环境因素对3种功能性蛋白物性的影响

大豆蛋白、乳清蛋白和酪蛋白均为具有良好功能特性的营养丰富的蛋白。在加工的过程中,加工条件带来的环境因素变化(如pH值、温度、离子强度)等,会使3种蛋白溶解性、凝胶性以及流变特性发生改变。因此,文章对不同环境因素对大豆蛋白、乳清蛋白以及酪蛋白的溶解性、凝胶性以及流变特性产生的影响展开研究,为后续更多的蛋白质添加剂的研究提供了基础。结果表明,相同pH值时,乳清蛋白溶解度最高,等电点与大豆蛋白相同pH值4~5,酪蛋白溶解度最低且等电点pH值3~4。凝胶性方面,酪蛋白在pH值5~9范围内以及NaCl浓度(0~2.1)mol/L范围内均不能成胶。盐浓度对大豆蛋白凝胶强度影响显著,对乳清蛋白影响不明显;改变pH值对大豆蛋白凝胶强度影响不明显,对乳清蛋白影响显著。流变特性方面,3种蛋白溶液均为剪切变稀流体。此研究结果通过研究3种蛋白特性,为向面团中外添蛋白奠定基础。     

采用Mixolab 和Rheometer 研究含外源蛋白燕麦面团的热机械学和动态流变学特性

通过酶流变分析仪(Mixolab)和动态流变仪(Pheometer)研究3种不同外源蛋白对燕麦面团体系热机械学和流变学特性的影响。Mixolab 分析结果表明：大豆蛋白和面筋蛋白都使燕麦面团的吸水率增大,蛋清蛋白使吸水率显著下降。3 种蛋白的添加都可显著提高面团形成时间,其中面筋蛋白影响最大,大豆蛋白最小。面筋蛋白和蛋清蛋白都使燕麦面团的稳定时间显著增加,其中含10% 面筋蛋白和15% 蛋清蛋白的燕麦面团具有最好的稳定性。含蛋清蛋白的燕麦面团在淀粉糊化时获得最大的峰值扭矩和回值,且随着其添加量增加而有所增大,大豆蛋白则相反,面筋蛋白对相关参数影响较小。动态流变学实验显示：含面筋蛋白和大豆蛋白的燕麦面团具有较大的弹性模量(G')和黏性模量(G"),且随着添加量的增大而增加,含蛋清蛋白的面团则相反。采用DSC 进一步分析面团的热力学特性显示：蛋清蛋白和大豆蛋白可显著提高燕麦面团的峰值温度和终止温度,并在一定程度上提高面团的热焓值;面筋蛋白则作用不明显。     

不同种类大豆蛋白对冷冻发酵面团馒头品质的影响机制

旨在为大豆蛋白在冷冻发酵面团中的应用提供一定的理论依据，对添加大豆分离蛋白(SPI)、质构化大豆分离蛋白(TSP)、水解大豆分离蛋白(SPH)的冷冻发酵面团馒头及冷冻发酵面团进行研究，分析了添加不同种类大豆蛋白的冷冻发酵面团馒头的理化指标(比容、水分含量、pH),并通过测定冷冻发酵面团的二硫键含量、蛋白质二级结构和微观结构，探讨不同种类大豆蛋白对冷冻发酵馒头品质的影响机制。结果表明：添加SPH的发酵面团冷冻储藏前后所蒸制的馒头比容变化最小，在冷冻储藏40 d时蒸制的馒头比容相比冷冻储藏10 d增加了4.59%;同一冷冻储藏时间下添加SPH的发酵面团蒸制的馒头水分含量最低；添加大豆蛋白可以减小在冷冻储藏过程中发酵面团馒头pH的下降速率，至少可延长冷冻发酵面团10 d的保质期；通过傅里叶红外光谱和激光共聚焦对冷冻发酵面团蛋白质结构分析，得出添加3种大豆蛋白均会降低面筋蛋白网络结构的均匀性和连续性，SPI和TSP对面筋蛋白网络结构的影响小于SPH,但在冷冻储藏过程中添加SPH的发酵面团的面筋蛋白网络结构相对较为稳定。综上，大豆蛋白与面筋蛋白通过二硫键和非共价键相互作用，改变面筋蛋白网络结构的...     

改性方法对小麦麸皮面团及馒头品质的影响

研究超微粉碎、挤压和酶解3种改性方法对小麦麸皮面团及馒头品质的影响。结果表明：3种改性方法均改变了面团的热机械学特性、二级结构及馒头的质构特性和感官品质。与对照组相比，超微粉碎使面团的吸水率显著增加，但对面团的二级结构影响不大；挤压改性使面团的吸水率、稳定时间、α-螺旋、β-折叠和无规卷曲显著降低，β-转角含量显著增加(P<0.05);并且，挤压改性使馒头质构特性显著增加，能够生成特殊的风味物质，增加整体可接受性。酶解改性使面团的吸水率最高、形成时间最短、稳定时间最长、α-螺旋和β-折叠结构增加最大，但馒头的硬度、黏性和咀嚼性降低，弹性增加。     

面粉特性对荞麦馒头预拌粉品质的影响

测定8种不同面粉的基本性质、面团流变特性、发酵特性,并用其制备成荞麦馒头预拌粉制作荞麦馒头,通过测定荞麦馒头的比容、质构特性、感官品质等指标,探究面粉特性对荞麦馒头预拌粉品质的影响。试验结果表明:湿面筋含量在33%～34%,蛋白质含量在11%～12%的面粉其蛋白质弱化度较小,面团形成时间和稳定时间较长,面团的持气率较好,面团开始漏气时间较晚;对应编号制作的荞麦馒头比容较大,硬度、弹性、咀嚼性适中,感官评价总分较高;灰分0.4g/100g的面粉制作的荞麦馒头表面颜色光亮、色泽均匀。综上可得:湿面筋含量在33%～34%,蛋白质含量在11%～12%,吸水率在58%～60%,灰分0.4g/100g的面粉制作的荞麦馒头品质较好,比较适合制备荞麦馒头预拌粉。     

外源蛋白改良剂对米面团热力学性能及面包品质的影响

以小麦面包为对照,探究大豆分离蛋白、豌豆分离蛋白、玉米醇溶蛋白、乳清浓缩蛋白和蛋清蛋白5种外源植物和动物蛋白质对米面团及面包的混合特性、糊化特性、流变学特性、比容和感官分析的影响。结果表明,加入外源蛋白可以降低米面团的回生值到最小为211 cP,使面包的比容增加至1.810 mL/g,硬度下降约55.3%,胶着性降低至2 710.12 g。其中植物蛋白中添加量为12%的大豆蛋白组面包气孔数量最多,质地细腻且颜色均匀,持水性及感官品质最好。动物蛋白中9%的乳清浓缩蛋白组面包硬度显著下降,约2 032.9 g(P<0.05),此时面团硬度最接近于小麦面团,弹性为0.82%,口感较软,对米面包质构特性改善效果最佳。结论：在植物蛋白中大豆蛋白添加量为12%、动物蛋白中乳清浓缩蛋白添加量为9%的条件下可以改善米面包品质。     

大豆分离蛋白及其改性产物对馒头品质的影响

为研究大豆蛋白及其改性产物对馒头品质的影响,将大豆蛋白以不同比例添加到面粉中,通过研究馒头的质构特性、感官品质、理化特性以及混合粉特性的变化,对比不同大豆蛋白对馒头质量的影响差异。结果表明：与原面粉面团相比,添加1.5%SPI面团的稳定时间延长2.5 min,添加4.5%TSP面团的稳定时间延长1 min;添加1.5%SPH的面团稳定时间约缩短6 min。添加4.5%TSP的面团的面筋指数增大了2.22%,面团持气性增强;添加1.5%SPH的面团持气性减弱。添加1.5%SPI、4.5%TSP可以提高SDS可溶性麦谷蛋白、麦谷蛋白大聚体（GMP）及馒头的水分含量,增加馒头的弹性;而添加1.5%SPH降低了面团中SDS可溶性麦谷蛋白和GMP的含量,馒头弹性减小。结论：通过研究馒头的品质特性,选定SPI、TSP、SPH的添加量分别为1.5%,4.5%,1.5%时馒头品质最佳;经过对每种大豆蛋白最佳添加量的混合粉研究发现,不同种类的大豆蛋白对馒头的物理性质有不同的影响。     

挤压膨化玉米粉对小麦粉面团特性及馒头质构特性的影响

对比研究不同添加量的挤压膨化玉米粉和玉米粉对小麦面团粉质特性、糊化特性以及对馒头质构特性的影响。结果表明:挤压膨化玉米粉添加量增加到25%时,面团吸水率升高6.72%、稳定时间下降82.64%、蛋白质弱化度升高60.78%、形成时间下降88.37%、峰值黏度降低55.60%、低谷黏度降低60.91%、最终黏度降低58.41%、崩解值降低34.07%、回生值降低50.43%;膨化玉米粉添加量为10%时,馒头的弹性、内聚性和回复性最大,硬度显著的低于对照(p<0.05),馒头的口感柔软、筋道,爽口不黏牙,品质最好。玉米粉添加量、面团的粉质特性、糊化特性与馒头的质构特性显著相关,可通过混合粉面团的粉质特性和糊化特性对馒头的质构特性进行预测。与玉米粉相比,挤压膨化玉米粉能够提高面团的吸水率,增强小麦粉的热稳定性,延缓面团的老化,改善了馒头的品质。     

磷脂与食品中蛋白质相互作用机制及对蛋白质特性的影响研究进展

食品中磷脂与蛋白质的相互作用一直是食品领域研究的热点。蛋白质是食品组分中具有重要生理功能的物质,其功能特性和结构的变化对食品品质影响较大。磷脂是一种有效的天然乳化剂,是重要的两性离子表面活性剂,已广泛用于食品加工中。磷脂与蛋白质通过疏水相互作用、氢键等方式结合,进而影响蛋白质的结构和功能特性。本文对食品中大豆蛋白、酪蛋白、乳清蛋白、肌原纤维蛋白等蛋白质与磷脂相互作用机制、影响因素及其对蛋白质功能特性的影响进行综述,以期为磷脂改善蛋白质的功能特性和提高食品品质提供参考。     

酪蛋白和乳清蛋白比例对新鲜干酪品质的影响

通过向原料乳中添加不同比例的乳清浓缩蛋白(WPC80)和牛乳浓缩蛋白(MPC80),研究对新鲜干酪品质的影响,通过测定新鲜干酪和乳清的理化指标及TPA质构和感官评价,确定最佳蛋白质配比。结果表明:酪蛋白和乳清蛋白比例不同,对新鲜干酪的理化指标和TPA质构均有显著影响;2种蛋白质添加比例为1:3时新鲜干酪达到最高感官评分。     

Structural properties of stirred yoghurt as influenced by whey proteins

The effect of whey protein addition on structural properties of stirred yoghurt systems at different protein and fat content was studied using laser diffraction spectroscopy, rheology and confocal laser scanning microscopy (CLSM). The composition of heated milk systems affected micro- and macroscopic properties of yoghurt gels. Particle size increased as a function of increasing whey protein content and decreased as a function of increased fat level. Firmness (elastic modulus) and apparent viscosity of manufactured yoghurt samples increased as a function of increased interparticle interactions, mainly caused by self-aggregation of whey proteins or aggregated whey protein-coated fat globules, respectively. The resistance towards shear-induced disruption of yoghurt gels increased with an increasing proportion of casein protein in the protein mixture, whereas products with high whey protein level revealed lower resistance behaviour towards shear-forces. CLSM images illustrated that the presence of large whey protein aggregates and lower number of fat globules lead to the formation of an interrupted and coarse gel microstructure characterised by large interstitial spaces. The higher the casein fraction and/or the fat level, the less interspaced voids in the network were observed. However, it is evident that the addition of whey proteins reinforces firmness properties of low-fat yoghurts comparable to characteristics of full-fat yoghurt.     

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.     

卡拉胶/大豆11S蛋白共混体系相容性及凝胶性质研究

研究了大豆11S蛋白分别与3种不同荷电量卡拉胶组成共混体系的相容性、热性质、凝胶流变性质及微结构,并探讨了共混凝胶的成胶动力学及机理。结果表明:ι-卡拉胶对大豆11S蛋白的相容性比κ-卡拉胶弱,添加λ-卡拉胶样共混体系更易发生相分离;添加3种卡拉胶均提高了大豆11S蛋白的热变性温度,但降低了热焓值,影响效果依次是λ-卡拉胶﹥ι-卡拉胶﹥κ-卡拉胶;共混凝胶随卡拉胶所带负电荷的增加其弹性模量值呈降低趋势,且凝胶网络结构由蛋白-多糖双连续结构转变为蛋白凝胶网络单连续结构;增加卡拉胶所带负电荷可降低共混凝胶形成过程表观活化能,同时降低了温控程序终点的弹性模量值。     

Effect of minor milk proteins in chymosin separated whey and casein fractions on cheese yield as determined by proteomics and multivariate data analysis

The objective of this work was to find regressions between minor milk proteins or protein fragments in the casein or sweet whey fraction and cheese yield because the effect of major milk proteins was evaluated in a previous study. Proteomic methods involving 2-dimensional gel electrophoresis and mass spectrometry in combination with multivariate data analysis were used to study the effect of variations in milk protein composition in chymosin separated whey and casein fractions on cheese yield. By mass spectrometry, a range of proteins significant for the cheese yield was identified. Among others, a C-terminal fragment of β-casein had a positive effect on the cheese yield expressed as grams of cheese per 100 g of milk, whereas several other minor fragments of β-, α_s1-, and α_s2-casein had positive effects on the transfer of protein from milk to cheese. However, the individual effect of each identified protein was relatively low. Therefore, further studies of the relations between different proteins/peptides in the rennet casein or sweet whey fractions and cheese yield are needed for advanced understanding and prediction of cheese yield.     

Effect of denatured whey protein concentrate and its fractions on cheese composition and rheological properties

The objectives of this study were (1) to assess the effect of a denatured whey protein concentrate (DWPC) and its fractions on cheese yield, composition, and rheological properties, and (2) to separate the direct effect of the DWPC or its fractions on cheese rheological properties from the effect of a concomitant increase in cheese moisture. Semihard cheeses were produced at a laboratory scale, and mechanical properties were characterized by dynamic rheometry. Centrifugation was used to induce a moisture gradient in cheese to separate the direct contribution of the DWPC from the contribution of moisture to cheese mechanical properties. Cheese yield increased and complex modulus (G*) decreased when the DWPC was substituted for milk proteins in milk. For cheeses with the same moisture content, the substitution of denatured whey proteins for milk proteins had no direct effect on rheological parameters. The DWPC was fractionated to evaluate the contribution of its different components (sedimentable aggregates, soluble component, and diffusible component) to cheese yield, composition, and rheological properties. The sedimentable aggregates were primarily responsible for the increase in cheese yield when DWPC was added. Overall, moisture content explained to a large extent the variation in cheese rheological properties depending on the DWPC fraction. However, when the effect of moisture was removed, the addition of the DWPC sedimentable fraction to milk increased cheese complex modulus. Whey protein aggregates were hypothesized to act as active fillers that physically interact with the casein matrix and confer rigidity after pressing.     

高大豆蛋白营养棒原料的选择及其对质构的影响

研究了制作焙烤类高大豆蛋白营养棒最适原料的选择,原料物质添加比例对面团性质和产品质构的影响。结果表明,实验所用三种大豆蛋白制品中,脱脂脱腥豆粉最适宜用来制作焙烤类大豆蛋白营养棒。质构测试结果表明,随着脱脂脱腥豆粉替代传统原料比例的增加,面团的硬度、弹性均呈上升的趋势;结果还表明在其替代饼干粉生产营养棒的过程中,脱脂脱腥豆粉的加入会增加营养棒的硬度;最终在脱脂脱腥豆粉添加量90%,乳清蛋白粉10%时,制得的营养棒感官评分最高,并达到了高蛋白的要求。     

A novel technique for differentiation of proteins in the development of acid gel structure from control and heat treated milk using confocal scanning laser microscopy

The incorporation of caseins and whey proteins into acid gels produced from unheated and heat treated skimmed milk was studied by confocal scanning laser microscopy (CSLM) using fluorescent labelled proteins. Bovine casein micelles were labelled using Alexa Fluor 594, while whey proteins were labelled using Alexa Fluor 488. Samples of the labelled protein solutions were introduced into aliquots of pasteurised skim milk, and skim milk heated to 90 degrees C for 2 min and 95 degrees C for 8 min. The milk was acidified at 40 degrees C to a final pH of 4.4 using 20 g glucono-delta-lactone/l (GDL). The formation of gels was observed with CSLM at two wavelengths (488 nm and 594 nm), and also by visual and rheological methods. In the control milk, as pH decreased distinct casein aggregates appeared, and as further pH reduction occurred, the whey proteins could be seen to coat the casein aggregates. With the heated milks, the gel structure was formed of continuous strands consisting of both casein and whey protein. The formation of the gel network was correlated with an increase in the elastic modulus for all three treatments, in relation to the severity of heat treatment. This model system allows the separate observation of the caseins and whey proteins, and the study of the interactions between the two protein fractions during the formation of the acid gel structure, on a real-time basis. The system could therefore be a valuable tool in the study of structure formation in yoghurt and other dairy protein systems.     

Indicators of non-enzymatic browning in the evaluation of heat damage of ingredient proteins used in manufactured infant formulas

Twelve infant formula ingredients of animal origin (caseinates, whey proteins and hydrolysates of casein and of whey proteins) and three of vegetable origin (soybean proteins) were analyzed. Furosine, hydroxymethylfurfural (HMF) and pyrraline were studied as indicators of thermal damage and available lysine as nutritional indicator, determined by HPLC in phase reverse and UV detector. The objectives were to evaluate heat damage to ingredients used in commercial infant formulas by measuring non-enzymatic browning indicators and to determine the nutritional value of these ingredients by available lysine determination. Very high furosine values were detected in whey proteins, ranging from 354 to 1,435 mg/100 g of protein. Lower furosine values were found in the remaining ingredients, ranging from 1.36 mg/100 g in hydrolyzed casein to 60.5 mg/100 g in sodium caseinate. Available lysine content ranged from 1.85 g/100 g of protein in hydrolyzed casein to 7.91 g/100 g in calcium caseinate. HMF was detected in whey protein samples between 0.16 and 2.47 mg/100 g of protein. Pyrraline was only detected in one sample of whey proteins at 41 mg/100 g of protein. Similar ingredients from different manufacturers show varied heat damage and nutritional values     

Effects of microencapsulated glucose oxidase on wheat flour dough properties and Chinese steamed bread quality

This study was to investigate the effects of microencapsulated glucose oxidase (MGO), in comparison with free glucose oxidase (GO), on wheat flour dough properties and Chinese steamed bread (CSB) quality. Effects on wet gluten (WG) content, farinograms and extensograms properties, dynamic rheological properties, microscopic structure, texture profile and sensory evaluation scores were studied. The results demonstrated that MGO catalysed the oxidation of dough at a much slower speed and exerted relatively great advantages in many aspects such as WG content, extensibility, G′ (Elastic modulus), G″ (viscous modulus), tan δ (equal to G′/G″), microstructure and texture properties and sensory evaluation scores of CSB, compared with free GO. The results suggested that slow oxidation of MGO was superior to free GO based on the improvements of wheat flour dough properties and subsequent CSB quality.