in the specific volume of bread as compared to other hydrocolloids. Schober,
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Messerschmidt, Bean, Park, Arendt, (2005) also reported a similar trend in loaf volume of gluten-free breads
167
made from sorghum. This behaviour of xanthan gum is due to its ionic nature caused by the presence of two 5
Leavened gluten-free millet bread
168
negatively charged carboxyl groups on its side, hydrogen bonds are formed with water and starch by these
169
groups forming a rigid gel at higher concentrations of the gum. Thus, xanthan gum supplemented breads were
170
more cohesive and resilient, however the springiness did not exhibit any stand-out trend (Fig. 3). Similar
171
observations have been made in the past while using hydrocolloids for gluten-free dough systems (Lazaridou
172
et al., 2007; Crockett, Ie, & Vodovotz, 2011).
173
During the dough making it was also observed that there was a slight increase in water requirement for dough
174
formation due to use of hydrocolloids. This may be attributed to hygroscopic nature of hydrocolloids, as also
175
reported by Rosell, Rojas, & Benedito de Barber, (2001). In gluten free doughs system adequate hydration is
176
critical for strengthening the three-dimensional batter structure (Morreale et al., 2017).
177
3.2 Effect of variables on loaf quality
178
The results of the regression analysis have been reported in Table 3, wherein it can be seen that all the second
179
order models were found to be statistically significant (p<0.01) and capable to represent the variability (R > 80
180
per cent) of the data set to capture the individual (linear and quadratic terms) and interactive effect of the
181
input variables over the responses. It was observed that among all the input variables, proofing time (Pt) has
182
had the maximum instances of playing a significant role in affecting the responses followed by baking time (Bt)
183
and baking temperature (BT). The overwhelming effect of Pt can be attributed to the fact that all the
184
responses were indicative of the bread quality which are directly or indirectly reflective of bread volume and
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the generation of gases during Pt directly related to volume of the bread (Lazaridou et al., 2007; Matos and
186
Rossel, 2013; Morreale et al., 2017).
187
3.2.1 Individual effect
188
The significant individual effect of the parameters can be deciphered in terms of their linear or quadratic effect
189
on the responses. A negative coefficient of a linear term indicates an inverse relationship of the response with
190
the input variable and vice versa. Quadratic term with a negative sign indicates that the particular response is
191
maximum at the centre point (coded value: 0) of the respective input variable and it decreases as one moves
192
towards the augmented points (coded value: -1.68 or +1.68). A quadratic term was considered a better
193
predictor of behaviour of variables as it could describe the variability of the response across the experimental
194
range.
195
Consumer acceptance of bread has a direct relation with loaf volume, better the volume of the loaf more is the
196
consumer acceptance. In the present research work, expansion and specific volume were the two indices by
197
means of which variations in loaf volume of gluten-free breads were comprehended. Effect of Pt on
198
‘expansion’ was significantly maximum at the centre point values of the input variables for pearl millet
199
(p<0.05), little millet (p<0.05) and kodo millet (p<0.1). Specific volume of pearl millet bread exhibited a trend
200
opposite to that of the other two breads. While the specific volume was maximum (p<0.1) at centre point for
201
pearl millet bread, the same was maximum at the augmented point for the other two types of bread. Specific
202
volume of the bread increases significantly (p<0.01) across the whole experimental range of Bt. However, for
203
pearl millet bread alone, the specific volume decreased till the centre point and thereafter increased. The
204
second order model could not establish any significant relationship between expansion and specific volume of
205
bread with baking temperature (BT). Hydrocolloid incorporated breads expand less and are stiff due to the
2
6
Leavened gluten-free millet bread
206
increased water binding and reduction in water availability for hydration of starch. Textural characteristics of
207
bread assume massive importance due to the intense dependence of crumb features towards consumer
208
acceptance. It is always desirable of the bread to have a soft flexible crumb. An increase in Pt contributed to a
209
significant (p<0.05) increase in the hardness of the little millet and kodo millet bread. There would be a
210
significant (p<0.1) increase in the hardness of the pearl millet bread through the entire experimental range of
211
Bt. The hardness of pearl millet would increase significantly (p<0.01) beyond the centre point of BT.
212
Variations in baking time (Bt) and baking temperature (BT) had similar effect on hardness of little and kodo
213
millet breads. In case of little (p<0.05) and kodo (p<0.01) millet bread, hardness would peak at the centre point
214
and then diminished towards the augmented points. Heat treatment caused as a result of increased BT lead to
215
uncoiling of existing xanthan chains with water and starch. The open links of chain now cling as ionic bond with
216
proteins present in the millet matrix resulting in increased hardness with increase in temperature. Since
217
amylose containing starch is more in pearl millet so this trend has been reported after the centre point values.
218
The cohesiveness (p<0.01) of all the breads was best at the centre point values of Pt (p<0.1) and Bt (p<0.01)
219
which would subsequently decrease beyond this point. Cohesiveness for the breads across all the parameters
220
increases till the centre point and then decrease. Similar significant (p<0.01) effect was cast by Pt on the kodo
221
millet bread only. Limited size of pores due to strength induced to the lamella of the cells by the xanthan gum
222
resulted in formation of a firm mesh like structure of the crust with thick cell walls (Lazaridou, Duta,
223
Papageorgiou, Belc, & Biliaderis, 2007). However, upon increase in Bt and BT the enhanced diffusive or
224
convective transport of water from crumb towards crust which was otherwise trapped by xanthan gum
225
resulted in a crumbly texture and incoherent structure.
226
The firm gas cell walls also turned brittle leading to a fragile crumb. Most resilient millet bread (p<0.05) was
227
obtained at the centre point value of BT. Springiness of all the breads were significantly (p<0.01) consistent
228
with Pt, this response peaked at the extreme point and minimised at the centre point. The significant linear
229
terms of Bt (p<0.05) and BT (p<0.1) indicate that the springiness of pearl millet and kodo millet bread would
230
decrease with increase in these variables. Xanthan gum is reported to increase dough elasticity by increasing
231
G’ (Crockett et al., 2011), but this increase is followed by the dough becoming too stiff to rise during proofing.
232
This results in less entrapped air during proofing leading to leavened bread, but with limited springiness.
233
3.2.2 Interactive effect
234
The interactive effect of input variables on responses was comprehended with the help of the contour plots
235
(Fig 4). It was observed during the regression analysis of the second order models that only some of the
236
responses were being affected significantly (p<0.01) by the interaction of input variables. Across all flours,
237
expansion was affected (p<0.01) by interaction of Pt-Bt. The interaction of Pt-BT was common for all three
238
flour dough to affect (p<0.01) specific volume of the bread; interaction (p<0.01) of both Pt-Bt and Pt-BT had a
239
direct bearing on springiness of bread.
240
It can be seen in Fig. 4 (B, C) that expansion is more at longer proofing time. Absence of gluten in the millet
241
flours necessitates a longer Pt and the same is a vital requirement for expansion and gas retention (Demiralp,
242
Celik, & Koksel, 2000). Pearl millet was the coarsest of all the flours with D [4, 3] = 94.8 µm, may be that is the
243
reason that it is exhibiting high expansion at low Pt (Fig. 4 A). This fact was also observed by de la Hera, 7
Leavened gluten-free millet bread
244
Gomez, & Rosell (2013) that coarser corn flours provide breads with higher volume and softer crumb due to
245
their ability to retain carbon dioxide during proofing. Specific volume of the bread was more for all the millet
246
flours at increased Pt (Fig. 4 D, E, F) within the experimental range. It has been reported by other researchers
247
that increase in bread volume in high fibre dough systems requires a combination of high Pt and lower BT
248
(Foschia, Peressini, Sensidoni, & Brennan, 2013) observed in the present research work. Springiness followed
249
the same trend across all flours while displaying significant (p<0.01) interactive effect of both Pt-Bt and Pt-BT
250
(Fig. 4 G, H, I, J, K, L). Combinations of low Pt and low Bt /BT or a combination of high Pt and high Bt/BT over
251
the experimental range resulted in maximum springiness.
252
3.3 Optimization and model validation
253
The optimum bread making condition was decided based on the loaf volume characteristics and the textural
254
characteristics. While expansion and specific volume were constrained with being maximised, hardness was
255
aimed at being minimum, rest of the textural features were not given any specific goal. Results of the
256
numerical optimization solutions for the statistically significant second order models had a desirability of 0.96
257
(Table 4).
258
The predicted quality of RWF bread was better as compared to the corresponding predicted quality
259
parameters of leavened gluten-free millet bread. The results are in concordance with the observations that
260
have been made by other researchers (Robin, Schuchmann, & Palzer, 2012). The veracity of the model
261
predicted results was established by preparing the breads at model predicted optimum condition (Fig. 5) and
262
recording the quality of the breads. The model predicted quality indices were compared with that of the
263
breads prepared under optimum conditions. The results of two tailed t-test (Table 5) for all the millet breads
264
revealed that there was no significant difference between the model predicted values and the actual values
265
4. Conclusion
266
Intake of fibre rich foods lessens the chances of onset of many chronic disorders and diseases in human beings.
267
Millets are a potent source of dietary fibres, but they are gluten-free and hence are not suitable for being used
268
for making leavened breads. Suitability amongst the hydrocolloids, - tragacanth gum, gum arabic, guar gum
269
and xanthan gum to be used as an ingredient for mimicking the action of gluten has been carried out based on
270
the gluten-free millet (pearl, little and kodo) bread quality in terms of expansion (cm), specific volume (mL/g)
271
and textural characteristics. Xanthan gum was found to be the most suitable hydrocolloid for rendering an
272
acceptable structure to the bread. Gluten free yeast leavened breads were made using a central composite
273
rotatable experimental design of response surface methodology with proofing time (Pt), 1.3 - 4.7 h, baking
274
time (Bt), 32 – 48 min and baking temperature (BT), 158 – 192 C as input variables. Statistically significant
275
(p<0.01) second order models were used to understand effect of variables upon the responses. The textural
276
property of little millet flour bread was observed to be better amongst all the millet breads. Optimum
277
conditions for little millet bread in terms of Pt, Bt and BT was 3.5 h, 48 min and 190 C, respectively. Under the
278
optimum conditions the little millet bread exhibited minimum hardness and best springiness values. A 2-tailed
279
paired t-test revealed that quality characteristics of bread prepared at model predicted values did not
280
significantly (p<0.01) differ from that actually prepared at optimum condition.
o
o
8
Leavened gluten-free millet bread
281
6. References
282
AACC, (1998). Approved Laboratory Methods (9 ed.). Guidelines for Measurement of Volume by Rapeseed
283
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10
Figure 1 Measure of expansion for leavened bread. Figure 2 A representative figure of texture profile analysis curve and definition of terms. Figure 3 Effect of different hydrocolloids at various levels on the quality characteristics of bread. Figure 4 Contour plots representing the significant (p<0.01) interactive effect of two input variables (third variable at centre point) on the various responses of leavened breads made from pearl millet (A, D, G, J), little millet (B, E, H, K) and kodo millet (C, F, I, L) flours. Figure 5 Leavened breads prepared from (a) Refined wheat (b) Pearl millet (c) Kodo millet (d) Little millet.
Table 1 Ingredients for bread making Ingredients
RWF bread
Millet flour bread
Base flour
40 g
40 g
Water
21 ml
100 ml
1g
1g
Yeast
2.4 g
3g
Sugar
1.25 g
1.25 g
Tapioca starch
NA
60 g
Hydrocolloid
NA
Fixed amount
Baking time
20 min
Salt
Baking temperature Butter
o
195±3 C
As
per
experimental
design
For greasing the baking pan to easily lift the bread
Table 2 Experimental plan and observed values of input variables Actual values
Coded values o
Pt, h
Bt, min
BT, C
1.3
31.6
158
-1.68
2
35
145
-1
3
40
175
0
4
45
185
+1
4.7
48.4
192
+1.68
Experimental design as coded values
No. of experiments
0
0
0
6
±1
±1
±1
8
±1.68
0
0
2
0
±1.68
0
2
0
0
±1.68
2
Total number of experiments
20
Pt - proofing time, Bt - baking time, BT - baking temperature
Table 3 Regression analysis and ANOVA of second order models for the various responses Pearl millet Predi
R1
R2
R3
Little millet
R4
R5
R6
R1
R2
R3
ctor Pt Bt
0.039
0.002
-0.022
-1.380
0.021
*
1.324
0.009
0.019
**
***
*
-0.018 -0.017
-0.060
***
1.962
*
-0.008 0.040
Bt × Pt
0.025 -0.168
***
-0.890
-0.023 0.037
BT × Bt
0.025
0.015 -0.090
Pt × Bt -0.175
***
**
0.050
**
0.019
0.075
-0.001
-0.419
-0.020
2
-0.007 0.043
BT
0.004
***
2.481
***
0.023
***
-0.021
**
-0.024
*
***
0.022 0.046
***
0.002 0.027
0.010
0.075
-0.795
2
Bt
-0.002
** *
-0.026
-0.043
-0.017
0.035
*
0.015
-0.042 -0.070
***
*
2
***
*
**
0.020
-0.013 -0.038
-0.033
3.275
**
*
0.980 -0.037
Pt
R4
R5
R6
R1
R2
R3
R4
R5
R6
Coefficients **
***
BT
Kodo millet
**
-1.001 -0.025
***
0.083
***
-0.119
-0.052
***
**
0.002
-0.073
0.015
0.046
***
0.001
0.025
0.082
*
0.016
*
0.025
***
0.013
0.006 0.020
0.003 -0.068
***
-0.007
-0.005 -3.554
***
-0.034
-0.006 -0.049
***
0.011
0.003
**
-0.005
***
***
-0.004
**
-0.006
***
0.011
0.935 -0.029
***
**
1.246
-
**
0.528
-0.001
-0.055
-0.841 -0.036
-0.125
***
3.822 0.041
0.050
**
**
0.016
-0.005 -8.233
-0.002
0.003
**
0.017
**
-0.015
-0.015
*
-0.032
**
***
0.029
*
***
0.004
**
0.016
***
-0.020
0.035
***
0.033
***`
0.020
-2.281 -0.036
***
***
-0.021
***
-0.045
-9.110
0.016
-0.012
***
-0.037
-0.009
*
**
4.126
*
-0.012 -0.007
-0.175
***
0.024
0.003 0.036
0.441 0.023
-1.615
-0.017
**
0.039
-0.008
***
-1.264
**
***
0.155
*
-0.004
0.020
0.038
***
***
***
-0.001 -0.008
-0.652 -0.035
**
0.054
-1.788
**
0.006 0.018
***
-0.045
-0.042
**
***
***
**
1.209
0.024
*
**
0.002 -0.057
***
***
-0.005 -0.042
***
ANOVA ***
***
7.53
***
5.23
***
16.07
***
7.86
3.71
6.36
6.83
5.51
8.91
9.41
3.47
91.3
94.5
81.8
82.8
87.9
87.2
82.5
93.5
R ,%
8.07
***
19.19
2
4.99
***
F-value 11.67 c.v., %
4.98
***
5.87
***
***
***
***
9.79
8.23
***
10.4
***
5.85
***
12.84
***
8.07
***
***
12.74
11.32
7.53
6.69
4.80
4.47
5.40
9.36
4.36
16.45
6.20
5.51
8.91
84.1
91.9
91.1
89.8
88.1
90.3
84.1
92.4
87.9
87.2
Pt - proofing time, Bt - baking time, BT - baking temperature; R1, Expansion, cm; R2, Specific volume, mL/g; R3, Hardness, N; R4, Resilience; R5, Springiness; R6, Cohesiveness. ***
significant at p< 0.01, **significant at p< 0.05, *significant at p< 0.1
Table 4 Optimum conditions for RWF and millet breads Input variables
RWF bread
Pearl millet bread
Little millet bread
Kodo millet bread
Pt, h
0.67 (40 min)
4.2
3.5
2.0
Bt, min
25
33
48
45
195
180
190
165
Expansion, cm
1.2
1.0
0.9
0.8
Specific volume, mL/g
2.62
1.21
1.16
1.72
Hardness, N
1.6
9.3
3.1
5.3
Resilience
0.38
0.49
0.32
0.32
Springiness
0.97
0.48
0.48
0.38
Cohesiveness
0.80
0.38
0.36
0.35
o
BT, C Responses
Pt - proofing time, Bt - baking time, BT - baking temperature
Table 5 Model testing by using two-tailed t-test for little millet bread Response
Predicted
Actual value@
Standard
Mean
% Variation
tcal
value (µo)
(µ1) ± SD
error
difference
Expansion, cm
0.9
0.82± 0.08
0.037
0.08
11.11
2.14
Specific volume, mL/g
1.16
1.26± 0.14
0.061
0.1292
10.37
2.12
Hardness, N
3.10
3.46± 0.34
0.154
0.06
1.73
0.39
Resilience
0.32
0.33± 0.09
0.040
0.012
2.26
0.30
Springiness
0.48
0.51± 0.06
0.027
0.01
1.96
0.37
Cohesiveness
0.36
0.382± 0.05
0.022
0.042
7.34
1.89
ho: µo = µ1, tcal
L
L’
Expansion (cm) = L’- L Figure 1
Figure 2
7
Hardness, N Resilience
6
Springiness Cohesiveness
5
Specific Volume, ml/g 4 3 2 1 0 1g RWF Bread
1.5g
2g
Arabic
2.5g
1g
1.5g
2g
2.5g
1g
Guar
1.5g
2g
Tragacanth
Hydrocolloid(s) level Values are average of triplicates and error bars represent standard deviation.
Figure 3
2.5g
1g
1.5g
2g
Xanthum
2.5g
Expansion
Expansion
50.00
1.10 0.32
0.46
Baking time, min
0.58
40.00
0.58 0.84 0.32 0.06
45.00
0.65 0.59
40.00
0.46 0.72 0.33
1.10
2.00
3.00
4.00
5.00
1.00
2.00
3.00
A
4.00
1.13
1.00
2.00
200.00
3.00
4.00
5.00
Proofing time, hr
B
C Specific Volume
200.00
1.845
1.837
Baking temperature, oC
0.738
o
Baking temperature, C
0.87
0.35
35.00
5.00
Specific Volume
1.801
1.446 1.092
1.326
175.00
1.326 1.446 162.50
0.61
Proofing time, hr
Specific Volume
187.50
40.00
30.00
Proofing time, hr
200.00
0.61
0.09
30.00
1.00
45.00
0.20
30.00
0.35
0.87
0.59
35.00
Expansion 1.13
0.65
1.092
1.801
Baking temperature, oC
Baking time, min B: Baking time
0.84 45.00
35.00
50.00
0.33
Baking time, min
50.00
1.652 1.466
187.50
1.393
1.466 175.00
1.281 1.652 162.50
1.837
1.096
1.660 1.475
187.50
1.417 1.475
175.00
1.290
1.660 162.50
1.845
1.105
2.155 150.00
150.00
150.00 2.00
3.00
4.00
1.00
5.00
2.00
3.00
D
0.614 0.549
40.00
0.483 0.483 0.549 0.614
0.600 0.58
45.00
0.52 0.40 0.46
40.00
0.41 0.41
0.46 35.00
0.369
45.00
0.542 0.484
40.00
0.427 0.427 0.484
35.00
0.542
0.40
0.679
0.600 30.00 2.00
3.00
4.00
5.00
0.58
1.00
Proofing time, hr
30.00 2.00
G
4.00
0.578
0.503
175.00
0.40 0.46
0.503 0.468
0.41
0.46 0.40
162.50
0.578 0.652
0.58
3.00
4.00
5.00
0.379
0.510
0.444
1.00
0.415
0.444
0.415 0.510 0.576 0.379
0.34 150.00
150.00
Proofing time, hr
0.576
162.50
0.52
0.429 150.00
0.313
175.00
0.41
5.00
187.50
0.52
175.00
0.468
4.00
Springiness
200.00
0.58
187.50
0.429
3.00
I
0.34
o
0.652
Baking temperature, C
0.355
J
2.00
Proofing time, hr
Springiness
200.00
187.50
2.00
1.00
5.00
H
Springiness
200.00
3.00
Proofing time, hr
Baking temperature, oC
1.00
Baking temperature, oC
5.00
F
0.52
30.00
1.00
4.00
Springiness
50.00
0.34
Baking time, min
Baking time, min
0.679
162.50
3.00
Proofing time, hr
Springiness
50.00
0.418
35.00
2.00
E
Springiness
45.00
1.00
5.00
Proofing time, hr
Proofing time, hr
50.00
4.00
Baking time, min
1.00
2.00
3.00
4.00
Proofing time, hr
K Figure 4
5.00
1.00
2.00
3.00
4.00
Proofing time, hr
L
5.00
(a)
(b)
(c)
(d) Figure 5
•
Leavened bread can be made from pearl, little & kodo millet.
•
Xanthum gum was observed to be the best suited to introduce leavening.
•
Optimum condition for leavened bread made using millets has been reported.
•
Millet bread has lesser loaf volume, harder, less springy than traditional bread.
Conflict of Interest and Authorship Conformation Form Please check the following as appropriate:
o
All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version.
o
This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue.
o
The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript
o
The following authors have affiliations with organizations with direct or indirect financial interest in the subject matter discussed in the manuscript:
Author’s name
Affiliation Agro Produce Processing Division, ICAR - Central
Subir Kumar Chakraborty
Institute of Agricultural Engineering, Bhopal, India
Nachiket Kotwaliwale
Agro Produce Processing Division, ICAR - Central Institute of Agricultural Engineering, Bhopal, India
Surekha Ashok Navale
College of Agricultural Engineering and Technology, DBS Konkan Agricultural University, Dapoli, India
S0023-6438(19)31220-4
DOI:
https://doi.org/10.1016/j.lwt.2019.108878
Reference:
YFSTL 108878
To appear in:
LWT - Food Science and Technology
Received Date: 2 April 2019 Revised Date:
2 October 2019
Accepted Date: 22 November 2019
Please cite this article as: Chakraborty, S.K., Kotwaliwale, N., Navale, S.A., Selection and incorporation of hydrocolloid for gluten-free leavened millet breads and optimization of the baking process thereof, LWT - Food Science and Technology (2019), doi: https://doi.org/10.1016/j.lwt.2019.108878. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier Ltd.
Leavened gluten-free millet bread
1
Selection and incorporation of hydrocolloid for gluten-free leavened millet breads and optimization of the
2
baking process thereof 1a
3
1
2
Subir Kumar Chakraborty , Nachiket Kotwaliwale , Surekha Ashok Navale 1
4
Agro Produce Processing Division, ICAR - Central Institute of Agricultural Engineering, Bhopal, India
2
5
College of Agricultural Engineering and Technology, DBS Konkan Agricultural University, Dapoli, India
6
a
7
Senior Scientist, Agro Produce Processing Division, ICAR – Central Institute of Agricultural Engineering,
8
Nabibagh, Berasia Road, Bhopal, India. email - [email protected], Orchid: 0000-0002-1560-1728
Corresponding author
9
Abstract
10
Suitability amongst the hydrocolloids, - tragacanth gum, gum arabic, guar gum and xanthan gum to be used as
11
an ingredient for mimicking the action of gluten was carried out based on gluten-free millet (pearl, little and
12
kodo) bread quality in terms of expansion (cm), specific volume (mL/g) and textural characteristics. Xanthan
13
gum was found to be the most suitable hydrocolloid for rendering an acceptable structure to the bread.
14
Gluten-free leavened breads were made using central composite rotatable experimental design of response
15
surface methodology with proofing time (Pt, 1.3 - 4.7 h), baking time (Bt, 32 - 48 min) and baking temperature
16
(BT, 158 – 192 C) as input variables. Statistically significant (p<0.01) second order models were used to
17
understand effect of variables upon the responses. Textural property of little millet flour bread was observed
18
to be better amongst all the millet breads. Optimum conditions for little millet bread in terms of Pt, Bt and BT
19
was 3.5 h, 48 min and 190 C, respectively; under these conditions this bread exhibited best expansion,
20
springiness and hardness. 2-tailed paired t-test revealed that quality characteristics of bread prepared at
21
model predicted values did not significantly (p<0.01) differ from that actually prepared under optimum
22
condition.
o
o
23 24
Keywords: Bread quality; Gluten-free; Hydrocolloids; Kodo millet; Pearl millet; Little millet
1
Leavened gluten-free millet bread
25
1. Introduction
26
The world is witnessing an upsurge of consciousness among the consumers for nutritional and safety aspect of
27
food like never before. Across the world, consumption of baked goods is common and widespread. Refined
28
wheat flour (RWF) is the key ingredient in all such culinary preparations. RWF provides carbohydrate, protein
29
and some minerals (magnesium, phosphorus, iron) but, it is failing the consumers on two counts, one - RWF is
30
deficient in fibre and has high glycemic index (GI); two - RWF contains gluten, incidence of gluten intolerance
31
causing allergic reaction for individuals resulting in inflammation of the small intestine leading to mal
32
absorption of several important nutrients and intestinal mucosal damage. This is called coeliac disease, which
33
does not have a pharmaceutical cure; initiation of clinical recovery is possible only by a strict adherence to
34
gluten-free diet throughout the lifetime of the patient (Gallagher, Gormley, & Arendt, 2004).
35
Millets are gluten free, high in fibre content and rich in minerals (Chakraborty, Singh, & Kumbhar, 2014). Fibre
36
rich foods have low GI and can reduce the risk of postprandial oxidative stress (a factor for onset of several
37
chronic diseases) (Jenkins, Josse, Wong, Nguyen, Kendall, 2007). Consumption of millets lessens the chance of
38
cardio vascular diseases, certain forms of cancer, abnormal blood pressure, obesity and results in a healthy
39
gastrointestinal tract (Jones and Larzelere, 2008). Also, bolstering gluten-free baked products with dietary
40
fibres is helpful for coeliac patients as they have a low intake of fibres attributed to their gluten-free diet
41
(Thompson, 2000).
42
Gluten provides a plastic structure that entraps gases generated during proofing and temporarily binds water
43
required to gelatinize starch. Hydration of proteins of gluten during dough formation and gelatinization of
44
starch ensures the desirable structure of bread crumb. Millets do not contain gluten and bread made from
45
gluten free dough pose a big challenge to any baker. Gluten-free bread suffers from structural and textural
46
defects (Renzetti and Arendt, 2009). Millet doughs are liquid and similar to a batter because of an unstable
47
starch and the existence of mutually repulsive forces between the starch granules (Onyango, Mutungi,
48
Unbehend, & Lindhauer, 2010). The resultant incoherent structure is unsuitable for entrapping gases
49
generated during batter mixing and proofing. Thus, the batter does not rise resulting in a bread with rigid and
50
crumbly texture.
51
Gluten-free doughs must show appropriate viscoelastic characteristics to enhance the acceptance of the final
52
product by the consumer. Hydration during dough formation define the rheological properties of the gluten-
53
free dough (Crockett et al., 2011). Adding the right volume of water can control quality aspects of gluten-free
54
bread such as, - loaf specific volume and crumb hardness (Rozylo et al., 2015). Water-starch system relies on
55
fragile intermolecular bonds for structural stability or the lack of it, hence the gluten-free dough has a low
56
mixing tolerance and poor extensional property (Lazaridou, Duta, Papageorgiou, Belc, & Biliaderis, 2007).
57
Adding an extra source of starch as an ingredient to gluten free bread formulation is widespread and well
58
researched. It has been reported that tapioca starch inherits the polymeric substances that makes it a suitable
59
gluten-free ingredient (Milde, Ramallo, & Puppo, 2012). It can reproduce the viscoelastic properties of gluten
60
and can provide the structure to retain gases produced during proofing (McCarthy, Gallagher, Gormley,
61
Schober, & Arendt, 2005).
2
Leavened gluten-free millet bread
62
Characteristic properties of gluten-free dough, say millet dough, can be improved with the presence of
63
hydrocolloids (Meza et al., 2011). Hydrocolloids exhibit a special function in gluten-free dough in order to help
64
to mimic the gluten properties (Moreira, Chenlo, Torres, & Rama, 2014). The gel network structure of the
65
hydrocolloids serves to stabilization of the gluten-free dough system by increasing the dough intermolecular
66
viscosity (Houben, Höchstötter, & Becker, 2012) resulting in a higher gas retention during leavening and
67
specific volume of breads (Mancebo, San Miguel, Martínez, & Gómez, 2015)
68
A variety of hydrocolloids have been investigated for making good quality gluten-free bread, these include
69
guar gum, xanthan, hydroxyl propyl methyl cellulose, methylcellulose, carboxy methyl cellulose, locust bean
70
gum, and psyllium gum (Houben et al., 2012; Lazaridou et al., 2007). However, their utility and suitability is
71
based on the objective purpose.
72
This study envisages to develop leavened bread using a suitable hydrocolloid amongst tragacanth gum, gum
73
arabic, guar gum and xanthum gum as an ingredient for mimicking the action of gluten. The bread made
74
thereof has been evaluated on quality (expansion, specific volume and textural characteristics) aspects based
75
on the varying baking conditions in terms of proofing time (Pt), baking time (Bt) and baking temperature (BT).
76
2. Materials and methods
77
2.1 Materials
78
Based on the rheological studies conducted by Chakraborty, Kotwaliwale, & Navale (2018), the following
79
millets were used for preparing gluten-free breads, - pearl millet (Pennisetum glaucum), little millet (Penicum
80
milliare) and Kodo millet (Paspalum scrobiculatum). Kodo and little millet were donated by M.P. Vigyan Sabha,
81
Bhopal, India (a non-government organization working in the tribal areas of Central India since 1985) as whole
82
grain, dehusking was carried out by ICAR - CIAE millet mill. Pearl millet and other miscellaneous ingredients
83
were purchased from the local market of Bhopal. Cleaned and dehusked millets were pulverized in an attrition
84
mill. Hydrocolloids (Thomas Baker Pvt. Ltd., Mumbai, India) used for the present study were tragacanth gum,
85
gum arabic, guar gum, xanthum gum.
86
2.2 Hydrocolloids
87
The hydrocolloids tragacanth gum, gum arabic, guar gum and xanthan gum were used in the present study.
88
Separate series of experiments were conducted to select a hydrocolloid and its level (g), to be included as
89
bread ingredient by comparing specific volume and texture profile of the millet bread developed using each
90
hydrocolloid.
91
2.3 Particle size distribution
92
The results of rheological studies are affected by particle size of flour used for dough making (Servais, Jones, &
93
Roberts, 2002). Availability of particle size allows comparison of rheological data across various researches
94
(Fraiha, Biagi, & Ferraz, 2011). Particle size analysis (Mastersizer, Malvern Inc., Worcestershire, United
95
Kingdom) of all the flours has been reported in terms of D[4,3] or the volume or mass moment mean or the De
96
Broucker mean and as D[3,2] surface area moment mean or Sauter Mean Diameter (SMD). 4,3 =
∑ ∑
(1)
3
Leavened gluten-free millet bread
3,2 =
∑ ∑
(2)
97
Where, d is diameter of sphere (µm) best representing the particle
98
2.4 Bread making
99
Bread made from RWF was considered as a control sample to set target for the quality parameters of the
100
gluten-free millet breads. Several preliminary experiments were conducted to set limit of input variables, -
101
proofing time (Pt, h), baking time (Bt, min), baking temperature (BT, C) and a fixed quantity of a particular
102
hydrocolloid ranging from 2 to 5 per cent (Crockett et al., 2011). Finally, bread was made with Pt, Bt and BT as
103
input variables and responses were expansion, specific volume and instrumental textural profile.
104
Millet bread was made by straight dough method (Moore, Schober, Dockery, Arendt, 2004). The volume and
105
temperature of water used for dough making was 100ml (for 40g millet flour along with all the other
106
ingredients) and 40 C, respectively. Temperature of water was given a consideration because, traditionally
107
non-wheat-based dough preparation is carried out by using warm water; this initiates the gelatinization of the
108
starch which acts as the only resort for assisting the dough formation in the absence of gluten (Hoseney,
109
Finney, Pmeranz, & Shogren, (1971)
110
Compressed yeast used in bread making process was kept under refrigerated conditions before being used for
111
experiments. The yeast was thawed in lukewarm water at 30±2˚C, as recommended by Thiessen (1942). All the
112
ingredients were mixed before any water was added. Mixing is normally designed to achieve a target energy
113
input into dough or a target final dough temperature. Over mixing can retard the metabolism of yeast.
114
Kneading of the dough was carried out by heel of the hand to push and finger tips were used to lift and fold it
115
before repeating the same process again and again for 8 -10 min. After mixing and kneading, the round shaped
116
dough with all its ingredients (Table 1) was kept in a lightly oiled pan (Schober, Bean, Boyle, & Park, 2008).
117
Improved viscoelastic zein-starch doughs for leavened gluten-free breads: Their rheology and microstructure.
118
Journal of Cereal Science, 48, 755-767.
119
). A damp cotton towel was used as a wrap to prevent a skin formation on dough whilst resting in a draught-
120
free place to allow the dough to rise/proof. Thus, the proofing took place at 100 per cent relative humidity (Rh)
121
and at ambient temperature of 35±2 C. The Pt (h), Bt (min) and BT ( C) were as per the experimental design.
122
The baked bread was allowed to cool down before recording the quality parameters.
123
2.5 Bread quality
124
The quality of the bread was assessed in terms of expansion, cm; specific volume, mL/g; and texture profile
125
analysis (TPA). Expansion: Vertical rise in shape of dough measured as the difference of height (cm) before (L)
126
and after (L’) baking (Fig. 1).
127
Specific volume (Sv, mL/g): The volume (V, mL) of the bread was measured by mustard displacement method
128
(AACC, 1998) and then weighing (W, g) the baked dough (Morreale, Garzón, & Rosell, 2017). Three replicates
129
were obtained for each experiment. Specific volume was expressed as,
o
o
o
o
(3)
=
130
Texture profile analysis: Instrumental texture was measured in terms of,- hardness, resilience, springiness and
131
cohesiveness of bread (Fig. 2) as these properties are considered to be appropriate indicators of textural 4
Leavened gluten-free millet bread
132
quality of a bread (Matos and Rossel, 2013; Morreale et al., 2017). The texture analysis was carried out by TA-
133
XT Texture Analyser of Stable Micro Systems, UK using the 75 mm diameter plate (P-75 probe). The
134
compression mode texture profile analysis was carried out with pre-test speed of 10.0 mm/s, test speed of 2.0
135
mm/s, post-test speed of 2.0 mm/s target strain of 40 per cent (Matos and Rosell, 2012) and a trigger force of
136
5 g.
137
2.6 Experimental design
138
Central composite rotatable design (CCRD) of response surface methodology (RSM) for three variables, -
139
proofing time (Pt, h), baking time (Bt, min), and baking temperature (BT, C) was obtained by using Design
140
Expert (ver. 10). There were six experiments conducted at centre point and two each for every variable at the
141
augmented points and 2 (where, n is the number of variables) experiments across all variables for factorial
142
points. In all twenty experiments were conducted (Table 2). Determination of coded values and augmented
143
point values for input variables were obtained by methods as described in Chakraborty et al. (2014). A perfect
144
solution for a multi response matrix can be obtained with Design Expert (ver. 10) by combining the goals into a
145
composite function D(x) called the desirability function (Myers and Montogomery, 2002), it is defined as:
o
n
=
146
×
×
× … … . .×
⁄
(4)
147
where, d1, d2, d3 .......dn are the responses and n is the total number of responses in the measure. Numerical
148
optimization solution is obtained as a point with maximum desirability.
149
2.7 Statistical analysis
150
The experimental data comprised responses from twenty experiments in terms of bread quality parameters.
151
Effect of input variables on the responses was understood by conducting regression analysis and analysis of
152
variance (ANOVA) by means of a second order polynomial model (eq. 5). n
P= βo +
n
βi Xi + i=1
n-1
βii X2i i=1
n
+
(5) βij Xi Xj
i=1 j=i+1
153
where, P is response, n is number of variables, X’s are the variables, βo, βi, βii and βij are the regression
154
coefficients.
155
3. Results and discussion
156
Selection of a particular hydrocolloid and its level was based on the ability of the hydrocolloid to impart
157
acceptable textural features to gluten-free bread. Bread was prepared using the selected hydrocolloid and the
158
processing variables were optimised.
159
3.1 Hydrocolloid selection
160
The amount of hydrocolloid to be used as an ingredient was finalized after a series of preliminary experiments.
161
All the four hydrocolloids, - gum arabic, guar gum, tragacanth gum and xanthum gum were used for preparing
162
leavened breads. The quality of breads was assessed on the basis of expansion, specific volume and textural
163
properties in terms of hardness, springiness, resilience and cohesiveness. The responses for the blends made
164
from non-gluten dough were compared with that of RWF dough (Fig. 3). Xanthum gum at a higher amount (2.5
165
g) exhibited a slight decrease in the specific volume of bread as compared to other hydrocolloids. Schober,
166
Messerschmidt, Bean, Park, Arendt, (2005) also reported a similar trend in loaf volume of gluten-free breads
167
made from sorghum. This behaviour of xanthan gum is due to its ionic nature caused by the presence of two 5
Leavened gluten-free millet bread
168
negatively charged carboxyl groups on its side, hydrogen bonds are formed with water and starch by these
169
groups forming a rigid gel at higher concentrations of the gum. Thus, xanthan gum supplemented breads were
170
more cohesive and resilient, however the springiness did not exhibit any stand-out trend (Fig. 3). Similar
171
observations have been made in the past while using hydrocolloids for gluten-free dough systems (Lazaridou
172
et al., 2007; Crockett, Ie, & Vodovotz, 2011).
173
During the dough making it was also observed that there was a slight increase in water requirement for dough
174
formation due to use of hydrocolloids. This may be attributed to hygroscopic nature of hydrocolloids, as also
175
reported by Rosell, Rojas, & Benedito de Barber, (2001). In gluten free doughs system adequate hydration is
176
critical for strengthening the three-dimensional batter structure (Morreale et al., 2017).
177
3.2 Effect of variables on loaf quality
178
The results of the regression analysis have been reported in Table 3, wherein it can be seen that all the second
179
order models were found to be statistically significant (p<0.01) and capable to represent the variability (R > 80
180
per cent) of the data set to capture the individual (linear and quadratic terms) and interactive effect of the
181
input variables over the responses. It was observed that among all the input variables, proofing time (Pt) has
182
had the maximum instances of playing a significant role in affecting the responses followed by baking time (Bt)
183
and baking temperature (BT). The overwhelming effect of Pt can be attributed to the fact that all the
184
responses were indicative of the bread quality which are directly or indirectly reflective of bread volume and
185
the generation of gases during Pt directly related to volume of the bread (Lazaridou et al., 2007; Matos and
186
Rossel, 2013; Morreale et al., 2017).
187
3.2.1 Individual effect
188
The significant individual effect of the parameters can be deciphered in terms of their linear or quadratic effect
189
on the responses. A negative coefficient of a linear term indicates an inverse relationship of the response with
190
the input variable and vice versa. Quadratic term with a negative sign indicates that the particular response is
191
maximum at the centre point (coded value: 0) of the respective input variable and it decreases as one moves
192
towards the augmented points (coded value: -1.68 or +1.68). A quadratic term was considered a better
193
predictor of behaviour of variables as it could describe the variability of the response across the experimental
194
range.
195
Consumer acceptance of bread has a direct relation with loaf volume, better the volume of the loaf more is the
196
consumer acceptance. In the present research work, expansion and specific volume were the two indices by
197
means of which variations in loaf volume of gluten-free breads were comprehended. Effect of Pt on
198
‘expansion’ was significantly maximum at the centre point values of the input variables for pearl millet
199
(p<0.05), little millet (p<0.05) and kodo millet (p<0.1). Specific volume of pearl millet bread exhibited a trend
200
opposite to that of the other two breads. While the specific volume was maximum (p<0.1) at centre point for
201
pearl millet bread, the same was maximum at the augmented point for the other two types of bread. Specific
202
volume of the bread increases significantly (p<0.01) across the whole experimental range of Bt. However, for
203
pearl millet bread alone, the specific volume decreased till the centre point and thereafter increased. The
204
second order model could not establish any significant relationship between expansion and specific volume of
205
bread with baking temperature (BT). Hydrocolloid incorporated breads expand less and are stiff due to the
2
6
Leavened gluten-free millet bread
206
increased water binding and reduction in water availability for hydration of starch. Textural characteristics of
207
bread assume massive importance due to the intense dependence of crumb features towards consumer
208
acceptance. It is always desirable of the bread to have a soft flexible crumb. An increase in Pt contributed to a
209
significant (p<0.05) increase in the hardness of the little millet and kodo millet bread. There would be a
210
significant (p<0.1) increase in the hardness of the pearl millet bread through the entire experimental range of
211
Bt. The hardness of pearl millet would increase significantly (p<0.01) beyond the centre point of BT.
212
Variations in baking time (Bt) and baking temperature (BT) had similar effect on hardness of little and kodo
213
millet breads. In case of little (p<0.05) and kodo (p<0.01) millet bread, hardness would peak at the centre point
214
and then diminished towards the augmented points. Heat treatment caused as a result of increased BT lead to
215
uncoiling of existing xanthan chains with water and starch. The open links of chain now cling as ionic bond with
216
proteins present in the millet matrix resulting in increased hardness with increase in temperature. Since
217
amylose containing starch is more in pearl millet so this trend has been reported after the centre point values.
218
The cohesiveness (p<0.01) of all the breads was best at the centre point values of Pt (p<0.1) and Bt (p<0.01)
219
which would subsequently decrease beyond this point. Cohesiveness for the breads across all the parameters
220
increases till the centre point and then decrease. Similar significant (p<0.01) effect was cast by Pt on the kodo
221
millet bread only. Limited size of pores due to strength induced to the lamella of the cells by the xanthan gum
222
resulted in formation of a firm mesh like structure of the crust with thick cell walls (Lazaridou, Duta,
223
Papageorgiou, Belc, & Biliaderis, 2007). However, upon increase in Bt and BT the enhanced diffusive or
224
convective transport of water from crumb towards crust which was otherwise trapped by xanthan gum
225
resulted in a crumbly texture and incoherent structure.
226
The firm gas cell walls also turned brittle leading to a fragile crumb. Most resilient millet bread (p<0.05) was
227
obtained at the centre point value of BT. Springiness of all the breads were significantly (p<0.01) consistent
228
with Pt, this response peaked at the extreme point and minimised at the centre point. The significant linear
229
terms of Bt (p<0.05) and BT (p<0.1) indicate that the springiness of pearl millet and kodo millet bread would
230
decrease with increase in these variables. Xanthan gum is reported to increase dough elasticity by increasing
231
G’ (Crockett et al., 2011), but this increase is followed by the dough becoming too stiff to rise during proofing.
232
This results in less entrapped air during proofing leading to leavened bread, but with limited springiness.
233
3.2.2 Interactive effect
234
The interactive effect of input variables on responses was comprehended with the help of the contour plots
235
(Fig 4). It was observed during the regression analysis of the second order models that only some of the
236
responses were being affected significantly (p<0.01) by the interaction of input variables. Across all flours,
237
expansion was affected (p<0.01) by interaction of Pt-Bt. The interaction of Pt-BT was common for all three
238
flour dough to affect (p<0.01) specific volume of the bread; interaction (p<0.01) of both Pt-Bt and Pt-BT had a
239
direct bearing on springiness of bread.
240
It can be seen in Fig. 4 (B, C) that expansion is more at longer proofing time. Absence of gluten in the millet
241
flours necessitates a longer Pt and the same is a vital requirement for expansion and gas retention (Demiralp,
242
Celik, & Koksel, 2000). Pearl millet was the coarsest of all the flours with D [4, 3] = 94.8 µm, may be that is the
243
reason that it is exhibiting high expansion at low Pt (Fig. 4 A). This fact was also observed by de la Hera, 7
Leavened gluten-free millet bread
244
Gomez, & Rosell (2013) that coarser corn flours provide breads with higher volume and softer crumb due to
245
their ability to retain carbon dioxide during proofing. Specific volume of the bread was more for all the millet
246
flours at increased Pt (Fig. 4 D, E, F) within the experimental range. It has been reported by other researchers
247
that increase in bread volume in high fibre dough systems requires a combination of high Pt and lower BT
248
(Foschia, Peressini, Sensidoni, & Brennan, 2013) observed in the present research work. Springiness followed
249
the same trend across all flours while displaying significant (p<0.01) interactive effect of both Pt-Bt and Pt-BT
250
(Fig. 4 G, H, I, J, K, L). Combinations of low Pt and low Bt /BT or a combination of high Pt and high Bt/BT over
251
the experimental range resulted in maximum springiness.
252
3.3 Optimization and model validation
253
The optimum bread making condition was decided based on the loaf volume characteristics and the textural
254
characteristics. While expansion and specific volume were constrained with being maximised, hardness was
255
aimed at being minimum, rest of the textural features were not given any specific goal. Results of the
256
numerical optimization solutions for the statistically significant second order models had a desirability of 0.96
257
(Table 4).
258
The predicted quality of RWF bread was better as compared to the corresponding predicted quality
259
parameters of leavened gluten-free millet bread. The results are in concordance with the observations that
260
have been made by other researchers (Robin, Schuchmann, & Palzer, 2012). The veracity of the model
261
predicted results was established by preparing the breads at model predicted optimum condition (Fig. 5) and
262
recording the quality of the breads. The model predicted quality indices were compared with that of the
263
breads prepared under optimum conditions. The results of two tailed t-test (Table 5) for all the millet breads
264
revealed that there was no significant difference between the model predicted values and the actual values
265
4. Conclusion
266
Intake of fibre rich foods lessens the chances of onset of many chronic disorders and diseases in human beings.
267
Millets are a potent source of dietary fibres, but they are gluten-free and hence are not suitable for being used
268
for making leavened breads. Suitability amongst the hydrocolloids, - tragacanth gum, gum arabic, guar gum
269
and xanthan gum to be used as an ingredient for mimicking the action of gluten has been carried out based on
270
the gluten-free millet (pearl, little and kodo) bread quality in terms of expansion (cm), specific volume (mL/g)
271
and textural characteristics. Xanthan gum was found to be the most suitable hydrocolloid for rendering an
272
acceptable structure to the bread. Gluten free yeast leavened breads were made using a central composite
273
rotatable experimental design of response surface methodology with proofing time (Pt), 1.3 - 4.7 h, baking
274
time (Bt), 32 – 48 min and baking temperature (BT), 158 – 192 C as input variables. Statistically significant
275
(p<0.01) second order models were used to understand effect of variables upon the responses. The textural
276
property of little millet flour bread was observed to be better amongst all the millet breads. Optimum
277
conditions for little millet bread in terms of Pt, Bt and BT was 3.5 h, 48 min and 190 C, respectively. Under the
278
optimum conditions the little millet bread exhibited minimum hardness and best springiness values. A 2-tailed
279
paired t-test revealed that quality characteristics of bread prepared at model predicted values did not
280
significantly (p<0.01) differ from that actually prepared at optimum condition.
o
o
8
Leavened gluten-free millet bread
281
6. References
282
AACC, (1998). Approved Laboratory Methods (9 ed.). Guidelines for Measurement of Volume by Rapeseed
283
Displacement. St. Paul: American Association of Cereal Chemists (AACC Method 10-05).
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Chakraborty, S.K., Kotwaliwale, N., & Navale, S.A. (2018). Rheological characterization of gluten free millet
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flour dough. Journal of Food Measurement and Characterization, 12, 1195-1202.
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Chakraborty, S.K., Singh, D.S., & Kumbhar, B.K. (2014). Influence of extrusion conditions on the colour of millet-
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legume extrudates using digital imagery. Irish Journal of Agriculture and Food Research, 53, 65-74.
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Crockett, R., Ie, P., & Vodovotz, Y. (2011). How do xanthan and hydroxypropyl methylcellulose individually
289
affect the physicochemical properties in a model gluten-free dough? Journal of Food Science, 76, 274–282.
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de la Hera, E., Gomez, M., & Rosell, C.M. (2013). Particle size distribution of rice flour affecting the starch
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enzymatic hydrolysis and hydration properties. Carbohydrates Polymers, 98, 421-427.
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Demiralp, H., Celik, S., & Koksel, H. (2000). Effects of oxidizing agents and defatting on the electro phoretic
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patterns of flour proteins during dough mixing. European Food Research Technology, 21, 322-325.
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Foschia, M., Peressini, D., Sensidoni, A., & Brennan, C.S. (2013). The effects of dietary fibre addition on the
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Fraiha, M., Biagi, J.D., & Ferraz, A.C.O. (2011). Rheological behaviour of corn and soy mix as feed ingredients.
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Gallagher, E., Gormley, T.R., & Arendt, E.K. (2004). Recent advances in the formulation of gluten-free cereal-
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Hoseney, R. C., Finney, K. F., Pmeranz, Y., & Shogren, M. D. (1971). Functional (Bread making) and biochemical
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properties of wheat flour components. (VIII Starch). St. Paul: American Association of Cereal Chemists.
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Houben, A., Höchstötter, A., & Becker, T. (2012). Possibilities to increase the quality in gluten-free bread
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production: An overview. European Food Research and Technology, 235(2), 195–208.
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Jenkins, D. J., Josse, A. R., Wong, J. M., Nguyen, T. H., Kendall, C. W. (2007). The portfolio diet for
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cardiovascular risk reduction. Current Atherosclerosis Reports, 9, 501-507.
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Jones, G. N., & Larzelere, M. M. (2008). Stress and health. Primary Care: Clinics in Office Practice, 35, 839-856.
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Lazaridou, A., Duta, D., Papageorgiou, M., Belc, N., & Biliaderis, C. G. (2007). Effects of hydrocolloids on dough
308
rheology and bread quality parameters in gluten-free formulations. Journal of Food Engineering, 79, 1033-
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Mancebo, C. M., San Miguel, M. Á., Martínez, M. M., & Gómez, M. (2015). Optimization of rheological
311
properties of gluten-free doughs with HPMC, psyllium and different levels of water. Journal of Cereal Science,
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61, 8–15.
313
Matos, M. E., Rosell, C. M. (2012). Relationship between instrumental parameters and sensory characteristics
314
in gluten-free breads. European Food Research Technology, 235, 107–117.
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McCarthy, D. F., Gallagher, E., Gormley, T. R., Schober, T. J., & Arendt, E. K. (2005). Application of response
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surface methodology in the development of gluten-free bread. Cereal Chemistry Journal, 82, 609–615.
th
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Meza, B. E., Chesterton, A. K. S., Verdini, R. A., Rubiolo, A. C., Sadd, P. A., Moggridge, & G. D., Wilson, D. I.
318
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Figure 1 Measure of expansion for leavened bread. Figure 2 A representative figure of texture profile analysis curve and definition of terms. Figure 3 Effect of different hydrocolloids at various levels on the quality characteristics of bread. Figure 4 Contour plots representing the significant (p<0.01) interactive effect of two input variables (third variable at centre point) on the various responses of leavened breads made from pearl millet (A, D, G, J), little millet (B, E, H, K) and kodo millet (C, F, I, L) flours. Figure 5 Leavened breads prepared from (a) Refined wheat (b) Pearl millet (c) Kodo millet (d) Little millet.
Table 1 Ingredients for bread making Ingredients
RWF bread
Millet flour bread
Base flour
40 g
40 g
Water
21 ml
100 ml
1g
1g
Yeast
2.4 g
3g
Sugar
1.25 g
1.25 g
Tapioca starch
NA
60 g
Hydrocolloid
NA
Fixed amount
Baking time
20 min
Salt
Baking temperature Butter
o
195±3 C
As
per
experimental
design
For greasing the baking pan to easily lift the bread
Table 2 Experimental plan and observed values of input variables Actual values
Coded values o
Pt, h
Bt, min
BT, C
1.3
31.6
158
-1.68
2
35
145
-1
3
40
175
0
4
45
185
+1
4.7
48.4
192
+1.68
Experimental design as coded values
No. of experiments
0
0
0
6
±1
±1
±1
8
±1.68
0
0
2
0
±1.68
0
2
0
0
±1.68
2
Total number of experiments
20
Pt - proofing time, Bt - baking time, BT - baking temperature
Table 3 Regression analysis and ANOVA of second order models for the various responses Pearl millet Predi
R1
R2
R3
Little millet
R4
R5
R6
R1
R2
R3
ctor Pt Bt
0.039
0.002
-0.022
-1.380
0.021
*
1.324
0.009
0.019
**
***
*
-0.018 -0.017
-0.060
***
1.962
*
-0.008 0.040
Bt × Pt
0.025 -0.168
***
-0.890
-0.023 0.037
BT × Bt
0.025
0.015 -0.090
Pt × Bt -0.175
***
**
0.050
**
0.019
0.075
-0.001
-0.419
-0.020
2
-0.007 0.043
BT
0.004
***
2.481
***
0.023
***
-0.021
**
-0.024
*
***
0.022 0.046
***
0.002 0.027
0.010
0.075
-0.795
2
Bt
-0.002
** *
-0.026
-0.043
-0.017
0.035
*
0.015
-0.042 -0.070
***
*
2
***
*
**
0.020
-0.013 -0.038
-0.033
3.275
**
*
0.980 -0.037
Pt
R4
R5
R6
R1
R2
R3
R4
R5
R6
Coefficients **
***
BT
Kodo millet
**
-1.001 -0.025
***
0.083
***
-0.119
-0.052
***
**
0.002
-0.073
0.015
0.046
***
0.001
0.025
0.082
*
0.016
*
0.025
***
0.013
0.006 0.020
0.003 -0.068
***
-0.007
-0.005 -3.554
***
-0.034
-0.006 -0.049
***
0.011
0.003
**
-0.005
***
***
-0.004
**
-0.006
***
0.011
0.935 -0.029
***
**
1.246
-
**
0.528
-0.001
-0.055
-0.841 -0.036
-0.125
***
3.822 0.041
0.050
**
**
0.016
-0.005 -8.233
-0.002
0.003
**
0.017
**
-0.015
-0.015
*
-0.032
**
***
0.029
*
***
0.004
**
0.016
***
-0.020
0.035
***
0.033
***`
0.020
-2.281 -0.036
***
***
-0.021
***
-0.045
-9.110
0.016
-0.012
***
-0.037
-0.009
*
**
4.126
*
-0.012 -0.007
-0.175
***
0.024
0.003 0.036
0.441 0.023
-1.615
-0.017
**
0.039
-0.008
***
-1.264
**
***
0.155
*
-0.004
0.020
0.038
***
***
***
-0.001 -0.008
-0.652 -0.035
**
0.054
-1.788
**
0.006 0.018
***
-0.045
-0.042
**
***
***
**
1.209
0.024
*
**
0.002 -0.057
***
***
-0.005 -0.042
***
ANOVA ***
***
7.53
***
5.23
***
16.07
***
7.86
3.71
6.36
6.83
5.51
8.91
9.41
3.47
91.3
94.5
81.8
82.8
87.9
87.2
82.5
93.5
R ,%
8.07
***
19.19
2
4.99
***
F-value 11.67 c.v., %
4.98
***
5.87
***
***
***
***
9.79
8.23
***
10.4
***
5.85
***
12.84
***
8.07
***
***
12.74
11.32
7.53
6.69
4.80
4.47
5.40
9.36
4.36
16.45
6.20
5.51
8.91
84.1
91.9
91.1
89.8
88.1
90.3
84.1
92.4
87.9
87.2
Pt - proofing time, Bt - baking time, BT - baking temperature; R1, Expansion, cm; R2, Specific volume, mL/g; R3, Hardness, N; R4, Resilience; R5, Springiness; R6, Cohesiveness. ***
significant at p< 0.01, **significant at p< 0.05, *significant at p< 0.1
Table 4 Optimum conditions for RWF and millet breads Input variables
RWF bread
Pearl millet bread
Little millet bread
Kodo millet bread
Pt, h
0.67 (40 min)
4.2
3.5
2.0
Bt, min
25
33
48
45
195
180
190
165
Expansion, cm
1.2
1.0
0.9
0.8
Specific volume, mL/g
2.62
1.21
1.16
1.72
Hardness, N
1.6
9.3
3.1
5.3
Resilience
0.38
0.49
0.32
0.32
Springiness
0.97
0.48
0.48
0.38
Cohesiveness
0.80
0.38
0.36
0.35
o
BT, C Responses
Pt - proofing time, Bt - baking time, BT - baking temperature
Table 5 Model testing by using two-tailed t-test for little millet bread Response
Predicted
Actual value@
Standard
Mean
% Variation
tcal
value (µo)
(µ1) ± SD
error
difference
Expansion, cm
0.9
0.82± 0.08
0.037
0.08
11.11
2.14
Specific volume, mL/g
1.16
1.26± 0.14
0.061
0.1292
10.37
2.12
Hardness, N
3.10
3.46± 0.34
0.154
0.06
1.73
0.39
Resilience
0.32
0.33± 0.09
0.040
0.012
2.26
0.30
Springiness
0.48
0.51± 0.06
0.027
0.01
1.96
0.37
Cohesiveness
0.36
0.382± 0.05
0.022
0.042
7.34
1.89
ho: µo = µ1, tcal
L
L’
Expansion (cm) = L’- L Figure 1
Figure 2
7
Hardness, N Resilience
6
Springiness Cohesiveness
5
Specific Volume, ml/g 4 3 2 1 0 1g RWF Bread
1.5g
2g
Arabic
2.5g
1g
1.5g
2g
2.5g
1g
Guar
1.5g
2g
Tragacanth
Hydrocolloid(s) level Values are average of triplicates and error bars represent standard deviation.
Figure 3
2.5g
1g
1.5g
2g
Xanthum
2.5g
Expansion
Expansion
50.00
1.10 0.32
0.46
Baking time, min
0.58
40.00
0.58 0.84 0.32 0.06
45.00
0.65 0.59
40.00
0.46 0.72 0.33
1.10
2.00
3.00
4.00
5.00
1.00
2.00
3.00
A
4.00
1.13
1.00
2.00
200.00
3.00
4.00
5.00
Proofing time, hr
B
C Specific Volume
200.00
1.845
1.837
Baking temperature, oC
0.738
o
Baking temperature, C
0.87
0.35
35.00
5.00
Specific Volume
1.801
1.446 1.092
1.326
175.00
1.326 1.446 162.50
0.61
Proofing time, hr
Specific Volume
187.50
40.00
30.00
Proofing time, hr
200.00
0.61
0.09
30.00
1.00
45.00
0.20
30.00
0.35
0.87
0.59
35.00
Expansion 1.13
0.65
1.092
1.801
Baking temperature, oC
Baking time, min B: Baking time
0.84 45.00
35.00
50.00
0.33
Baking time, min
50.00
1.652 1.466
187.50
1.393
1.466 175.00
1.281 1.652 162.50
1.837
1.096
1.660 1.475
187.50
1.417 1.475
175.00
1.290
1.660 162.50
1.845
1.105
2.155 150.00
150.00
150.00 2.00
3.00
4.00
1.00
5.00
2.00
3.00
D
0.614 0.549
40.00
0.483 0.483 0.549 0.614
0.600 0.58
45.00
0.52 0.40 0.46
40.00
0.41 0.41
0.46 35.00
0.369
45.00
0.542 0.484
40.00
0.427 0.427 0.484
35.00
0.542
0.40
0.679
0.600 30.00 2.00
3.00
4.00
5.00
0.58
1.00
Proofing time, hr
30.00 2.00
G
4.00
0.578
0.503
175.00
0.40 0.46
0.503 0.468
0.41
0.46 0.40
162.50
0.578 0.652
0.58
3.00
4.00
5.00
0.379
0.510
0.444
1.00
0.415
0.444
0.415 0.510 0.576 0.379
0.34 150.00
150.00
Proofing time, hr
0.576
162.50
0.52
0.429 150.00
0.313
175.00
0.41
5.00
187.50
0.52
175.00
0.468
4.00
Springiness
200.00
0.58
187.50
0.429
3.00
I
0.34
o
0.652
Baking temperature, C
0.355
J
2.00
Proofing time, hr
Springiness
200.00
187.50
2.00
1.00
5.00
H
Springiness
200.00
3.00
Proofing time, hr
Baking temperature, oC
1.00
Baking temperature, oC
5.00
F
0.52
30.00
1.00
4.00
Springiness
50.00
0.34
Baking time, min
Baking time, min
0.679
162.50
3.00
Proofing time, hr
Springiness
50.00
0.418
35.00
2.00
E
Springiness
45.00
1.00
5.00
Proofing time, hr
Proofing time, hr
50.00
4.00
Baking time, min
1.00
2.00
3.00
4.00
Proofing time, hr
K Figure 4
5.00
1.00
2.00
3.00
4.00
Proofing time, hr
L
5.00
(a)
(b)
(c)
(d) Figure 5
•
Leavened bread can be made from pearl, little & kodo millet.
•
Xanthum gum was observed to be the best suited to introduce leavening.
•
Optimum condition for leavened bread made using millets has been reported.
•
Millet bread has lesser loaf volume, harder, less springy than traditional bread.
Conflict of Interest and Authorship Conformation Form Please check the following as appropriate:
o
All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version.
o
This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue.
o
The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript
o
The following authors have affiliations with organizations with direct or indirect financial interest in the subject matter discussed in the manuscript:
Author’s name
Affiliation Agro Produce Processing Division, ICAR - Central
Subir Kumar Chakraborty
Institute of Agricultural Engineering, Bhopal, India
Nachiket Kotwaliwale
Agro Produce Processing Division, ICAR - Central Institute of Agricultural Engineering, Bhopal, India
Surekha Ashok Navale
College of Agricultural Engineering and Technology, DBS Konkan Agricultural University, Dapoli, India