Influence of process conditions on the separation behaviour of starch–gluten systems

Separation of wheat flour into its constituents starch and gluten was studied using a cone-cone shearing device, with emphasis on the effect of rotation rate, processing time, temperature and water content. This study confirms the two step mechanism previously proposed for the gluten migration: aggregation of gluten protein into gluten domains that subsequently migrate to the apex of the cone. The results show that optimal process conditions for gluten migration are different from the process conditions for gluten aggregation. While gluten agglomeration (step 1) benefits from high temperature, low rotation rate and high water content, gluten migration (step 2) is positively influenced by a high dough viscosity and higher rotation rate.     

谷朊粉和小麦淀粉添加量对重组面团冻藏品质的影响

面团的冷冻保存品质无法满足鲜湿面条工业化生产的要求。为了研究面团主要组分（面筋蛋白和淀粉）对面团冷冻品质的影响,以高筋小麦面粉（50%）、谷朊粉和小麦淀粉（不同比例）为原料进行面团重组,-18℃冻藏20 d分析其水分分布、流变特性、糊化特性、凝胶强度、微观结构以及氢键强度,以100%原小麦面粉作为对照组。结果表明,随着谷朊粉:小麦淀粉比例从4:1减小至1:4,冷冻重组面团中的水分分布逐渐由结合水向自由水迁移,弹性模量从125900 Pa降低至73020 Pa;样品的各项糊化参数增大,凝胶硬度也由114.30 g增大到181.39 g。扫描电镜观察发现,谷朊粉:小麦淀粉比例越低越不利于面筋蛋白网络结构的均匀性。添加了谷朊粉和小麦淀粉后,重组面团中的氢键强度均大于对照组,且随着谷朊粉:小麦淀粉比例的减小不断增大。当谷朊粉:小麦淀粉为4:1时,冻藏20 d的重组面团的弹性模量值比对照组高49.95%,有效延缓了面团在冻藏过程中的品质劣变。将淀粉与面筋蛋白进行面团重组可以提高面团的黏弹性,进而有利于其冷冻保存品质。     

Dynamic rheology of wheat flour dough. I. Non‐linear viscoelastic behaviour

Controlled stress rheometry was used to investigate the effects of starch and gluten fractions on the non‐linearity of wheat flour dough. Flour–water dough showed non‐linear viscoelastic behaviour over all stress values in a cyclic stress sweep. The amplitude‐dependent behaviour of the starch and amplitude‐independent nature of the gluten revealed that starch is responsible for the non‐linearity of the flour–water dough system. Adding starch to gluten caused a substantial narrowing of its linear viscoelastic range. © 2002 Society of Chemical Industry     

Effects of ball‐milling on the glass transition of wheat flour constituents

BACKGROUND: Starch and gluten, the major components of wheat flour, greatly influence the structural characteristics of food products made with wheat flour. The effects of ball‐milling on the change in the semicrystalline structure of starch granules to the amorphous state have been reported. However, the effects of ball‐milling of native wheat flour on physicochemical changes in wheat flour constituents have not been elucidated. Therefore in this study the effects of ball‐milling on the glass transition of wheat flour constituents were investigated. RESULTS: Crude gluten, non‐gluten proteins and separated starch were obtained from wheat flour ball‐milled for 0–10 h, and the glass transition temperature (T_g) of these constituents was evaluated. The T_g of all wheat flour constituents decreased with increasing ball‐milling time. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that changes in band position and intensity did not occur for gluten but did occur for non‐gluten proteins. X‐ray diffraction revealed decreased crystallinity and greater plasticisation by water in separated starch as the ball‐milling time was prolonged. CONCLUSION: The results showed that the ball‐milling process decreased the T_g of wheat flour constituents as a function of milling time. The decrease in T_g was probably due to changes in conformation of protein subunits in gluten and depolymerisation of the non‐gluten protein fraction. The information obtained here about the physical alteration of wheat flour constituents may enhance the ability to successfully use ball‐milled wheat flour in food applications. Copyright © 2008 Society of Chemical Industry     

Changes of chemical composition and dough rheology in two fractions of sieve‐classified Polish spring wheat flour

The study of chemical composition and dough rheology changes in sieve‐classified two fractions (up to 60 and 60–240 μm particles) of wheat flour was the subject of this study. The straight grade flours were obtained by the milling of three Polish varieties of spring wheat, differing in ?? abbreviation? (PSI) values. The flours were separated with the use of a SZ‐1 laboratory sifter. The yield of fine fraction was in the range 50.0–55.7%. The obtained fractions were assayed for the content and composition of free lipids, gluten proteins, damaged starch, ash, water absorption and amylograph viscosity. Dough rheology (extrusion in OTMS cell, alveograph and farinograph tests) and baking trials were also performed. The content of free lipids, including the non‐polar and phospholipids was lower and the content of glycolipids was higher in fine flours. Those fractions were more rich in linoleic acid but the lower content of oleic and linolenic acids resulted in a higher oxidizability index of free lipids. Fine flours contained less ash and significantly more damaged starch. At the same time, they were characterized by a higher content of wet gluten, water absorption, amylograph viscosity and better dough parameters. This was reflected in the bread volume, which was higher by 6.3–10.7%. The influence of the changes in composition and the content of free lipids upon the rheology of the dough after the 90 days flour storage has not been defined unambiguously and requires further research.     

马铃薯全粉在面条中的应用研究

将马铃薯全粉添加到小麦粉中,并辅助添加谷朊粉,制成马铃薯全粉面条。从质构特性、微观结构和面条的理化性质三个层面对三个不同马铃薯全粉添加比例的面条组别进行研究,发现马铃薯全粉对面团的力学性质,面筋网络的形成和构造以及面条的蒸煮参数和外观都会产生一定的影响。结果表明：马铃薯全粉添加量为20%（g/g）,谷朊粉添加为0.03%（g/g）时,总体指标最好;马铃薯全粉对面团的作用具有双向性,马铃薯淀粉对面团的影响偏负向,但是其中的多糖和蛋白质可能对面团和面筋网络有正向影响,同时谷朊粉的添加对面团的稳定性和面条的质量有改善作用。     

Impact of endogenous constituents from different flour milling streams on dough rheology and semi-sweet biscuit making potential by partial substitution of a commercial soft wheat flour

A flour fractionation-reconstitution procedure was used to study the substitution of a commercial soft wheat flour with gluten, water extractables, prime starch and starch tailing fractions isolated from patent and clear flour streams on dough rheology and semi-sweet biscuit characteristics. Substitution of soft wheat flour with increasing levels of the native patent and clear flour streams raised the dough consistency, hardness and elastic properties as well as the biscuit textural attributes (density, hardness). The dough stickiness of the base flour was also reduced and the biscuits were free of cracks. Gluten isolated from the patent flour had a greater impact on dough consistency, hardness and elastic properties than gluten obtained from the clear flour, likely due to the superior protein quality of the former. Additionally, with increasing gluten levels in the fortified flour there were moderate increases in biscuit density, hardness, and lower crunchiness. The addition of starch tailings produced the largest impact on consistency and hardness of the dough. This fraction also exerted a pronounced effect on biscuit density and hardness, while it lowered crunchiness, presumably due to its higher pentosan content. Overall, the dough rheological properties and biscuit characteristics were controlled by the amount-nature of the fractions added; i.e., besides gluten (amount and quality), other constituents such as pentosans and the overall composition of the flour blends can largely affect the quality of the semi-sweet biscuits.     

小麦胚中脂类对小麦粉品质的影响

按一定梯度向小麦粉中添加同种小麦提取的麦胚所制成的胚芽油,测定白度、降落数值、湿面筋含量、干面筋含量及面团流变学特性,并做面条质构及感官评价实验,研究麦胚脂类的添加对小麦粉、面团及面条品质的影响.实验表明,麦胚脂的添加对小麦粉干、湿面筋含量、降落数值没有影响;与白度、吸水率、延伸度呈显著线性负相关;与形成时间、粉质质量指数、拉伸面积、最大拉伸阻力、最大拉伸比呈显著正相关.在一定范围内(0%～6%)面条感官评价总评分随着麦胚脂添加量增大而增大,超过此范围则正好相反;在6%添加量时,面条感官综合评分最高.     

添加糯小麦粉对小麦粉及其面条品质特性的影响

糯小麦与普通小麦的主要差异是糯小麦不含直链淀粉或其含量很低,其对面制品的制作品质产生一定的影响。本研究利用"济糯1号"分别与"济麦20"和"济麦22"按20%、40%、60%和80%的添加量进行配粉,研究糯小麦粉对普通小麦粉品质特性的影响及其面条制品品质的改良作用。结果表明:"济糯1号"的淀粉糊化回升值为449 c P,显著低于"济麦20"和"济麦22";籽粒硬度达64.89,籽粒蛋白质含量(干基)达16.14%,面筋指数为66.08%,粉质仪稳定时间为2.00 min,鲜面条色泽变化小,2 h和24 h的ΔE*分别为3.83和5.29;"济糯1号"与"济麦20"的配粉中,随糯小麦粉添加量的增加,配粉的淀粉回升值降低,面筋指数降低,吸水率增加,面团稳定时间变短,鲜面条色泽2 h和24 h的ΔE*逐渐变小,配粉面条的适口性和光滑性更好;"济糯1号"与"济麦22"的配粉中,随糯小麦粉添加量的增加,面粉蛋白含量增加、面筋指数升高、吸水率增加、淀粉糊化的回升值降低,鲜面条色泽2 h和24 h的ΔE*逐渐变小,配粉的面条制作品质好,面条的适口性和光滑性均改善;糯小麦粉的添加使配粉的面粉品质特性和淀粉特性更有利于面条制作品质的改良,"济糯1号"适宜添加量为20%~40%。     

小麦粉吸水速率与其蛋白组成特性的关系

蛋白质理化特性的差异会导致小麦粉吸水速率的不同。本文以不同吸水速率的小麦粉为研究对象,测定面粉中粗蛋白含量、面筋蛋白含量、湿面筋含量、面筋指数、沉降值、谷蛋白溶胀指数、氨基酸含量及观测面团内部微观网络结构。结果表明,当粗蛋白含量13.25%降低到6.98%时,小麦粉的吸水速率从0.17 g/s增大到3.87 g/s;当麦醇溶蛋白含量从4.02%下降到1.53%及麦谷蛋白含量从5.28%下降到2.77%时,因形成的面筋膜的质量下降使小麦粉的吸水速率增大。同时吸水速率随湿面筋含量的减小而显著性增大,面筋指数对吸水速率无显著性影响。沉降值从69.50m L降到32.50 mL,谷蛋白溶胀指数从5.24%下降到3.33%,均与吸水速率呈显著性负相关(p0.05)。半胱氨酸含量从0.14%降低到0.04%,导致二硫键含量下降,使蛋白质间的分子作用力下降。当面团内部面筋网络结构紧密时,面粉成团时的阻力越大,其吸水速率越小。本研究表明蛋白质性质与小麦粉吸水速率呈负相关。     

Effect of soybean proteins on gluten depolymerization during mixing and resting

BACKGROUND: Gluten and soy proteins interact as a consequence of dough mixing; however, there is no evidence of the effect of soy protein on gluten depolymerization. The aim of this study was to assess the depolymerizing effect of soy protein on gluten network after mixing and resting of mixed doughs. Therefore, the changes in glutenin macropolymer (GMP) content, protein composition and free sulfhydryl content were evaluated. RESULTS: The protein profile from gluten–soybean blends, obtained by multistacking SDS‐PAGE, showed differences when compared to gluten profile. Soy and gluten proteins were extracted together with SDS buffer, which showed that soy proteins remained associated to insoluble wheat proteins even after hand‐washing the dough to obtain gluten. GMP content was determined to analyze the effect of soy protein on GMP gel formation. Protein content of GMP obtained from flour mixes and doughs was increased by inactive soy flour because soy proteins became insoluble and precipitated together with GMP. Active soy flour decreased GMP content due to gluten depolymerization. CONCLUSION: Soy proteins were associated to wheat protein through physical interaction and covalent and non‐covalent bonds during mixing and resting. These interactions produced large and medium‐size polymers. This fact increased SDS solubility of insoluble gluten proteins, producing a weakening of the gluten network. Physicochemical status of soy protein in the product had a great influence on how wheat–soy proteins interact. Copyright © 2007 Society of Chemical Industry     

Separation of bread wheat flours into starch and gluten fractions: effect of water temperature alone or in combination with water to flour ratio

Two different commercial bread wheat flours (BF‐I, 65% extraction and BF‐V, 86% extraction) were separated into gluten and starch milk by making a dough, allowing some time for maturation, dispersing the dough in water and wet sieving/washing. The effect of using of warm water (20–45 °C) for dough making and washing on separation was studied for BF‐I flour at 640 g kg^?1 water to flour ratio of and 300 s maturation time, and the separation was found to improve with increase in temperature. The combined effects of water temperature (20–50 °C) and water to flour ratio (640–780 g kg^?1 for BF‐I and 620–870 g kg^?1 for BF‐V) were studied at 600 s maturation time. The quantities and dry matter contents of the gluten fraction and starch milk were measured; a sample of starch milk was centrifuged to obtain decantate, tailing and prime starch fractions, and the dry matter contents of each were determined. All the dried samples were also analysed for protein content, and the fractional recoveries of dry matter and protein in the gluten fraction, prime starch, tailings and decantate were calculated. The results indicated the optimum point for BF‐I flour to be the combination of optimum farinograph water absorption and 40 °C. BF‐V showed very poor separation behaviour within the ranges studied. At the optimum farinograph water absorption the use of warm water for dough making and 20 °C water for washing steps was also tried, but no significant improvement over the 20 °C results was obtained. © 2002 Society of Chemical Industry     

Rheological properties of gluten derived from wheat cultivars with identical HMW glutenin subunit composition†

Ten spring wheat cultivars possessing identical HMW glutenin subunits (2*, 7+8, 5+10) were evaluated for gluten and protein content. Gluten content was related to flour protein content (r=0·98). Addition of freeze-dried gluten to the base flour (cv Alpha) to a constant protein level of 12% generally increased dough strength. However, the magnitude of variation in mixing patterns depended more on the type of the supplemental gluten. Fortification of the base flour with the freeze-dried gluten from the cv Glenlea produced mixographs with the longest mixing development time (MDT), and highest band width energy (BWE) and energy to peak (ETP), suggesting that the source of gluten had a strong effect on dough rheology. The viscoelastic properties of undiluted wet gluten varied between cultivars during mixing reflecting differences in gluten quality. Freshly prepared wet gluten of Glenlea showed extended mixing tolerance as compared to Norseman or Alpha gluten. The wet gluten from cv Glenlea was less extensible with high maximum resistance to extension and had a larger area under the extensigraph curve than gluten obtained from cv Norseman. Gluten prepared from the cultivars Glenlea, Bluesky and Wildcat were less soluble in aqueous propanol and produced more froth when the dough was washed with deionised water. The froth proteins, separated by SDS-PAGE, predominantly contained strongly stained bands in the region corresponding to molecular weight <50 kDa. The rapid tests such as froth formation and alcohol solubility used in this study to discriminate various glutens were highly correlated with the mixograph parameters. These methods can be of practical value in evaluating gluten quality. © 1998 Society of Chemical Industry.     

羧甲基化和乳化沙蒿胶对小麦粉的增筋作用

沙蒿胶可经羧甲基化和油基乳化提高水溶性和乳化性,其适用于小麦粉加工的增筋效果有待研究。本研究通过沙蒿胶的羧甲基化和乳化改性,分析其在小麦粉面团形成以及含油面团制作中的增筋效果。结果表明,羧基化改性可使沙蒿胶在小麦粉中的最佳添加量从1.0%降至0.4%,有效提高小麦粉的湿面筋量、面筋指数、吸水率、形成时间和稳定时间,降低弱化度,但在含油脂小麦粉中未表现出增筋性能的提升。与之对比,经小麦胚芽油或棕榈硬脂两种油相乳化处理的沙蒿胶则更适用于含油脂面团的调制,1.0%沙蒿胶和5%油脂以乳化方式添加,可降低液态和固态油脂在面团形成中的差异,并有效改善面团质构特性。本研究表明,羧甲基化可降低沙蒿胶应用于小麦粉增筋的使用剂量,而沙蒿胶乳化则适用于水油面团的增筋。     

小麦麸皮微波处理对全麦粉面筋品质和流变学特性的影响

目的 探讨小麦麸皮微波处理灭酶对全麦粉面筋品质特性和流变学特性的影响.方法 以中高筋小麦为原料,对麸皮微波处理后再回添到小麦粉中制得全麦粉,设置麸皮水分含量、微波处理时间和麸皮厚度3个变量因素,固定其中2个变量因素,探讨另1个变量因素对全麦粉中面筋特性和流变学特性的影响.结果 麸皮水分含量对湿面筋含量、面筋吸水率、面团...     

Wet separation of wheat flours into starch and gluten fractions: the combined effects of water to flour ratio–dough maturation time and the effects of flour aging and ascorbic acid addition

The process of making a dough, allowing time for maturation, dispersing the dough in water and wet sieving/washing to obtain a protein fraction and starch milk was studied using response surface methodology by changing the water to flour ratio in dough making (400–710 g kg^?1), maturation time (45–660 s) and the type of flour. Two grades of bread wheat flour and durum clear flour were studied. The effects of aging at ambient temperature for up to 29 days and the addition of ascorbic acid at 100 or 500 mg kg^?1 flour on separation behaviour were also studied for freshly milled high‐grade (65% extraction) bread wheat flours at constant maturation time, 600 s, and at optimum farinograph water absorption value. The quantities and dry matter contents of the protein fraction and starch milk were measured; a sample of starch milk was centrifuged to obtain decantate, tailings and prime starch fractions, and the dry matter contents of each were determined. All the dried samples were also analysed for protein content. The fractional recoveries of dry matter and protein in the protein fraction, prime starch, tailings and decantate were calculated for each experiment. The acid values of flour oils were also determined on some aged flour samples. The results indicated superior separation characteristics in high‐grade wheat flour compared with lower‐grade flours. The water to flour ratio was more influential than maturation time within the range studied. Contrary to the initial expectation, no statistically significant effect of flour aging was observed in the studies with no additive, and ascorbic acid addition was not found to improve the wet separation behaviour, the separation behaviour becoming even worse at the 100 mg kg^?1 level. Acid value showed a slight increase with time. © 2002 Society of Chemical Industry     

Navy Bean Flour Particle Size and Protein Content Affect Cake Baking and Batter Quality1

Whole navy bean flour and its fine and coarse particle size fractions were used to completely replace wheat flour in cakes. Replacement of wheat flour with whole bean flour significantly increased the protein content. The protein content was adjusted to 3 levels with navy bean starch. The effect of navy bean flour and its fractions at 3 levels of protein on cake batter rheology and cake quality was studied and compared with wheat flour samples. Batters prepared from navy bean flour and its fractions had higher viscosity than the cake flour. Reducing the protein content by addition of starch significantly lowered the viscosity of cake batters. The whole navy bean flour and coarse bean fraction cakes were softer than cakes made with wheat flour but had reduced springiness. Principal component analysis showed a clear discrimination of cakes according to protein. It also showed that low protein navy bean flour cakes were similar to wheat flour cakes. Navy bean flour with protein content adjusted to the level of cake (wheat) flour has potential as a healthy alternative in gluten‐free cakes.     

Effects of endogenous flour lipids on the quality of short‐dough biscuits

Fractionation and reconstitution techniques were used to study the contribution of endogenous flour lipids to the quality of short‐dough (shortcake type) biscuits. Biscuit flour was defatted with chloroform and baked with bakery fat, but without endogenous lipid. Short‐dough biscuits baked from defatted flour had smaller diameters, and were flatter, denser and harder than control biscuits. Defatted flour shortcake doughs exhibited different rheological behaviour from the control samples, showing higher storage and loss moduli (G′ and G″ values), ie higher viscoelasticity. Functionality was restored when total non‐starch flour lipids were added back to defatted flour. The polar lipid fraction had a positive effect in restoring flour quality whereas the non‐polar lipid fraction had no effect. Both fractions were needed for complete restoration of both biscuit quality and dough rheological characteristics. A study of the microstructure of defatted biscuits revealed that their gluten protein was more hydrated and developed than the gluten of the control biscuits. This conclusion was supported by the higher water absorption of the defatted gluten. Copyright © 2004 Society of Chemical Industry     

Evaluation of baking procedures for incorporation of barley roller milling fractions containing high levels of dietary fibre into bread

BACKGROUND: Roller milling of hull‐less barley generates fibre‐rich fractions (FRF) enriched in non‐starch polysaccharides from the endosperm cell walls (β‐glucans and arabinoxylans). This investigation was initiated to compare the suitability of different baking processes and to determine the optimal conditions for incorporation of barley FRF into pan bread. RESULTS: Addition of FRF from waxy and high‐amylose starch hull‐less barley genotypes was evaluated in pan bread prepared from Canada Western Red Spring (CWRS) and Canada Western Extra Strong (CWES) wheat flour. Three bread processes were used: Canadian short process (CSP), remix‐to‐peak, and sponge‐and‐dough. Addition of 20% FRF (equivalent to enrichment with 4.0 g of arabinoxylans and β‐glucans per 100 g of flour) disrupted dough properties and depressed loaf volume. CSP was not suitable for making FRF‐enriched bread because dough could not be properly developed. FRF‐enriched remix‐to‐peak bread was better, especially for the stronger CWES flour. The better bread quality compared to CSP was probably due to redistribution of water from non‐starch polysaccharides to gluten during fermentation prior to remixing and final proof. The sponge‐and‐dough process produced the best FRF‐enriched bread because of the positive effect of sponge fermentation on gluten development and hydration. FRF was added at the dough stage to fully developed dough. CONCLUSION: The method of bread production strongly influences bread quality. Pre‐hydration of FRF improved bread quality. CWRS and CWES flour produced comparable FRF‐enriched sponge‐and‐dough bread. Addition of xylanase to the sponge‐and‐dough formula improved the loaf volume, appearance, crumb structure and firmness of FRF‐enriched bread. Copyright © 2007 Society of Chemical Industry     

小麦面粉蛋白质特性和面团流变学特性的关系

目的探究小麦面粉蛋白质理化特性与面团流变学特性之间的关系。方法以19份抗旱节水鉴定品种小麦籽粒为试验材料,测定了蛋白质、湿面筋、谷蛋白大聚体含量、沉降指数等面粉蛋白质理化特性,以及粉质参数和拉伸参数等面团流变学特性,采用通径分析研究了面粉蛋白质理化特性与面团流变学特性的关系。结果面粉蛋白质含量对面团吸水率直接增强效应较大,但对稳定时间、拉伸长度的抑制效应较大;谷蛋白大聚体含量对形成时间、最大拉伸阻力、拉伸面积的直接增强效应和综合增强效应均较大;沉降指数对稳定时间和最大拉伸阻力、拉伸面积的直接增强和综合增强效应较大;所测蛋白质理化特性中未发现对拉伸长度有增强效应的指标。结论面粉中谷蛋白大聚体含量和沉降指数是对面团形成时间、稳定时间、拉伸阻力影响较大的因素,影响为正效应,可为专用面粉生产质量控制提供参考。