豆浆在凝固过程中的动态流变特性研究

为了研究豆腐的凝固工序,实现豆腐的规格化和标准化生产,本研究对豆浆在凝固过程中的动态流变特性进行了研究,并进行了动力学分析。在凝固温度分别为75℃、80℃、85℃时进行动态时间扫描,得出豆浆的凝固过程由两段一级反应组成且符合连续一级反应模型;第一段反应速率远远大于第二段反应速率;根据弹性模量和黏性模量计算所得活化能分别为19.19×101 k J/mol和8.67×101 k J/mol;当温度小于70℃时,豆浆不能形成豆腐凝胶;当温度在75℃时,弹性模量G'和黏性模量G\"相交,豆浆的凝胶温度为75℃。通过动态温度扫描得出豆浆的凝固过程可分为三个阶段:诱导阶段(65~70℃),弹性模量G'和黏性模量G\"缓慢增大,豆浆体系中有絮状沉淀生成;加速阶段(70~92℃),弹性模量G'和黏性模量G\"急剧增大;稳定阶段(温度大于92℃),弹性模量G'和黏性模量G\"趋于稳定,凝胶反应结束,豆腐凝胶形成。     

糖对牛奶布丁流变性的影响

奉文采用哈克流变仪研究了不同质量分数下几种糖时鲜奶布丁体系的流变学性质,所用的糖质量分数依次为2%、4%、8%和16%,未著淀耢质量分数为6%. 结果表明:牛奶布丁是-种非宾汉塑性流体,测得的剪切速率和相应的剪切应力的关系符合Casson模型. 随着糖质量分数的提高,牛奶布丁的屈服应力、表观黏度和剪切应力均随糖质量分数的增大而增大.     

糖对卡拉胶基斗奶布丁凝胶过程及其动态粘弹性的影响

通过小变形动态振荡测试检测了蔗糖和麦芽糖时卡拉胶基牛奶布丁凝胶过程及动态粘弹性的影响.添加一定浓度的蔗糖(5%～15%)提前了牛奶布丁的凝胶起始点,而更高浓度(20%)则又重新延缓了凝胶起始点;麦芽糖浓度(5%～20%)则对凝胶起始点影响不大.所有的凝胶体中都呈现储能模量G'>耗能模量G",说明凝胶动态模量中弹性的贡献超过了粘性.溶液发生了凝胶化,并形成了三维交联的网络结构,而且随振荡频率f的增加,G'和G"的值都在增加,表明该布丁是介于完全固态与液态之间的粘弹体.随着糖浓度的提高,凝胶粘弹性也较显著提高.     

鸡蛋蛋白质凝胶特性影响因素的研究进展

为了进一步了解不同因素对鸡蛋蛋白质凝胶特性的影响,国内外研究者已经针对性的进行了大量的研究工作.本文综合论述了鸡蛋中蛋白质的组成和凝胶的形成机理,分析了温度、压力、pH、酶、盐、蛋白质浓度、处理时间等因素对鸡蛋蛋白质凝胶特性的影响,其中温度、压力、pH、盐、处理时间几个因素对鸡蛋蛋白质凝胶特性的影响研究已较为全面,但生...     

淀粉对鸡蛋蛋白凝胶特性的影响

研究了几种淀粉对鸡蛋蛋白凝胶特性的影响,着重研究了绿豆淀粉对鸡蛋蛋白凝胶特性的影响,并在此基础上,研制出一种新型的速冻食品-甜蛋。     

3种薯类淀粉的流变与凝胶特性研究

对比了马铃薯、红薯和木薯淀粉的糊化、流变及凝胶特性。当浓度从5%增至10%时,3种薯类淀粉的峰值黏度增加2~7倍。马铃薯淀粉糊的触变性最强;在50~95℃范围内,马铃薯淀粉糊的动态黏弹性高于红薯和木薯淀粉糊。马铃薯淀粉凝胶的硬度和胶黏性最高,红薯淀粉凝胶的弹性最大;3种淀粉的凝胶都呈网络结构,网孔大小为20~350μm;马铃薯淀粉凝胶的网孔轮廓最为清晰紧凑。     

褐藻胶凝胶体系对带鱼鱼糜流变和凝胶特性的影响

为了提高带鱼鱼糜凝胶特性,利用流变仪、质构仪、扫描电镜等方法研究了褐藻胶凝胶体系对带鱼鱼糜流变和凝胶特性的影响。结果表明:带鱼鱼糜在加入褐藻胶凝胶体系后,褐藻胶-鱼糜复合凝胶体系的储能模量G′增大,损耗因子tanδ减小,4h后达到平衡。最终所形成的复合凝胶是一种结构稳定的强凝胶。复合凝胶体系随着温度的升高,G′减小,加热后温度降低,G′增大。褐藻胶浓度越高,复合凝胶体系受温度变化影响越大。添加褐藻胶凝胶体系能够提高带鱼鱼糜的凝胶强度,其中破断强度受褐藻胶浓度的影响非常显著。对添加量进行优化后的结果表明,在褐藻胶添加量为1.56%～1.75%时,复合凝胶体系的凝胶强度和硬度均达到市售A级鱼糜的标准。     

右旋糖酐/蚕豆蛋白复合凝胶的流变特性

为研究乳酸菌右旋糖酐对蚕豆蛋白食品相关性质的影响,采用哈克流变仪和质构仪等测定了添加不同浓度右旋糖酐时GDL诱导的酸致蚕豆蛋白复合凝胶质构和流变特性等指标。结果表明：添加右旋糖酐能显著增加蚕豆蛋白凝胶保水性,空白组蚕豆蛋白凝胶保水性为60.38%,1%右旋糖酐与蚕豆蛋白形成的复合凝胶保水性为70.08%（p<0.05）;右旋糖酐浓度在0.25%~1%之间,对复合蛋白凝胶色泽有一定影响;0.5%右旋糖酐与蚕豆蛋白形成的复合凝胶强度为0.27 N,与空白组蚕豆蛋白凝胶（0.37 N）差异显著,可软化含高蚕豆蛋白食品质构特性;右旋糖酐/蚕豆蛋白复合凝胶流动曲线符合carreau模型（R2>0.99）,具有假塑性流体的特性;应变扫描的弹性模量G''均高于黏性模量G'',说明右旋糖酐/蚕豆蛋白复合凝胶的弹性占主导;频率扫描结果显示添加右旋糖酐可软化蚕豆蛋白凝胶,使凝胶G''、G''降低,更易于加工。在蚕豆食品中添加右旋糖酐可改善蚕豆蛋白的质构和流变特性,为拓展其应用范围提供参考。     

卡拉胶凝胶特性及其在巧克力牛奶中的应用

针对卡拉胶水凝胶的两个主要指标凝胶强度和胶体黏度,研究了卡拉胶含量、钾离子浓度和pH值三个主要因素对卡拉胶水凝胶特性的影响,结果表明:凝胶强度随胶体含量的增加线性增大后渐趋平稳、受钾离子的影响出现峰值、在pH值8.0和10处出现两个拐点;胶液黏度随卡拉胶含量增加迅速增大、随钾离子浓度提高而减小、中性时的黏度最大.通过正交实验确定了影响卡拉胶凝胶因素的主次顺序为卡拉胶浓度、钾离子浓度和溶液的pH值,最佳条件组合为卡拉胶浓度1.2%,钾离子浓度1.2%,pH值9.0;通过考察单独使用卡拉胶以及卡拉胶与魔芋胶、刺槐豆胶及结冷胶等几种食品胶在巧克力牛奶中形成凝胶时的结构状态,判定卡拉胶与刺槐豆胶的协同作用效果最佳.     

鸡蛋松花蛋腌制中蛋白质凝胶特性及颜色变化

以新鲜鸡蛋为原料,采用现代“锌法”腌制工艺加工鸡蛋松花蛋,并分析松花蛋内蛋白质凝胶变性、色差等随腌制时间的变化。结果表明：在腌制过程中,松花蛋内游离碱度、硬度、弹性、咀嚼性等显著上升,蛋白质凝胶能力逐渐降低（P＜0.05）,在腌制28 d后变化趋势逐渐稳定（P＞0.05）;松花蛋在腌制过程中蛋白质分解主要表现在腌制0～14 d,大于86.6 kD的蛋白质逐渐分解;随着松花蛋内碱度的增加,小分子肽类物质（14.3、10 kD）不断累积,蛋清及蛋黄内游离氨基酸含量显著降低（P＜0.05）,在腌制21～28 d后无明显的变化;腌制时间对鸡蛋松花蛋颜色变化有重要的影响,蛋清及蛋黄颜色变化与腌制时间、游离碱度及游离氨基酸含量成显著负相关;主要表现为在腌制过程中L*、b*值变化趋势与a*值变化趋势相反,蛋清及蛋黄整体颜色变化（白度值）趋势成负相关。     

Microstructural changes in casein supramolecules during acidification of skim milk

Pasteurized skim milk was acidified using different levels of glucono-δ-lactone at 10, 20, 30, and 40°C to give slow, medium, and fast rates of acidification. Milk coagulation was monitored by measuring turbidity and curd firmness, and microstructural changes during acidification were observed on glutaraldehyde-fixed, agar-solidified milk samples using transmission electron microscopy. Rate of acidification had little influence on changes observed during acidification, except at 10°C. At 40°C, the casein supramolecules were spherical throughout acidification, whereas at lower temperatures they became progressively more ragged in appearance. All of the milks gelled at the same pH (pH 4.8), as measured by curd firmness, whereas increases in turbidity, assumed to be brought about by an increase in number of light-scattering particles, were observed to start at about pH 5.2 to 5.4. As the milk was acidified, aggregates of loosely entangled proteins were observed, presumably originating from proteins that had dissociated from the casein supramolecules. These aggregates were often as large as the casein supramolecules, particularly as the pH of the milk approached the isoelectric point of the caseins. Larger aggregates were observed at 40°C than at the lower temperatures, suggesting the involvement of hydrophobic interactions between the proteins. A 3-phase model for acid-induced gelation of milk is proposed in which the first phase involves temperature-dependent dissociation of proteins from the casein supramolecules, with more dissociation occurring as temperature is decreased. Dissociation continues as milk pH is lowered, with the released proteins forming into loosely entangled aggregates, some as large as the casein supramolecules. The second phase of acid gelation of milk occurs between pH 5.3 and pH 4.9 and involves a reassociation of proteins with loosely entangled protein aggregates forming into more-compact colloidal particles or combining with any remaining casein supramolecules. The third and final phase involves rapid aggregation of the colloidal casein supramolecules into a gel network at about pH 4.8. Different gel structures were formed based on temperature of acidification, with a coarse-stranded gel network formed at 40°C and a fine-stranded gel network at 10°C.     

Effect of pH on the gelation properties of skim milk gels made from plant coagulants and chymosin

The effect of three milk pH values, 6.0, 6.3 and 6.7, on gelation properties was monitored by small amplitude oscillatory rheology as well as a large deformation (yield) test for gels induced by the plant coagulants, Cynara cardunculus L. and Cynara humilis L., and chymosin. Gel microstructure was studied using confocal scanning laser microscopy. For each coagulant, a decrease in pH of milk resulted in a decrease in gelation time (tg), and an increase in the rate of increase in storage modulus (G'). At pH 6.0 and 6.3, plant coagulant-induced gels reached a maximum value in G' (G'max) followed by a decrease in G' values during the rest of the experiment, reflecting higher proteolytic activity of plant coagulants towards caseins as determined by SDS-PAGE. Gels produced at pH 6.0 and 6.3, exhibited a minimum in loss tangent (tan delta) followed by slight increase in tan delta during gel aging, that may have been associated with faster rearrangements of the gel network structure. In gels aged for approximately 6 h, the values for G', tan delta at low frequency (0.006 Hz) and yield stress were higher for chymosin than for plant-induced gels. For gels with the same pH value, no major differences were observed in microstructure between coagulants. Gels made at low pH values (6.3 and 6.0) appeared to have a denser or more interconnected structure than gels made at pH 6.7. Our results suggest that, at a low pH, the type of coagulant used in gelation is likely to have a considerably impact on gel/cheese structure.     

无糖布丁牛奶的研制开发

无糖布丁牛奶是以新鲜牛乳为主要原料，通过添加木糖醇、卡拉胶、天然玉米淀粉以及一些相应的风味料（如咖啡、可可粉等），研制成的一种营养丰富、风味独特的新型低热量乳制品。本文通过L9（34）正交试验，得到了合理、可行的产品配方、生产工艺和产品质量控制指标。试验结果表明：鲜牛奶添加量为90％。天然玉米淀粉添加量为5％，木糖醇添加量为10％，卡拉胶添加量为0．2％时布丁牛奶的风味、口感等各项指标最佳。     

Effect of salt content on gelation of normal and wooden breast myopathy chicken pectoralis major meat batters

This study investigated the effects of salt content (0–4%) on water holding capacity (WHC), textural characteristics, rheological properties, and microstructure of cooked normal (NOR) and wooden breast (WB) chicken meat batters. Results indicated with 0–2% salt addition, the WB batters had significantly lower WHC and storage modulus (G’) compared with the NORs (P < 0.05). However, these differences were eliminated when salt contents were increased to 3% or 4%. In addition, the NORs formed more regular and pored networks than the WBs (0–2%). Salt level significantly affected the textural properties of both batter types (P < 0.05). The hardness of the WB batters was lower than NORs at all NaCl levels (P < 0.05). Overall, compared with NORs, the WB batters showed inferior gelation properties at salt contents of 0–2%, while increasing salt content to 3–4% can improve the WHC and microstructure of gels.     

肌原纤维蛋白与脂肪替代品混合样品流变特性研究

以鸡胸肉为原料提取肌原纤维蛋白(MP),采用流变仪,研究MP与脂肪替代品(FS)的质量浓度比、pH值以及离子强度等因素对MP-FS混合样品流变特性的影响.在单因素试验的基础上,以储能模量G '为响应值,采用响应面Box-Behnken试验研究MP与FS质量浓度比、pH值以及离子强度对G '的影响.结果表明:各因素影响混合样品凝胶G’的顺序为:pH＞MP与FS质量浓度比＞离子强度,MP与FS质量浓度比20∶10、pH6.0、离子强度0.6时,G’取得最佳值153Pa.     

不同漂洗处理后冻藏对鲤鱼蛋白功能特性的影响

蛋白质氧化是引起食品加工及贮藏过程中品质发生劣变的一个主要原因。本文以鲤鱼肉为研究对象,主要研究鱼糜加工过程中经不同漂洗处理后冻藏对鲤鱼肌原纤维蛋白功能特性的影响。把鱼肉经不同方式漂洗[未漂洗;传统漂洗;添加抗坏血酸钠漂洗;添加没食子酸丙酯(PG)漂洗]后置于-25℃,经不同时间(0、30、60、90、120 d)冷冻贮藏后,利用质构仪、电子显微镜、流变仪等设备对鲤鱼肌原纤维蛋白乳化性、凝胶性以及流变性等指标进行测定,结果表明冻藏过程中发生的蛋白质氧化会引起鲤鱼肌原纤维蛋白各项功能特性降低,在漂洗过程中加入PG处理的鱼肉功能特性改变最小,说明添加PG漂洗可以有效地抑制蛋白质氧化的发生,从而减少鲤鱼肌原纤维蛋白功能特性的改变。     

乳蛋白体系流变学研究进展

乳蛋白体系的流变学特性与乳制品的质构和生产工艺关系密切。近年来,基于乳蛋白组分在食品中的重要性,食品科学家对乳蛋白体系的流变学性质进行了深入研究。文章就乳清蛋白和酪蛋白的凝胶特性以及乳清蛋白溶液的粘度流变特性作了介绍。