干酪生产中影响凝乳酶活力因素的研究

干酪生产中凝乳酶活力是决定其添加量的重要指标，本试验就影响活力的多种因素进行探讨。其中原料乳中非脂乳固体含量，凝乳温度、酸度、ＣａＣｌ２加入量，稀释液中盐含量和凝乳酶浓度是重要的凝乳条件。     

凝乳酶在干酪生产中的应用

酪蛋白凝聚是干酪生产中的基本工序，通常情况下，这一过程由凝乳酶来完成。文章分别对凝乳酶液状、粉朱状及锭状制剂的制作过程．凝乳酶凝结牛乳的机理及实际生产过程中直接影响凝乳酶活力测定以厦凝乳酶活性的因素等问题进行了详细地探讨。     

凝乳酶及其在干酪生产中的应用

凝乳酶是制造干酪过程中起凝乳作用的关键性酶。本文介绍了凝乳酶的一般特性、小牛皱胃酶的代用品及其鉴别，以及凝乳酶在干酪生产中的应用。     

不同种凝乳酶在牛奶干酪生产中应用效果的研究

分别用羔羊皱胃酶(A)、微生物凝乳酶(B)、猪胃蛋白酶(C)、无花果蛋白酶(D)、木瓜蛋白酶(E)和小牛皱胃酶(F)作为凝乳剂,研究不同蛋白酶对硬质牛奶干酪的出品率、感官品质和成熟过程中蛋白质降解的影响.按照GB5420-85所列指标和评分方法进行感官评定.结果表明,6种酶处理在外形、色泽上打分极接近,而在滋味气味上和组织状态上A和F组优于B组,B组优于Ca,C组优于D和E组.pH=4.6可溶性氮和质量分数为12%的TCA-N测定结果表明,随成熟期延长,微生物酶对酪蛋白具有明显的高分解活性.6种酶处理对成熟期中质量分数为5%的PTA-N无显著影响.     

不同凝乳酶在干酪生产中应用效果的研究

对不同凝乳酶在干酪生产中的凝乳特性、干酪出品率及成熟2个月的干酪品质进行了研究。结果表明,小牛皱胃酶和羔羊皱胃酶是干酪生产的最佳凝乳酶;其次为毛霉凝乳酶和胃蛋白酶;木瓜蛋白酶和无花果蛋白酶应用效果较差。在小牛皱胃酶和羔羊皱胃酶中添加20%木瓜蛋白酶或25%毛霉凝乳酶,可获得较为理想的效果。     

不同凝乳酶在干酪生产中应用效果的研究

对不同凝乳酶在干酪生产中的凝乳特性、干酪出品率及成熟2个月的干酪品质进行了研究。结果表明,小牛皱胃酶和羔羊皱胃酶是干酪生产的最佳凝乳酶;其次为毛霉凝乳酶和胃蛋白酶;木瓜蛋白酶和无花果蛋白酶应用效果较差。在小牛皱胃酶和羔羊皱胃酶中添加20%木瓜蛋白酶或25%毛霉凝乳酶,可获得较为理想的效果。      

凝乳酶对干酪品质影响研究进展

凝乳酶对干酪的品质具有重要影响。本文介绍了凝乳酶的种类,以及其在干酪生产中的作用和机理,论述了凝乳酶对干酪品质影响研究进展,并对其研究前景进行了展望。     

凝乳酶对超滤浓缩乳生产Quark干酪的影响

采用每100g超滤乳中添加0、50、100、150、200、250μL六个水平的凝乳酶,研究了不同的凝乳酶添加量对Quark干酪组成、凝乳硬度、贮藏期产品感官品质和干酪中水溶性氮含量的影响。结果表明,当凝乳酶的添加量从0μL/100g增大到250μL/100g时,产品的水分含量上升了1·49%,粗产率和校正产率分别上升了1·42%和0·99%,固形物的回收率下降了3·5%,凝乳硬度从16·83g增大到40·84g,但干酪的苦味和水溶性氮含量,随着贮存期的延长和凝乳酶用量的增加而增大。      

干酪加工专用凝乳酶及其基因工程酶的研究

凝乳酶是干酪加工中必须用到的酶制剂,本文详细的介绍了凝乳酶的结构,凝乳酶的不同来源,凝乳机理以及影响凝乳酶活性的因素等内容,并阐述了基因工程凝乳酶的研究现状及凝乳酶的发展前景,为解决我国凝乳酶的短缺问题提供思路.     

对不同凝乳酶制作羊奶干酪效果的研究

别应用羔羊皱胃酶（Ａ组）、微生物凝乳酶（Ｂ组）和猪胃蛋白酶（Ｃ组）作为凝乳剂，研究了不同蛋白酶对ｃｏｌｂｙ羊奶干酪的出品率、组织结构、感官品质和成熟过程中蛋白质降解的影响．按照ＧＢ５４２０－８５所列指标和评分方法进行感官评定，三种酶处理在纹理图案、外形、色泽上打分极接近，而在滋味气味上和组织状态上Ａ组优于Ｂ组，Ｂ组优于Ｃ组．ｐＨ＝４．６可溶性氮和１２％ＴＣＡ－Ｎ测定结果表明，随成熟期延长，微生物酶对酪蛋白具有明显的高分解活性．三种酶处理对成熟期中５％ＰＴＡ－Ｎ含量无显著影响     

Reverse-Phase HPLC Analysis of Cheese Samples Aged by a Fast-Ripening Process

Cheese ripening accelerated by adding enzyme extracts derived from lactic bacteria promoted proteolysis and produced an acceptable novel cheese based on sensory tests. However, HPLC profiles for watersoluble compounds were considerably different from those for control Cheddar cheese without the added enzyme extracts, probably indicating a different mechanism of proteolysis. The samples did not follow the usual aging pathway on a similarlity scattergram, when HPLC data were processed by principal component similarity (PCS) analysis. Such analysis was useful for evaluating effects of accelerated cheese ripening.     

微生物产蛋白酶的研究进展

蛋白酶是目前应用最为广泛的工业化酶制剂,其产值占世界酶制剂总产值的60％,而工业上超过三分之二的蛋白酶来自于微生物发酵生产.本文对微生物产蛋白酶的工业化生产菌种、高产菌株的选育、酶学性质、分离纯化方法及在食品行业的应用进行了概述,以期对微生物产蛋白酶有更系统地了解,为进一步研究和发掘微生物产蛋白酶,促进蛋白酶的工业化生...     

新型干法工艺制备阳离子淀粉的研究

采用经过改装的挤压反应器作为干法反应装置,以玉米淀粉为原料,以3-氯-2-羟丙基氯化铵(CTA)为醚化剂制备阳离子淀粉。通过单因素试验研究了醚化剂添加量、NaOH添加量、含水量、挤压反应器温度、转速等因素对取代度和反应效率的影响;通过正交试验确定出新型干法制备阳离子淀粉的最佳工艺参数为:醚化剂添加量为5%,NaOH与醚化剂物质的量比为2∶1,水分含量为20%,挤压反应器温度为130℃,转速为400 r/min。研究结果表明,采用改进后挤压反应器制备阳离子淀粉是一种高效、连续、节能的新型干法工艺。     

Development of a Continuous Process for the Production of Ricotta Cheese

A process was developed for the continuous production of Ricotta cheese. The process consists of multistep heating to 92°C, whey protein denaturation in a 10-min holding tube, acid injection to induce coagulation (2.5% citric acid), curd formation in a clear plastic holding tube (10 min), followed by separation of curd from deproteinated whey on a nylon conveyer belt. The process resulted in 98.1% removal of the recoverable solids. Recoveries of protein and fat were 99.5 and 99.6%, respectively.Cheese, prepared from a blend of 80% sweet whey and 20% whole milk, contained 33.5% total solids, 16.30% protein, and 11.6% milk fat. Italian Ricotta, prepared from whey ultrafiltered 4.5 to 1, contained 19.8% total solids, 15.9% protein, and 2.4% fat. The pH of Ricotta prepared from the whey and milk blend (80:20) ranged from 5.6 to 5.8, whereas pH of Ricotta prepared from only ultrafiltered whey (4.5 to 1) was 5.7 to 5.9.The process has advantages over other conventional mechanized cheese processes in terms of reduced capital and operating costs. The process is suitable for cheese factories that may wish to produce Ricotta as a protein base for other food products, such as cream cheese, processed cheese, snack food dips, and quiches.     

Partial Demineralization of Cottage Cheese Whey Using a Heat Treatment Process

Heat treatment of concentrated cottage cheese whey ultrafiltrate resulted in loss of calcium and phosphorus. Heat treatment at 100°C for 120 min resulted in a decrease of 21% of the calcium, 14% of the phosphorus, and 7% of the magnesium. Minimal browning of the concentrate occurs after 120 min. At 120°C, minimal browning had occurred after 60 min. Levels of calcium, phosphorus and magnesium had dropped by 41%, 36%, and 20%, respectively. Forty-eight percent of the calcium, 40% of the phosphorus and 26% of the magnesium were removed by heat treatment at 140°C for 24 min. At that point, browning was minimal. Losses of sodium and potassium were negligible for all cases. A first order rate expression was found to represent the precipitation process.     

Process for Low-fat Cheese from Ultrafiltered Milk

Our objective was to optimize the process for making low-fat cheeses using liquid pre-cheeses obtained by ultrafiltration (UF). The study was conducted to examine the effects of using different proportions of cow, sheep, and goat milk in different compositions on the characteristics of cheeses, and to determine the effect of heating of the retentate on texture. Using ultrafiltered semi-skim milk (total protein content of retentate of 13–14%), cheeses with acceptable quality and reduced fat content were produced. Heating of the retentate produced by UF at 68–72°C, 20 s, improved cheese texture.     

纯棉丝光烧毛筒子纱染色工艺

纯棉丝光烧毛筒子纱染色前应先半漂，选用KE型和HE型（双一氯均三嗪结构）染料染色，助剂含杂少并控制好染色温度和时间，再配合适当的后整理。     

Elongational Viscosity Measurements of Melting American Process Cheese

The elongational viscosity of melting process American cheese of two commercial brands was determined by compression tests at various temperatures in the range 36–62°C. The elongational viscosity determined at low strain rates (0.01–0.04 sec^-1) had little or no rate dependency in one brand and a moderate dependency in the other. Plots of log viscosity vs reciprocal of the absolute temperature indicated that both Arrhenius' and the WLF models failed to accurately account for the cheese melts temperature dependency and that the differences between the types of cheeses could be expressed in whether the plots had upward or downward curvature. Comparison with the Schreiber meltability index demonstrated that although the latter was associated with viscosity, it could not account for different flow rates at different temperatures.     

花生乳牛乳新鲜干酪加工工艺优化

用花生乳代替部分牛乳生产新鲜干酪,对花生乳添加比例、氯化钙添加量、凝乳酶添加量3个因素对凝乳效果的影响分别进行单因素试验,确定各自合适比例后,再采用L9(33)正交试验,确定花生乳牛乳新鲜干酪最佳生产工艺。结果表明花生乳添加量20%、氯化钙添加量0.06%、凝乳酶添加量0.002%时制作出的新鲜花生乳牛乳干酪成品呈乳白色、柔软、有弹性、具有花生风味,产品出品率为16.33%。     

筒子纱冷轧堆前处理工艺与实践

冷轧堆前处理工艺与热浴前处理工艺相比,大大节省了水、电、汽的消耗。但冷轧堆技术在筒子纱前处理上的应用还没突破。文中分析了筒子纱冷轧堆前处理工艺的特殊性和可行性,开发了专用助剂HK-LDA、HK-LDB,设计了棉筒子纱冷轧堆前处理工艺,并用于生产实践。结果表明,利用专用助剂HK-LDA、HK-LDB对棉筒子纱进行冷轧堆练漂是可行的;筒子纱冷轧堆前处理工艺明显地节约了水、电、汽的消耗,提高了经济效益,减少了废水处理的压力。