Shelf-life stability of artisanally and industrially produced durum wheat sourdough bread (“Altamura bread”)

Shelf-life stability of artisanally and industrially produced durum wheat sourdough bread (“Altamura bread”)

ARTICLE IN PRESS LWT 41 (2008) 58–70 www.elsevier.com/locate/lwt Shelf-life stability of artisanally and industrially produced durum wheat sourdough...

782KB Sizes 9 Downloads 142 Views

ARTICLE IN PRESS

LWT 41 (2008) 58–70 www.elsevier.com/locate/lwt

Shelf-life stability of artisanally and industrially produced durum wheat sourdough bread (‘‘Altamura bread’’) Emma Chiavaroa,, Elena Vittadinia, Marilena Muscib, Federica Bianchib, Elena Curtia a

Dipartimento di Ingegneria Industriale, Universita` degli Studi di Parma, viale G.P. Usberti 181/A, 43100 Parma, Italy Dipartimento di Chimica Generale ed Inorganica, Analitica, Chimica Fisica, Universita` degli Studi di Parma, viale G.P. Usberti 17/A, 43100 Parma, Italy

b

Received 17 August 2006; received in revised form 22 January 2007; accepted 24 January 2007

Abstract Physico-chemical properties and volatile compounds of three commercial Altamura breads were evaluated during storage at 25 1C. Two protected denomination of origin (PDO) artisanally produced Altamura breads (Bari, Italy), characterized either by high (High A) or low (LowA) loaf, and an industrial product, commercialized as ‘‘Altamura like’’ (IndA), were studied. HighA and LowA breads had a tick crust that was also detached from the crumb creating an air cushion between crust and crumb. IndA products had a thinner crust, a more homogeneous crumb structure as well as a more homogeneous water distribution among the different portion of the bread loaf than HighA and LowA. A more pronounced water gradient characterized the artisanal breads. Crust and under crust portion of all breads, and crumb for IndA product, underwent a significant reduction of moisture content and aw during storage. Both artisanal breads were subjected to a more significant crumb hardening than IndA sample. Fresh crusts of artisanally produced breads were also significantly harder than IndA. Fresh IndA samples were significantly less cohesive and less springy than artisanal products; cohesiveness significantly decreased in all samples during storage. A more complex gas chromatographic profile was found in the artisanal bread as a larger amount of volatile compounds was present as compared to the IndA bread. Volatile compounds originated both from microbial activity and non-enzymatic browning. Larger amount of volatile compounds characteristics of yeast fermentation was found in IndA. Volatiles decreased over storage in both samples, more significant in the IndA product. r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. Keywords: Altamura bread; Shelf life; Texture; Moisture content; Volatile compounds

1. Introduction In the Mediterranean area, durum wheat flour has been used in the formulation of several types of bread, often associated to sourdough fermentation to give products largely appreciated by the consumers for their characteristic organoleptic attributes (Quaglia, 1988). Altamura bread, produced in Altamura (Bari, Apulia, Southern Italy) was recently authorized by the Commission of the European Community to receive the protected denomination of origin (PDO) (European Union, 2003). PDO Altamura bread production asks, among the others, for flour of durum wheat varieties (Appulo, Arcangelo, Duilio and Simeto) grown in the Altamura area (at least 80% of Corresponding author. Tel.: +39 0521 905888; fax: +39 0521 905705.

E-mail address: [email protected] (E. Chiavaro).

the total flour) and a prolonged sponge-dough procedure (refreshed at least three times). The use of durum wheat flour in straight-dough bread making was reported to offer technological benefits by prolonging the shelf life of commercial products as compared to wheat bread (Boyaciog˘lu & D’Appolonia, 1994a, b). The longer Shel-life was possibly associated to the higher water binding capacity of durum wheat flour; durum wheat bread was also reported to have higher crumb firmness and lower loaf volume (Boyaciog˘lu & D’Appolonia, 1994b). Pasqui, Carcea, Paletti, and Cubadda (1994) reported that 100% durum wheat semolina bread obtained by a straight-dough baking method had a softer crumb than wheat bread during 4 days storage at room temperature. Also a partial addition (10–20%) of durum wheat flour to wheat bread (sponge-dough procedure) resulted in lower firming of bread crumb during storage

0023-6438/$30.00 r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2007.01.018

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

(Boggini, Pagani, & Lucisano, 1997). Hareland and Puhr (1998) reported that 60% addition of durum wheat flour to spring wheat flour (sponge-dough bread making procedure) led to a bread with higher crumb moisture and lower crumb firmness (during 72 h storage) than bread added with soft flour. A few studies investigated the baking performance of durum wheat flours obtained from different Italian durum wheat cultivars for Altamura bread production (Pasqualone, Blanco, Simeone, & Fares, 2002; Simeone, Blanco, Pasqualone, & Fares, 2001). In particular, Raffo et al. (2003) reported that Altamura bread produced with durum wheat flours with higher protein content and higher water adsorption underwent lower moisture loss and firming in the crumb during 8 days storage. Sourdough fermentation is widely used in the production of whole grain rye bread but it is less common when using wheat. Sourdough consist of a piece of dough saved from the previous baking that is then mixed with flour, salt and water to produce bread. Sourdoughs are complex biological systems characterized by a dynamic interaction among endogenous lactic acid bacteria (LAB), yeasts, and the substrate as previously reported (Gobbetti, 1998). Altamura bread sourdoughs were reported to be rich in facultative heterofermentative LAB (Lactobacillus plantarum, Lb. paracasei and L. casei) (Ricciardi, Parente, Piratino, Paraggio, & Romano, 2005), while Saccharomices cerevisiae was the only yeast isolated (Ricciardi et al., 2002). The use of sourdough is reported to improve the aroma of bread in comparison with a straight-dough process, mainly due to the long fermentation that leads to the formation of large amounts of volatiles and aromatic compounds. The extended fermentation also frees a larger amount of amino acids that can act as substrate for Maillard reactions during baking and develops a higher acidity in the dough that can further affect flavour development (Hansen & Hansen, 1996; Hansen & Schieberle, 2005; Thiele, Ga¨nzle, & Vogel, 2002). Sourdough processing has been reported to contradictory affect the shelf-life of bread and its influence on staling was not completely elucidated. In particular, differences in the staling rate of sourdough breads was explained as result of LAB strain-specific gluten proteolytic and starch hydrolitic activities although the relationship between bacterial activity and physicochemical changes in bread during storage was not completely understood (Corsetti et al., 1998, 2000). The rate of crumb firming as well as the rate of starch retrogradation during storage was reported to be dependent to the level of sourdough addition (Barber, Ortola, Barber, & Fe´rnandez, 1992; Crowley, Schober, Charmaine, & Arendt, 2002). In particular, sourdough wheat breads (produced with 20% sourdough, flour basis) were reported to have lower pH and higher lactic/acetic ratio that resulted in higher volume and lower staling rate in comparison with straight dough breads (Barber et al., 1992). Crowley et al. (2002) also found that the addition of

59

20% sourdough to wheat bread reduced crumb firmness and slowed down firming in comparison with breads made with no or larger addition of sourdough (40% flour basis). The objective of this study was to characterize physicochemical properties and the volatiles compounds present in two types of artisanally produced Altamura bread and in an industrial ‘‘Altamura-like’’ bread during storage at 25 1C. 2. Materials and methods 2.1. Materials Three types of breads were considered in this study. Two types of breads were collected from an artisanal bakery located in Altamura (Bari, Italy), commercialized as PDO ‘‘Altamura breads’’. The two Altamura breads were characterized either by high (HighA) or a low (LowA) loaf and both produced by traditional baking method that consisted in a prolonged sponge-dough procedure where the sourdough was refreshed three times before final dough was made. In addition, an industrially produced bread (IndA) commercialized as ‘‘Altamura like’’ was obtained from a local market. The names reported into brackets will be used to refer to the different samples in the remaining of the text. 2.2. Bread making procedures and storage One kilogram loaves of Artisanal Altamura breads were produced with the following recipe: Durum wheat flour (100), NaCl (2), sourdough (20) and water (60) where the number given in parentheses are the percentages referred to the flour. At least 80% of durum wheat flour was of the varieties grown in the geographical area as required by the EC regulation (European Union, 2003). The sourdough was produced by adding water and durum wheat flour (in three successive aliquots, up to 20% of the total flour) to a portion of the dough retained from the previous days. The sourdough was then added to the remaining ingredients that were kneaded for 20 min. The so formed dough was allowed to rest for 90 min at room temperature, covered with a cotton cloth. The dough was then divided into 1 kg piece, allowed to rest for 30 min, then shaped and allowed to rest for additional 15 min. The loafs were then placed into a gas-fired oven (at 250 1C) that was at first kept open for 15 min, and then closed to complete bread baking in 45 min. The two types of Artisanal Altamura breads differed because of a different shaping procedure: High-A dough was cut, with a hand, in two pieces that were then overlapped while Low-A dough was rolled and pressed. Industrially produced ‘‘Altamura-like’’ bread was prepared using durum wheat flour, salt, water and yeast, as indicated on the label. No further information is available on the details of the bread making procedure used. All breads were packaged in a microporous bag and kept at 25 1C in a temperature controlled chamber (ISCO 9000,

ARTICLE IN PRESS 60

E. Chiavaro et al. / LWT 41 (2008) 58–70

Milan, Italy) up to 8 days and analysed at predetermined times (1, 3, 5 and 8 days post-production). Three loafs were used for characterization of each bread type at each storage time for a total of 12 loaves each bread type for batch. Two batches were analyzed for each bread type. 2.3. Image acquisition and analysis The crumb grain of the loaves was assessed using a digital image analysis system. Images of the three central slices (20 mm thickness) from each loaf were captured with a flatbed scanner (Model Scanjet 8200, HP, Cupertino, USA), with a resolution of 600 dots per inch (dpi) and converted from true colour to 256 level grey scale. The images were processed using an Image-Pro Plus 4.5 (Media Cybernetics Inc., USA) software. The whole crumb portion of each slice was evaluated considering the different slice profile of each bread type. Crumb grain was characterized by enumerating the pores present in five preselected dimensional classes based on their area (class 1 ¼ 0.05–0.49 mm2; class 2 ¼ 0.50–0.99 mm2; class 3 ¼ 1.00–4.99 mm2; class 4 ¼ 5.00–49.99 mm2; class 5 ¼ 450 mm2) and the number of pores and the area occupied by each class (expressed as percentage of the total number of pores and total pore area, respectively) was evaluated. Crust thickness was also measured (size function of Image-Pro Plus) on three preselected points of the crust. 2.4. Colour analysis Colour determination was carried out on crust and crumb using a Minolta Colourimeter (CM 2600d, Minolta Co., Osaka, Japan) equipped with a standard illuminant D65. L* (lightness), a* (redness) and b* (yellowness) were quantified on each sample using a 101 position of the standard observer. Crust colour was determined on nine pre-selected locations on the crust of each loaf. Crumb colour was determined on three points on the three central slices of each bread loaf. 2.5. Water activity and moisture content determinations Water activity (aw) was measured at 25 1C using a Decagon Aqualab Meter Series 3TE (Pullman, WA, USA). All samples were broken into small pieces immediately before water activity measurement. Moisture content was determined by vacuum oven drying according to the AOAC approved method 925.09 (Association of Official Analytical Chemistry, 2002). Both analyses were carried out on samples obtained from the crust and on two different portion of the crumb (in proximity of the crust and at the slice centre). Triplicate samples were analyzed for each bread loaf.

2.6. Textural measurement Instrumental texture evaluation of crust and crumb was performed using a TA.XT2 Texture Analyzer equipped with a 25 kg load cell (Stable Micro Systems, Goldalming, UK) and a Texture Expert for Windows software (version 1.22) for data analysis. A puncture test was used to measure crust hardness using a 3 mm diameter stainless steel probe and a test speed of 60 mm min1. Maximum peak force (N) was measured from the penetration curve and taken as crust hardness. Six measurements were taken on the crust of each loaf at preselected locations. Texture profile analysis (TPA) was carried out to evaluate crumb texture using a cylindrical aluminium probe (35 mm diameter) and a crosshead speed of 60 mm min1 to compress a crumb samples to 50% of their original height. Measurements were carried out on three slices (20 mm thickness) taken from the centre of the loaf. Three crumb samples (20  20  20 mm) were extracted from the centre of each slice. The textural parameters considered were hardness (peak force of the first compression cycle in N), cohesiveness (ratio of positive force area during the second compression to that during the first compression area, dimensionless), springiness (ratio of the time duration of force input during the second compression to that during the first compression, dimensionless) (Bourne, 1978). 2.7. Volatile extraction and gas chromatography–mass spectrometry analysis Samples of crust and crumb of LowA and IndA samples, previously separated, were frozen under liquid nitrogen and ground in a domestic blender, then stored in screw-cap glass vials at 20 1C until analysis. 1.5 g of frozen bread was placed in a 200 ml Erlenmayer flask at 40 1C. Purified helium (40 ml min1) was passed through the system for 30 min and the extracted volatiles were adsorbed on a glass tubes trap filled with Tenax TA (90 mg, 20–35 mesh) (Chrompack, Middelburg, The Netherlands). The volatile compounds were subsequently thermally desorbed and transferred to the GC system by using a TCT thermal desorption cold trap (TD800, Fisons Instruments, Milan, Italy). Desorption was performed at 280 1C for 10 min under a helium flow (10 ml min1) and the substances were cryofocussed in a glass lined tube at 120 1C with liquid nitrogen. The volatile components were injected into the GC capillary column by heating the cold trap to 230 1C. Three independent DHS extractions were performed for each sample. Blank analyses were also performed using an empty 200 ml Erlenmayer flask following the sample procedure. Gas chromatography–mass spectrometry analysis of the bread headspace was carried out using a system consisting of a TRACE GC 2000 gas chromatograph and of a TRACE MS quadrupole mass spectrometer (Thermo

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

61

Electron Corporation, Milan, Italy). The interface and the source temperatures were kept at 230 and 200 1C, respectively. Electron impact mass spectra were recorded at 70 eV ionization energy by scanning the mass spectrometer from m/z 35 to 350 (scan time, 0.5 s). The carrier gas was helium (pressure, 70 kPa). Chromatographic separation was performed on a fused-silica bonded-phase capillary column Supelcowax 10TM (30 m  0.25 mm; d.f. ¼ 0.25 mm) (Supelco, Palo Alto, CA, USA). The GCoven temperature programme used was: 40 1C for 8 min, from 40 to 160 1C at 6 1C min1, from 160 to 200 1C at 20 1C min1, 200 1C for 1 min. The mass spectrometer data acquisition was performed using the release 1.2 XcaliburTM software (Thermo Electron Corporation, Milan, Italy). The identification of the volatile compounds was carried out by comparing their mass spectra with those stored in the National Institute of Standards and Technology (NIST) US Government library. Retention indices (RI) were finally calculated for the GC peaks by interpolation of the retention times of the volatile compounds with those of normal alkanes (C7–C17) analysed under the same chromatographic conditions. Calculated RI were compared with those stored in a home-made database obtained for the same kind of stationary phase (polyethylenglicole) by injection of pure standards, as previously reported (Bianchi, Careri, Mangia, & Musci, 2007; Bianchi, Careri, & Musci, 2005). To evaluate semi quantitative differences in the gas chromatographic profiles related to baking procedure, GC peak areas were calculated. 2.8. Statistical analysis Means and standard deviations (SD) were calculated with SPSS statistical software (Version 12.0, SPSS Inc., Chicago, IL, USA). SPSS was used to perform one-way analysis of variance (ANOVA) and least significant difference test (LSD) at a 95% confidence level (pp0.05) to identify differences of evaluated parameters both among bread types (discussed in the text) and during storage (results reported in figures).

Fig. 1. Characteristic images of the central slice of HighA (A), LowA (B) and IndA (C) breads.

3. Results and discussion 3.1. Crust and crumb appearance Characteristic images of the central slice of the breads considered in this study are reported in Fig. 1 for high Altamura (1A), low Altamura (1B) and the industrial ‘‘Altamura-like’’ (1C) samples. The loaf of the high Altamura bread was characterized by an asymmetrical ‘‘hat-like’’ shape while the other two products had a lower and more classical loaf development, with the LowA more expanded and higher then the IndA product. The crust of both HighA and LowA product appeared thicker than in the IndA bread, as confirmed also by objective measurement with the Image ProPlus Software. The average crust thickness of the breads was found to be 7.070.7, 5.270.6

and 3.770.5 mm for HighA, LowA and IndA, respectively. The significantly different loaf geometries of the Artisanally produced breads were due to the different shaping procedure followed during their production while the shape of the IndA product likely resulted not only from a specific (and unknown) shaping process but also from a different fermentation pattern. Colour analysis of the crust indicated that HighA and LowA had a significantly lower lightness (lower L*, Table 1) and higher yellowness (higher b*, Table 1) than the IndA breads. The crust appeared to be detached from the crumb in both HighA and LowA breads with the presence of a hollow layer acting as an air cushion between crust and crumb (Fig. 1A and B). In particular, a very large pore was always observed ‘‘under the hat’’ in the HighA

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

62

Table 1 Colour determination results (L*, a*, b*) on crust and crumb for each bread type at day 1 Crust Bread type

L*

HighA LowA IndA

48.4 72.5 47.9b71.4 54.2a71.3

a,b,c

Crumb a*

b

b*

9.6 70.7 9.8ab70.5 10.9a71.3 b

L*

13.5 71.4 11.7b71.0 20.1a72.8 b

a*

72.2 71.5 72.9a71.1 73.0a72.1 a

b*

0.4 70.1 0.1c70.1 0.7a70.1 b

15.2b70.8 13.3c70.4 16.1a70.5

Same letters within each column do not significantly differ (n ¼ 9; pp0.05).

bread loafs. On the contrary, no clear discontinuity between crust and crumb was found in the IndA product (Fig. 1C). Colour of the crumb indicated that HighA and LowA were significantly less yellow (lower b*, Table 1) than the IndA breads. The different colour found both in the crust and in the crumb may have been related to the use of different durum wheat varieties, and/or to different fermentation processes that may have lead to the production of compounds differently active in the browning process during cooking (non-enzymatic browning). A more heterogeneous crumb structure characterized HighA and LowA products as compared to the IndA. Pores present in the crumb of both HighA and LowA spanned over a wider dimensional range, with the presence of larger and more asymmetrical cavities as compared to a finer and more homogenous pore distribution characteristic of the industrial product. The presence of larger and more heterogeneous pores is likely the result of a more complex fermentation process occurring in an artisanal bakery as compared to a controlled industrial setting. The objective evaluation of number of pores and the total percent area occupied by the pores of each dimensional class are reported in Fig. 2. A large number of small (0.05–0.49 mm2) pores was present in all samples (Fig. 2A) but, while they represented less than 10% in both HighA and LowA products, they accounted for more than 20% of the total pore area in the IndA bread. A similar trend was observed also for pores in the 0.50–0.99 and 1.00–4.99 mm2 dimensional classes. Larger pores (450 mm2) were found only in the artisanal products. Number of pores and consequently total percent area occupied by the pores of each dimensional class did not significantly change during storage in all samples (data not shown) suggesting that no detectable change in crumb grain characteristics occurred during storage for all bread types. These findings are in contrast with those reported by Crowley and co-workers (2002) who found, by means of digital image analysis, crumb shrinkage in sourdough wheat breads produced with 20% and 40% sourdough (on flour basis). 3.2. Water activity and moisture content Water activity and water content of the crust, the undercrust and central crumb for the three types of breads

considered in this work are shown in Fig. 3 for the fresh products and during storage. All fresh samples had moisture content of 19% and 23% (H2O/sample) in the crust and under-crust portions, respectively, with no significant differences among bread types (Fig. 3A–C). On the contrary, the total moisture content of the crumb at the loaf centre was significantly lower (40.770.9% H2O/ sample, Fig. 3C) in the IndA than in the artisan Altamura breads (46.470.7% and 46.370.8% H2O/sample for HighA (Fig. 3A) and LowA (Fig. 3B), respectively). Significant differences were found in the water activity of the fresh samples. A significantly lower aw was found in the crust of HighA (0.77270.003, Fig. 3D) and LowA (0.76170.006 Fig. 3E) as compared to IndA (0.8417 0.003, Fig. 3F). Water activity was significantly higher in the artisanal (both under-crust and crumb) than in the industrial samples (Fig. 3D–F). A more homogeneous water distribution among the different portion of the bread loaf was, therefore, found in the IndA product while a more pronounced water gradient characterized the artisanal breads. The total moisture content at the three selected locations did not change significantly in the HighA bread during the 8 days of storage, suggesting that a macroscopic migration of water from the crumb to the crust did not occur (Fig. 3A). In the LowA sample the total moisture content of the crumb did not change during storage while a significant reduction of moisture content was observed both in the crust and in the under-crust locations at the longest storage time (Fig. 3B). The IndA sample underwent significant dehydration in the crumb and under-crust locations after 6 days of storage. Dehydration furthered to significance in all the three locations at day 8 of storage (Fig. 3C). This quicker and more significant macroscopic moisture redistribution observed in the IndA sample was not expected given the higher homogeneity of moisture content in this product as compared to the artisanal samples. The reason for the higher ‘‘moisture stability’’ of the artisanal bread may be due a different interaction of water with the solids of the products. A role may have also been played by the presence of the previously described ‘‘air cushion’’ between crust and crumb that may have null the sucking action of the drier crust mimicking a without crust storage (Baik & Chinachoti, 2000; He & Hoseney, 1990; Piazza & Masi, 1995).

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

63

90

%

80

70 20

10

0 0.05 - 0.49 0.50 - 0.99 1.00 - 4.99 5.00- 49.99

> 50.00

mm2

80

%

60

40

20

0 0.05 - 0.49 0.50 - 0.99 1.00 - 4.99 5.00- 49.99

> 50.00

mm2 Fig. 2. Number of pores as percentage of the total number of pores (A) and area as percentage of total pore area (B) for the selected five-dimensional classes for HighA (black histogram), LowA (light grey histogram) and IndA (dark grey histogram) breads.

Generally, the presence of the water gradient between crumb and crust, causing migration of moisture from the inner portion to the outside of the product, is known to be one of the macroscopic manifestation (associated to hardening and softening of the crumb and crust, respectively) of staling of bread stored in sealed bags (Baik & Chinachoti, 2000; He & Hoseney, 1990; Piazza & Masi, 1995). In this work, breads were packaged in a microporous material that allowed for loss of water from the crust to the environment. Water activity did not follow the changes observed for the total moisture content during storage suggesting that this parameter is more sensible to water dynamics than that

the total moisture content. For example, aw of the crust of HighA and LowA increased significantly at short storage times and, then, decreased at longer storage (Fig. 3D and E); aw of the under crust portion decreased significantly after 3–6 days of storage. Changes in aw in both crust and under-crust locations were found in the IndA product at 6 days of storage. Water activity of the crumb remained unchanged in the artisanal bread for the 8 days of storage (Fig. 3D and E) while it decreased in the IndA sample (Fig. 3F). This was probably due to the presence of the ‘‘air cushion’’ between crust and crumb that created storage conditions of a sample without crust as also reported by Baik and Chinachoti (2000, 2002) who found no reduction

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

64

D

50 a

40 30

a

a

a

a a

a High A

20 a

a

10

a

a

a

a

b

b

b

0.8 b

c

a c

0.6

B

E 50

1.0 a

40 30

a

a

a

a

a

a

ab

b

Low A

20 10

a

a

a

a

a

a

a water activity

moisture content (%)

0.9

a

0.7

0

a

0.9

b b

0.8 a

b 0.7

b

c

c

0.6

0

C

F 50

1.0 a

40 30

a

a

b

ab

Ind A

b

20 a

a

a

a

a

a

b

0.9

b a

0.8

b

a b

b

0.7

b

10

a

c

c water activity

a moisture content (%)

1.0 a a

a water activity

moisture content (%)

A

0.6

0 0

2

4 6 Time (days)

8

10

0

2

4 6 Time (days)

8

10

Fig. 3. Moisture content and water activity of crust (black symbol), under the crust (white symbol) and crumb (grey symbol) for HighA (squares; A, D), LowA (circles; B, E) and IndA (triangles; C, F) during storage. Error bars represent 71 standard deviation (n ¼ 3). Mean significant differences for each sample and each location during storage are shown. Symbols (of same shape and colour) with the same letters are not significantly different (pp0.05).

and a decrease in aw in breads stored without and with crust, respectively. 3.3. Textural properties Textural properties of the three bread samples were recorded during storage and the results are shown in Fig. 4. Crumb hardness was not significantly different among the three bread types both at days 1 and 3 of storage, while at longer storage times both HighA and LowA became significantly harder than the IndA sample (Fig. 4A). It is noteworthy that the changes observed in the samples were not correlated to the changes in moisture content. Both artisanal breads underwent more significant hardening (Fig. 4A) while their moisture content remained unchanged (Fig. 3A and B). On the contrary the IndA sample

hardened to a lesser degree (Fig. 4A) but its moisture content was significantly reduced (Fig. 3C). These findings are in contrast with the findings of He and Hoseney (1990) who reported that a higher crumb moisture resulted in a slower firming rate and lower final hardness in bread produced with a straight-dough method. Addition of some form of anti-staling agent may be hypothesized for the IndA bread that may have masked the role of water. Raffo et al. (2003) reported crumb hardness for fresh Altamura breads made with different durum flour similar to those found in this study; they also reported hardening of the samples during storage to values comparable to those found in this work, especially with the product produced with a Simeto flour, one of the durum wheat variety allowed for Altamura bread production according by the EU regulation (European Union, 2003).

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

65

30

0.50 a a

a

a b 0.45

Hardness (N)

b bc

20 b

b

15

c

b

0.40 c

a

c

10

b a

5

b 0.35

b

b

b

Cohesiveness (N)

a

25

c

c

c 0 30

0.30 1.00 a

a

25

ab b

0.95

b

20

c

a

a

c

b

b

15 b a

10

0.90

b

b a

a

a

Springiness

Hardness (N)

b

0.85

a

a

5 b

b

b

0

0.80 0

2

6 4 Time (days)

8

10 0

2

4 6 Time (days)

8

10

Fig. 4. Hardness (crumb, A; crust, B), cohesiveness (C) and springiness (D) of HighA (squares), LowA (circles) and IndA (triangles) during storage. Error bars represent 71 standard deviation, (n ¼ 9). Mean significant differences for each bread type during storage are shown. Symbols with the same letters are not significantly different (pp0.05).

Significant differences were observed in crust hardness where LowA and HighA were significantly harder than IndA in the fresh products (Fig. 4B). During storage hardness of the IndA remained constant until day 6 and then significantly hardened at day 8 (Fig. 4B). On the contrary, significant crust softening was observed in the HighA product both at day 3 and 6 while at day 8 it hardened again to values comparable to those of the fresh product (Fig. 4B). LowA crust hardness did not change in the first 3 days of storage while at longer storage times the crust hardened to a very high degree (Fig. 4B). Crust softening is generally expected in bread products in conjunction with moisture uptake from the crumb (Baik & Chinachoti, 2000, 2002; Gray & Bemiller, 2003; Kulp & Ponte, 1981) and was also observed in sourdough wheat bread by Crowley and co-workers (2002), an event that we did not measure in LowA and IndA products (Fig. 3). Change in crust texture during storage followed the variation in water activity confirming a role for this parameter in describing water dynamics during storage. Cohesiveness of the crumb was found, in the fresh samples, to be significantly lower in the IndA sample than in the artisan breads (that were not significantly different).

A significant decrease in cohesiveness was found in all samples, as expected, during storage (Fig. 4C). Fresh IndA bread was significantly less springy than the other two samples (with springiness of HighA significantly higher of LowA; Fig. 4D). Springiness of HighA and LowA samples significantly decreased during storage (at 3 or 6 days of storage, respectively) while springiness of IndA remained constant during storage (Fig. 4D). 3.4. Volatile compounds Crust and crumb of LowA and IndA were analysed with DHS–GC–MS technique and about 80 volatile compounds were identified on crust and crumb for both types of fresh bread; the most important compounds are summarized in Table 2. Good reproducibility was obtained (CVp10%). The volatile compound originated both from microbial metabolism (alcohols, aldehydes and ketones) and nonenzymatic browning reactions (aldehydes and ketones, furans, pyrroles and pyrazines) (Martı´ nez-Anaya, 1996) and they may have a role in the development of the bread flavour. Esters are also important flavour sources resulting from microbial fermentation but they are largely lost

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

66

Table 2 Main classes of volatile compounds of the crust and crumb of fresh breads: mean peak areas7standard deviation (  1000 counts) Volatile compounda

IDa

Crust LowA

Crumb IndA

LowA

IndA

Aldehydes Propanal 2-Methyl-propanal 2-Propenal Butanal 2-Methylbutanal 3-Methylbutanal Pentanal Hexanal 2-Methyl-2-butenal Heptanal Octanal trans-2-heptenal Nonanal trans-2-octenal Phenylacetaldehyde decanal Benzaldehyde trans-2-nonenal

MS,RI MS,RI MS MS,RI MS,RI MS,RI MS,RI MS,RI MS MS,RI MS,RI MS,RI MS,RI MS,RI MS MS,RI MS,RI MS,RI

61007600 91,0007870 1100780 30007210 76,00072100 68,00071500 64007290 34,00071200 26007250 44007900 31007120 1100750 45007300 280725 260710 14007110 39007120 240710

27007260 83,00072600 830779 21007170 91,00078000 70,0007600 NDb 35,00071600 17007170 30007300 32007130 460748 40007240 300711 220710 770760 26007250 250720

19007100 21,00074500 690765 16007110 58007130 12,0007600 ND 15,00071200 ND 31007310 680752 ND 15007150 ND ND 420745 1100790 ND

150071400 21,00071200 650760 13007100 60007140 11,00071100 ND 22,00071400 ND 970780 490720 ND 990790 ND ND ND 510730 ND

Ketones Acetone 2-Butanone 2,3-Butanedione (diacetyl) 2,3-Pentanedione 3-Penten-2-one 3,4-Hexandione 2-Heptanone 3-Hydroxy-2-butanone (acetoin) 6-Methyl-5-hepten-2-one 2-Cyclopenten-1,4-dione Acetophenone

MS,RI MS,RI MS,RI MS,RI MS MS,RI MS,RI MS,RI MS,RI MS MS,RI

33,0007880 26,0007300 66,00075300 76,0007990 28007320 350721 15007110 71007700 390730 670730 330738

22,00072200 11,00071300 55,00075400 33,00073300 380749 ND 26007160 85007800 480737 320734 ND

13,0007800 40007420 22,00071500 53007530 ND ND 61079 30007250 220710 ND ND

12,00071100 29007200 40,00073900 690071100 ND ND 540730 12,00071900 240714 ND ND

Esters Ethyl acetate

MS,RI

17,0007950

10,0007960

61007600

85007500

Alcohols Ethanol 1-Propanol 2-Methyl-1-propanol 1-Butanol 2-Methyl-1-butanol 1-Pentanol 1-Hexanol 2-Octen-1-ol Ethyl hexanol

MS,RI MS,RI MS,RI MS,RI MS,RI MS,RI MS,RI MS MS,RI

140,00079600 53007280 10,00071100 16007100 17,00071200 820711 590760 540750 660760

120,00079000 62007520 44,00074200 710770 63,00076400 22007220 17007160 390750 970790

190,000730000 60007650 43,00073500 ND 66,00079000 18007200 21007160 230717 280720

210,000720000 50007470 37,00072800 ND 200,000711000 39007240 62007500 17072 ND

MS,RI MS,RI MS MS MS

18,00071300 26007200 810720 31007200 31,00072500

92007900 26007180 920710 24007190 13,0007600

490740 ND ND 34007380 66007100

ND ND ND 15007120 3500730

MS MS,RI MS MS MS,RI MS MS,RI MS MS

11007100 78,00076000 770750 640770 70007200 690710 33007300 3707110 420720

420730 66,00076600 ND 285714 78007270 630740 42007390 200721 280736

ND 49007440 ND ND 500750 ND 590760 ND ND

ND 95007300 ND ND 910780 ND 150710 ND ND

Furans 2-Methylfuran 2-Ethylfuran 2,3,5-Trimethylfuran 2-Pentylfuran Dihydro-2-methyl-3(2H) furanone Furan-3-carboxaldehyde Furfural Furfuryl methyl sulfide Furfuryl formate 2-Acetylfuran Furfuryl acetate 5-Methyl-2-furaldehyde 2,20 -Bifuran 2,20 -Methylen difuran

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

67

Table 2 (continued ) Volatile compounda

IDa

Crust LowA

Dihydro-2(3H)-furanone 2-Furanmethanol

MS MS

Crumb IndA

LowA

IndA

73718 10,0007100

ND 33007200

ND 360740

ND 27079

Pyrazines Pyrazinec 2-Methyl pyrazinec 2,5-Dimethylpyrazine 2,6-Dimethylpyrazine Ethylpyrazine 2,3-Dimethylpyrazine 2-Ethyl-6-methylpyrazine 2-Ethyl-3-methylpyrazine

MS,RI MS,RI MS,RI MS,RI MS,RI MS,RI MS,RI MS,RI

40007150 36007350 390740 1100790 22007210 650736 780738 620766

20007180 33007100 220724 350720 1700790 360735 320734 470780

ND ND ND ND 370730 ND ND ND

3100730 620780 ND ND 400730 ND ND ND

Pyrroles 2-Acetyl-1-pyrrolinec 1-Methylpyrrole Pyrrole

MS MS MS

10074 21007170 3300785

110710 ND ND

1071 ND ND

ND ND ND

a

ID: MS ¼ identification by comparison with NIST mass spectrum, RI ¼ identification by comparison with retention indices (RI home–made database). b ND ¼ not detected. c Extracted ion chromatogram.

during baking due to their high volatility (Hansen, Lund, & Lewis, 1989). Larger amounts of volatile compounds were found in the crust than in the crumb of fresh sample, as expected, due to more extended non-enzymatic browning occurring in the crust of the product during baking. Aldehydes and ketones (both in crust and crumb) were generally present in higher amounts in the artisanal than in the IndA products although some compounds reported by Schieberle and Grosch (1987) as crust flavour compounds responsible for malty and tallowy notes (e.g. 3-methylbutanal, 2-methylpropanal and 2-nonenal) were found in comparable amount in the crust of both bread types. The presence of larger amounts of carbonyl compounds in the artisanal breads possibly originated from a longer and more complex fermentation process. On the contrary, 2,3-butanedione and 3-hydroxy-2-butanone (crumb) were present in larger amounts in the IndA bread. 2, 3-Butanedione (diacetyl) was reported to impart positive characteristics to bread flavour giving buttery note while 3-hydroxy-2-butanone (acetoin) was not aromatic (Martı´ nez-Anaya, 1996). These compounds were previously associated to the addition of yeast to sourdough (Hansen & Schieberle, 2005) and their larger presence may likely be due to the addition of non-endogenous yeast to the IndA product. Alcohols were not markedly different between the two samples with an overall total presence higher in the IndA bread as compared to the LowA (Table 2), as expected since alcohols are known to originate from yeast metabolism (Hansen & Schieberle, 2005). In particular, both bread types showed high content of 2-methyl-1-propanol and 2-methyl-1-butanol, besides ethanol, that was previously

observed in rye (Hansen et al., 1989) and wheat bread crumbs (Hansen & Hansen, 1996) produced with sourdough fermented with homofermentative cultures of lactic acid bacteria also in association with yeasts. Furans, pyrazines and pyrroles were found in higher amounts in LowA crust with the exception of 2-acetyl-1pyrroline, responsible for the roasty, popcorn-like aroma of the wheat bread crust (Schieberle & Grosch, 1987) that was found in similar amount in the crust of the two bread types. Different temperature and/or duration of the cooking treatments in artisanal and industrial bread production may have influenced the formation of these volatile compounds originating from non-enzymatic browning reactions. A strong reduction of volatile compounds was observed in the crust of both samples during storage. Volatile compounds of the crust decreased of about 2–5 times in LowA and of 3–10 in IndA (Fig. 5), indicating a slower loss of volatile compounds in the artisanal product, that may be more appealing to the consumer also after 8 days of storage. On the contrary, volatile compounds in the crumb slightly decreased (1.5–3 times) in both samples during storage. Evaporation from bread surface, oxidative reactions, as well as diffusion from the crust to the centre of bread and entrapment of volatiles by the protein and starch components of the crumb was reported to explain the different loss from crust and crumb (Schieberle & Grosch, 1992). 4. Conclusions The artisanal and industrial Altamura breads objects of this study were found to differ significantly both in

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

68

2.31 3.35 4.73

100

15.43

7.66 8.39

20.98

90 80 70

13.60

60 1.55

50

9.12

40 1.28

30 Relative Abundance

25.32

21.90

16.24

6.43

10.82 12.71 11.02

20 5.77

10

22.31 23.48

14.36 19.06 17.39

20.14

23.78

0 2.30

100

3.73

25.76 26.59 28.66

30.97 32.47

34.13

20.98

90 80

4.70

70 60 1.30

50

7.60 8.35

40

13.64

19.05

15.44

30 6.44

20

16.23

9.31

10

5.88

10.72

12.67

21.91

17.57

14.31

22.32

19.30

0 0

2

4

6

8

10

12

14

16

18

20

22

25.33 25.78 27.06 28.77

24

26

28

30

31.90 33.36 34.82

32

34

Time (min) 7.60 8.34 9.44

2.30 3.42 4.71

100

20.98

13.69

90 80 70

6.43

1.49

60

21.90

1.36

50 40

15.39

16.22

Relative Abundance

30

23.47

19.03

20

12.63

10

10.62

5.89

25.32

17.40 19.29

23.77

0

25.76 27.75 28.66 30.79 32.00 33.96

100 90 80 2.32

70

13.68

4.70

60 50

1.14

16.20

40

20.97

30 20

6.44

10

5.78

0 0

2

4

6

9.39 8.35 7.61

8

10.64

10

15.40

12.64

12

14

25.33

18.01 19.04

16

18

21.90 23.48

20

22

24

25.78 25.74 28.57

26

28

30

31.28 32.62

32

34

Time (min)

Fig. 5. GC–MS chromatograms (full scan) of fresh (day 1) and stored (day 8) LowA (5A and 5B, respectively) and IndA (5C and D, respectively) bread crust. Retention times (min) of the main identified compounds: 2,3-Butandione (4.71); 2,3-pentanedione (7.60); hexanal (8.34); 2-methyl-1-propanol (9.44); 3-hydroxy-2-butanone (16.22); nonanal (19.03); furfural (20.98); 2-acetyl-furan (21.90); 5-methyl-2-furaldehyde (23.47); 2-furanmethanol (25.32).

ARTICLE IN PRESS E. Chiavaro et al. / LWT 41 (2008) 58–70

macroscopic appearance and physico-chemical properties. Artisanal Altamura products were more heterogeneous both in crumb structure and water distribution than the industrially produced breads. Surprisingly the redistribution of water among different location of bread loaves during storage was more significant in the industrial product. The presence of an ‘‘air cushion’’ between crust and crumb of the artisanal breads may have probably given a fundamental contribution to reduce water redistribution. This is more evident in HighA loaves that were characterized by a more detached crust than LowA. Crumb hardening was more evident in artisanal bread in comparison with industrial products where the addition of some anti-staling agents could have probably prevented the loss of softness and springiness of the crumb. Finally, a larger amount of volatile compounds were detected in artisanal Altamura bread and they were also retained more (by both crust and crumb) during storage in comparison with the industrial products. Retention of volatile compounds and limited moisture redistribution may play an important role in the claimed longer shelf-life (PDO specification) attributed to the Altamura bread. Acknowledgements The authors gratefully acknowledge the assistance of Miss Doralice Grossi and Mr. Joel Bernard in running some experiments. References Association of Official Analytical Chemistry. (2002). In official methods of analysis of AOAC international (16th ed). Arlington, VA: AOAC International. Baik, M. Y., & Chinachoti, P. (2000). Moisture redistribution and phase transition during bread staling. Cereal Chemistry, 77, 484–488. Baik, M. Y., & Chinachoti, P. (2002). Effects of glycerol and moisture redistribution on mechanical properties of white bread. Cereal Chemistry, 79, 376–382. Barber, B., Ortola, C., Barber, S., & Fe´rnandez, F. (1992). III. Effects of sour dough and addition of acids on bread characteristics. Zeitschrift fur Lebensmittel Untersuchung und Forschung A, 194, 442–449. Bianchi, F., Careri, M., Mangia, A., & Musci, M. (2007). Retention indices in the analysis of food aroma volatile compounds in temperature-programmed gas chromatography: Database creation and evaluation of precision and robustness. Journal of Separation Science, accepted for publication. Bianchi, F., Careri, M., & Musci, M. (2005). Volatile norisoprenoids as markers of botanical origin of Sardinian strawberry-tree (Arbutus unedo L.) honey: Characterisation of aroma compounds by dynamic headspace extraction and gas chromatography–mass spectrometry. Food Chemistry, 89, 527–532. Boggini, C., Pagani, M. A., & Lucisano, M. (1997). Breadmaking quality of common and durum wheat flour blends. Tecnica Molitoria, 7, 781–791 (English abstract available). Bourne, M. C. (1978). Texture profile analysis. Food Technology, 32, 62–66. Boyaciog˘lu, M. H., & D’Appolonia, B. L. (1994a). Durum wheat and bread products. Cereal Foods World, 39, 168–174. Boyaciog˘lu, M. H., & D’Appolonia, B. L. (1994b). Characterization and utilization of durum wheat for breadmaking. III Staling properties of

69

bread baked from bread wheat flours and durum wheat flours. Cereal Chemistry, 71, 34–41. Corsetti, A., Gobbetti, M., Balestrieri, F., Paletti, F., Russi, L., & Rossi, J. (1998). Sourdough lactic acid bacteria effects on bread firmness and staling. Journal of Food Science, 63, 347–351. Corsetti, A., Gobbetti, M., De Marco, B., Balestrieri, F., Paletti, F., Russi, L., et al. (2000). Combined effect of sourdough lactic acid bacteria and additives on bread firmness and staling. Journal of Agriculture and Food Chemistry, 48, 3044–3051. Crowley, P., Schober, T. J., Charmaine, I. C., & Arendt, E. K. (2002). The effect of storage time on textural and crumb grain characteristics of sourdough wheat bread. European Food Research and Technology, 214, 489–496. European Union. (2003). Official Journal of European Union L 181(July 19), EC Regulation 1291/2003, 46, 12–19. Gobbetti, M. (1998). The sourdough microflora: interactions of lactic acid bacteria and yeasts. Trends in Food Science and Technology, 9, 267–274. Gray, J. A., & Bemiller, J. N. (2003). Bread stealing: Molecular basis and control. Comprehensive Reviews in Food Science and Food Safety, 2, 1–21. Hansen, A˚., & Hansen, B. (1996). Flavour of sourdough wheat bread crumb. Zeitschrift fur Lebensmittel Untersuchung und Forschung A, 202, 244–249. Hansen, A., Lund, B., & Lewis, M. J. (1989). Flavour of sourdough rye bread crumb. Lebensmittel Wissenschaft und Technologie, 22, 141–144. Hansen, A˚., & Schieberle, P. (2005). Generation of aroma compounds during sourdough fermentation: Applied and fundamental aspects. Trends in Food Science and Technology, 16, 85–94. Hareland, G. A., & Puhr, D. P. (1998). Baking performance of durum and soft wheat flour in a sponge-dough breadmaking procedure. Cereal Chemistry, 75, 830–835. He, H., & Hoseney, R. C. (1990). Changes in bread firmness and moisture during long-term storage. Cereal Chemistry, 67, 603–605. Kulp, K., & Ponte, J. G., Jr. (1981). Staling of white pan bread: Fundamental causes. CRC Critical Reviews in Food Science and Nutrition, 15, 1–48. Martı´ nez-Anaya, M. A. (1996). Enzymes and bread flavor. Journal of Agriculture and Food Chemistry, 44, 2469–2480. Pasqualone, A., Blanco, A., Simeone, R., & Fares, A. (2002). Breadmaking quality evaluation of durum wheat cultivars for the production of the Altamura bread. Tecnica Molitoria, 8, 770–779 (English abstract available). Pasqui, L. A., Carcea, M., Paletti, F., & Cubadda, R. (1994). Characterization of durum wheat for bread making: Influence of cultivar and protein content. Tecnica Molitoria, 3, 223–228 (English abstract available). Piazza, L., & Masi, P. (1995). Moisture redistribution throughout the bread loaf during staling and its effect on mechanical properties. Cereal Chemistry, 72, 320–325. Quaglia, G. B. (1988). Other durum wheat products. In G. Fabriani, & C. Lintas (Eds.), Durum wheat: Chemistry and technology (pp. 263–274). St. Paul, MI: American Association of Cereal Chemistry. Raffo, A., Pasqualone, A., Sinesio, F., Paoletti, F., Quaglia, G., & Simeone, R. (2003). Influence of durum wheat cultivar on the sensory profile and staling rate of Altamura bread. European Food Research and Technology, 218, 49–55. Ricciardi, A., Paraggio, M., Salzano, G., Andreotti, G., De Fina, M., & Romano, P. (2002). Microflora of the sourdoughs used to produce two typical Southern Italy breads: Cornetto of Matera and Altamura bread. Tecnica Molitoria, 8, 780–787 (English abstract available). Ricciardi, A., Parente, E., Piratino, P., Paraggio, M., & Romano, P. (2005). Phenotypic characterization of lactic acid bacteria form sourdoughs for Altamura bread produced in Apulia (Southern Italy). International Journal of Food Microbiology, 98, 63–72. Schieberle, P., & Grosch, W. (1987). Evaluation of the flavour of wheat and rye bread crusts by aroma extract dilution analysis. Zeitschrift fur Lebensmittel Untersuchung und Forschung A, 185, 111–113.

ARTICLE IN PRESS 70

E. Chiavaro et al. / LWT 41 (2008) 58–70

Schieberle, P., & Grosch, W. (1992). Changes in the concentrations of potent crust odourants during storage of white bread. Flavour and Fragrance Journal, 7, 213–218. Simeone, R., Blanco, A., Pasqualone, A., & Fares, A. (2001). Current state of the Altamura bread production and evaluation of bread-making

properties of the durum wheat semolinas used. Tecnica Molitoria, 1, 34–44 (English abstract available). Thiele, C., Ga¨nzle, M. G., & Vogel, R. F. (2002). Contribution of sourdough lactobacilli, yeasts, and cereal enzymes to the generation of amino acids in dough relevant for bread flavor. Cereal Chemistry, 79, 45–51.