EFFECT OF ADDED SALT ON TEXTURAL PROPERTIES OF HEAT-INDUCED GELS MADE FROM GUM–PROTEIN MIXTURES

Large deformation rheological tests were employed to determine the textural differences in heat‐induced gel systems. Three different large deformation rheological methods (viscosity index and apparent elasticity, texture profile analysis (TPA) and torsional fracture) were employed to study the dependence of the ion type on the textural properties of heat‐induced mixed protein–gum gels. Protein–gum mixed solutions were prepared with bovine serum albumin (BSA) or egg white albumin (EWA) (20% w/v) with κ‐carrageenan (KCG), gellan (GLN) or xanthan gums (XNT) (0.5% w/v) at 0.1 M sodium chloride (NaCl), potassium chloride (KCl) or no added salt. Despite inherent differences in protein type, the main effect on the textural properties evaluated was for the kind of salt added, since potassium ions, with a strong influence on KCG and GLN gelation, affected the parameters related to the structure or hardness of the samples. There was no significant effect on parameters associated with sample ductility or elasticity. GLN formed stronger gels than KCG, whereas XNT did not perform as well in gel formation since it does not contribute to protein matrix formation. The results indicated that potassium may be substituted for sodium ions at low ionic strengths in foods where the incorporation of KCG or GLN helps to improve texture and related features.     

EFFECT OF DE-ESTERIFICATION ON THE RHEOLOGICAL PROPERTIES OF κ-CARRAGEENAN GELS

The effect of de-esterification on the rheological properties of κ-carrageenan gels was studied by stress relaxation and dynamic mechanical measurements. By means of de-esterification, the elastic modulus of κ-carrageenan gels increased. This was attributed to the increase of alternation of D-galactose and 3,6-anhydro-D-galactose, and then the stabilization of the double helical structure in the κ-carrageenan gels.     

κ-卡拉胶对大豆分离蛋白乳浊凝胶特性的影响

研究了κ 卡拉胶在不同pH的条件下对大豆分离蛋白乳浊凝胶质构特性和流变特性的影响。研究结果表明 ,pH 7 3条件下的乳浊体系比 pH 6 8的体系更易形成凝胶。卡拉胶质量分数为 0 0 5 %时 ,因与大豆分离蛋白发生静电吸引相互作用形成连接型凝胶而显著提高了凝胶的质构特性和流变特性。 0 2 %时则形成相分离型凝胶 ,降低了凝胶的弹性和内聚性。     

EFFECT OF ALKALI METAL IONS ON THE RHEOLOGICAL PROPERTIES OF κ-CARRAGEENAN AND AGAROSE GELS

Stress relaxation and dynamic measurements were carried out on κ-carrageenan and agarose gels to examine the effect of alkali metal ions. The elastic modulus of κ-carrageenan gels increase remarkably by adding alkali metal ions Li⁺, Na⁺, K⁺, Cs⁺. This was explained as follows: the electrostatic repulsion of sulfate groups in κ-carrageenan gels are prevented by the shielding action of the alkali metal ions stabilizing the double helical structure of κ-carrageenan gels. The increase of the modulus was in the order: Cs⁺ > K⁺≫ Na⁺ > Li⁺. The difference between these two groups (Cs⁺, K⁺) and (Na⁺, Li⁺) is that the former group belongs to the structure disordering ions while the latter group belongs to the structure ordering ions. Thus, the former group prevents the repulsion of sulfate groups more directly than the latter. Agarose gel, which lacks sulfate groups, is not influenced so much by adding the alkali metal ions.     

全脂大豆蛋白对面条品质影响的探讨

通过在面粉中添加不同比例的全脂大豆蛋白，探讨了其对蛋白质品质、面团流变学特性、面条色泽、断条率、咀嚼感、爽口感及面条蒸煮品质和感官品质的影响。结果表明，在面粉中加入8％的全脂大豆蛋白可显著提高面粉的蛋白含量和湿面筋含量，改善了面团的流变学特性及面条的韧性和口感，既增加了面条营养价值，又提高了面条的质量和加工性能。     

POY内在质量对其后加工性能的影响

本文针对台湾东云ＰＯＹ的后加工性能较国产ＰＯＹ好这一现象,对它们的羧基含量、二甘醇含量、分子量分布及强伸均匀性、热性能、结晶与取向进行了一系列测试,结果表明其羧基含量、二甘醇含量、分子量分布具有较大的差异,同时其热性能有一定的差异,强伸均匀性差异亦较为明显,这些差异可能是国产ＰＯＹ后加工性能较台湾东云ＰＯＹ差的重要原因。     

EFFECT OF SUCROSE ON THE MECHANICAL AND ACOUSTIC PROPERTIES OF FREEZE‐DRIED AGAR,K‐CARRAGEENAN AND GELLAN GELS1

Agar, K‐carrageenan and gellan gels (2%) with and without infused sucrose (5, 10 and 12.5%) were freeze dried and the mechanical and acoustic signatures of the resulting solid sponges recorded. For comparison, agar gels with 5 and 10% starch were also prepared and likewise tested. The presence of the sugar, or starch, in the dried gels increased their density in a manner that could not be predicted from the corresponding stoichiometric relations between the gum and additive indicating that the sugar, or starch, were not inert fillers. In general, the presence of the sucrose in the dried gel solid matrix increased the brittleness of the sponges. The effect could be quantified in terms of the increase in the mechanical signature's apparent fractal dimension (Richardson's and Kolmogorov's). The more brittle dried gels also had a “richer” acoustic signature whose apparent fractal dimension was determined with the “blanket” algorithm. Despite the irregular and jagged appearance of all the dry gels stress‐strain relationships, they could be described by the same kind of a three parameter empirical model originally derived for soft baked products and polymeric foams. Although the added sugar, or starch, stiffened the dehydrated gels the effect could not be quantified unambiguously because of the differences in the density and in the overall shape of the stress‐strain curve.     

不同测定方法对大豆分离蛋白乳化性测定结果的影响

采用离心法、分光光度法、电导法对几种不同的大豆分离蛋白的乳化性进行测定，测定结果表明，采用不同方法测定四种大豆分离蛋白的乳化性，其总的趋势基本相同，说明这几种方法都可用于测定大豆分离蛋白的乳化性。相对而言，离心法简单可行，是一种比较适用的方法，其它两种方法仪器设备要求较高，且操作步骤比较繁琐。     

十二烷基硫酸钠对盐酸的标准热力学性质的影响

本文测定了Pt,H_2(1.01325×10~5Pa)|HCI(m) SDS H_2O|AgCI-Ag电池的电动势,应用最小二乘法确定了标准电动势E和E随温度变化的关系式。依据热力学函数关系式,求出HCI在十二烷基硫酸钠(SDS)溶液中处于标准状态和在纯水中处于标准状态时,诸热力学函数的差值,即△G_t、△H_t和△S_t之值。结果表明△G_t均为负值,△H_t和△S_t均为正值。     

大豆蛋白改性粘胶纤维力学性能研究

对大豆蛋白改性粘胶纤维作了力学性能的研究与分析.通过对大豆蛋白改性粘胶纤维与普通粘胶纤维作对比, 分别在干态、湿态下测定其强伸性能进而分析其性能.不同加持方式的拉伸试验得出加持方式对纤维性能影响也很大.对大豆蛋白改性粘胶纤维在不同应变下的松弛性能作了一定探讨并采用origin对其拟合分析.     

螺旋藻蛋白质浓缩物的制备及其功能特性的研究

本文研究了螺旋藻蛋白质浓缩物制备工艺条件,并对螺旋藻粉及其蛋白质浓缩物蛋白质质量及其功能特性进行了比较研究,初步结论为:浓缩物的氨基酸含量及组成较螺旋藻粉有很大提高;浓缩物的水吸附能力较螺旋藻粉为差,而脂肪吸附能力、乳化能力和起泡能力均优于原藻粉。     

凝固条件对再生蛋白/PVA共混纤维形貌与性能的影响

以再生动物蛋白/聚乙烯醇(PVA)为成纤聚合物湿法纺丝制备再生蛋白质纤维。研究凝固条件对纤维性能及形貌的影响。结果表明:较高的浓度和适当降低温度有利于形成物理机械性能良好的纤维,制得的纤维强度为3.49 cN/dtex,伸长率为8.6%。     

EFFECT OF TYPE AND LEVEL OF STARTER CULTURE ON THE RHEOLOGICAL PROPERTIES OF SET YOGURT DURING GELATION PROCESS

The effect of type and level (2, 3, 5%) of starter cultures on the rheological properties of set yogurt during gelation process was studied using a cylindrical rotational viscometer. At the beginning of the gelation process the viscosity was constant after which the viscosity rose rapidly and reached a maximum value and then gradually decreased. The results indicate that the starter type and level have a definite effect on yogurt viscosity during gelation process. The Ostwald-de Waele power-law model was used to characterize the flow behavior of the curd.     

ENZYMATIC HYDROLYSIS OF DEFATTED WHEAT GERM BY PROTEASES AND THE EFFECT ON THE FUNCTIONAL PROPERTIES OF RESULTING PROTEIN HYDROLYSATES

Endogenous enzymes of wheat germ were inactivated by heating for 15 min at 105C in an oven. The germ was defatted using supercritical carbon dioxide, smashed and solubilized by enzymatic hydrolysis. The enzyme hydrolysate was continuously stirred under conditions of optimum hydrolysis and centrifuged. Defatted wheat germ protein (DWGP) was obtained when the supernatant was spray‐dried. The enzymes were used to enhance the solubilization of protein so as to increase the yield of DWGP. Alcalase and flavourzyme® solubilized 85 and 80% of the protein, respectively, while papain, neutrase and protamex solubilized 73, 66 and 61%, respectively. The functional properties of DWGP solubilized using alcalase were as follows: nitrogen solubility, 74% at pH 6; emulsifying activity, capacity and stability were 64, 62 and 57%, respectively. Water retention of DWGP solubilized using alcalase was 232% at pH 7 and temperature of 70C. DWGP is a potential source of functional protein for possible food applications.