不同水对面团性质影响

通过在等量面粉中分别加入5种不同的水制成面团,测定其形成湿面筋含量、色泽及质构性质并进行比较。结果表明:去离子水不适于制作面团;加农夫山泉(矿物质水)和自来水制作面团性质略有改善,但色泽变差;加盐水制作面团粘性小,面团形成湿面筋含量增加、延伸性好、色泽好;加碱水可加速和面进程,产生淡黄色外观,但不能添加过量,否则会恶化面团品质。     

传统自然发酵黏豆包面团微生物菌群结构分析

以采集不同原料制备的黑龙江省传统自然发酵黏豆包面团为研究对象,利用聚合酶链式反应-变性梯度凝胶电泳技术研究黏豆包中微生物群落结构及其多样性,结果表明：收集到的6?份黏豆包发酵面团样品中细菌组成主要为食窦魏斯氏菌（Weissella cibaria）、融合魏斯氏菌（W. confuse）、肠系膜明串珠菌（Leuconostoc mesenteroides）、乳酸乳球菌（Lactococcus lactis）和罗氏乳杆菌（Lactobacillus reuteri）,此外还有一些不能培养的细菌。黏豆包发酵面团中含有酵母菌主要为：诞沫假丝酵母（Candida zeylanoides）、卡利比克毕赤酵母（Pichia caribbica）、普兰久浩酵母（Guehomyces pullulans）和一些不能培养的酵母。传统自然发酵黏豆包面团微生物菌群结构与面团原料组成有一定相关,本研究可为改良黏豆包品质,开发专属发酵剂,实现黏豆包工业化、规模化、自动化生产提供理论支持。     

小麦面团粘度影响因素研究进展

该文介绍国内外对小麦面团粘度影响因素研究进展;粘度是由面团粘结特性和内聚特性所共同决定一种特性,粘度过大会造成生产中断,且最终产品质量也会有所降低;麦谷蛋白及醇溶蛋白比例及结构、戊聚糖、1BL／1RS易位均对面团粘度产生影响。     

Secalin蛋白检测及其与面团黏性关系的研究

用SDS—PAGE检测了70个小麦品种是否带有黑麦Secalin蛋白，并测试了它们的面团黏性，用PCR检测了部分品种是否含有1RS染色体片断，结果表明：70％的品种为1B／1R易位系；有54．3％的品种面团发黏；带有黑麦Secalin蛋白的品种约有72．5％面团发黏，而不带有黑麦Secalin蛋白的品种只有30％面团发黏；影响面团黏性的主要因素为来源于黑麦的Secalin蛋白；PCR扩增结果表明，在我国存在不带有Sec-1基因的1B／1R小片断易位系。     

THE RHEOLOGICAL BASIS OF DOUGH STICKINESS

Stickiness in wheat flour doughs was studied as a function of rheological and surface properties. Adhesion was measured using a modified peel test at various water additions, peel rates and peel layer thicknesses. Peeling energy gave a strong positive correlation with subjective bakery stickiness ratings. Peeling forces were highly rate dependent and showed transitions from sticky to nonsticky behvaiour with increasing rate of peeling. Dynamic storage modulus showed a negative correlation with stickiness ratings, suggesting stickiness is primarily a rheologically controlled process. Stress relaxation gradients were greater for sticky doughs and were very similar to peeling force vs. rate slopes, again indicating that adhesion is principally a function of the rheological properties of the dough. Surface tension measurements of sticky and nonsticky dough/liquor interfaces showed no significant differences and are typical of protein solutions. Calculated values of the interfacial surface energy between dough and interface were about 100 mJ/m², typical of secondary bonding interactions such as polar or van der Waals bonding.     

Isolation and chemical characterisation of water-extractable arabinoxylans from wheat and rye during breadmaking

Water-extractable arabinoxylans from wheat and rye flour, dough and bread were isolated and characterised by the determination of the carbohydrate composition and the ferulic acid and diferulic acid contents. For both wheat and rye, the yield of water-extractable arabinoxylans decreased during the breadmaking process, indicating that some of the water-extractable arabinoxylans had become water-insoluble, possibly by the formation of ferulic acid–protein cross-links. The determination of ferulic acid and diferulic acids showed a low degree of dimerisation (less than 1%), which did not increase during the breadmaking process. Separation of the water-extractable arabinoxylans by size-exclusion chromatography showed that the molecular mass distribution of the arabinoxylans changed during breadmaking for both wheat and rye. Dual detection by measurement of the refractive index and the UV absorbance at 310 nm enabled screening for ferulic acid in the molecular mass fractions. Water-extractable arabinoxylans from wheat contained a medium molecular mass fraction which was not UV-active. The determination of ferulic acid in this fraction showed that it was free of ferulic acid.     

Dough rheological, Mixolab mixing, and nutritional characteristics of almond cookies with and without xylanase

The effects of California almond skin flour (CASF) and xylanase on empirical dough rheology of the flour and texture of cookies as well as sensory evaluation were evaluated. Mixolab and Rapid Viscosity Analyzer studies showed that CASF addition resulted in higher water absorption (MWA), a longer development time (MDT) and a lower peak viscosity (RPV). Xylanase incorporation into the dough caused a higher MWA and RPV, and a lower MDT. The CASF made the dough less sticky, but xylanase played the reverse role. The 20% addition of CASF produced cookies with greater spread ratio and lower breaking force. Xylanase allowed the amount of CASF to be increased from 20% to 23%, which improved protein and dietary fiber (DF) contents, particularly water-soluble DF, while the spread ratio and breaking force remained unaffected. Sensory evaluation results showed good overall acceptability scores for the CASF cookies with and without xylanase.     

Role of NaCl level on the handling and water mobility in dough prepared from four wheat cultivars

In bread, NaCl plays a number of roles including improving flavor, functionality, dough handling, and prevention of sticky dough. Its reduction can create significant processing challenges. As such, the dough handling properties for four wheat cultivars (Pembina, Roblin, McKenzie, and Harvest) were investigated as a function of NaCl (0–4%) level. In terms of dough rheology, both cultivar and NaCl level were significant factors. The maximum deformation (J_max) in the dough decreased with increasing NaCl levels, indicating that the gluten network became stronger so that it was able to resist the imposed stress. For extensibility, increasing the levels of NaCl resulted in increased resistance to extension for all cultivars. Dough stickiness was shown to be both cultivar and salt level dependent, with weaker cultivars showing higher stickiness. Findings for water association indicated that with the addition of NaCl there was less free water among the different cultivars and an increase in the water associated with the starch-fraction. Dough morphology measurements supported rheology trends; the stronger dough producing cultivars created more elongated protein polymers with a unidirectional network whereas the weaker cultivars created porous multidirectional networks. Overall, Pembina and Roblin formed stronger gluten networks than McKenzie and Harvest, however, the effect of NaCl level was shown to be cultivar dependent. Findings indicate that careful cultivar selection will help mitigate challenges in dough handling within a reduced NaCl environment.     

Effect of β‐Glucan–Rich Barley Flour Fraction on Rheology and Quality of Frozen Yeasted Dough

Research has shown that prolonged frozen storage of bread dough reduces the quality of the end product. In this study, the effect of air‐classified barley flour fraction rich in β‐glucan (approximately 25%) on rheology and quality of frozen yeasted bread dough was investigated. Wheat flour (W) was replaced by air‐classified barley flour fraction (B) at 10% without or with 1.4% vital gluten to produce β‐glucan enriched barley dough (WB) or barley dough plus gluten (WB + G). Dough products were stored at ?18 ºC for 8 wk and their rheological properties were investigated weekly. During frozen storage dough extensibility increased, while elastic and viscous moduli decreased. Differential scanning calorimeter and nuclear magnetic resonance data indicated that WB and WB + G dough products contained approximately 10% less freezable water and 9% more bound water compared to the control dough (W). β‐Glucan enriched dough also exhibited less changes in gluten network as shown by SEM photographs. The addition of air‐classified barley flour fraction at 10% in frozen dough reduced deterioration effects caused by frozen storage via minimizing water redistribution and maintaining rheological properties of frozen dough.     

The chemistry of bread making: The role of salt to ensure optimal functionality of its constituents

Large consumptions of dietary sodium have been shown to lead to hypertension, one of the main causative factors in cardiovascular disease. Bread (and other cereal products) accounts for ~30% of the overall sodium intake in our diet; therefore, industry has been developing strategies to significantly reduce its usage. However, at reduced sodium levels, dough handling can be affected due to sticky dough phenomena creating major processing issues and a poor quality final product. It is hypothesized that the formation of a strong gluten network plays a crucial role in developing nonsticky dough, a process that is strengthened in the presence of NaCl. However, at low NaCl levels, a weaker gluten network forms resulting in the prevalence of other wheat flours’ constituents impact on water mobility within the dough to contribute to the stickiness phenomenon. This review discusses the underlying mechanisms that can influence the formation of sticky dough within a low sodium environment and discusses strategies used to help circumvent them.     

Mixing properties and rheological characteristics of dough used to make potato‐cereal soft wraps

We have studied mixing, rheology and stability of potato‐cereal flour doughs. These were prepared using samples of two varieties of cooked and cold‐stored potatoes. Dependent on variety a minimum duration of 24–48 h cold‐storage was required. Dough mixing torque plateau was inversely related to potato water content. This should be <79 g/100 g. It was also necessary to have a stable dough mixing torque plateau of >2 Nm at a specific total mechanical energy input of 18–22 kJ kg^?1. The resting temperature of the dough was also inversely related to its strength (plateau elastic modulus at time zero). Target dough strength should be about 25 kPa in a bob‐cup. Above 15 °C it decreased as a function of time and within 1 h it became too sticky for commercial processing. At 4 °C the dough remained stable. Sufficient potato starch retrogradation is a pre‐requisite to make optimal potato‐cereal flour dough for commercial processing.     

蒙古栎橡子-小麦混粉的流变学特性

将蒙古栎橡子粉与小麦粉按不同的比例混合,利用布拉本德粉质仪与拉伸仪测定蒙古栎橡子-小麦混粉面团的流变学特性,并对混粉中的理化指标与混粉面团流变学参数之间进行相关性分析,探讨蒙古栎橡子粉对小麦粉品质的影响。结果表明：随着橡子粉含量增加,混粉的吸水率呈先减小后增大的趋势,面团的形成时间与稳定时间缩短,弱化度提高;所有样品的拉伸阻力与拉伸比例随醒发时间的增长而增大,而混粉面团的延伸度与能量均呈下降趋势;在相同的醒发时间下,拉伸参数随橡子粉添加比例的增加呈先增大后减小的趋势。与混粉面团流变学特性呈高度正相关的理化指标是混粉面团湿面筋及蛋白质的含量。提示不同比例的蒙古栎橡子粉可以显著影响面团的流变学特性。     

Origin and practical significance of the sticky dough factor in 1BL/1RS wheats

When translocated into wheat, the short arm of the 1R chromosome of rye carries with it linked resistance genes to powdery mildew, stripe rust, leaf rust and stem rust. The translocation is also reported to increase yield potential of hard wheats. However, many doughs made from some 1BL/1RS hard wheats are unacceptable for breadmaking purposes because of excessive stickiness and mixing intolerance. 1BL/1RS wheats may be sticky because of: the inheritance of secalin proteins from rye and absence of key glutenin subunits; higher amounts and/or differences in the composition of cell wall polysaccharides, β‐glucans and pentosans; and/or the presence of a ferulic acid ester moiety residing with the water‐soluble fraction of 1BL/1RS flours. None of these hypotheses has been proven or disproven, to date, as a cause of excessive stickiness. Investigators have found that 1BL/1RS doughs are not uniformly sticky and are in some instances less sticky than non‐1BL/1RS doughs. Significant genotype–environment interactions have been reported for dough stickiness and flour quality characteristics of 1BL/1RS wheats. Investigators have generally failed to find significant differences in the breadmaking performance of 1BL/1RS and non‐1BL/1RS hard wheats despite a report that 1BL/1RS doughs break down and soften during high‐speed mixing. The 1BL/1RS translocation has been shown to reduce cookie spread of soft wheat flours but has no deleterious effects on cake volume or texture. © 2002 Society of Chemical Industry     

海藻酸丙二醇酯对全麦冷冻面团冻藏稳定性和烘焙特性的影响

本文研究了海藻酸丙二醇酯（Propylene glycol alginate,PGA）对全麦冷冻面团冻藏期间稳定性的影响,并探究了冷冻面团烘焙面包品质的变化。将0.3%的PGA加入全麦面团,通过测定冷冻面团冻藏1、2、3、4和5周后发酵特性、流变特性、蛋白质二级结构、微观结构以及面包的比容、质构特性、内部纹理结构和老化程度等,研究冷冻面团冻藏期间的稳定性。结果表明,随着冻藏时间的延长,添加PGA的冷冻面团在冻藏5周后具有较好的保水性,其发酵特性及流变特性相对于对照组均有所改善。冻藏5周后,对照组与PGA组其面包比容分别下降了19.872%和14.153%;面包硬度分别升高了64.186%和36.386%;气孔表面积分率分别下降了3.497%和2.300%;老化焓值分别上升了65.142%和42.416%。添加PGA能延缓冷冻面团冻藏期间β-折叠含量的上升和β-转角相对含量的下降。电镜扫描图（SEM）显示,随着冻藏时间的延长,PGA组的冷冻面团孔洞数目相比对照组明显减少且大小均匀,面筋网络结构完整性和连续性提高。研究结果表明PGA可以有效地延缓冷冻面团在冻藏期间的品质劣变,维持冷冻面团的稳定性并提高面包的烘焙特性。     

Small and large deformation rheology for hard wheat flour dough as influenced by mixing and resting

ABSTRACT:  The effects of mixing and resting on the physicochemical properties of doughs prepared with strong and weak hard wheat flours were investigated, specifically concerning aspects related to their rheological behavior and molecular mobility. Small deformation dynamic tests showed that, during the initial resting period, the complex modulus G * decreased and phase angle decreased for undermixed dough, whereas overmixed dough showed opposite trends. G * values for optimally mixed dough did not vary during the resting period investigated. This was more obvious for the strong dough. Large deformation tests more clearly showed differences among optimal, under-, and overmixed dough, and also between doughs prepared with strong and weak flour. Optimally mixed dough exhibited the highest peak stress and strain for both samples. In addition, the peak stress of dough prepared with the strong flour was higher than that of dough prepared with weak flour. Inconsistent results between small and large deformation tests implied that small and large deformation tests reflected different structural aspects of dough. NMR measurements were performed to estimate the relaxation properties of the sample upon resting. Decreased water mobility during resting, indicated by decreasing T ₁ relaxation time, was possibly attributed to increasing molecular interactions caused by continued hydration. Evidence of additional molecular interactions created by mixing was also observed.     

车前子壳粉-未漂洗鱼糜模拟面团的流变及凝胶性质

研究和开发高膳食纤维、高蛋白、低升糖指数的面团和对应主食在适应当前人们的饮食结构需求和健康需要方面具有重要的意义。使用车前子壳粉(psyllium husk powder,PHP)和未漂洗鲅鱼鱼糜代替传统面团中的淀粉和蛋白质组分,混合后制备新型模拟面团,并对其流变特性进行系统评估。静态流变结果显示,随着PHP添加量的增加,所有面团的触变性增加,流动性和刚度以及回复性均呈现逐渐减弱的趋势。相互作用分析结果表明,鱼糜蛋白和PHP中多糖分子间只存在氢键等弱键连接,PHP添加量(质量分数)为6%时蛋白质和多糖的相互作用最弱。在加热过程中,所有面团均可形成良好的凝胶体且蛋白质的存在显著提高了PHP的溶解温度。进一步的凝胶特性分析结果显示,添加质量分数为6%的PHP时,面团的凝胶强度达到最大,为4305.74g·mm,拉伸性能较佳。微观结构的观察结果显示,此时面团结构最为均一,孔洞细密,推测形成了蛋白质-多糖的互穿型微相分离凝胶网络。PHP和未漂洗鲅鱼鱼糜可以制备品质较好的面团,在添加质量分数6%的PHP时面团性能较好,基于PHP-未漂洗鱼糜面团制备的凝胶主食品质也较佳。     

Effects of aleurone-rich fraction on the hydration and rheological properties attributes of wheat dough

This study aimed to evaluate the effects of incorporation of aleurone-rich fraction (ALF) on the hydration and rheological properties of wheat dough. Incorporation of ALF significantly increased water absorption (P < 0.05) and competition for water in dough was observed. Peak viscosity, through viscosity, and final viscosity decreased with the amount of ALF added (P < 0.05), whereas 20% ALF had stronger gel ability than whole-wheat flour. Dynamic rheological experiments revealed ALF blend dough were more stable than whole-wheat dough, which was in accord with the higher dough stability and strength observed in Mixolab. Scanning electron microscopy showed that disruption of gluten network with ALF incorporation, whereas 20% ALF showed better stability dough structure than the whole-wheat dough. Considering those influences on dough properties, the 20% ALF seems to be a promising substitute for whole-wheat flour to producing dietary fibre-rich products.     

Evaluation of l-ascorbic acid oxidation on SH concentration in soy-wheat composite dough during resting period

The effect of l-ascorbic acid (l-AA) on free sulfhydryl concentration (SH) was evaluated in soy-wheat composite dough from 100-500 (g/kg) soy flour substitution for wheat flour. Raw soy flour (RSF) and physically modified soy flours (PMSF1 and PMSF2) were used for the preparation of the composite dough with wheat flour. The two physically modified soy flours were prepared by steam flushing (PMSF2) and water boiling (PMSF1) of raw soy beans before flour preparation. Using a timer, dough blends were manually mixed (at approximately 60 rpm) to dough development time after which, dough was sampled for the estimation of free SH groups. l-AA (0.05% w/w) was mixed with the dough after dough development and the dough was sampled after 1 h of resting the dough. The results showed that l-AA (0.05% w/w) acted as a reducing agent by increasing SH levels in all soy-wheat dough blends (P<0.05). After 1 h of resting, soy-wheat composite dough without l-AA had lower concentrations of SH than that with l-AA. A positive correlation was shown between soy flour concentrations and SH concentration before and after dough resting. A negative correlation existed between l-AA consumption and SH concentration for RSF-wheat, PMSF1-wheat and PMSF2-wheat doughs. The results indicated that soy flour weakened wheat flour dough by increasing SH concentration and that l-AA could have a synergistic effect on the reduction of gluten proteins and thus weakening the dough.     

Studies on heat stabilized wheat germ and its influence on rheological characteristics of dough

Wheat germ, a nutrient dense by-product has a very poor shelf life. In order to improve its keeping quality, so that it can be used into different products, various heat treatments were tried and studied to investigate their influence on proximate composition as well as on the rheological characteristics of wheat flour dough. Different heat treatments have shown insignificant effect on proximate composition of wheat germ. Retention of vitamin E was greater in steamed and dried germ. Except for fluidized bed dried germ, all the heat treatments employed completely inactivated the lipase enzyme, whereas the lipoxygenase enzyme was inactivated to an extent of 80–92%. Quality evaluation of germ samples during 60 days storage indicated that steamed and dried germ retained the sensory attributes to a greater extent. Rheological study of wheat flour blends with germ upto 20%, showed marginal increase in water absorption and over-pressure values. However incorporation of treated wheat germ caused dough weakening in terms of reduction in dough stability and rupture at abscissa values.     

RHEOLOGY AND MICROSTRUCTURE OF WHEAT DOUGH DEVELOPED WITH CONTROLLED DEFORMATION

Undeveloped wheat dough samples were strained in shear and extensional flow between parallel plates to produce a controlled level of development. Dough made in a standard Farinograph, considered developed dough, was used for comparison. Scanning electron microscopy images of deformed dough were subjected to numerical image processing to characterize the protein matrix present. Results were compared to dynamic rheological properties to evaluate the influence of strain deformation on the formation of microstructure. Viscoelastic moduli of wheat dough showed that developed dough had the greatest amount of structure formation, followed by extensionally-strained and shear-strained samples, respectively. Undeveloped dough showed the lowest levels of structure development. Image analysis indicated statistically significant differences between protein matrices in developed and undeveloped samples; however, results were not significantly different between shear- and extension-ally-strained samples.