Utilization of dairy byproduct proteins, surfactants, and enzymes in frozen dough

Use of natural additives is gaining popularity among the masses as they are becoming more conscious about their diet and health. Frozen dough products are one of the recent examples of value-added cereal products which face stability problems during extended storage periods of times. Dairy whey proteins, surfactants, and certain enzymes are considered important natural additives which could be used to control the water redistribution problem in the dough structure during the storage condition. They interact with the starch and gluten network in a dough system and thus behave as dough improvers and strengtheners. These natural additives not only help to bind extra moisture but also to improve texture and sensory attributes in frozen dough bakery products.     

Glycosylation and expanded utility of a modified whey protein ingredient via carbohydrate conjugation at low pH

Whey protein, at one time considered a by-product of the cheese-making process, is now commonly used in foods for its thickening and emulsifying properties. Currently, approximately 30% of these proteinaceous resources remain under-utilized. Previously, an acidified, thermally treated whey protein concentrate (mWPC) was developed to produce a cold-set thickening ingredient. Mass spectroscopy revealed an approximate 2.5-fold decrease in the lactosylation of β-lactoglobulin in mWPC starting materials compared with commercial whey protein concentrates, manufactured at a higher pH. Potentially, this should increase the number of reactive sites that remain available for carbohydrate attachment. With this study, the formation of glycoprotein complexes was demonstrated between the mWPC ingredient and lactose, naturally occurring in mWPC powders, or between mWPC protein components with dextran (35 to 45 and 100 to 200 kDa) materials at low pH. In fact, additional dry heating of mWPC powders showed a 3-fold increase in the amount of lactosylated β-lactoglobulin. Evidence of Maillard reactivity was suggested using colorimetry, o-phthaldialdehyde assays, and sodium dodecyl sulfate PAGE followed by glycoprotein staining. Resultant glycoprotein dispersions exhibited altered functionality, in which case steady shear and small amplitude oscillatory rheology parameters were shown to be dependent on the specific reducing sugar present. Furthermore, the emulsion stability of mWPC-dextran fractions was 2 to 3 times greater than either mWPC or commercial WPC dispersions based on creaming index values. The water-holding capacity of all test samples decreased with additional heating steps; however, mWPC-dextran powders still retained nearly 6 times their weight of water. Scanning electron microscopy revealed that mWPC-dextran conjugates formed a porous network that differed significantly from the dense network observed with mWPC samples. This porosity likely affected both the rheological and water-binding properties of mWPC-dextran complexes. Taken together, these results suggest that the functionality of mWPC ingredients can be enhanced by conjugation with carbohydrate materials at low pH, especially with regard to improving the emulsifying attributes.     

改良剂对面团流变学性质的影响

为了探讨小麦粉改良剂对面团流变学性质的影响,以宁麦15面粉为原料,分别加入不同比例的谷元粉、瓜尔豆胶和变性淀粉,用粉质仪和拉伸仪研究其对面团流变学特性的影响,以期生产出符合市场需求的面条专用粉。利用响应面法中心组合试验设计,采用综合加权评分法评估改良剂对多指标流变学性质的影响。结果表明:各因素对综合加权评分值的影响程度为谷元粉>变性淀粉>瓜尔豆胶,两两因素之间存在相互作用。适宜配粉条件为:谷元粉1.4%、瓜尔豆胶1.5%,变性淀粉2.2%。在此条件下流变学指标的综合加权评分预测值为0.869,验证值为0.856,与预测值的相对误差为1.5%。表明添加适量的改良剂能够显著提高宁麦15面粉的品质特性。     

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.     

棕榈油添加量对面团质量的影响

目的:探寻棕榈油在生产馕、面包、馒头、苏打饼干及冷冻面制品等发酵面团中的应用工艺。方法:利用旋转流变仪测定棕榈油添加量对发酵面团流变特性的影响,并通过扫描电镜观察面团微观结构分析棕榈油添加量对面团组分的作用机理。结果:在小麦粉中分别添加4%,6%,8%,10%,12%(以小麦粉的总质量为100%计)的棕榈油,面团的发酵特性和流变特性发生显著变化。当棕榈油添加量为4%~10%时,有效地改善了面团发酵特性,延缓了面团老化速度。但当棕榈油添加量为12%时,会稀释面筋蛋白,降低面筋网络结构的稳定性,增大发酵面团的硬度和黏性。随着棕榈油添加量的增加,面团的发酵体积、持水性和黏弹性先递增后递减。结论:添加适量棕榈油有利于面筋网络结构的形成和稳定,改善面团的发酵及流变特性,棕榈油添加量为6%~8%时面团发酵效果较好。     

Glutathione affects rheology and water distribution of wheat dough by changing gluten conformation and protein depolymerisation

The effects of reduced glutathione (GSH) on dough rheology, water state and distribution, gluten conformation, and protein molecular weight distribution were investigated. Addition of GSH (0.02−0.04%) resulted in a more viscous and less elastic dough with decreased G′ and increased tanδ values, which suggested decreased cross-links in gluten network and a weakened dough structure. The molecular weight of proteins was reduced by the GSH-induced cleavage of intermolecular disulphide bonds. Fourier transform infrared spectroscopy showed a high fraction of β-sheet formation at the expense of α-helix and β-turns, indicating a destabilised secondary structure and protein depolymerisation. GSH increased water release from the gluten network in dough resulting in an increase in freezable water content and caused water redistributed from bound water to weakly bound water. This study provided insights into correlation between wheat dough rheological properties and gluten structure influenced by GSH.     

Tannins improve dough mixing properties through affecting physicochemical and structural properties of wheat gluten proteins

The quality of wheat flour is largely determined by the properties of gluten proteins. Chemical components that influence gluten proteins are used as flour improvers in the flour industry. In this study, tannins which are natural occurring polyphenols were found to improve dough mixing properties. The effects of tannins on the physicochemical and structural properties of gluten proteins were examined, and the results showed that tannins promoted the non-covalent interactions among gluten proteins, although they induced SH/SS interchange reactions in the dough. The β-turn and α-helix conformations were increased, whereas the β-sheet conformation was decreased in dough containing tannins as detected by FTIR. Moreover, the addition of tannins promoted the aggregation of gluten proteins, modified the microstructure of gluten networks, and improved the mixing properties. The positive effects of tannins on dough properties implied the potential of tannins as a new flour improver.     

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。     

Impact of sodium chloride on wheat flour dough for yeast‐leavened products. I. Rheological attributes

BACKGROUND: The rheological properties of wheat dough for yeast‐leavened products were tested at different levels of sodium chloride (NaCl) addition ranging from 0 to 40 g NaCl kg^?1 wheat flour. Rheological tests carried out to make this evaluation included (1) empirical rheological methods of the Farinograph, load extension and a dough stickiness test and (2) fundamental rheological methods of creep recovery and dynamic rheometry. Modifications to the gluten matrix microstructure by NaCl were examined by confocal laser‐scanning microscopy. RESULTS: Highly significant (P?0.001) differences due to NaCl addition could be determined in particular by the stickiness test as well as by examination of the creep test with the Burger model. Rheological changes measured in the creep test probably depend on protein charge shielding due to NaCl interaction, resulting in an improvement in gluten network formation. An increase in dough stickiness was measured when using NaCl. CONCLUSION: The present result for stickiness is contrary to the common subjective results. Therefore the theory proposed here for increased stickiness suggests that it is based on more non‐protein‐bound water in the dough system due to NaCl interaction and thus more viscous dough behaviour, which leads to higher stickiness as measured with the stickiness test. This may also suggest that the objectively measured ‘stickiness’ in this case does not properly indicate the subjectively measured stickiness it was designed to represent. Copyright © 2011 Society of Chemical Industry     

复配品质改良剂对南方馒头冷冻面团冻藏品质的影响

为提升和改善冷冻面团南方馒头的品质,分析冻藏过程中复配品质改良剂(海藻糖添加量4%、磷酸二氢钠添加量0.15%、黄原胶添加量0.05%、羧甲基纤维素钠添加量0.04%)对冷冻面团南方馒头比容、硬度、感官品质的影响,并从面团拉伸特性、动态流变特性、微观结构、蛋白质二级结构等方面探究复配品质改良剂在南方馒头冷冻面团中的作用机理。结果表明:冻藏过程中,冰晶会对淀粉颗粒、面筋蛋白及网络结构造成伤害,导致面团品质下降。复配品质改良剂可以保护面团中的面筋结构,减少面筋蛋白二级结构的变化,进而延缓弹性模量和黏性模量的降低速度,改善面团最大拉伸阻力和延伸度劣变,提升南方馒头硬度、比容和感官品质等品质,保持南方馒头松软的风味。     

Improvements of Modified Wheat Protein Disulfide Isomerases with Chaperone Activity Only on the Processing Quality of Flour

Wheat protein disulfide isomerase (wPDI) with oxidoreductase activity, isomerase activity, and chaperone activity catalyzes the formation of disulfide bonds in gluten in vitro; the addition of wild-type wPDI weakened yet the flour processing quality. To develop the potential flour improvers from wPDI, the modified wPDIs were prepared by the biological or chemical method, and their effects on the processing quality of flour in connection with bread making were investigated by farinograph, texture profile analysis, electrophoresis, size exclusion chromatography, and scanning electron microscopy. A truncated protein of wPDI, fragment AB with oxidoreductase, and isomerase activities only was firstly confirmed to exert deteriorative effects similar to wPDI on the dough and bread quality. Then other two modified wPDIs, mPDI and aPDI, were prepared by site-directed mutagenesis and alkylation, respectively. Both mPDI and aPDI considerably retained the chaperone activity of wPDI but completely lost oxidoreductase and isomerase activities. After adding the appropriate amount of mPDI or aPDI, the stability time of dough was significantly prolonged from 3.60 to 4.15 or 4.13 min, respectively. The enhanced gluten network matrix and decreased hardness and chewiness of bread further suggested that dough was strengthened by the treatment of mPDI or aPDI. Moreover, the formation of gluten network was facilitated by the modified wPDIs with chaperone activity only for the increase amount of gluten macropolymer and the decrease content of SDS-soluble gluten. Consequently, mPDI and aPDI are valid candidates of flour improvers in food industry.     

抗冻蛋白的制备及对冷冻面筋蛋白的改良研究进展

冷冻面团在运输储藏过程中,温度波动引起的冰晶生长和重结晶会导致面团品质劣变,致使最终产品感官特性变差,消费性下降,这限制了冷冻面团的大规模应用。面筋蛋白作为冷冻面团的重要组分,在冻藏过程中冰晶对其特性的影响与冷冻面团的品质密切相关。抗冻蛋白（AFPs）能够与冰晶结合,调控冰晶生长行为,对冷冻面筋蛋白有着很好的改良效果。但生物体内的天然AFPs含量少,提取纯化困难,这使AFPs一直以来难以实现工业化生产与应用,因此,探寻合适的制备方法提高AFPs的产量对于AFPs的发展是至关重要的。本文即综述了AFPs的生产现状及对冷冻面筋蛋白的改良研究,以期为AFPs在冷冻面制品中的应用提供理论基础。     

全麦冷冻面团研究进展

冷冻面团是全麦食品的一种良好载体,可简化生产操作,降低加工难度,加快全麦食品的工业化生产。综述了全麦食品中的膳食纤维对面团及冷冻面团品质的影响,在冷冻和冷藏过程中全麦冷冻面团的发酵特性和流变学特性的变化,以及食品改良剂对全麦冷冻面团的品质改善等研究。通过分析全麦冷冻面团中面筋蛋白、淀粉、发酵特性、流变学特性等在冷冻和冷藏过程中劣变原因,为改善全麦冷冻面团的品质提供理论基础和实践参考。     

Effects of protein oxidation on the rheological behaviour of different wheat flour

Wheat flour proteins are subject to oxidation reactions during production, processing and storage. The quality of protein and the rheological properties of wheat are crucial for the flour industry. However, the impact and mechanism of protein oxidised on wheat flour quality remain unclear. In this study, ozone was used to oxidise wheat grains, the secondary structure of protein in flour and the rheological properties of dough were analysed by FTIR and Mixolab. The proportion of α-helix and β-folding of protein were decreased significantly, as were the development time (DDT), stability time (DST) and protein weakening (C2) value of dough. Meanwhile, starch gelatinisation (C3), amylase activity (C4) and retrogradation (C5) were increased significantly, along with the elastic modulus (G′) and viscous modulus (G″). Microstructure analysis indicated that protein oxidation destroyed the gluten network structure in the dough. In addition, the L* value of dough was decreased and a* and b* values were increased significantly. The results showed that the oxidation of protein reduced the stability of protein secondary structure, weakened the structure and stability of the gluten network in dough, and changed the viscoelasticity and colour of dough. Overall, these findings provide a better understanding of rheological behaviour in wheat flour.     

谷朊粉对糙米粉面团性质影响研究

研究了谷朊粉添加量对糙米粉面团性质的影响,主要包括粉质特性、热机械性质、流变学性质、微观结构等。结果表明:随着谷朊粉添加量增大,面团的吸水率、形成时间、稳定时间、淀粉衰减值和回生程度均在逐渐增长,蛋白弱化度在逐渐降低。糙米粉面团的弹性模量和粘性模量均在增大,且弹性模量大于粘性模量。扫描电镜结果显示:随着谷朊粉添加量增大,面团的网络结构越来越明显,淀粉颗粒镶嵌在蛋白形成的网络结构中,增加了面团的弹性及变形的阻力。     

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。     

Effect of glutens of different quality on dough characteristics and breadmaking performance

Glutens of different quality were extracted from commercial flours of distinct breadmaking performance and employed as improvers at a level of 1 g/100 g. The same flours used as a source of gluten were employed for testing the gluten effect. Flours were characterized by farinographic and alveographic assays and their protein profile was determined by SDS-PAGE. Rheology of each dough without and with gluten addition was studied by empirical and fundamental assays. Breadmaking performance was evaluated by loaf volume measurements and crumb texture.Though protein content was similar for all flours (11 g/100 g), dough exhibited different breadmaking characteristics which could be related to a different gliadin/glutenin proportion and a different protein profile. The weakest flour lacked two glutenin subunits (83 and 64.5 kDa) and showed a lower number of bands of gliadins respect to the other ones. Adding any of the three types of gluten to the weakest flour resulted in an increase of farinographic stability. The medium and inferior quality flours showed an increase in dough elasticity when the strongest gluten was added. In breadmaking assays the medium quality flour and its mixtures with gluten showed the highest specific volumes.     

Influence of soy protein on rheological properties and water retention capacity of wheat gluten

A better understanding of the physicochemical and rheological changes in soy/wheat composite dough may lead to overcome the problems caused by the incorporation of high levels of soy products on bread formulation. The effects of commercial soy protein isolate (SPI) on uniaxial extension and creep behavior, microstructure and free water of hydrated gluten were studied. Different solid:moisture ratios were used. Results showed that the substitution of wheat protein by soy protein negatively affected the gluten-SPI mixture rheological properties due to network weakening. It was demonstrated that gluten was weakened as a consequence of the interference effect of soy proteins on their structure, and the smaller availability of water to the build-up of the gluten network. A greater amount of moisture could partially improve the rheological performance of the gluten-SPI mixture.     

TSP与SPH复合物对面团特性及面条品质的影响机制

为了减少大豆水解蛋白(soy protein hydrolyzate,SPH)对面筋网络的弱化作用,将质构化大豆蛋白(texturized soy protein,TSP)与SPH(水解度为4.54%)复配后添加到面粉中(TSP、SPH替代面粉的量分别为6.0%、2.2%),比较面条品质、面筋特性、粉质特性、动态流变学特性等变化。与原面粉相比,添加TSP-SPH的面粉制成的面条弹性降低,面团的弱化度减小,评价值增大,干、湿面筋含量分别降至5.10%和15.65%,面筋指数增至89.24%;TSP-SPH面团的储能模量和损耗模量增大,损耗因子减小,面筋蛋白中的麦谷蛋白大聚体含量显著增加。结果表明,TSP-SPH通过二硫键与面筋蛋白相互作用,面团内部交联结构增加,一定程度缓解了SPH对面筋网络的弱化作用。     

SPI与SPH及其复配产物对面团特性和面条品质的影响机制

为提高面制品的营养品质,研究并比较了添加大豆分离蛋白(soy protein isolate,SPI)、大豆水解蛋白(soy protein hydrolyzates,SPH,水解度为4.54%)以及SPI和SPH复配产物(SPI-SPH)的混合粉的面筋特性和粉质特性,面团的动态流变学特性、蛋白质组分、二硫键和非共价键变化,以及面条的品质变化。添加SPI后面粉的湿面筋含量升高,干面筋含量下降,面筋指数降低,粉质特性评价值升高;面团的醇溶蛋白和麦谷蛋白含量增加,黏弹性增大,弹性比例增加。添加SPI-SPH的面粉面筋特性和面团特性变化趋势与添加SPI的面粉一致,其粉质特性评价值增大。添加SPH的面粉中无面筋洗出,粉质特性评价值升高;面团盐溶蛋白含量显著增加(P<0.05),弹性比例降低。添加大豆蛋白的面团中二硫键含量均增加,疏水相互作用减弱,氢键增强。与原面粉面条相比,SPI面条的硬度增大10.82%,SPI-SPH和SPH面条的弹性分别减小7.23%和6.02%,且添加SPH后面条的蛋白质保留率由93.02%降至87.31%。研究表明,大豆蛋白与面筋蛋白通过二硫键交联以及非共价键相互作用,阻碍面筋网络形成,破坏了面筋网络的连续性。并且,SPI和SPH复配在一定程度上减弱了SPH对面筋的弱化作用。