碱性蛋白酶水解劣质干酪素制备酪蛋白磷酸肽的研究

本实验采用一种微生物酶碱性蛋白酶2709水解劣质干酪素制备酪蛋白磷酸肽(CPPs),采用正交实验优化其水解条件,得出了其最佳水解条件为底物浓度15%,酶浓度800u/g,pH9.0,温度55,时间2.5h.。其N/P为4.371,产率为12.88%。     

猪肉肠中亚麻籽胶、大豆分离蛋白、酪蛋白的相互作用研究

研究猪肉肠中亚麻籽胶、大豆分离蛋白和酪蛋白的相互作用。采用析因试验设计,在猪肉肠加工过程中,同时添加不同质量分数的亚麻籽胶、大豆分离蛋白和酪蛋白,分析上述添加物对产品保水性、保油性的影响。结果显示：添加亚麻籽胶对猪肉肠在60℃条件下烘20min的保水能力有极显著的影响(P＜0.01),然而,亚麻籽胶对猪肉肠在60℃条件下烘40min的保水能力没有显著的影响(P＞0.05)。酪蛋白的添加对猪肉肠在60℃条件下烘20min和40min的保水能力有显著的影响(P＜0.05)。保水能力上,从高到低依次为：酪蛋白、亚麻籽胶、大豆分离蛋白。亚麻籽胶的添加显著地影响了用乙醚浸提20、40、60min猪肉肠的保油性(P＜0.05),大豆分离蛋白和酪蛋白也有类似结果。大豆分离蛋白对猪肉肠用乙醚浸提60min的保油性有极显著性影响(P＜0.01),并且,亚麻籽胶与大豆分离蛋白有显著的交互作用(P＜0.05)。在保油能力上,大豆分离蛋白强于酪蛋白。     

Effect of SDS on Casein Micelles: SDS-Induced Milk Gel Formation

ABSTRACT: The addition of sodium dodecyl sulfate (SDS) during skim-milk reconstitution contributed to a modification of hydrophobic interactions and, consequently, to change in the micellar structure. SDS-induced modifications in casein micelles were investigated by biochemical measurements (soluble mineral and protein analyses, granulometric and electrokinetic potential measurements, and casein micelle solvation). SDS induced micellar κ-casein dissociation and caused a decrease in steric, hydration, and electrostatic repulsive forces between casein micelles and as a result altered micellar stability. Consequently, SDS-modified micelle aggregation occurred. Mineral analysis indicated that Ca, PO₄^3- and Mg partitioning between aqueous phase and curd is similar, suggesting a possible bridging mechanism via minerals and SDS molecules.     

等温滴定量热法探索酪蛋白磷酸肽单体与不同钙盐的相互作用

本研究探讨了在模拟小肠末端环境下酪蛋白磷酸肽（β-casein phosphopeptides(1-25),简称CPP）与不同钙盐的相互作用情况。实验以等温滴定量热仪为方法,以热力学参数、化学计量数及亲和力常数为指标,评价不同钙盐与CPP的相互作用情况。结果表明,CPP与不同钙盐两两相互作用,且均为由熵驱动的自发反应（pH 8.0,37 ℃）,该反应的主要推动力为离子相互作用力。不同钙盐与CPP反应时,焓变,熵变及自由能无明显差别（p>0.05）,而化学计量数和亲和力常数存在显著性差异（p<0.05）。CPP与葡萄糖酸钙,乳酸钙和氯化钙相互作用时,化学计量数较高（3~4 mol/mol）,而与天冬氨酸钙结合的化学计量数较低（2~3 mol/mol）。此外,相比其他钙盐,乳酸钙与CPP结合的亲和力常数最低。多肽与钙盐结合数高且亲和力较低时有利于小肠对钙的吸收。因此,相对于其他钙盐,CPP与乳酸钙结合可能更有利于小肠对钙的吸收。本研究为更好地了解CPP与不同钙盐溶液在模拟小肠末端环境下的热力学变化及结合情况奠定坚实的基础。     

Paramyosin-Myosin-Actin Interactions in Gel Formation of Invertebrate Muscle

Even when actomyosin dissociated into myosin and actin in the paramyosin-natural actomyosin system, the indices of gel properties increased on increasing the paramyosin content; however, their increases were smaller. Also, in the paramyosin-myosin system gels, the indices of gel properties increased on increasing the paramyosin content; however, the increases were smaller than those for the paramyosin-natural actomyosin system gels. In both systems, a high linearity was observed between each index of gel properties and paramyosin. It was likely that the paramyosin-myosin interaction did not bring about the characteristic texture of invertebrate muscle gel directly, but the binding of myosin and actin might be indispensable if the contribution of paramyosin was to occur.     

Adsorption of Positively-Charged β-Lactoglobulin Derivatives to Casein Micelles

Positively-charged β-lactoglobulin derivatives prepared by amidation or esterification of available carboxyl groups of the native protein were bound strongly by casein micelles. Increasing amounts of these additives progressively decreased rennet coagulation time of casein micelles. Higher concentrations of positively-charged proteins coagulated casein micelles without addition of rennet extract. Of the modified proteins tested, approximately 1.0 g amidated β-lactoglobulin, 2.0 g ethyl-esterified β-lactoglobulin, or 1.0 g methyl-esterified β-lactoglobulin would be required to coagulate 100 ml of casein micelles at concentrations in milk.     

Lactobacillus helveticus 9的酪蛋白水解作用研究

基于酪蛋白水解度和多肽含量数据,研究了两株瑞士乳杆菌(L.helveticus 9和L.helveticus 6)与酪蛋白共培养后的蛋白水解效果,菌株L helveticus 9蛋白水解活性显著高于菌株L.helveticus 6.在不同发酵时间下,菌株L.helveticus 9对酪蛋白的水解作用随时问延长而逐渐递增,培养48h时酪蛋白的水解度可达17.3%,多肽含量达到0.62mg/ml:SDS-PAGE分析和Sephadex G-25层析鉴定表明,酪蛋白水解产物多肽含量随培养时间延长而增加.显然,具有较高蛋白水解活力的菌株L.helveticus 9可以用于从酪蛋白中来制备潜在的生物活性肽.     

牛奶纤维——21世纪的生态纤维材料

近年来发达国家大量废弃的服装已造成环境污染 ,研制新型“绿色”生态纺织品已成为人们的迫切需要。为了解决纺织品生态环保问题 ,一些国家投入了大量的科研经费和人力进行绿色纺织品的研究开发。如目前国内外市场上已经和正在出现的众多的绿色纺织品 ,他们采用的是生产过程无污染的纤维 ,像Ｔｅｎｃｅｌ纤维、牛奶纤维、甲壳素纤维、罗布麻纤维、木浆纤维、竹纤维、豆饼纤维、玉米纤维、天然彩色棉纤维以及有机天然纤维 (指一种作物不论什么化学品都不应当接触它 ,不仅如此 ,而且有待种植这种作物的田地在种植前至少应有 3年未施用化学品而…     

酪蛋白改性

综述了酪蛋白的化学及酶法改性的方法,通过改性可以提高酪蛋白的功能性质和营养价值,从而扩大其在食品中的用途。     

Effects of Iron Source on Iron Availability from Casein and Casein Phosphopeptides

ABSTRACT: :
Iron availability from FeSO₄ in samples containing sodium caseinate (SC), casein phosphopeptides (CPP) or whey protein concentrate (WPC), and from ferric citrate (Fe-CA) in samples containing SC or CPP was measured using an in vitro digestion/Caco-2 cell culture model. In FeSO₄ spiked samples, relative availability was CPP > SC, CPP = WPC, and CPP = FeSO₄ alone. In samples containing Fe-CA, a soluble iron chelate, relative availability was CPP = SC and CPP < Fe-CA alone. These results suggest that CPP enhances iron availability from foods with low availability but does not improve and may inhibit availability from soluble iron species.     

Contribution of Protein Flexibility to the Foaming Properties of Casein

The effect of biopolymer flexibility on the foaming properties of casein was investigated. Flexibility was altered by: (1) chemical modification (covalent binding of a monosaccharide on the lysyl residues) or (2) pH change. Electron Spin Resonance was used to measure the reorientational frequency of casein residues labeled with nitroxide radicals. High levels of glycosylation induced increased protein flexibility and improved the foaming capacity. Good agreement was observed between higher values of flexibility and improved surface properties near the isoelectric point.     

酶凝干酪素凝胶性研究进展及其在干酪中的应用

介绍酶凝干酪素凝胶形成机理和冷却机制研究进展,概述乳化盐、蛋白和脂肪、pH 值、温度、钙离子对凝胶形成的影响：乳化盐能促进蛋白质溶解形成凝胶,蛋白和脂肪含量可对凝胶的复合模量和黏弹性产生影响,适当的温度和pH 值条件能形成良好的凝胶结构,钙离子增加对凝胶形成不利,以及酶凝干酪素在加工干酪中的应用。     

Association of Triclosan to Casein Proteins Through Solvent-Mediated High-Pressure Homogenization

ABSTRACT:  The association of triclosan (TCS), a widely used hydrophobic compound, to the bovine casein micelle is investigated in this study. The use of high-pressure homogenization (HPH) at 0, 100, 200, and 300 MPa was introduced as a method for the dissociation of casein micelles in a skim milk/ethanol solution (1: 1, v/v) in the presence of TCS at 20, 80, and 160 mg/L where ethanol evaporation served as the final step for TCS association to caseins. The majority of TCS (over 80%) was associated with the caseins regardless of initial TCS concentration or applied pressure. TCS association to caseins was enhanced by 30% with continued pressurization to 300 MPa. Micellar dissociation and reassociation was found to be an irreversible process as evidenced by microscopy images. Pressurization to 300 MPa resulted in the formation of an integrated protein network of casein proteins and noncovalently linked whey proteins where the solubility of TCS was enhanced up to 40 times its reported water solubility at the highest initial TCS level of 160 mg/L. Reformed micelles exhibited Newtonian flow behavior at all pressure levels. This study provides evidence for the solubility enhancing quality of TCS through the solvent-mediated pressure/shear-induced dissociation of casein proteins.     

辣木凝乳酶水解酪蛋白位点及其酪蛋白磷酸肽、酪蛋白糖巨肽

基于十二烷基硫酸钠-聚丙烯酰胺凝胶电泳,液相色谱-串联质谱法研究辣木凝乳酶对酪蛋白的酶切位点和水解特性,并分析该凝乳酶水解产生的酪蛋白糖巨肽和酪蛋白磷酸肽.结果表明,辣木凝乳酶酶切κ-酪蛋白的Arg 93-His 94位点导致凝乳,区别于其他已报道的凝乳酶,具有明显特异性.酶作用下κ-酪蛋白的米氏常数Km=0.49 m...     

牛乳酪蛋白的人乳化改性研究

由于牛乳酪蛋白不易为婴儿消化吸收，通过对牛乳酪蛋白人乳化改性的研究，即运用犊牛皱胃酶的作用，减少牛乳α＿ｓ＿１－酪蛋白的量，使β－酪蛋白与α＿ｓ＿１－酪蛋白的比例由原来的０．７提高到３．ｏ以上，从而接近了人乳的消化吸收性。经人乳化改性后的牛乳可适用于新生婴儿配方乳的制造。     

Pulse NMR of Casein Dispersions

The spin-spin relaxation time, T₂, of skimmilk, sodium caseinate dispersions and milk ultrafiltrate was measured as a function of pH and temperature using pulse proton NMR. The T₂ shows a maximum around pH = 5.2 for skimmilk, decreases with decreasing pH for sodium caseinate dispersions and is independent of pH for milk ultrafiltrate. For all systems studied T₂ increases with temperature, but, the extent of increase depends on the system. It is concluded that the T₂ of casein dispersions is mainly determined by factors determining the state of aggregation of the caseins. Apart from affecting the extent of aggregation of the casein particles, micellar calcium phosphate probably contributes also directly to the measured T₂.     

添加酪蛋白水解肽改善酸乳的加工特性

向牛乳中添加不同含量菠萝蛋白酶酪蛋白水解肽（0.1%、0.3%、0.5%）,测定酸乳发酵及冷藏过程中理化、微生物和风味指标变化。结果表明,添加酪蛋白水解肽（casein hydrolytic peptides,CHP）加快了酸乳发酵后期pH值下降,缩短发酵时间;CHP添加量为0.1%时发酵时间较对照组缩短了34 min。微流变测定表明,添加CHP降低了发酵后期酸乳的弹性指数（elasticity index,EI）和流动性指数（fluidity index,FI）,但宏观黏度指数（macroscopic viscosity index,MVI）有所升高。扫描电镜图像显示,各组酸乳样品均呈多孔网状结构,适量添加CHP（0.1%）可以改善酸乳的胶体结构,使酸乳网络结构更致密均匀。酸乳冷藏期间,添加CHP可以提高发酵剂菌株的活菌数,一定程度地促进酸类、醛类和酮类等风味化合物的形成,添加0.3%的CHP降低了酸乳EI;随着CHP添加量的增加（0.3%、0.5%）,酸乳的硬度及胶着性逐渐下降,但对持水力、内聚性及黏性无明显影响。本研究为CHP在酸乳加工中的应用及产品品质和功能性提升提供技术参考。