Effect of freezing and frozen storage of doughs on bread quality

The effects of freezing and storage in frozen conditions on bread quality, crumb properties, and aggregative behavior of glutenins were analyzed. The effect of different additives on bread quality was also studied. The results obtained showed that freezing and storage at -18 degrees C decreased the bread quality. Samples stored in frozen conditions supplemented with diacetyl-tartaric acid ester of monoglycerides, gluten, and guar gum produced breads of greater volume and more open crumb structure than those prepared with the base formulation (without additives). All additives analyzed increased the proof time. Crumb firmness increased with dough frozen storage and bread aging time at 4 degrees C. A decrease in the amount of glutenin subunits of high molecular mass was observed by electrophoresis analysis of the SDS-soluble proteins aggregates extracted from the frozen dough. This result suggested that the protein matrix of bread underwent depolymerization during storage in frozen conditions.     

Rheology,Microstructure, and Baking Characteristics of Frozen Dough Containing Rhizopus chinensis Lipase and Transglutaminase

The beneficial effects of a new recombinant lipase (Rhizopus chinensis lipase [RCL]) and transglutaminase (TG) were investigated on frozen dough systems and their breadmaking quality. Rheological properties and microstructure of doughs were measured using a dynamic rheometer, rheofermentometer F3, and scanning electron microscopy (SEM). Measurements of viscoelastic properties showed that both G′ and G″ of dough containing RCL and TG were greater than those of the control after 35 days of frozen storage. The SEM micrographs showed that dough containing RCL and TG had the most starch granules embedded in or attached to the gluten network, and the gluten seemed more powerful and resilient than for the control dough after 35 days of frozen storage. Results of the gas production and dough development tests indicated that RCL and TG improved the rheofermentative characteristics of frozen dough. RCL and TG could improve water‐holding capacity and significantly increase the glycerol content of the control dough. Image analyses showed that bread crumbs containing RCL and TG had a more open network and uniform crumb structure, which resulted in higher specific volume. This combination also yielded a product with higher sensory scores for test breads.     

Impact of Sodium Alginate and Xanthan Gum on the Quality of Steamed Bread Made from Frozen Dough

The impact of freezing on dough rheology, fermentation performance, and final steamed bread quality was investigated in this study. Also, the incorporation of sodium alginate and xanthan gum into the frozen dough formulation, in comparison with 0.1% salt, was studied to test their suitability as frozen dough improvers. Incorporating these hydrocolloids into steamed bread revealed their totally different characteristics from those in baked bread. Freezing of dough led to diminished specific volumes of proofed dough and steamed bread, and it also caused higher crumb firmness for steamed bread. The incorporation of sodium alginate and xanthan gum did not improve the quality of the steamed bread but led to further reduction in specific volume and increase in crumb firmness at the higher levels of 0.3, 0.5, and 1.0% and 0.07 and 0.1%, respectively. Xanthan gum and sodium alginate showed dough strengthening effects by increasing resistance to uniaxial deformation, bubble burst stress, and declining dough weakening coefficients at these levels, but decreased dough extensibility and bubble burst strain were revealed at these concentrations tested.     

Effect of Dough Processing Conditions and DATEM on Norwegian Hearth Bread Prepared from Frozen Dough

The objective of this study was to examine treatments that directly influence Norwegian lean doughs destined to be frozen. Therefore a strip-block experimental design with four dough treatment factors (wheat flour blend, diacetyl tartaric acid esters of monoglycerides [DATEM], water absorption, and dough temperature) and two storage factors (frozen storage time and thawing time) was used. Four levels were selected for frozen storage time and two levels were selected for the remaining factors. After frozen storage (2–70 days), the doughs were thawed and baked. Principal component analysis showed that to obtain a high loaf volume and bread score after freezing, a high dough temperature after mixing (27°C) was essential. The highest form ratio (height/width) level was obtained after 28 days of frozen storage and with a short thawing time (6 hr). Analysis of variance (ANOVA) of dough treatments showed that an increase in dough temperature from 20 to 27°C after mixing resulted in a significant increase in loaf volume (1,653 to 2,264 mL), form ratio (0.64 to 0.69), and bread score (1.7 to 3.2), and a reduction in loaf weight (518.4 to 512.5 g) and crumb score (7.9 to 5.9, i.e., a more open bread crumb). Also, the addition of DATEM significantly increased loaf volume (1,835 to 2,081 mL), form ratio (0.64 to 0.69), and bread score (2.2 to 2.6). Frozen dough storage time significantly affected loaf volume, loaf weight, bread score, and crumb score. Increasing thawing time from 6 to 10 hr significantly increased loaf volume (1,855 to 2,121 mL), and reduced the form ratio (0.69 to 0.63) and loaf weight (516.8 to 511.4 g). ANOVA of the interaction between dough treatment and frozen storage time showed that decreasing water absorption significantly increased the loaf volume.     

Frozen Bread Dough Properties Modified by Thermostable Ice Structuring Proteins Extract from Chinese Privet (Ligustrum vulgare) Leaves

Thermostable ice structuring proteins (TSISPs) extracted from Chinese privet (Ligustrum vulgare) leaves were used in frozen dough. TSISPs extract thermal hysteresis activity ranged from 0 to 0.27°C based on different ice fractions in solution. The effects of the TSISPs extract on melting enthalpy of ice (ΔH), water molecular state, microstructure, rheofermentation capacity, and baking properties of doughs during frozen storage were investigated by differential scanning calorimetry, thermal gravimetric analysis, scanning electron microscopy, rheofermentometer, and texture analyzer. The addition of TSISPs in frozen dough caused a decrease in freedom of water molecules and ΔH, which resulted in improved microstructure, fermentation capacity, and baking properties of frozen doughs. Residual gluten fibril increased, exposed starch granules decreased, and gas production and retention of frozen doughs was enhanced. These effects resulted in an increase in specific volume and a decrease in crumb hardness of baked frozen dough.     

Utilization of enzyme mixtures to retard bread crumb firming

The influence of enzyme mixtures containing amylase and lipase activities on straight dough bread staling was studied. Amylopectin retrogradation, crumb firming, amylose-lipid complexes, and dextrin production were analyzed in bread samples supplemented with two enzyme mixtures. The addition of enzyme mixtures to bread formula causes a beneficial effect on bread keeping properties and the formation of a more thermostable amylose-lipid complex than the one found in control bread. Amylopectin retrogradation was inhibited by the use of the enzyme; the effect was accompanied by reduced crumb-firming rates. The enzymatically generated water-soluble dextrins (maltose and DP3, DP4, DP5, and DP6 dextrins) are the most effective in preserving crumb softness during bread storage.     

Effects of Baking Temperature on Crumb-Staling Kinetics

This study evaluated the effects of bread baking temperature on the staling kinetics of crumb. Bread dough was leavened and baked in sealed molds. Cooking trials were performed at various temperatures ranging from 90 to 110°C. The crumb samples were then stored at 20°C at constant moisture, and staling was evaluated by measuring crumb elastic modulus (using an Instron dynamometer) and starch retrogradation degree (using differential scanning calorimetry). Results show that the cooking temperature greatly influences bread staling. The lower the cooking temperature, the lower the staling rate, both in terms of crumb hardening and of starch retrogradation. Starch and protein solubility was evaluated on crumb cooked at 90 and 110°C. An increase in cooking temperature resulted in an increase in protein insolubilization and starch granule disruption.     

Effects of Commercial Hydrolytic Enzyme Additives on Japanese‐Style Sponge and Dough Bread Properties and Processing Characteristics

The effects of increasing levels of eight commercial fungal enzymes enriched in four types of activity (α‐amylase, protease, xylanase, or cellulase) on Japanese‐style sponge and dough bread quality and processing characteristics have been studied using a Canadian red spring wheat straight‐grade flour. At optimum levels, the enriched α‐amylases, xylanases, and cellulases increased loaf volume and bread score and reduced crumb firmness, while the proteases only reduced crumb firmness. For α‐amylases, xylanases, and cellulases, optimum levels for crumb firmness were obtained at higher levels of addition than for loaf volume and bread score. At high levels of addition, all four enriched enzyme types reduced loaf volume and bread score and increased crumb firmness relative to optimum levels, with the proteases showing the most dramatic effects. α‐Amylases and cellulases had little impact on dough mixing requirements, while xylanases increased and proteases greatly reduced mixing requirements. All enzymes at optimum levels reduced sheeting work requirements, resulting in softer more pliable dough. Optimum bread properties for α‐amylases, xylanases, and cellulases were attained within a relatively narrow range of dough sheeting work values. This similarity in response suggests a dominant common nonspecific mechanism for their improver action, which is most likely related to water release and the resulting impact on physical dough properties.     

不同种类大豆蛋白粉对面包加工特性的影响

为探索大豆蛋白作为营养补充剂在面包中应用时，对面团物理特性和焙烤特性产生的影响，该文考察了不同种类的大豆蛋白制品，包括大豆分离蛋白、灭酶全脂粉、活性全脂粉、活性脱脂粉、灭酶脱脂粉对面团粉质特性、拉伸特性和焙烤特性的影响。结果表明，面粉的吸水率与大豆蛋白粉氮溶解指数显著相关，面团的抗拉阻力受大豆蛋白添加量的影响明显。大豆蛋白粉的加入，对面包比体积产生不利影响，下降趋势与大豆蛋白粉对面团拉伸特性的影响显著相关。大豆蛋白粉有软化面包质地的作用，活性全脂粉表现最为明显。大豆蛋白粉的加入量占面粉质量分数的3%时，对面包口感影响不明显，当加入量超过面粉质量分数的7％时，容易出现发粘和豆腥味等现象。     

Pyranose Oxidase from Trametes multicolor Impacts Dough and Bread Microstructure

Pyranose oxidase (P₂O) improves wheat flour dough stability and bread quality. We related its effect on dough spread behavior to that on dough and bread crumb structure. Increasing P₂O addition levels gradually reduced dough flow. High P₂O addition levels further increased dough strength, significantly increased dough cell wall thickness, and decreased bread loaf volume. Taken together, affecting dough spread behavior impacts dough and bread (crumb) structure, and dough structure largely determines bread crumb structure.     

Volatiles in Selected Commercial Breads

Selected types of commercial breads obtained from local markets, including white sandwich, Irish oatmeal, soft rye, hearty rye, sour dough, home-like white, and onion-basil, were analyzed for volatiles. Using a purge and trap instrument, volatiles were purged directly from fresh crumb and crust samples of each bread type, collected on a trap (Tenax-TA), and transferred to a gas chromatograph. Separated components were detected and identified using mass and infrared spectroscopic detectors. Many components were present in all of the bread samples, with relative amounts varying among bread types and crust and crumb samples of a given bread type. Alcohols were generally the most abundant, followed in approximate order by aldehydes, esters, ketones, acids, various aromatics, terpenes, and hydrocarbons. Flavor additives, such as limonene, carvone, and other related compounds, were found mostly in rye and onion-basil breads. Composition of volatiles from sour dough bread differed greatly from the other breads, especially in increased levels of aldehydes, acids, and certain esters. Unsaturated aldehydes, such as 2-hexenal and 2-heptenal, were most abundant in sour dough bread.     

Impact of Wheat Fiber on Frozen Dough Shelf Life and Bread Quality

Freezing and prolonged frozen storage of dough results in constant deterioration in the overall quality of the final product. In this study the effect of wheat bran and wheat aleurone as sources of arabinoxylan (AX) on the quality of bread baked from yeasted frozen dough was investigated. Wheat fiber sources were milled to pass through a 0.5 mm screen, prehydrated for 15 min, and incorporated into refined wheat flour at 15% replacement level. Dough products were prepared from refined flour (control A), whole wheat flour (control B), aleurone composite flour (composite flour A), and bran composite flour (composite flour B) and stored at –18°C for 28 weeks. Dough samples were evaluated for breadmaking quality at zero time, 14 weeks, and 28 weeks of storage. Quality parameters evaluated were loaf weight, loaf specific volume, and crumb firmness. Composite flour bread samples showed the most resistance to freeze damage (less reduction in the overall product quality), indicating a possible role of some fiber components (e.g., AX) in minimizing water redistribution in the dough system and therefore lessening adverse modifications to the gluten structure. The data suggest that the shelf life of frozen dough and quality of obtained bread can be improved with the addition of an AX source.     

Quantitative Assessment of Gas Cell Development During the Proofing of Dough by Magnetic Resonance Imaging and Image Analysis

The structure of bread crumb is an important factor in consumer acceptance of bakery products. The noninvasive monitoring of the gas cell formation during the proofing of dough can aid in understanding the mechanisms governing the crumb appearance in the baked product. The development of gas cells during the proofing of dough was monitored in a noninvasive manner using magnetic resonance imaging (MRI) at 4.7‐T. The acquired MRI time series were analyzed quantitatively using image analysis (IA) techniques. The effects of both kneading temperature and mechanical damage by molding were studied. When additional rheological stress was introduced during molding, a more heterogeneous (coarse) gas cell size distribution was observed, and the dough had a smaller specific volume (as measured by MRI). These characteristics were preserved in the bread crumb structure after baking. The fast‐deformation during molding also resulted in an isotropic growth of the dough during proofing, whereas slow‐deformation during molding resulted in anisotropic growth. This can be related to a better conservation of stress in the dough under a moderate molding operation. A higher temperature during kneading also resulted in a coarser distribution of the gas cells and a smaller MRI specific dough volume. No effect of kneading temperature on the growth anisotropy could be detected, however. This indicates that temperature has a smaller effect on the conservation of stress in the dough than molding. The current work illustrates the capability of MRI/IA for understanding and predicting the influence of food processing parameters on consumer‐relevant features in a food product (bread).     

Effects of Yeast Freezing in Frozen Dough

The effects of freezing and frozen storage of bread dough and compressed yeast on bread quality were studied. Besides, the effects of compressed yeast freezing on cell viability, gas production and release of substances by the yeast cells were examined. Freezing and frozen storage of dough made with fresh yeast had more negative effects on baking quality than the addition of frozen yeast to dough. When the compressed yeast is frozen and stored at ‐18°C, the CO₂ production decreased, while the amount of dead cells, the total protein, and the total reducing substances leached from the yeast increased as the length of yeast frozen storage increased. SDS‐PAGE showed that the substances leached from frozen yeast caused an increase in the solubility of some gluten proteins. On the other hand, size‐exclusion chromatography (SEC) pointed out that the relative amount of two protein fractions of low molecular weight leached from frozen yeast increased for longer yeast frozen storage periods. The yeast leachates had an adverse effect on loaf volume.     

Elucidating the mechanism of laccase and tyrosinase in wheat bread making

Cross-linking enzymes generate covalent bonds in and between food biopolymers. These enzymes are interesting tools for tailoring dough and bread structures, as the characteristics of the biopolymers significantly determine the viscoelastic and fracture properties of dough and bread. In this study, the influence of oxidative cross-linking enzymes, tyrosinase from the filamentous fungus Trichoderma reesei and laccase from the white rot fungus Trametes hirsuta, on dough and bread were examined. Oxidation of low molecular weight phenolic model compounds of flour, cross-linking of gluten proteins, dough rheology, and bread making were characterized during or after the enzymatic treatments. In the dough and bread experiments, laccase and tyrosinase were also studied in combination with xylanase. Of the model compounds tyrosine, p-coumaric acid, caffeic acid, ferulic acid, and Gly-Leu-Tyr tripeptide, tyrosinase oxidized all except ferulic acid. Laccase was able to oxidize each of the studied compounds. The phenolic acids were notably better substrates for laccase than l-tyrosine. When the ability of the enzymes to cross-link isolated gliadin and glutenin proteins was studied by the SDS-PAGE analysis, tyrosinase was found to cross-link the gliadin proteins effectively, whereas polymerization of the gliadins by laccase was observed only when a high enzyme dosage and prolonged incubation were used. Examination of large deformation rheology of dough showed that both laccase and tyrosinase made doughs harder and less extensible, and the effects increased as a function of the enzyme dosage. In bread making, interestingly, the pore size of the breads baked with tyrosinase turned out to be remarkably larger and more irregular when compared to that of the other breads. Nevertheless, both of the oxidative enzymes were found to soften the bread crumb and increase the volume of breads, and the best results were achieved in combination with xylanase.     

Correlations Between Empirical and Fundamental Rheology Measurements and Baking Performance of Frozen Bread Dough

Empirical and fundamental rheology measurements were made on fresh and frozen dough to investigate the effects of freezing, frozen storage, and additives. These results were compared with results of a standard baking test. Four formulations were tested: a control dough, and doughs with additions of 100 ppm of ascorbic acid (AA), 0.5% sodium stearoyl lactylate (SSL), and 0.5% diacetyl tartaric acid esters of monoglycerides (DATEM). Rheological and baking tests were performed on fresh doughs and on doughs after two, five, and eight weeks of frozen storage. Resistance to extension was higher for doughs with additives in fresh and frozen doughs. There was a decrease in resistance to extension due to freezing. Complex modulus in fresh doughs was highest for doughs with SSL. There was a decrease complex modulus after freezing and thawing. In frozen doughs at 10 Hz, doughs with additives had higher complex modulus values and lower phase angle values when compared to the control. The additives used all had a positive effect on proof time, loaf volume, and crumb firmness, and all formulations deteriorated in quality during frozen storage. Resistance to extension and complex modulus were positively correlated with loaf volume (r = 0.86 and r = 0.64, P < 0.01). Phase angle was negatively correlated with loaf volume (r = -0.74, P < 0.01).     

Effects of Monoglycerides of Varying Fatty Acid Chain Length and Mixtures Thereof on Sponge‐and‐Dough Breadmaking Quality

Monoglycerides are widely used in the baking industry because of their antistaling effects, mainly suppressing crumb firming. Commercial monoglycerides are normally prepared from hydrogenated fats, with stearate being the most common fatty acid. In a previous study, monoglycerides such as monopalmitate (C16) and monostearate (C18) had positive effects on Canadian short process bread but no improvements on sponge‐and‐dough process (SDP) bread. The objective of this study was to investigate the effects of saturated monoglycerides of varying fatty acid chain length (C14–C22) on SDP breadmaking quality by using volume judgment, crumb image analysis, and texture measurements. Higher levels (1.00–1.50%) of all monoglycerides (C14, C16, and C18) significantly (P < 0.05) increased loaf volume and cell diameter. The larger cell diameter with increasing levels of these monoglycerides may have resulted from softer, more extensible dough handling properties and greater gas cell stability during baking. Addition of C16 and C18 caused the largest increase in crumb softness with increasing monoglyceride levels but showed relatively low resilience, which might be related to larger loaf volume (i.e., lower density of bread). However, addition of blended monoglycerides C14+C16 increased crumb softness and loaf volume while partially retaining resilience. Each monoglyceride had a different function in breadmaking quality and somewhat positive effects on SDP.     

Influence of Nitrogen Fertilizer Treatments on Spring Wheat (Triticum aestivum L.) Flour Characteristics and Effect on Fresh and Frozen Dough Quality

Growers are targeting hard red spring wheat (Triticum aestivum L.) (HRSW) for frozen dough end uses. Consequently, it is important to determine whether increasing nitrogen (N) fertilizer rates and grain protein content (GPC) improve frozen dough quality. Four HRSW cultivars were grown in low‐N soils at three locations over two years in North Dakota and fertilized with N rates of 0 kg/ha, 67.2 kg/ha, and 134.4 kg/ha. End use characteristics were analyzed using farinograph, extensigraph, and baking tests. Fresh and frozen doughs were analyzed to determine the effects of N treatments on frozen storage. A cultivar × N treatment interaction existed for extensigram curve area of fresh dough. A significant increase in GPC existed between the 0 and 67.2 kg/ha N treatments. Farinograph water absorption, arrival times, and peak times increased significantly at the 67.2 kg/ha N treatment. Bread loaf volume of fresh dough increased significantly with all treatments, while loaf volume of frozen dough increased significantly only at the 67.2 kg/ha N treatment. Therefore, aside from fresh dough loaf volume, there appears to be no improvement in frozen dough quality with the use of higher than typical N application.     

Food allergy to wheat products: the effect of bread baking and in vitro digestion on wheat allergenic proteins. A study with bread dough, crumb, and crust.

The effect of baking and digestion on the allergenicity of wheat flour proteins has been studied. Pooled sera of patients suffering from food allergy to wheat products were tested for IgE binding to the proteins of the wheat dough and of the bread crumb and crust, before and after being in vitro digested. During in vitro digestion, the IgE binding protein components of the unheated dough tended to disappear, whereas a permanence of IgE recognition was evident for both the bread crumb and crust. This indicates that the baking process increases the resistance of the potential allergens of the wheat flour to proteolytic digestion, allowing them to reach the gastrointestinal tract, where they can elicit the immunological response. Therefore, the effects of baking must be carefully considered in studying food allergies to wheat products.     

Fermented Sorghum as a Functional Ingredient in Composite Breads

Whole sorghum flour was fermented (a five‐day natural lactic acid fermentation) and dried under forced draught at 60°C, and evaluated for its effect on sorghum and wheat composite bread quality. In comparison with unfermented sorghum flour, fermentation decreased the flour pH from 6.2 to 3.4, decreased total starch and water‐soluble proteins, and increased enzyme‐susceptible starch, total protein, and the in vitro protein digestibility (IVPD). Fermentation and drying did not decrease the pasting temperature of sorghum flour, but slightly increased its peak and final viscosity. In comparison with composite bread dough containing unfermented sorghum flour, fermented and dried sorghum flour decreased the pH of the dough from 5.8 to 4.9, increased bread volume by ≈4%, improved crumb structure, and slightly decreased crumb firmness. IVPD of the composite bread was also improved. Mixing wet fermented sorghum flour directly with wheat flour (sourdough‐type process) further increased loaf volume and weight and reduced crumb firmness, and simplified the breadmaking process. It appears that the low pH of fermented sorghum flour inactivated amylases and increased the viscosity of sorghum flour, thus improving the gas‐holding capacity of sorghum and wheat composite dough. Fermentation of sorghum flour, particularly in a sourdough breadmaking process, appears to have considerable potential for increasing sorghum utilization in bread.