酪素的改性及改性产品的性能

本文选用不同的单体及配比对酪素进行了改性。研究了反应条件、单体种类和单体的配比对改性产品的质量影响。同时，对改性酪素的成膜性能、涂饰应用性能进行了研究。结果表明：通过对酪素改性，提高了其成膜性能，得到了软性和硬性酪素产品。改性酪素应用于猪服装革的涂饰，涂层耐干、湿擦及耐折牢度均达到要求。     

改性酪素涂饰剂的研究现状

本文总结了酪素成膜剂的优缺点，探讨了由于制革工业的需要而对酪素进行改性的物理方法和化学方法，详细论述了对酪素涂饰剂进行化学改性的研究进展、在皮革涂饰巾的应用及其牛物可降解性，并展望了改性酪素涂饰剂在制革工业中的应用前景。     

聚氨酯改性酪素皮革涂饰剂的研究

本文论述了以聚氨酯改性酪素的原理和工艺条件。酪素是古典皮革涂饰材料，虽然具有光亮的涂膜及良好的透水汽性、耐高温性，但涂层耐湿擦和耐曲挠性较差，经过聚氨酯改性后，不仅保留了酪素涂饰剂的特点，而且耐干、湿擦可达到５级，明显提高涂饰效果。     

酪素接枝改性的研究现状

从酪素的物理化学性质、接枝改性的原因及方法、接枝共聚引发体系、接枝共聚反应机理等方面,对酪素的接枝改性进行了阐述,重点介绍了两步单电子转移反应机理和三步配位聚合反应机理,并就酪素接枝改性后在皮革涂饰方面的应用给予了展望。     

关于酪素成膜材料的化学改性方法探讨

本文探讨了皮革涂饰用酪素的化学改性方法以及国内外的研究进展。     

聚氨酯性酪素皮革涂饰剂的研究

本文论述了以聚氨酯改性酪素原理和工艺条件。酪系是古典涂饰材料，虽然具有有光亮的涂膜及良好的不汽性，耐高温性，但涂层耐湿擦和耐曲挠性较差，经过聚氨酯改性后，不仅保留了酪素涂饰剂的特点，而且耐干，湿擦可达到５级，明显提高涂饰效果。     

聚氨酯改性酪素的研究

本论文叙述了用聚氨酯对酪素进行接枝改性的研究。采用正交试验法研究了各反应因素对接枝共聚反应的影响,找出了较为理想的合成工艺。测定了接枝效率,并用红外光谱验证了反应的发生,浅析了反应机理。以酪素,及礤改性产品进行了对比涂饰试验,结果表明该改性酪素产品即保持了天然酪素涂饰的优点,又在一定程度上改进了其耐湿擦牢度和耐曲挠性。     

纳米TiO2改性明胶在合成革后整理中的应用

采用原位有机-无机杂化技术将纳米TiO2引入明胶体系,制备了纳米TiO2的改性蛋白材料,通过扫描电镜(SEM)发现,原位生成的TiO2颗粒直径都在100 nm左右,相对未经改性的明胶具有良好的耐热稳定性.将改性明胶应用于合成革的后整理中,且与传统酪素涂饰的成革在透湿性、表面接触角和抗菌性能等方面的比较研究,结果表明:加入改性明胶涂饰后的成革的透湿性与酪素涂饰后的成革相当;并且由于改性明胶亲水基团的增加,表面接触角与酪素的相当,降低了表面张力,改善了再涂性;经改性明胶涂饰后的合成革还具有良好的抗菌性,这是酪素所不具备的.充分说明改性明胶可以取代酪素在合成革后整理中的应用.另外,改性明胶价格低廉、易于制备,这对促进行业技术进步,提高企业经济效益都有积极的意义.     

聚氨酯改性酪素皮革涂饰剂的制备与应用

本文提出了NaHSO3封闭-NCO基的聚氨酯改性酪素皮革涂饰剂.在加热过程中,热解闭聚氨酯释放出-NCO基与酪素中的活泼氢反应,显著地提高了酪素的耐水性、耐曲挠性,并在多种鞋面革中进行了应用试验.     

有机硅改性酪素皮革涂饰剂的合成与应用

本文提出了用含端基氮丙环(-N CH2 CH2）的有机硅氧烷与酪素结构中的氨基(-NH2)、羧基(-COOH)反应，提高改性酪素的耐水、耐曲挠、耐摩擦等综合性能的新方法，该改性产品在多种鞋面革中进行了涂饰实验。     

皮革涂饰用酪素及其改性产品

本文论述了酪素的基本性质及其改性方法,交例举一个用乙烯基单体改性酪素的实例。     

牦牛与奶牛酪蛋白制备CPPs的酶工艺优化及其离子交换纯化研究

优化了以牦牛酪蛋白与奶牛酪蛋白为原料酶法制备酪蛋白磷酸肽（CPPs）的工艺条件，并评估了离子交换对CPPs粗制品的纯化效果。结果表明，牦牛酪蛋白与奶牛酪蛋白的产率最优化条件以及氮磷比r（N／P）最优化的酶解工艺条件均基本一致，产率最大的胰蛋白酶酶解工艺条件为：底物浓度13．1％，酶解反应时间104min，酶底物浓度比0．9％；r（N／P）最优（小）的酶解工艺条件为：底物浓度7．6％，酶解反应时间155min，酶底物浓度比1．2％。牦牛及奶牛CPPs粗制品经过阴离子交换树脂纯化后，所获得的精制CPPs其，（N／P）均明显降低，对于CPPs的产率最优样品其，（N／P）由原来的12．2～12．4降低到6．3～6．9；对于r（N／P）最优样品，其r（N／P）由原来的9．90～0．95进一步降低至5．6～5．8。研究表明：无论以产率或制品质量为优化指标，牦牛与奶牛酪蛋白的酶解工艺优化条件基本一致。而且利用阴离子交换树脂处理可以有效地降低CPPs粗制品的r（N／P）、提高制品的质量。     

酪蛋白水解物替代乳清蛋白的加工性能评价研究

利用复合蛋白酶水解酪蛋白制备适度及深度水解酪蛋白产品,测定酪蛋白水解物的加工性能。结果表明,经过酶解后,适度水解酪蛋白溶解度接近90%,深度水解酪蛋白溶解度接近100%,显著高于酪蛋白和乳清蛋白。此外,适度水解酪蛋白吸油性、起泡性分别约为乳清蛋白的3倍和1.5倍。深度水解酪蛋白在起泡性和乳化性上也显著高于乳清蛋白。可见,两款酪蛋白水解物在起泡性、乳化性、吸油性、溶解性等方面均在一定程度上优于乳清蛋白,可广泛替代乳清蛋白在食品工业中大规模应用。     

Gelation mechanism of milk as influenced by temperature and pH; studied by the use of transglutaminase cross-linked casein micelles

Casein micelles in milk are colloidal particles consisting of four different caseins and calcium phosphate, each of which can be exchanged with the serum phase. The distribution of caseins and calcium between the serum and micellar phase is pH and temperature dependent. Furthermore, upon acidification casein micelles lose their colloidal stability and start to aggregate and gel. In this paper, we studied two methods of acid-induced gelation, i.e., 1) acidification of milk at temperatures of 20 to 50 degrees C and 2) decreasing the pH at 20 degrees C to just above the gelation pH and subsequently inducing gelation by increasing the temperature. These two routes are called T-pH and pH-T, respectively. The gelation kinetics and the properties of the final gels obtained are affected by the gelation route applied. The pH-T milks gel at higher pH and lower temperature and the gels formed are stronger and show less susceptibility to syneresis. By using intramicellar cross-linked casein micelles, in which release of serum caseins is prevented, we demonstrated that unheated milk serum caseins play a key role in gelation kinetics and characteristics of the final gels formed. This mechanism is presented in a model and is relevant for optimizing and controlling industrial processes in the dairy industry, such as pasteurization of acidified milk products.     

Effect of composition on coagulation,curd firming,and syneresis of goat milk

The present study investigated the effect of different levels of fat, protein, and casein on (1) traditional milk coagulation properties, and (2) curd firming over time parameters of 1,272 goat milk samples. Relationships between fat, protein, and casein and some indicators of udder health status (lactose, pH, somatic cells, bacterial count, and NaCl) were also investigated. Traditional milk coagulation properties and modeled curd-firming parameters were analyzed using a mixed model that considered the effect of days in milk, parity, farm, breed, the pendulum of the instrument, and different levels of fat, protein, and casein. Fat, protein, and casein were also tested with the same model but one at a time. Information provided by this model demonstrated the effect of one component alone, without contemporarily considering that of the others. The results allowed us to clarify the effect of the major milk nutrients on coagulation, curd firming, and syneresis ability of goat milk. In particular, milk rich in fat was associated with better coagulation properties, whereas milk rich in protein was associated with delayed coagulation. The high correlation of fat with protein and casein contents suggests that the effect of fat on the cheese-making process is also attributable to the effects of protein and casein. When only protein or only casein was included in the statistical model, the pattern of coagulation, curd firming, and syneresis was almost indistinguishable. The contemporary inclusion of protein and casein in the statistical model did not generate computing problems and allowed us to better characterize the role of protein and casein. Consequently, given their strong association, we also tested the effect of casein-to-protein ratio (i.e., casein number). Higher values of casein number led to a general improvement in the coagulation ability of milk, suggesting that casein-to-protein ratio, not just protein or casein, should be considered when milk is destined for cheese making. These results are especially useful for dairy farmers who want to increase their profits by improving the technological quality of the milk produced.     

Invited review: Microfiltration-derived casein and whey proteins from milk

Milk, a rich source of nutrients, can be fractionated into a wide range of components for use in foods and beverages. With advancements in filtration technologies, micellar caseins and milk-derived whey proteins are now produced from skim milk using microfiltration. Microfiltered ingredients offer unique functional and nutritional benefits that can be exploited in new product development. Microfiltration offers promise in cheesemaking, where microfiltered milk can be used for protein standardization to improve the yield and consistency of cheese and help with operation throughputs. Micellar casein concentrates and milk whey proteins could offer unique functional and flavor properties in various food applications. Consumer desires for safe, nutritious, and clean-label foods could be potential growth opportunities for these new ingredients. The application of micellar casein concentrates in protein standardization could offer a window of opportunity to US cheese makers by improving yields and throughputs in manufacturing plants.     

牦牛"曲拉"乳酸干酪素生产工艺研究

采用乳酸凝结剂、护色、离心分离等方法，通过正交试验筛选出活性炭最佳使用参数（质量分数2．0％，吸附温度50℃，吸附时间30min）。复合护色剂配合比例mNa2S2O3：mNa2SO3：mNaHSO3=1.0：2．0：2．5），以及离心工艺参数（转速8000r／min，时间10min，温度50℃）：确定了牦牛“曲拉”乳酸干酪素生产工艺；制品在感官、理化、微生物等方面符合QB／T3780-1999要求。     

Short communication: Separation and quantification of caseins and casein macropeptide using ion-exchange chromatography

The aim of this work was to improve an existing method to separate and quantify the 4 major caseins from milk samples (i.e., containing whey proteins) using ion-exchange chromatography. The separation process was carried out using a mini-preparative cation exchange column (1 or 5 mL of column volume), using urea acetate as elution buffer at pH 3.5 with a NaCl gradient. All 4 major caseins were separated, and the purity of each peak was assessed using sodium dodecyl sulfate-PAGE. Purified casein fractions were also added to raw milk to confirm their elution volumes. The quantification was carried out using purified caseins in buffer as well as added directly to fresh skim milk. This method can also be employed to determine the decrease in κ-casein and the release of the casein-macropeptide during enzymatic hydrolysis using rennet. In this case, the main advantage of using this method is the lack of organic solvents compared with the conventional method for separation of macropeptide (using reversed phase HPLC).     

Casein interactions studied by the surface plasmon resonance technique

Surface plasmon resonance technique was investigated for the first time to study the apparent hydrophobicity and association properties of the major bovine caseins: alpha(s)-(alpha(s1)- and alpha(s2)-caseins in a 4:1 proportion), beta-, and kappa-caseins. The apparent hydrophobicities of the caseins were evaluated by a new method based on the binding level of casein on a hydrophobic sensor chip, and kinetic and equilibrium affinity constants were determined for the following casein interactions: alpha(s)/alpha(s), alpha(s)/beta, alpha(s)/kappa, beta/beta, and beta/kappa, using a sensor chip modified with covalent immobilized caseins. The study by surface plasmon resonance technology of these casein interactions under different conditions (pH, ionic strength, calcium concentration, chemical modification) demonstrated that, at neutral pH, electrostatic repulsive forces play an important role since an increase in ionic strength of the medium resulted in a stronger interaction. When charge repulsions were reduced by either acidification, increase in ionic strength, or dephosphorylation, casein interactions were reinforced, presumably due to weak attractive forces. Moreover, in this molecular model, we showed that addition of calcium greatly increased the binding response between the most phosphorylated caseins and that the added calcium (2 mM) participated directly in the formation of bridges between the phosphate groups of the casein molecules.