Effect of quick-freezing temperature on starch retrogradation and ice crystals properties of steamed oat roll

Oat roll is one of the traditional oat wholemeal foods. The purpose of this work was to investigate the effects of quick freezing at −20 °C, −40 °C and −80 °C for 90 min before frozen storage on the quality of frozen steamed oat roll. Quick freezing at −40 °C and −80 °C inhibited the increase of peak gelatinization temperature, enthalpy and the ordered degree of oat roll starch, therefore postponing starch retrogradation. The cross-section microstructure confirmed that reducing the quick-freezing temperature could prevent the increase of ice crystals size, ruptured structures and maintain the integrity of internal structure. As the storage time extend, the ice recrystallization led to an increase in size of ice crystals, while a decrease in their number. Frozen steamed oat roll starch had the highest swelling power at the quick-freezing temperature of −80 °C, that indicated strongest water absorption and binding ability when gelatinized again. Texture analysis demonstrated that hardness increased during frozen storage, quick freezing at −80 °C had the best texture properties. Therefore, declining the quick-freezing temperature could obtain a higher quality of frozen steamed oat roll, by means of delaying the starch retrogradation and minimising the size of ice crystals.     

Quality characteristics of northern-style Chinese steamed bread prepared from soft red winter wheat flours with waxy wheat flour substitution

Quality characteristics of northern-style Chinese steamed bread (CSB) prepared from two soft red winter (SRW) wheat flours blended with 0–30% waxy wheat flour (WWF) were analyzed to estimate the influence of starch amylose content. The increased proportion of WWF in blends raised mixograph absorption with insignificant changes in protein content and dough strength-related parameters. WWF incorporation generally increased specific volume and crumb softness of CSB. The analysis of covariance revealed that CSB quality attributes were little affected by protein content and dough strength-related parameters, indicating that starch amylose content was largely responsible for the changes in CSB quality. Flour blends with 5–10% WWF, of which starch amylose content was 22.4–24.7%, produced CSB with superior crumb structure compared to other blends, but insignificant changes in surface smoothness, stress relaxation and total score compared to the respective control wheat flours. Flour blends with 15% WWF to produce a starch amylose content of 21.4–22.7% exhibited reduced staling of CSB with total scores comparable to the respective control wheat flours. CSB prepared from blends with more than 10% WWF exhibited a higher soluble starch content, indicative of reduced starch retrogradation, than that prepared from wheat flours without WWF during storage for 3 days.     

Impact of baking conditions and storage temperature on staling of fully and part-baked Sangak bread

Bread staling involves a combination of physico-chemical phenomena that leads to a reduction of quality. This study aims at evaluating the impact of baking conditions (280 °C, 8 min; 310 °C, 5.5 min; 340 °C, 4 min), baking type (of fully baked (FB) and part-baked (PB)) and storage temperature (−18, 4 and 20 °C) on the staling of Sangak bread. Results showed that lower baking temperature with longer baking time produced drier bread with higher firmness. In FB Sangak breads, amylopectin retrogradation, amount of unfreezable water and firmness (measured by compression test) increased during storage at positive temperatures but hardness (determined by Kramer shear test) decreased significantly during first day of storage. The recrystallized amylopectin traps the free water resulting in crumb hardening. Water is also absorbed by the dry crust resulting in changes of rheological properties in the crust and crumb, and finally in staling. Storage at 4 °C resulted in increasing melting enthalpy of amylopectin crystallite in comparison with storage at 20 °C. Also it was found that firmness of PB breads due to rebaking was significantly lower than FB breads. There were no significant changes in staling parameters of FB and PB stored at −18 °C.     

Effects of allelic variation of HMW-GS and LMW-GS on mixograph properties and Chinese noodle and steamed bread qualities in a set of Aroona near-isogenic wheat lines

High-molecular-weight glutenin (HMW-GS) and low-molecular-weight glutenin (LMW-GS) subunits play an important role in determining wheat quality. To clarify the contribution of each subunit/allele to processing quality, 25 near-isogenic lines with different HMW-GS and LMW-GS compositions grown at two locations during the 2010 cropping season were used to investigate the effects of allelic variation on milling parameters, mixograph properties, raw white Chinese noodle (RWCN) and northern style Chinese steamed bread (NSCSB) qualities. The results showed that Glu-B1 and Glu-B3 made a large contribution to determining mixograph properties and processing quality, respectively. Subunit pairs 17 + 18 and 5 + 10, and alleles Glu-A3b, Glu-A3d, Glu-B3g and Glu-D3f made significant contributions to mixograph properties and no significant difference was detected on most parameters of RWCN and NSCSB for the allelic variation of HMW-GS and LMW-GS. The allelic interactions among glutenin loci had significant effects on wheat quality. The line with 1, 17 + 18, 2 + 12, Glu-A3c, Glu-B3b, Glu-D3c associated with superior mixograph properties, the line with 1, 7 + 9, 2 + 12, Glu-A3c, Glu-B3d, Glu-D3c had superior viscoelasticity of RWCN, and the line with 1, 7 + 9, 2 + 12, Glu-A3e, Glu-B3b, Glu-D3c had the highest total score of NSCSB. These results provide useful information for genetic improvement of the qualities of traditional Chinese wheat products.     

Effect of glutathione on wheat dough properties and bread quality

Reduced glutathione (GSH), released from lysed yeast cells, is well-known for weakening dough structure. However, its influence on bread texture and staling has not yet been completely elucidated. Herein, this study aims at assessing the effects of GSH on dough properties and bread quality, especially bread staling, using Rheofermentometer analysis, texture profile analysis (TPA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and low-field nuclear magnetic resonance (LF-NMR). The results revealed that GSH substantially decreased the dough height and gas-retention capacity during fermentation. The weakened dough structure was attributed to GSH-induced disulfide bond cleavage in gluten proteins and the depolymerization of glutenin polymers. The addition of 0.005%–0.01% GSH resulted in acceptable bread quality. However, bread supplemented with 0.015%–0.03% of GSH exhibited a coarser and more open crumb microstructure, as well as high level of hardness and low resilience during aging. GSH promoted crumb water loss and drove the water shift from the immobilized to the bound state. The DSC and XRD analyses further confirmed that GSH promoted starch retrogradation and recrystallization. These results suggest that apart from the gluten structure, GSH also altered gluten−starch interactions and water redistribution, ultimately decreasing bread quality and accelerating bread staling.     

QTL mapping for quality traits of northern-style hand-made Chinese steamed bread

QTLs for quality traits of northern-style hand-made Chinese steamed bread (CSB) were mapped based on recombinant inbred lines (RILs) derived from the cross between two Chinese winter wheat varieties, Chuang 35050 and Shannong 483. We detected eight putative QTLs for eight quality traits on seven chromosomes, 2B, 2D, 4A, 5B, 5D, 6B and 7B. The contributions of QTLs ranged from 9.88 to 64.87%. The additive effects of QTLs for color, elasticity, and stickiness were positive, with Chuan 35050 increasing the effects. Additive effects for volume, specific volume, appearance, smell, and total score were negative, with Shannong 483 increasing the effects. Two co-location QTLs were detected in the marker region Xgwm644–Xgwm193–Xgwm608b on chromosome 6B. The contributions of four QTLs for appearance, stickiness, smell and total score were very high (29.80–64.87%), indicating that these traits are controlled by major gene loci. The contribution of the smell QTL in Xissr25b–Xissr23b–Xwmc308–Xsrap7c on chromosome 4A was the highest (64.87%). We speculate that a major gene related to the smell or taste is located on chromosome 4A.     

Evaluation of partial-vacuum baking for gluten-free bread: Effects on quality attributes and storage properties

The purpose of this study was to evaluate the impact of partial-vacuum baking on the quality and storage properties of gluten-free bread (GFB). Conventional (180°C-30 min at atmospheric pressure) and partial-vacuum (180°C-15 min at atmospheric pressure and at 180°C-15 min at 60 kPa vacuum pressure) methods were conducted to bake GFB. Quality attributes (specific volume, colour, texture, total water loss) were assessed, DSC and SEM analyses were carried out to understand the effect on the bread's microstructure when using vacuum during baking. No significant differences (p > 0.05) were observed in the hardness and specific volume of the partial-vacuum baked GFB; however, changes in the total water loss and in the total colour change were statistically significant (p < 0.05). The DSC, SEM and XRD results showed that more crystalline structure and different starch crystal types formed after partial-vacuum baking. Storage properties were also investigated over a 3-day period. Partial-vacuum baking significantly affected the total water loss and the texture parameters (p < 0.05) during storage. Partial-vacuum baked samples were softer and had a tendency to become stale more slowly than the control. The findings indicate that the partial-vacuum baking method increases the shelf life of gluten-free products by modifying the microstructure of the bread.     

Influence of puroindoline alleles on milling performance and qualities of Chinese noodles,steamed bread and pan bread in spring wheats

Two trials with a total of 75 spring bread wheat cultivars and advanced lines, were used to evaluate single kernel characterization system hardness, puroindoline alleles, milling yield, flour ash content, flour colour, and end-use qualities for Chinese noodles, steamed bread and pan bread. The results indicated that all International Maize and Wheat Improvement Center hard wheat lines surveyed were Pina-D1b genotype, whereas Pinb-D1b was the most common allele in the remaining cultivars. Genotypes with Pinb-D1b possess significantly lower flour ash content and higher milling yield than those of genotypes with Pina-D1b. For steamed bread, mean scores for loaf volume, crumb colour, width, structure and total score of Pinb-D1b genotypes were significantly higher than those of genotypes with Pina-D1b and wild type. For Chinese fresh white noodles, means for noodle a*, colour score, viscoelasticity and total score with Pinb-D1b were significantly higher than those of Pina-D1b and wild type. Means of loaf volume, texture and total score for Pinb-D1b genotypes were significantly higher than those of Pina-D1b genotypes. This study further illustrated the superiority of the Pinb-D1b allele on milling and processing qualities for various end products and provides useful information for wheat quality improvement.     

Effect of sourdough fermentation on the quality of Chinese Northern-style steamed breads

The effect of spontaneous and lactic acid bacteria (LAB) fermentation (Lactobacillus plantarum (LP), Lactobacillus sanfranciscensis (LS), Lactobacillus brevis (LBr) and Lactobacillus delbrueckii subsp bulgaricus (LB) strains) on the specific volume, crumb texture, volatiles profile and other aspects of steamed bread quality were studied. The addition of sourdough starter significantly decreased dough water absorption, development time and stability while increasing steam bread specific volume. The fermentation with LAB starters reached the desired pH 4 five times faster than the spontaneous starters. Steamed bread leavened with LS and LB starters had the softest crumb texture whereas LP and LBr starters produced the lowest setback viscosity. From the total of 77 compounds identified in sourdough steamed bread, ethanol and 3-methyl-1-butanol were the most abundant. All sourdough steamed breads had 22 compounds in common, which represented about 90% of the total peak area. But unique volatile compounds were present in sourdough steamed bread with different starters.     

The final established physicochemical properties of steamed bread made from frozen dough: Study of the combined effects of gluten polymerization,water content and starch crystallinity on bread firmness

The gluten polymerization behavior, water content, starch crystallinity and firmness of Chinese steamed bread made from frozen dough were investigated and their correlations were also established in this study. The decreased degree of gluten polymerization in steamed bread was observed by the enhanced SDS-extractable proteins (SDSEPs) upon frozen storage. Less incorporation of glutenin in the glutenin–gliadin crosslinking of steamed bread mainly contributed to the decreased degree of gluten polymerization. The decreased moisture of steamed bread had a significant negative correlation with the sublimated water in frozen dough (r = −0.8850, P < 0.01). Frozen storage also induced an increase in starch crystallinity and bread firmness. A multiple linear regression model with SDS-extractable proteins, water content and melting enthalpy of starch crystals of steamed bread accounted for 86% of the variance in the natural logarithm of firmness and further revealed that starch crystallinity mainly contributed to bread firmness.     

Effect of inulin with different degree of polymerization on plain wheat dough rheology and the quality of steamed bread

The aim of this study was to evaluate the effect of different polymerization degree of inulin on plain wheat dough rheology and quality of steamed bread. It was found the water absorption of dough decreased with the increasing of short-chain (FS) and natural inulin (FI) and increased with the increasing of long-chain inulin (FXL) higher than 7.5%. Three kinds of inulin all increased the development time, stability and farinograph quality number and decreased softening degree of the dough. When proof time was less than 90min, the extensibility increased with the substitution of 5% of FS, 5% of FI and 2.5% of FXL. The resistance to extension, ratio number of resistance to extensibility and energy all increased with the increasing of FS and FI as well as the time. While the energy increased with FXL substation at 45min and dropped thereafter, regardless of the concentration. The addition of inulin all enhanced the brightness, specific volume and hardness of steamed bread and decreased the water content, vaporization enthalpy, springiness, recovery, and cohesiveness. During the storage, inulin reduced the change rates of relative hardness, recovery, and cohesiveness and increased the change rate of relative enthalpy, which restrained the staling rate of steamed bread.     

Effect of inulin with different degree of polymerization on water redistribution of steamed bread

The aim of this work was to study the influences of three types of inulin with different degree of polymerization on the water state of steamed bread during production and storage. The addition of inulin reduced the moisture content of the dough and facilitated the migration of free water to bound water. In the fermentation process, inulin had little impact on the bound water content in the dough, but could speed up the fermentation process. During the storage time, the freezable water content in steamed bread crumb decreased faster in the presence of inulin. The weaker interaction of freezable water with starch and protein chains became stronger, while the stronger interaction of tightly bound water with starch and protein chains decreased compared to the control. The changes of melting and vaporization enthalpies suggested that inulin could accelerate water migration of steamed bread from the inside to the outside.     

Contribution of common wheat protein fractions to dough properties and quality of northern-style Chinese steamed bread

Thirty-three cultivars and advanced lines originated from China, Mexico, and Australia were sown in four environments in Chinese spring wheat regions to investigate the association between gluten protein fractions determined by reversed-phase high-performance liquid chromatography (RP-HPLC), and dough properties and northern-style Chinese steamed bread (CSB) quality. The genotypes were divided into two groups of 10 and 23 entries with and without the 1B/1R translocation, respectively. 1B/1R translocation lines had significantly high amounts of ω  -gliadins, and low levels of glutenin and low molecular weight glutenin subunits (LMW-GS), but no significant difference in dough properties and CSB quality from non-translocation lines. The association between protein fractions and dough properties, and CSB quality largely depended upon the presence of 1B/1R translocation. Gliadin contributed more in quantity to flour protein content (FPC) than glutenin, while glutenin and its fractions contributed more to dough strength and CSB quality. Among non-translocation lines, moderate to high correlation coefficients between quantified glutenin and its fractions, and farinograph development time (DT, r=0.85$r=0.85$–0.92) and stability (ST, r=0.81$r=0.81$–0.93), extensograph maximum resistance (R_max, r=0.90$r=0.90$–0.93), CSB stress relaxation (SR, r=0.55$r=0.55$–0.61) and CSB score (r=0.56$r=0.56$–0.62), were observed. Gliadin:glutenin ratios showed significant and negative associations with dough properties and CSB quality. Correlation coefficients between gliadin:glutenin, gliadin:HMW-GS, gliadin:LMW-GS ratios, and CSB score were −0.79, −0.73, and −0.79 among non-translocation lines, respectively. HMW-GS and LMW-GS, x-type HMW-GS and y-type HMW-GS contributed similarly to dough properties and CSB quality for non-translocation lines. Weak correlations between protein fractions and dough properties, and CSB quality were observed among translocation lines. This information should be useful for improvement of dough properties and CSB quality.     

Functional bread: Effect of inulin-type products addition on dough rheology and bread quality

The concerns for a healthy diet in terms of the consumption of baked products as fibre-enriched ones have been highlighted by increased consumers demand, food legislation and targeting manufacturers offer to healthy food. The objective of this study was to assess the effect of some inulin-type products added in bread-making aimed at producing functional bakery goods. In this purpose some physico-chemical characteristics and technological properties of the Romanian wheat flour half-white with addition of 5%, 10%, 15% and 20% inulin commercial products (% basis flour) were evaluated. Rheological behaviour was investigated using mixolab Chopin and baking tests for fibre-enriched products were performed. Changes of the rheological behaviour were noticed, in terms of a general decreasing trend of dough machinability due to enzymatic reactions probably influenced by changing the ratio of the main compounds and their interactions. Overall the bread loaves characteristics mainly affected by inulin addition were the volume and crust colour.Results indicated that inulin potential as fibre enrichment in wheat bread is limited, 15% Fibruline DS being a maximum percent to be used in bread-making of half-white flour, a dosage above being critically for dough rheological behaviour and the quality of high-fibre bread.     

Effect of wheat germ flour addition on wheat flour,dough and Chinese steamed bread properties

Wheat germ flour (WGF) has been developed as a functional food ingredient with high nutritional value. In this study, WGF was applied in steamed bread-making in order to improve the quality of Chinese steamed bread (CSB). Partial substitution of wheat flour with WGF at levels of 3%, 6%, 9% and 12% (w/w) was carried out to investigate physicochemical properties of blends and their steaming performance. Falling number (FN) values of composite flours ranged from 199 to 223 s. Viscosity analysis results showed that wheat flour mixed with WGF had higher pasting temperature and lower viscosities. Dough rheological properties were also investigated using farinograph and extensograph. The addition of WGF diluted the gluten protein in dough and formed weak and inextensible dough, which can be studied by scanning electron microscope (SEM) analysis. CSB made with WGF had significantly lower volume, specific volume and higher spread ratio. The sensory acceptability and physicochemical quality of CSB were improved with the application of a low level of WGF (3% and 6%). However, results showed that a high level of WGF over 9% is not recommended because of unsatisfactory taste. As a whole, addition of appropriate level of WGF in wheat flour could improve the quality of CSB.     

Kinetics of crust formation during conventional French bread baking

64 breads were baked in a deck oven under conventional French baking conditions. Their hearth and surface temperatures were measured at various baking times using thermocouples and Infra-red thermometer; their moisture content was determined after sampling of the external layer, termed the “crust”, and by weighing breads. In addition, an image analysis method, based on saturation and colors, allowed determination of a mask of crust and the kinetics of its mean thickness. Associated with hydrothermal kinetics, it showed that the development of crust was achieved at a final local temperature of 160 °C and moisture of 5% for an average final thickness of 1.7 mm. DSC analysis of crust samples also underlined the significance of non gelatinized starch in the crust. This result was interpreted by representing the hydrothermal history of crust in a starch melting diagram.     

The influence of temperature extremes on some quality and starch characteristics in bread,biscuit and durum wheat

Environmental conditions during grain-fill can affect the duration of protein accumulation and starch deposition, and thus play an important role in grain yield and flour quality of wheat. Two bread-, one durum- and one biscuit wheat were exposed to extreme low (−5.5 °C for 3 h) and high (32 °C/15 °C day/night for three days) temperatures during grain filling under controlled conditions for two consecutive seasons. Flour protein content was increased significantly in one bread wheat, Kariega, under heat stress. Cold stress significantly reduced SDS sedimentation in both bread wheats. Kernel weight and diameter were significantly decreased at both stress treatments for the two bread wheats. Kernel characteristics of the biscuit wheat were thermo stable. Kernel hardness was reduced in the durum wheat for the heat treatment. Durum wheat had consistently low SDS sedimentation values and the bread wheat high values. Across the two seasons, the starch content in one bread wheat was significantly reduced by both high and low temperatures, as is reflected in the reduction of weight and diameter of these kernels. In the durum wheat, only heat caused a significant reduction in starch content, which is again reflected in the reduction of kernel weight and diameter.     

南方馒头加工中的辅料配比优化研究

为给改进实验室馒头制作和评价方法提供参考依据,以3种弱筋面粉(市售美玫牌面粉;磨自弱筋小麦品种宁麦9号和生选6号的面粉)为基础粉,采用响应面法中心组合试验设计,研究了酵母、糖、起酥油和泡打粉含量对南方馒头加工品质的影响,并建立了南方馒头感官得分与因素变量的二次回归模型方程,该模型回归显著。响应面分析结果表明,南方馒头加工中的最佳辅料配比条件为:酵母含量1.0%、糖含量15.0%、起酥油含量1.8%、泡打粉含量1.0%。在此配比条件下,3种弱筋粉制作南方馒头的感官得分预测值分别为86.5、88.3和84.5分,验证值分别为86.1、87.8和83.7分,与预测值的相对误差分别只有0.46%、0.57%和0.95%。     

Quality and microbial characteristics of part-baked Sangak bread packaged in modified atmosphere during storage

The effect of part-baking and modified atmosphere packaging (MAP) on quality and microbial stability of part-baked flat bread (Sangak) was investigated. Part-baked Sangak bread was packaged in 100% CO₂, 50% CO₂:50% N₂, 25% CO₂:75% N₂ and air as a control and stored at 25 °C for 21 days. Color, firmness, moisture, density and microbiological analyses of the package breads were carried out at 3-day intervals during storage. No significant effect of MAP was found on moisture, color and texture during the storage of part-baked bread, while the total aerobic plate count (APC) and the mold and yeast count (M + Y) were dependent on the concentration of CO₂ in the package headspace. With increasing concentration of CO₂, microbial counts were decreased. Density of part-baked bread was also somewhat influenced by the MAP. The observed reduction in the density of control samples during storage was less than those in MAP. The results of the present study demonstrated that it is possible to prolong the shelf-life of Sangak bread from a few days to about 21 days by using bake-off technology (BOT) and MAP under high CO₂ concentration.     

Effects of different milling methods on flour quality and performance in steamed breadmaking

Three types of wheat: 8901 (hard wheat), Nanyang white wheat, NYWW (medium wheat), and Australian white wheat, AWW (soft wheat) were milled after debranning by abrasion and friction, and by conventional milling. The quality of flours produced by the two procedures and their performance in steamed breadmaking were evaluated. The results showed that debranning affected both the quality of flour and the steamed bread, especially for 8901 and NYWW. Debranning lowered the gluten index, maximum resistance and starch damage; whereas, it increased pericarp content, ash content, L* value, falling number and particle size distribution. The pasting properties such as peak viscosity and final viscosity of NYWWDII and 8901DII were higher than those of NYWWCII and 8901CII. Debranning had positive effects on the quality scores, volume, volume/weight, height and structure of steamed bread from second flour, except for those from soft wheat. For the two other samples, the quality scores for steamed bread were lower than that for the conventional flour. The shape and structure of steamed bread from the top flours of AWWCII and 8901CII were better than from debranned flour. The milling methods did not affect the texture of steamed bread, except in the case of second flour of NYWW.