Residual clotting activity and ripening properties of vegetable rennet from Cynara cardunculus in La Serena cheese

Vegetable rennet extracted from Cynara cardunculus flowers is traditionally used in the manufacture of La Serena cheese. High levels of proteolytic enzymes of the flowers are responsible for its clotting activity and strong proteolytic action. The presence of residual coagulant in cheese and whey was measured by adding known amounts of vegetable rennet as internal standard. We found no differences between the residual coagulant activity of La Serena cheese compared with other types of cheese. The coagulant content detected at the end of four cheesemakings (vat of 830 l) in cheese and whey represented 27 and 78%, respectively, of the total amount added to milk. When measurements were carried out in 16 different cheeses, vegetable rennet appeared to be highly stable during cheese ripening. Cheese composition (moisture, pH, NaCl, fat and protein) was kept relatively constant during ripening, which seems to contribute to stability of residual activity. Electrophoretic analyses of water insoluble fractions from cheeses manufactured with vegetable rennet showed that α_s-casein was less susceptible to proteolysis than β-casein. The water soluble nitrogen/total nitrogen (WSN/TN) exhibited higher levels only during the first 30 days of ripening although non-protein nitrogen/total nitrogen (NPN/TN) ratio and amino acid nitrogen (NH₂-N) increased with ripening time.     

Casein breakdown during ripening of Idiazabal cheese: influence of starter and rennet type

The objective of this work was to determine the effect of starter and rennet type on casein breakdown during Idiazabal cheese ripening. Four batches of cheeses were manufactured with two rennets, commercial calf rennet and artisanal lamb rennet, and the use of natural flora or a commercial starter. Electrophoretic analysis of cheese samples showed six bands identified as α_s1‐, α_s2 + β‐, α_s1‐I‐, γ₁‐, β‐I‐ and para‐κ‐casein. As expected, the casein breakdown during cheese ripening was considerably affected by rennet type and the use of a commercial starter. The artisanal lamb rennet produced a higher hydrolysis of casein fractions than the commercial calf rennet, probably owing to its high percentage of chymosin (around 78%). The effect of addition of starter on proteolysis was dependent on the casein fractions generated by artisanal lamb rennet or commercial calf rennet. © 2000 Society of Chemical Industry     

Rheological Evaluation of Maturing Cheddar Cheese

A number of Cheddar cheese samples of different age, pH and moisture content have been examined rheologically and electrophoretically to determine whether the progressive changes in cheese texture were related to casein proteolysis. The force-compression curves obtained by crushing cubes of cheese between small flat plates at constant speed were different for the different cheese samples and were affected by the moisture content, pH and extent of α_sl-casein proteolysis that had taken place in the cheese. These results support a model of cheese micro structure in which an extensive network involving α_sl- casein molecules traverses the cheese and as the cheese ripens, chymosin cleavage of α_sl-casein weakens the protein network. Such a model explains the rapid decrease in Cheddar cheese yield-force that occurs during the early stages of ripening.     

Biochemical patterns in ovine cheese: Influence of probiotic strains

This study was undertaken to evaluate the effect of lamb rennet paste containing probiotic strains on proteolysis, lipolysis, and glycolysis of ovine cheese manufactured with starter cultures. Cheeses included control cheese made with rennet paste, cheese made with rennet paste containing Lactobacillus acidophilus culture (LA-5), and cheese made with rennet paste containing a mix of Bifidobacterium lactis (BB-12) and Bifidobacterium longum (BB-46). Cheeses were sampled at 1, 7, 15, and 30 d of ripening. Starter cultures coupled with probiotics strains contained in rennet paste affected the acidification and coagulation phases leading to the lowest pH in curd and cheese containing probiotics during ripening. As consequence, maturing cheese profiles were different among cheese treatments. Cheeses produced using rennet paste containing probiotics displayed higher percentages of α_S1-I-casein fraction than traditional cheese up to 15 d of ripening. This result could be an outcome of the greater hydrolysis of α-casein fraction, attributed to higher activity of the residual chymosin. Further evidence for this trend is available in chromatograms of water-soluble nitrogen fractions, which indicated a more complex profile in cheeses made using lamb paste containing probiotics versus traditional cheese. Differences can be observed for the peaks eluted in the highly hydrophobic zone being higher in cheeses containing probiotics. The proteolytic activity of probiotic bacteria led to increased accumulation of free amino acids. Their concentrations in cheese made with rennet paste containing Lb. acidophilus culture and cheese made with rennet paste containing a mix of B. lactis and B. longum were approximately 2.5 and 3.0 times higher, respectively, than in traditional cheese. Principal component analysis showed a more intense lipolysis in terms of both free fatty acids and conjugated linoleic acid content in probiotic cheeses; in particular, the lipolytic pattern of cheeses containing Lb. acidophilus is distinguished from the other cheeses on the basis of highest content of health-promoting molecules. The metabolic activity of the cheese microflora was also monitored by measuring acetic, lactic, and citric acids during cheese ripening. Cheese acceptability was expressed for color, smell, taste, and texture perceived during cheese consumption. Use of probiotics in trial cheeses did not adversely affect preference or acceptability; in fact, panelists scored probiotic cheeses higher in preference over traditional cheese, albeit not significantly.     

Characteristics of Miniature Cheddar‐Type Cheese Made by Microbial Rennet from Bacillus amyloliquefaciens: A Comparison with Commercial Calf Rennet

Miniature Cheddar‐type cheeses were produced using microbial rennet from Bacillus amyloliquefaciens (milk‐clotting enzyme [MCE]) or calf rennet (CAR). With the exception of pH, there were no significant differences in gross composition between MCE‐cheese (MCE‐C) and CAR‐cheese (CAR‐C). The pH value of CAR‐C was significantly higher than that of MCE‐C at 40 and 60 d of ripening. The total nitrogen content of the pH 4.6‐soluble fraction obtained from MCE‐C was higher than that obtained from CAR‐C. However, nitrogen content of the 12% TCA‐soluble fraction was similar between CAR‐C and MCE‐C. The extent of α_s1‐casein and β‐casein hydrolysis, measured by urea‐PAGE, was similar in both cheese samples. The hydrolysis of β‐casein was lower than that of α_s1‐casein. Different reverse phase‐high‐performance liquid chromatography peptide profiles of ethanol‐soluble and ethanol‐insoluble fractions were obtained from CAR‐C and MCE‐C. The peptide content in the 2 cheese samples increased throughout ripening; the ratio of hydrophobic to hydrophilic peptides was lower in MCE‐C than in CAR‐C. Compared with CAR‐C, MCE‐C was softer as a result of higher protein hydrolysis. Microbial rennet from B. amyloliquefaciens contributed to higher proteolytic rates, which reduced ripening time.     

Compositional,biochemical and textural changes during ripening of Tulum cheese made with different coagulants

In the present study, biochemical, chemical and texture changes in Tulum cheeses made using calf rennet and microbial rennets (Aspergillus niger protease and Rhizomucor miehei protease) were compared during ripening for up to 90 days. A total of 15 free fatty acids (FFAs) were detected in the cheese samples. The peroxide values (PV) of the cheeses increased significantly (P < 0.05) during ripening and the cheese made with calf rennet had the highest PV. Proteolysis in the cheeses increased as the ripening time increased. α_s1‐casein and β‐casein degradation was higher in cheeses manufactured with R. miehei protease. Cheeses made with calf rennet were significantly (P < 0.05) harder, more adhesive, more cohesive and more resilient than those made with microbial rennet.     

Effects of genetic type,stage of lactation,and ripening time on Caciocavallo cheese proteolysis

The objective of this experiment was to evaluate the effects of genetic type, stage of lactation, and ripening time on proteolysis in Caciocavallo cheese. One hundred twenty Caciocavallo cheeses made from the milk of 2 breeds, Italian Brown and Italian Holstein and characterized by different stages of lactation were obtained and ripened for 1, 30, 60, 90, and 150 d. Cheese proteolysis was investigated by ripening index (ratio of water-soluble N at pH 4.6 to total protein, %) and by the study of degradation of the protein fractions (α_S1-, β-, and para-κ-casein), which was determined by densitometric analysis of isoelectric focusing results. The statistical analysis showed a significant effect of the studied factors. Ripening index was higher in Italian Brown Caciocavallo cheese and in cheeses made with early lactation milk, whereas casein solubilization was greater in the first 2 mo of ripening. Isoelectric focusing analysis of cheese samples during ripening showed extensive hydrolysis of caseins. In particular, the protein fraction that underwent major degradation by proteolytic enzymes was α_S1-casein, followed by β-casein, whereas para-κ-casein was less degraded. Italian Brown cheese showed a lower residual quantity of β- and para-κ-casein, whereas Italian Holstein cheese showed a lower residual quantity of α_S1-casein. In addition, significant interactions of both first and second order were found on both ripening index and degradation of protein fractions. This study demonstrated that the analyzed factors influenced proteolysis of Caciocavallo cheese, which forms the basis of new knowledge that could lead to the production of a pasta filata cheese with specific characteristics.     

酪蛋白降解对牦牛乳硬质干酪苦味的影响

针对牦牛乳硬质干酪的苦味缺陷,分别以小牛皱胃酶、微生物凝乳酶和木瓜蛋白酶制作的牦牛乳硬质干酪为研究对象,利用尿素聚丙烯酰胺凝胶电泳,研究牦牛乳硬质干酪pH 4.6水不溶性酪蛋白的降解程度,且对成熟过程中的牦牛乳硬质干酪苦味进行感官评价,探究牦牛乳硬质干酪pH 4.6水不溶性酪蛋白降解对其苦味的影响。结果表明：牦牛乳硬质干酪在成熟期间酪蛋白发生了明显的降解,且αs-酪蛋白均比β-酪蛋白降解速率快。经尿素聚丙烯酰胺凝胶电泳分离后,发现木瓜蛋白酶制作的牦牛乳硬质干酪pH 4.6水不溶性酪蛋白在Pre-αs-酪蛋白区域有较强的蛋白带。木瓜蛋白酶制作的牦牛乳硬质干酪pH 4.6水不溶性酪蛋白中αs-酪蛋白和β-酪蛋白降解程度均显著或极显著高于微生物凝乳酶和小牛皱胃酶制作的牦牛乳硬质干酪（P＜0.05或P＜0.01）,木瓜蛋白酶制作的牦牛乳硬质干酪的苦味值极显著高于微生物凝乳酶和小牛皱胃酶制作的牦牛乳硬质干酪的苦味值（P＜0.01）,通过主成分分析得出3 种凝乳酶制作牦牛乳硬质干酪的苦味值和未降解β-酪蛋白和αs-酪蛋白含量成极显著负相关。这为控制牦牛乳硬质干酪品质提供了理论参考。     

Slower proteolysis in Cheddar cheese made from high-protein cheese milk is due to an elevated whey protein content

A growing number of companies within the cheese-making industry are now using high-protein (e.g., 4–5%) milks to increase cheese yield. Previous studies have suggested that cheeses made from high-protein (both casein and whey protein; WP) milks may ripen more slowly; one suggested explanation is inhibition of residual rennet activity due to elevated WP levels. We explored the use of microfiltration (MF) to concentrate milk for cheese-making, as that would allow us to concentrate the casein while varying the WP content. Our objective was to determine if reducing the level of WP in concentrated cheese milk had any impact on cheese characteristics, including ripening, texture, and nutritional profile. Three types of 5% casein standardized and pasteurized cheese milks were prepared that had various casein:true protein (CN:TP) ratios: (a) control with CN:TP 83:100, (b) 35% WP reduced, 89:100 CN:TP, and (c) 70% WP reduced, 95:100 CN:TP. Standardized milks were preacidified to pH 6.2 with dilute lactic acid during cheese-making. Composition, proteolysis, textural, rheological, and sensory properties of cheeses were monitored over a 9-mo ripening period. The lactose, total solids, total protein, and WP contents in the 5% casein concentrated milks were reduced with increasing levels of WP removal. All milks had similar casein and total calcium levels. Cheeses had similar compositions, but, as expected, lower WP levels were observed in the cheeses where WP depletion by MF was performed on the cheese milks. Cheese yield and nitrogen recoveries were highest in cheese made with the 95:100 CN:TP milk. These enhanced recoveries were due to the higher fraction of nitrogen being casein-based solids. Microfiltration depletion of WP did not affect pH, sensory attributes, or insoluble calcium content of cheese. Proteolysis (the amount of pH 4.6 soluble nitrogen) was lower in control cheeses compared with WP-reduced cheeses. During ripening, the hardness values and the temperature of the crossover point, an indicator of the melting point of the cheese, were higher in the control cheese. It was thus likely that the higher residual WP content in the control cheese inhibited proteolysis during ripening, and the lower breakdown rate resulted in its higher hardness and melting point. There were no major differences in the concentrations of key nutrients with this WP depletion method. Cheese milk concentration by MF provides the benefit of more typical ripening rates.     

Proteolysis and texture changes of a Spanish soft cheese (‘Torta del Casar’) manufactured with raw ewe milk and vegetable rennet during ripening

Proteolysis and textural changes of the Spanish ewe raw milk soft cheese of the Protected Designation of Origin Torta del Casar were studied in four different stages of ripening, with 1, 30, 60 and 90 days. In general, proteolysis in Torta del Casar cheese was weak at 1 and 30 days and it was more intense between the 30–60 days of ripening. Soluble nitrogen non‐protein nitrogen, polypeptide N and free amino acids values significantly increased during cheese ripening. Protein and casein nitrogen decreased significantly after 60 days of ripening resulting in the increase of the other nitrogen fractions measured. Caseins changes determined by capillary zone electrophoresis showed that proteolysis of β‐casein occurred faster than αs1‐casein but the latter suffered higher proteolytic degradation at the end of ripening (day 90). This pattern of degradation of caseins is reversed in other cheeses made with animal rennet. Texture analysis showed that firmness and consistency decreased along ripening while adhesiveness increased. Highly significant correlations were found between textural parameters, residual caseins levels and nitrogen fractions during maturation, which shows the importance of proteolytic changes for an optimal texture formation.     

Texture and flavour development in Ras cheese made from raw and pasteurised milk

Texture, proteolysis and flavour development in Ras cheeses made from raw or pasteurised milk with two different thermophilic lactic cultures were monitored during ripening. Results showed that at day 1 of manufacture, the moisture content and pH were lower in raw milk cheese than in pasteurised milk cheeses. Levels of water-soluble nitrogen, casein breakdown, free amino groups and free fatty acids were higher in cheese made from raw milk than in that made from pasteurised milk. Textural characteristics, such as hardness, cohesiveness and chewines, increased in all treatments during the first 60 days of ripening due to the reduction in the moisture level during the second stage of salting (dry salting during the first 60 days of ripening). Cheese made from raw milk received the highest texture and flavour scores by panellists.     

Cheese-making properties of vegetable rennet from sodom apple (Calotropis procera)

Yield, chemical composition and texture profile of cheese made with vegetable rennet from sodom apple leaves were compared with those of a direct acid cheese made with calf rennet. Yield, moisture, fat and protein contents were 14·47%, 49·70%, 26·15% and 20·0%, respectively, for cheese made with vegetable rennet and 12·45%, 44·80%, 29·84% and 20·4%, respectively, for the direct acid cheese made with calf rennet. Cheese made with vegetable rennet had less soluble nitrogen than that made with calf rennet despite the fact that vegetable rennet was more proteolytic in casein solution than calf rennet. Relative to that made with calf rennet, cheese made with vegetable rennet was harder, less cohesive and more gummy, presumably because of differences in chemical composition and physical characteristics between the cheeses.     

Primary proteolysis and textural changes during ripening in Cheddar cheeses manufactured to different fat contents

The effects of varying fat content in Cheddar cheese, from 6.3 to 32.5 g 100 g⁻¹, on changes in pH, primary proteolysis and texture were monitored over a 225 d ripening period. Reduction in the fat content resulted in significant (P<0.05) increases in pH, moisture and protein contents and decreases in the concentration of moisture in the non-fat substance. The increase in pH as the fat content increased was attributed to the concomitant decrease in the lactate-to-protein ratio. Polyacrylamide gel electrophoresis showed that the concentration of intact casein decreased in all cheeses during ripening and that the rate of decrease was not affected by the fat content. However, for a given concentration of casein, α_s1-casein was degraded more slowly, and β-casein more rapidly, as the fat content was reduced. The slower degradation of α_s1-casein with decreased fat content coincided with a decrease in the ratio of residual chymosin activity to protein in the cheese. At most ripening times, reduction in the fat content resulted in significant increases in the concentration of intact casein, fracture stress, fracture strain, and cheese firmness. The effects of fat reduction on proteolysis and rheology are probably due to the interactive effects of the concomitant changes in composition.     

Emulsifying Salts Influence on Characteristics of Cheese Analogs from Calcium Caseinate

Cheese analogs were prepared from calcium caseinate, butter oil and emulsifying sodium salts (ES). Increasing ES levels gave cheese analogs with higher pH, degree of casein dissociation and degree of fat emulsification than the control without ES. Firmness of cheese analogs first increased, then decreased when the ES level was increased from 1 to 3%. Effects depended on the degree of polymerization of phosphate salts. Sodium citrate (>1%) or Na₂HPO₄ (>2%) made cheese analogs more able to melt upon reheating. Melting ability correlated with high pH, soft texture, high degree of casein dissociation and low degree of fat emulsification.     

Effect of β-casein concentration in cheese milk on rennet coagulation properties,cheese composition and cheese ripening

Effects of the use of a β-casein powder to enrich cheese milk on rennet coagulation properties of milk, cheese composition and cheese ripening were investigated. Casein content of control milk was 2.5%, whereas that for the three enriched milks was adjusted with β-casein powder at 2.7%, 2.9% and 3.1%. The β-casein to α-casein ratio of these cheese milks was, respectively, 0.70, 0.79, 0.89 and 0.99. Rennet coagulation properties were related not only to casein concentration but also to the proportion of β-casein and α_s-casein presents in milks. Milk with higher concentration of β-casein had poorer coagulation properties. Cheeses could be produced by using a miniature cheese making process. Moisture, ash and calcium contents decreased, while protein content and β-casein increased in cheese as casein and β-casein concentration increased in milk. As a result, hardness was higher in enriched cheeses than in control cheese. During cheese ripening, α-casein was hydrolyzed, but the rate of degradation of α-casein decreased as protein and β-casein concentration increased in cheese. β-Casein seemed to be not hydrolyzed. The rate of decrease of hardness was also slower for enriched cheeses.     

Influence of vegetable and animal rennet on proteolysis during ripening in ewes’ milk cheese

The renewed interest in using enzymes from thistles of the genus Cynara in the making of traditional ewes’ milk cheese prompted us to investigate the effect of vegetable and animal rennet on proteolysis during ripening of Los Pedroches cheese. Casein hydrolysis was found to be much more extensive and faster in cheese made by using vegetable rennet (the amount of soluble nitrogen at 60, 80 and 100 days of ripening was more than 28% greater than that in cheese produced using animal rennet). The levels of insoluble Tyr and Trp were higher in cheese produced with vegetable rennet. PAGE, using gels containing 7 M urea, revealed decreased contents in residual α_s-CN and β-CN, as well as markedly increased levels of the more mobile components in cheese produced from vegetable rennet at the end of ripening. On the other hand, the degree of proteolysis in terms of NPN or its main components (peptides, amino acids and ammonia) was similar in cheese produced using animal or vegetable rennet.     

Physicochemical analysis of full-fat, reduced-fat, and low-fat artisan-style goat cheese

The objective of this study was to examine the physicochemical properties of cheese elaborated via traditional artisan methods using goat milk containing 5, 1.5, or 0.4% fat and ripened for 1, 7, 14, or 28 d. Seventy-two cheeses were produced (2 batches × 3 fat levels × 4 ripening times × triplicate). Proximal composition, pH, texture analysis, and color were recorded in each cheese. Protein and moisture were increased in cheese, and fat and fat in DM were decreased with decreasing fat in milk. Internal and external pH was higher in low-fat and reduced-fat cheese, and pH values decreased during the first 2 wk of ripening but increased slightly on d 28. Cheese fracturability, cohesiveness, masticability, and hardness increased with decreasing fat, whereas elasticity and adhesiveness decreased. Cheese lightness and red and yellow indexes decreased with decreasing fat content; during ripening, lightness decreased further but yellow index increased.     

Influence of residual rennet and proteolysis on the exudation of whey from Feta cheese during storage

A change in the quantity of rennet added to the cheesemilk resulted in a corresponding change in the level of residual rennet in Feta cheese. Casein proteolysis and exudation of whey from Feta cheese during storage were proportional to the quantity of residual rennet in the cheese. It is likely that with proteolysis, the three-dimensional casein network becomes weaker and gradually disintegrates. The water-holding ability of the casein gels is thereby greatly reduced and moisture is released from the interstices of the casein gel. This free moisture and soluble material, including peptides and amino acids formed during proteolysis, are released as exudate during the storage of Feta cheese.     

解淀粉芽孢杆菌GSBa-1凝乳酶对羊奶干酪成熟特性的影响

为探究解淀粉芽孢杆菌GSBa-1凝乳酶制备的羊奶干酪(干酪B)成熟特性的变化,以采用商业凝乳酶和同批次羊奶制作的干酪(干酪A)为对照组,比较两组干酪在60d成熟期主要组分、质构特性、微生物指标及风味物质的变化。结果表明,两组干酪得率相差不大。成熟期间干酪的水分、蛋白质及脂肪含量呈先上升后下降趋势,干酪B始终高于干酪A;干酪游离氨基酸总量在成熟期间呈先下降后上升趋势,且干酪B中苯丙氨酸、天冬氨酸、异亮氨酸、甲硫氨酸、丝氨酸含量高于干酪A。成熟前期干酪B质构特性优于干酪A。干酪A成熟后乳酸乳球菌数量增加了(5.22±0.02)%,干酪B无显著变化(P>0.05)。成熟期内,两组干酪中挥发性风味物质种类和含量均增加,但干酪B中的壬酸、辛醇、2-庚酮、2-壬酮、二甲基砜使羊奶干酪风味独特、浓郁。因此,GSBa-1凝乳酶具备替代商业凝乳酶用于羊奶干酪生产的潜力,可对干酪风味的形成和品质的提升起到一定促进作用。     

利用酶凝干酪素制造模拟培尔干酪

为探讨生产模拟卡门培尔干酪的可行性,以酶凝干酪素为蛋白质原料制造模拟干酪,接种霉菌发酵剂,经成熟而制得模拟卡门培尔干酪,并分析其感官品质及成熟期间的理化特性。结果表明,模拟卡门培尔干酪的外观、质地、风味评定分数及感官评定分数,均与商品卡门培尔干酪无显著差异(p>0.05);成熟期间,随模拟卡门培尔干酪成熟时间的增加,非蛋白氮含量显著增加(p<0.01),硬度与剪切力显著降低(p<0.01);电镜观察显示,干酪的结构由最初的较为致密,在中期转变为空隙相对较大的纤维网状立体结构,并于后期变纤细,空穴变大、变稀疏、不均一,且形成脂肪槽。研究表明,利用酶凝干酪素能够生产感官品质与传统卡门培尔干酪相似的模拟卡门培尔干酪。