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国内凝乳酶的研究应用及其代替品的研发进展 总被引:2,自引:0,他引:2
为了发展我国的干酪产业,阐述了干酪生产的现状,凝乳酶的结构和凝乳机理,影响凝乳酶活性的因素为pH值、温度、Ca^2+及其它因素,并介绍了国内凝乳酶代替品动物性凝乳酶、植物性凝乳酶、微生物性凝乳酶和基因工程凝乳酶的研发进展。 相似文献
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凝乳酶在干酪生产中的应用 总被引:9,自引:3,他引:9
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。 相似文献
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不同凝乳酶在干酪生产中应用效果的研究 总被引:10,自引:0,他引:10
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。 相似文献
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木瓜凝乳蛋白酶在干酪及其副产物乳清中的应用 总被引:2,自引:0,他引:2
随着干酪产业的发展,凝乳酶替代品的研究引起了人们的广泛关注。综述了凝乳酶替代品的研究现状及木瓜凝乳蛋白酶的研究进展,并展望了木瓜凝乳蛋白酶在乳品生产中的应用前景。 相似文献
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In this work, pressure-assisted enzymatic gelation was applied to milk proteins, with the goal of enhancing the structure and stability of pressure-created milk protein gels. High-pressure processing (HPP) at 600 MPa, 3 min, and 5°C was applied to milk protein concentrate (MPC) samples of 12.5% protein concentration, both in the absence and in the presence of calf chymosin [up to 60 IMCU (international milk-clotting units)/kg of milk] or camel chymosin (up to 45 IMCU/kg of milk). Gel hardness, water-holding capacity, and degree of proteolysis were used to assess network strength and shelf stability. The processing trials and all measurements were conducted in triplicate. Statistical analyses of the data were performed by ANOVA, at a 95% confidence level. After HPP treatment, we observed significant structural changes for all samples. Pressurization of MPC, with or without chymosin addition, led to extensive protein aggregation and network formation. The strength of HPP-created milk protein gels without chymosin addition, as measured by the elastic modulus (G′), had a value of 2,242 Pa. The value of G′ increased with increasing chymosin concentration, reaching as high as 4,800 Pa for samples with 45 IMCU/kg of camel chymosin. During 4 wk of refrigerated storage, the HPP and chymosin MPC gels maintained higher gel hardness and better structural stability compared with HPP only (no chymosin) MPC gels. The water-holding capacity of the gels without chymosin remained at 100% during 28 d of refrigerated storage. The HPP and chymosin MPC gels had a lower water-holding capacity (91–94%) than the HPP-only counterparts, but their water-holding capacity did not decrease during storage. Overall, these findings demonstrate that controlled, fast structural modification of high-concentration protein systems can be obtained by HPP-assisted enzymatic treatment, and the created gels have a strong, stable network. This study provides insights into the possibility of using HPP for the development of milk-protein-based products with novel structures and textures and long refrigerated shelf life, along with the built-in safety imparted by the HPP treatment. 相似文献
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由于微生物凝乳酶过多的非专一性水解和热稳定性高导致干酪产量降低和成熟中出现苦味。应用重组技术和蛋白质工程技术,使酶的一级结构发生可选择的和系统的变化,得到的蛋白质便具有所期望的功能特性。应用蛋白质工程对酶改性涉及到改变亚基结构和更换残基,改变酶的动力学参数和热稳定性,改变底物特异性以及最适pH等。 相似文献
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《International Dairy Journal》2014,39(2):133-135
Retained coagulant in cheese initiates casein breakdown and influences cheese structure and flavour formation. This study investigated the influence of milk pH on retention of camel chymosin in curd and compared it with bovine chymosin. Milk at five different pH levels was coagulated with same coagulant activity of each chymosin and centrifuged. Chymosin activity in whey was determined using the synthetic peptide Pro-Thr-Glu-Phe-(NO2-Phe)-Arg-Leu as substrate and HPLC analysis of the resulting product. Camel chymosin had 2.7 times lower activity in milk than bovine chymosin at the same coagulation activity. The retention of camel chymosin in curd was rather constant at ∼20% between pH 6.65 and 6.00, while it increased almost linear from 2 to 21% for bovine chymosin. The lower pH dependence for retention of camel chymosin than of bovine chymosin may be explained by a lower negative charge of the camel chymosin molecule. 相似文献
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The aspartic proteinase, chymosin (EC 3.4.23.4) is the principal milk clotting enzyme used in cheese production and is one of the principal proteolytic agents involved in cheese ripening. Varietal differences in chymosin activity, due to factors such as cheese cooking temperature, fundamentally influence cheese characteristics. Furthermore, much chymosin is lost in whey, and further processing of this by-product may require efficient inactivation of this enzyme, with minimal effects on whey proteins. In the first part of this study, the thermal inactivation kinetics of Maxiren 15 (a recombinant chymosin preparation) were studied in skim milk ultrafiltration permeate, whole milk whey and skim milk whey. Inactivation of chymosin in these systems (at pH 6.64) followed first order kinetics with a D45.5 value of 100 +/- 21 min and a z-value of 5.9 +/- 0.3 degrees C. D-Values increased linearly with decreasing pH from 6.64 to 6.2, while z-values decreased as pH decreased from 6.64 to 6.4, but were similar at pH 6.4 and 6.2. Subsequent determination of chymosin activity during manufacture of Cheddar and Swiss-type cheese showed good correlations between predicted and experimental values for thermal inactivation of chymosin in whey. However, both types of cheese curd exhibited relatively constant residual chymosin activity throughout manufacture, despite the higher cooking temperature applied in the manufacture of Swiss cheese. Electrophoretic analysis of slurries made from Cheddar and Swiss cheese indicated decreased proteolysis due to chymosin activity during storage of the Swiss cheese slurry, but hydrolysis of sodium caseinate by coagulant extracted from both cheese types indicated similar levels of residual chymosin activity. This may suggest that some form of conformational change other than irreversible thermal denaturation of chymisin takes place in cheese curd during cooking, or that some other physico-chemical difference between Swiss and Cheddar cheese controls the activity of chymosin during ripening. 相似文献
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Effects of Ultrasound Treatment on the Properties of Chymosin 总被引:6,自引:0,他引:6
When chymosin was extracted by ultrasound curd tension and syneresis were significantly lower for Berridge substrate coagulated by the ultrasound-treated chymosin than by the control. Experimental chymosin had a shorter induction period and was more heat-sensitive than the control. Activation energy of chymosin obtained by ultrasound treatment was significantly lower than that of the control. Ultrasound treatment did not significantly change the chromatographic patterns of chymosin. Only two distinct enzymatically active proteins were observed with DEAE-cellulose chromatography. Electrophoretic properties were similar for chymosins obtained by ultrasound and control methods. 相似文献
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Beyaz peynir, a white brined cheese, was manufactured using different blends of camel chymosin (100, 75, 50, 25, and 0%) with calf chymosin and ripened for 90 d. The purpose of this study was to determine the best mixture of coagulant for Beyaz peynir, in terms of proteolysis, texture, and melting characteristics. The cheeses were evaluated in terms of chemical composition, levels of proteolysis, total free amino acids, texture, meltability, residual coagulant activity, microstructure, and sensory properties during 90 d of ripening. Differences in the gross chemical composition were statistically significant for all types of cheeses. Levels of proteolysis were highly dependent on the blends of the coagulants. Higher proteolysis was observed in cheeses that used a higher ratio of calf chymosin. Differences in urea-PAGE and peptide profiles of each cheese were observed as well. Meltability values proportionally increased with the higher increasing levels of calf chymosin in the blend formula. These coagulants had a slight effect on the microstructure of cheeses. The cheese made with camel chymosin had a harder texture than calf chymosin cheese, and hardness values of all cheese samples decreased during ripening. The cheeses with a high ratio of calf chymosin had higher residual enzyme activity than those made with camel chymosin. No significant difference in sensory properties was observed among the cheeses. In conclusion, cheeses made with a high level of calf chymosin had a higher level of proteolysis, residual coagulant activity, and meltability. The cheeses also had a softer texture than cheeses made with a high content of camel chymosin. Camel chymosin may be used as a coagulant alone if low or limited levels of proteolysis are desired in cheese. 相似文献
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The first step in cheesemaking is the milk clotting process, in which κ-caseinolytic enzymes contribute to micelle precipitation. The best enzyme for this purpose is chymosin because of its high degree of specificity toward κ-casein. Although recombinant bovine chymosin is the most frequently used chymosin in the industry, new sources of recombinant chymosin, such as goat, camel, or buffalo, are now available. The present work represents a comparative study of 4 different recombinant chymosins (goat and buffalo chymosins expressed in Pichia pastoris, and bovine and camel chymosin expressed in Aspergillus niger). Recombinant goat chymosin exhibited the best catalytic efficiency compared with the buffalo, bovine, or camel recombinant enzymes. Moreover, recombinant goat chymosin exhibited the best specific proteolytic activity, a wider pH range of action, and a lower glycosylation degree than the other 3 enzymes. In conclusion, we propose that recombinant goat chymosin represents a serious alternative to recombinant bovine chymosin for use in the cheesemaking industry. 相似文献