Improvement of the breadmaking quality of wheat flour by the hyperthermophilic xylanase B from Thermotoga maritima

The study was carried out to investigate the effect of hyperthermophilic xylanase B (XynB) from Thermotoga maritima on the properties of wheat bread and its staling during storage. The presence of XynB in the dough led to improvements in the breadmaking quality (i.e. specific volume and crumb structure) and provided an anti-staling effect on breads compared to the control. Addition of XynB could cause ≈60% increase in specific volume in comparison with the control. By fitting the crumb firming kinetics during storage to the Avrami equation, it showed that XynB retarded the bread staling by reducing the initial crumb firmness and the firming process during storage. XynB hydrolyzed the isolated WU-AX faster than WE-AX under the ratio of wheat AX in wheat flour. Improvement of bread quality by XynB can partly be ascribed to the enzyme specificity.     

Impact of microbial transglutaminase on the staling behaviour of enzyme-supplemented pan breads

The effects of microbial transglutaminase (TGM) when added singly and in combination with amylolytic (-amylase, NMYL) and non-amylolytic (xylanase) enzymes on the textural profile of fresh pan beads and pan breads stored for up to 20 days have been investigated in samples made with low and high extraction rate wheat flours following a sponge-dough process. White and whole-wheat enzyme-supplemented bread samples evidenced a similar sensory firming profile but a different quantitative instrumental staling pattern during storage. Two groups of samples with different staling behaviour can be defined according to the absence (faster staling kinetics) or the presence (slower kinetics) of NMYL in the bread formula, the separation being particularly clear for hardness, cohesiveness and resilience in white bread samples. TGM when added to NMYL-supplemented doughs induced synergistic beneficial effects on fresh bread quality and staling kinetics retardation. The binary combination led to breads with softer and less chewy fresh crumbs, increased initial crumb cohesiveness and resilience, and slower crumb staling kinetics and sensory deterioration during storage, particularly for samples made with white flour.     

Effect of different carbohydrases on fresh bread texture and bread staling

The effect of cellulase, xylanase and #-glucanase on the properties of wheat bread and its staling during storage was studied. The presence of the carbohydrases tested led to breads with high specific volume compared to the control. The texture profile analysis was greatly modified in that the firmness of bread crumb was reduced by all the carbohydrases. A kinetic study of the firmness along with the storage by the Avrami equation showed that the presence of carbohydrases produced softer crumbs and also reduced the rate of bread firming, although no great differences were found between enzymes. Since retrogradation of starch is one of most important factors related to bread staling, the modification of the amylopectin retrogradation was measured by scanning calorimetry. Those studies showed that all the carbohydrases decrease the starch retrogradation, and that the xylanases had the greatest effect. The simultaneous analysis of the firming and starch retrogradation results revealed that the anti-staling effect of xylanase might be due to the retardation in the starch retrogradation, while in the case of cellulase and #-glucanase some other mechanism should be implied in their anti-staling action.     

BREAD MAKING OF DURUM WHEAT WITH CHICKPEA SOURDOUGH OR COMPRESSED BAKER'S YEAST

Two ways of improving durum wheat bread-making quality were evaluated.
First, durum wheat (cultivar "Papadakis") was blended with bread wheat flour of good (A-flour) or medium (B-flour) quality (70% durum and 30% bread wheat flour). Durum wheat flour displayed the γ-gliadin 45 electrophoretic band and acceptable bread-making quality. Breads from flour blends had better volume, particularly the durum and A-flour blend. The addition of ascorbic and citric acid and malt flour improved dough rheological properties and thus bread volume, as well as staling rate and sensory characteristics. These were more pronounced in the blend of durum with B-flour.
Second, durum wheat flour alone was used to prepare chickpea sourdough-leavened bread, as flavor is important for consumer acceptance. With the addition only of salt, the chickpea sourdough-leavened durum wheat bread displayed acceptable loaf volume, distinguished flavor and longer shelf life compared with bread prepared with compressed baker's yeast.

PRACTICAL APPLICATIONS

One of the practical applications of this study is the possibility of using a common durum wheat cultivar instead of local varieties as is the case with traditional breads. Results of this work may be useful for promoting greater acceptance of durum wheat breads as well as expansion of the use of a traditional Mediterranean chickpea sourdough-leavened durum wheat bread with distinguished flavor and taste.
This work may serve as a guide for determining the quality of flours suitable for production of "home made" or "village" bread (which has high market value as specialty bread) by blending durum and bread wheat flours. Best results are obtained with good-quality bread wheat flour, regardless of the good quality of durum wheat cultivar used, together with the use of the dough improvers implemented in this work.     

耐热木聚糖酶对面包老化作用探讨

研究了纯化的耐热木聚糖酶对面包老化的影响作用,探讨了耐热木聚糖酶影响面包老化的动力学。研究证明,适量添加耐热木聚糖酶的面包品质得到了明显改善,并且老化速度变缓,老化速率常数相比对照组下降幅度高达48%。耐热木聚糖酶对面包老化的影响作用显著。     

Functional effects of xanthan gum on composite cassava-wheat dough and bread

The use of composite flour for bread making is gradually gaining prominence worldwide due to some economic and nutritional reasons. However, studies on the application of functional ingredients purposely to improve composite bread quality are very few. This paper examines the functional role of xanthan gum (XG) on the properties of dough and bread from composite cassava-wheat flour. The viscoelastic properties of dough and gas retention characteristics of batter as well as the fresh and storage properties of bread from the composite flour (90% wheat plus 10% cassava) were studied. The crumb cell structure was also studied using digital image analysis technique. Inclusion of XG had significant effects on the dough tenacity and extensibility and sensory acceptability of fresh composite bread. The oven spring, specific volumes of bread loaf and crumb softness were higher at 1% XG content. Also, addition of XG made the composite bread samples had more open crumb structure and better sensory acceptability. However, moisture loss and crumb firming during bread storage were best reduced when 1% XG was added to bread formulation.     

Effects of increasing levels of transglutaminase on cooking quality of bran supplemented spaghetti

This study investigated the possibility of incorporating high levels of bran into spaghetti formulation by using transglutaminase (TG)—catalyzed crosslinking, without deterioration in spaghetti quality. Two durum wheat samples and one bread wheat sample were milled to semolina or farina. Ground mixture of coarse and fine brans of each cultivar was substituted for a portion of semolina or farina obtained from the respective cultivar, at the levels of 15 and 30% and then processed into spaghetti. Bacterial TG was added to the spaghetti formula at the levels of 0.2% and 0.4% (w/w). The results indicated that the TOM values and the sensory characteristics of the spaghetti were generally affected by the cultivar, bran supplementation, and TG addition level. The samples with TG exhibited significantly lower scores for TOM and higher sensory scores for firmness, stickiness, and bulkiness when compared with the respective control sample of each cultivar. As a result, transglutaminase addition had a significant improving effect on spaghetti quality which was more obvious in the weaker cultivar and it was possible to overcome the deteriorative effects of bran on spaghetti quality.     

Effect of baking conditions and storage with crust on the moisture profile,local textural properties and staling kinetics of pan bread

To investigate the impact of baking conditions on staling kinetics and mechanical properties, pan breads were baked at 180 °C/34 min and 220 °C/28.6 min using a ventilated oven and metallic moulds. After baking, bread slices were stored with and without crust at 15 °C in hermetic boxes for 9 days. This investigation provides a textural and physical analysis by examining the Young's modulus, crumb density and crust/crumb ratio during storage. In order to understand the relationship between firmness and moisture content, a moisture profile and a Young's modulus profile were determined during the storage of bread. To fit the staling, a first order model was used. It was found that the kinetics were faster for samples baked with a fast heating rate than for those baked with a slow heating rate. Moreover, the staling rate of bread stored with crust was faster than for bread without crust and the outer crust area staled more rapidly than the centre of the bread slice. These results suggest that the firming of the crumb is related to moisture distribution between the crumb and crust and to the impact of local baking conditions on local firmness.     

Assessment of the agronomic and technological characteristics of Triticum turgidum ssp. dicoccum Schrank and T. spelta L

Recently, the peoples interest in natural and organic products led to a "rediscovery" of hulled wheat, particularly T. turgidum ssp. dicoccum, commonly known as "farro". Compared with durum wheat (T. turgidum ssp. durum), farro is characterized by low productivity and low quality semolina and flour, which makes it unsuitable for the production of bread and pasta. In this paper, the agronomic, technological and nutritional characteristics of three new varieties of farro obtained by crossing the T. turgidum ssp. dicoccum c.v. Molise with T. turgidum ssp. durum c.v. Simeto, were analysed. Data were then compared with those concerning older populations of T. turgidum and of two varieties of T. spelta. The aim of this work is to highlight the productive advantages of the new varieties and to emphasize their prospective use in the production of bread and pasta with considerable health properties due to nutritional characteristics of hulled cereals.     

Studies on glass transition and starch re-crystallization in wheat bread during staling using electrical impedance spectroscopy

Bread staling is a very complex phenomenon that is not yet completely understood. The present work explains how the electrical impedance spectroscopy technique can be utilized to investigate the effect of staling on the physicochemical properties of wheat bread during storage. An instrument based on electrical impedance spectroscopy technique is developed to study the electrical properties of wheat bread both at its crumb and crust with the help of designed multi-channel ring electrodes. Electrical impedance behavior, mainly capacitance and resistance, of wheat bread at crust and crumb during storage (up to 120 h) is investigated. The variation in capacitance showed the glass transition phenomenon at room temperature in bread crust after 96 h of storage with 18% of moisture in it. The resistance changes at bread crumb showed the starch recrystallization during staling.Industrial relevanceSimultaneous measurement of moisture content, glass transition and starch recrystallization is possible with the designed instrument without disturbing the experimental set-up. Thus, the present work is going to help manufacturers and researchers to understand the bread staling phenomenon at crust and crumb without opting very complex instrumental procedures.     

Fibre-rich additives--the effect on staling and their function in free-standing and pan-baked bread

BACKGROUND: The use of dietary fibre in bread products is increasing because of consumer demand for healthier products. However, an increase in dietary fibre level changes the rheological properties of the dough and also the quality properties of the final bread product. In this study, effects on dough and bread staling were followed after replacing 3% of wheat flour by fibre‐rich additives (fine durum, oat bran, rye bran and wheat bran). Free‐standing and pan‐baked loaves were baked to compare the influence of baking method and loaf shape. RESULTS: All additives increased dough stability, with oat bran giving the greatest stability and longest development time. Parameters measured during storage were distribution, migration and loss of water, cutability, crumbliness, firmness and springiness. Furthermore, amylopectin retrogradation and amylase‐lipid complex formation were assessed. Oat bran provided similar or better results than the control for all staling parameters, while other additives gave no general improvements. Cutability reached a plateau when crumb firmness was ≥ 4 N. CONCLUSION: Small amounts of fibre‐rich additives had a significant influence on staling. However, the baking method (free‐standing or pan‐baked bread) had a greater impact on staling than the additives, thus displaying the importance of the baking method. Cutability was found to be related to firmness. Copyright © 2011 Society of Chemical Industry     

Thermo-physical assessment of bread during staling

Staling of bread is a highly complex phenomenon that is not yet fully understood. This study examined the effect of staling on thermal (DSC) and thermo-physical (DMA) properties of bread. The staling process increased water migration from the crumb to the crust and increased unfreezable water (UFW) fraction. Amylopectin retrogradation incremented during bread staling, and it was showed that the loss in freezable water (FW) was caused from water incorporation into the starch crystalline structure and water migration from the crumb to the crust. DMA was able to follow the shrinking behavior of bread crumb during freezing. Crumb shrank through the entire cooling and freezing process. The matrix shifts through their freezing process incremented the rate of their contraction, probably due to the matrix dehydration as consequence of ice formation. The ageing process changes the thermo-mechanical profile of the crumb, and it was showed that a greater amount of retrogradated starch, affected significantly the contraction capacity of bread crumb.     

Impact of sourdough, yeast and gluten on small and large deformation rheological profiles of durum wheat bread doughs

The impact of percentage of sourdough (SD) addition and presence of yeast (Y) and/or commercial wheat gluten (G) -added singly and in binary combination- on both small and large deformation rheological performance and viscometric profile of durum wheat bread doughs was considered. Eight distinctive rheological dough features were identified as able/capable to clearly differentiate soured bread doughs made with semolina:remilled semolina rate of 80:20 into defined functional quality groups. The presence of added commercial wheat gluten provided firmer, more elastic and more extensible doughs with slightly lower viscometric profile. Simultaneous presence of yeast/sourdough and yeast/gluten modulate single effects of sourdough on the durum wheat bread dough mechanical properties. Several relationships were found between fundamental and empirical rheological properties and within viscometric features of soured semolina doughs.     

A survey of water‐extractable arabinopolymers in bread and durum wheat and the effect of water‐extractable arabinoxylan on durum dough rheology and spaghetti cooking quality

BACKGROUND: Information on the variation in water‐extractable arabinopolymers (WEAP) in durum wheat and their impact on pasta quality is limited. A survey of the content of WEAP in selected bread wheat varieties and durum wheat was conducted and the influence of water‐extractable arabinoxylans (WEAX) on dough and spaghetti quality was examined by fortifying low‐WEAP durum semolina with purified WEAX. RESULTS: Bread wheat typically possessed higher levels of WEAP than durum wheat, but the latter had a greater range. Purified WEAX was extracted from bread wheat cultivar Sunlin which possessed a high level of WEAP. The extract was used to fortify semolina (0.125–2% w/w) derived from durum wheat variety Tamaroi (low WEAP). Fortification caused a near linear increase in farinograph water absorption of approximately 12% over the range of addition, leading to dough weakening. Reduced cooked pasta stickiness was observed at all levels of WEAX addition. CONCLUSION: Increased WEAX content may be a means to improve pasta quality by reducing pasta stickiness. Durum wheat showed a wide range of WEAP contents, and this may well be exploited by developing cultivars with elevated WEAP levels. © 2008 Crown in the Right of the State of New South Wales and Society of Chemical Industry.     

Improvers and functional ingredients in whole wheat bread: A review of their effects on dough properties and bread quality

BackgroundDespite the associated health benefits of whole grains, consumption of whole grain products remains far below recommended levels. Whole wheat bread is often associated with many distinctive attributes such as low loaf volume, firm and gritty texture, dark and rough crust and crumb appearance, bitter flavor, and reduced shelf-life. There is a need to improve its quality and sensory characteristics so as to increase consumer appeal and, ultimately, increase the intake of whole wheat bread. The inclusion of various ingredients improves dough and bread properties.Scope and approachThis review examines the effects of enzymes, emulsifiers, hydrocolloids, and oxidants on the properties of whole wheat bread and dough, with particular attention to effects on loaf volume and hardness. Wheat gluten and other plant materials are also discussed. Gaps in the research into whole wheat bread are identified, and future research needs are recommended.Key findings and conclusionsXylanase reduces the water absorption of whole wheat flour and increases loaf volume and crumb softness by hydrolyzing ararbinoxylans. α-amylase can be beneficial under certain conditions. Phytase may activate endogenous α-amylase. G4-amylase is promising but needs validation by further research on its effect on loaf volume, crumb hardness, and staling. Vital wheat gluten overcomes many of the challenges of whole wheat bread production and is found in the majority of commercial whole wheat breads. Emulsifiers DATEM and SSL can improve the volume, texture and staling profile of whole wheat bread. Several types of improvers are generally needed in combination to provide the greatest improvement to whole wheat dough and bread.     

Effect of durum wheat varieties on bread quality

In this study, the effect of different durum wheat varieties on the sensorial and nutritional quality of bread was assessed. In particular, bread manufactured with six wheat cultivars was compared with bread based on commercial semolina mixtures. X‐ray microtomography was used to characterise the final cellular structure of the baked bread. The textural properties of baked bread and doughs were also investigated. In addition, the glucose equivalent (GE) of bread was also evaluated. Finally, the microstructural, sensorial and textural parameters were correlated with each other. Results highlighted that Cappelli and Saragolla bread samples showed higher protein and total soluble fibre content, respectively, in comparison with the reference samples. Moreover, the GE of the Cappelli, Claudio and Saragolla bread samples was similar to that of the reference samples and lower than that of the other samples. However, the sensorial properties of all bread samples showed a very positive score (up to 7.7).     

Quality characteristics improvement of low‐phenylalanine toast bread

This study was designed to prepare and evaluate low‐phenylalanine toast bread made from gliadin‐free wheat flour and hydrocolloids. Wheat protein fraction (gliadin) rich in phenylalanine was extracted using aqueous alcohol solution for the production of low‐phenylalanine wheat flour. Pectin, gum arabic and carboxymethylcellulose (CMC) were used separately to improve the quality of bread at levels of 1, 2 and 3%. Chemical, rheological, organoleptic, baking, staling and microstructure of bread were studied. Phenylalanine content of gliadin‐free bread samples reduced by 43.2% compared with control. Separation of gliadin negatively affected the rheological properties of dough and baking quality of bread, while rheological properties, baking quality and staling were improved upon hydrocolloids addition. Microscopic examination of crumb structure revealed remarkable differences in control and treated breads. It was found that acceptable bread could be produced using gliadin‐free wheat flour with the addition of pectin or CMC up to 2 and 3%, respectively.     

Staling in Starch Bread: the Effect of Gluten Additions on Specific Loaf Volume and Firming Rate

Hypotheses on the role of gluten in bread staling range from gluten having an anti-firming effect, or no effect on firming, to gluten-starch interactions being essential for bread firming. To test these hypotheses, the firming rate of starch bread made from protein-free synthetic flour was compared with that of starch-gluten breads made from synthetic flours containing 1–15% gluten (Fig. 1). Only loaves of similar specific loaf volume and crumb moisture content were compared to eliminate these parameters as variables that might influence firming rate. The starch breads clearly increased in firmness up to six days, indicating that gluten was not essential to the firming process, starch alone causing bread to firm with time. The starch-10% gluten breads and starch-15% gluten breads had very similar specific loaf volumes, moisture contents and firming rates to that of the starch breads. This indicates that protein possibly has some role in firming, because if only starch has a role in firming then adding gluten would effectively dilute the starch and reduce the rate of firming. We propose that increasing bread firmness results from glucan chains of partially leached amylose and amylo-pectin attached to swollen starch granules forming hydrogen bonds with other starch granules and, to a smaller extent, with gluten fibrils.     

Formulation optimisation of vegetable flour–loaded functional bread. Part II: effect of the flour hydration on the bread quality

In this work, the hydration process of durum wheat–based functional bread loaded with yellow pepper flour was optimised. In particular, the investigated vegetable flour and durum wheat semolina were mixed after they were separately hydrated. Three different amounts of water added to the yellow pepper flour were studied for assessing the effect of vegetable flour hydration level on the dough development and overall quality of bread. The bread formulation investigated in a previous work, based on 25% of yellow pepper and 2% of guar seed as structuring agent where the vegetable flour was directly added to the hydrated durum wheat semolina dough, was chosen as control sample. Results highlighted that dough samples with yellow pepper flour hydrated at highest water content showed a rheological behaviour similar to the durum wheat dough. Moreover, creep analysis showed that the sample added with no‐hydrated yellow pepper flour recorded the greatest resistance to deformation. Same results were obtained for the dough tensile and bread compression tests. The use of the hydrated yellow pepper flour also improved all sensorial attributes.