一种毛霉表面成熟干酪的蛋白质水解作用评价

从毛豆腐中分离出一株毛霉,并应用于表面成熟干酪,以研究干酪成熟过程中所发生的蛋白质水解作用。在90d 的成熟过程中,干酪的pH 值增加;蛋白质水解作用的评价指标,如干酪外层的水溶性氮- 总氮比、pH4.6水溶性氮- 总氮比、12g/100mL 三氯乙酸可溶性氮- 总氮比,在成熟90d 后分别增加至(23.68 ± 1.07)%、(19.38 ± 1.32)%和(8.61 ± 0.85)%,并且高于干酪的内部相应指标。SDS-PAGE 和毛细管电泳分析干酪的pH4.6 不溶性组分,结果表明酪蛋白在干酪成熟过程中被降解。对干酪成熟过程中分离出的水溶性组分进行RP-HPLC 分析,结果显示成熟过程中蛋白质被水解以及形成一些新肽分子。     

Proteolysis and microstructure of Piacentinu Ennese cheese made using different farm technologies

The aim of this study was to provide the biochemical and structural characterization of Piacentinu Ennese cheese and to evaluate the impact of different farm technologies on cheese proteolysis and microstructure. Fifteen cheeses were manufactured according to traditional technology, i.e., from raw milk and farmhouse rennet in the absence of starter culture. Pasteurized milk, commercial rennet, and starter were used for production of 20 nontraditional cheeses. Proteolysis in Piacentinu Ennese cheese was monitored during a 2- to 10-mo ripening time. Low rates of overall proteolysis were observed in cheese, as percentages of total N soluble at pH 4.6 and in 12% trichloroacetic acid were about 11.40 and 8.10%, respectively, after 10 mo of age. Patterns of primary proteolysis by urea-PAGE showed that alpha(s)-caseins were degraded to a larger extent than were beta-caseins, although a considerable amount of both caseins was still intact after 10 mo. Reversed phase-HPLC analysis of the cheese peptide fractions showed a slow decrease in the levels of hydrophobic peptides coupled to increasing levels of hydrophilic compounds as the cheese aged. The structural characteristics of Piacentinu Ennese cheese were evaluated by scanning electron microscopy after 2, 4, and 6 mo of age. The micrographs showed a sponge-like structural network with a well-distributed system of empty spaces, originally occupied by whey and fat. The microstructure changed during cheese ripening to become more compact with cavities of smaller size. Farm technology significantly affected cheese proteolysis and microstructure. Nontraditional cheeses had higher levels of pH 4.6-soluble N and showed a larger hydrolysis of alpha(s)-casein fractions by urea-PAGE analysis than did traditional cheeses. Large differences between cheese-types also concerned the patterns of secondary proteolysis. Nontraditional cheeses had higher levels of 12% trichloroacetic acid-soluble N and showed larger proportions of free amino acids and hydrophilic peptides in the HPLC profiles of the corresponding 70% ethanol-soluble N fraction than traditional cheeses. Nontraditional cheeses also had a more open structure with a coarser and less continuous appearance than did traditional cheeses. A large amount of variability in cheese proteolysis and structure within nontraditional treatment reflected farm-dependent changes in manufacturing conditions related to the use of various types of rennet and starter.     

The influence of ripening temperature and sampling site on the proteolysis in Reggianito Argentino cheese

The effects of elevated ripening temperature and sampling site on proteolysis in Reggianito Argentino cheese were evaluated. Cheeses ripened at 12 or 18 °C and 85% relative humidity were analysed at 2, 4 and 6 months in 2 sampling zones (central and external). Samples were analysed to determine the physicochemical and proteolysis parameters through the urea-PAGE of the urea-soluble fraction, RP-HPLC analysis of the water-soluble fraction at pH 4.6, and the free amino acid analysis. Proteolysis was significantly affected by ripening temperature and sampling site. Urea-PAGE analysis showed that elevated temperature increased the degradation of α_s1- and β-casein. The degradation of α_s1-casein was larger in the central zone than in the external one, while β-casein degradation was similar in both zones. The majority peaks detected by RP-HPLC of the water-soluble fraction at pH 4.6 and free amino acids were significantly affected by ripening temperature and sampling site. Glu, His, Val, Leu, and Lys had the higher concentrations. Principal component analysis showed useful groupings when results from chromatograms were studied. In conclusion, the results obtained not only are useful to characterise the ripening of an Argentinean hard cheese, but also to evaluate the effect of an increase of ripening temperature on Reggianito Argentino cheese proteolysis.     

Influence of lamb rennet paste on composition and proteolysis during ripening of Pecorino foggiano cheese

Rennet pastes produced by lambs subjected to three different feeding systems (mother suckling [MS], artificial rearing [AR], and artificial rearing with Lactobacillus acidophilus supplementation [ARLB]) and slaughtered at two different ages (20 and 40 d) were used for the manufacture of Pecorino foggiano cheese. Composition and proteolysis during ripening of Pecorino foggiano cheese (four replicates batches) were analyzed. Proteolysis was greater in cheeses made with rennet pastes from lambs slaughtered at 20 d, as shown by analysis of nitrogen fractions (water-soluble N and proteose peptones). Supplementation of milk substitute with L. acidophilus may have influenced the growth dynamics of lactic acid bacteria in the rennet pastes, with positive effects on levels of lactobacilli in cheese at the beginning of the ripening time. Lower pH values in ARLB cheese during ripening, together with higher cell loads, suggest that supplementation of milk replacer with L. acidophilus resulted in higher proteolytic activity, as also confirmed by the composition of the pH 4.6—insoluble nitrogen fraction. No differences were found in total concentration of free amino acids among the experimental cheeses; phenylalanine, isoleucine, leucine, lysine were found at the highest levels. The addition of probiotic bacteria to milk substitute in lamb rearing appears to give good-quality lamb rennet paste.     

Acceleration of cheese ripening at elevated temperature. An estimation of the optimal ripening time of a traditional Argentinean hard cheese

The effect of elevated ripening temperature on physicochemical, biochemical and sensory characteristics in Reggianito Argentino cheese was evaluated to determine the optimal time for cheese ripening at 18 °C that ensures typical cheese characteristics. Cheeses ripened at 12 or 18 °C and 85% relative humidity were analysed at 2, 4 and 6 months. Seventy-eight variables (as determined by urea-PAGE, RP-HPLC of the water-soluble at pH 4.6 fraction, free amino acids, free fatty acids and sensory analysis) were considered for the principal component analysis. The statistical analysis allowed determination of the optimal time for ripening Reggianito Argentino cheese at 18 °C, which was ranged between 2 and 3 months. In conclusion, the results obtained were not only useful in characterising the ripening of an Argentinean hard cheese, but also in evaluating the effect of an increase of ripening temperature on the main physicochemical, biochemical and sensory changes of Reggianito Argentino cheese.     

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.     

Effects of ventilation rate and of dietary protein level in an intensive dairy sheep system on the features of Canestrato Pugliese cheese

Effects of ventilation rate and of dietary protein level in an intensive dairy sheep system on the features of Canestrato Pugliese cheese were studied. Cheeses were manufactured from the bulk milk obtained from ewes subjected to four different experimental treatments: (1) low dietary crude protein (CP) of 13% in dry matter (DM) at a low ventilation rate (23.5 m3/h per ewe) (LPLV); (2) low dietary CP at a moderate ventilation rate (47 m3/h per ewe) (LPMV), (3) moderate dietary CP of 16% DM at a low ventilation rate (MPLV); and (4) moderate dietary CP dietary at a moderate ventilation rate (MPMV). Bulk milk and cheeses (at 1, 15, 45 and 90 d of ripening) were analysed for chemical composition, N fractions and plasmin-plasminogen activities. The pH 4.6-soluble and insoluble N fractions were analysed by urea-PAGE. Bulk milk from ewes receiving the low CP diet displayed higher casein and lower urea contents. Ewes subjected to the low ventilation rate displayed a higher plasminogen activity in milk, whereas no differences emerged among treatments in the conversion of zymogen to plasmin. During ripening the plasmin-plasminogen system in cheese did not display significant changes across treatments. At 90 d of ripening, the cheese produced with milk from ewes receiving the low CP diet and exposed to the low ventilation rate displayed more markedly stained bands in the area of gamma-caseins in pH 4.6-insoluble N fraction. As from 15 d of ripening, the pH 4.6-soluble fraction showed a greater number of bands in the LPMV and MPMV than in the LPLV and MPLV cheeses. The results showed that Canestrato Pugliese cheese manufactured with milk from ewes fed the low CP diet and exposed to the moderate ventilation rate was characterized by higher protein and casein content in the fresh cheese and by a greater proteolysis after 90 d of ripening.     

The effect of fat content on the microbiology and proteolysis in cheddar cheese during ripening dairy foods

We investigated the effect of incremental reduction in fat content, in the range 33 to 6% (wt/wt), on changes in the microbiology and proteolysis of Cheddar cheese, over a 225-d ripening period at 7 degrees C. A reduction of fat content resulted in significant increases in contents of moisture and protein and a decrease in the concentration of moisture in nonfat substance. Reduced fat had little effect on the age-related changes in the population of starter cells. The populations of nonstarter lactic acid bacteria decreased with fat content, and counts in the low fat cheese (6% wt/wt) were significantly lower than those in the full fat cheese (33% wt/wt) at ripening times >1 and <180 d. Proteolysis as measured by the percentage of total N soluble at pH 4.6 or in 70% ethanol decreased significantly as the fat content decreased. However, the content of pH 4.6 soluble N per 100 g of cheese was not significantly influenced by fat content. At ripening times >60 d, the content of 70% ethanol soluble N per 100 g of full fat (33% wt/wt) cheese was significantly lower than that in either the half fat (17% wt/wt) or low fat (6% wt/wt) cheeses. The concentration of AA N, as a percentage of total N, was not significantly affected by fat content. However, when expressed as a percentage of total cheese, amino acid N increased significantly with decreasing fat content. Analysis of pH 4.6 soluble N extracts by reverse phase- and gel permeation HPLC revealed that fat content affected the pattern of proteolysis, as reflected by the differences in peptide profiles.     

相对湿度对牦牛毛霉霉菌奶酪成熟过程中品质的影响

为研究不同相对湿度对牦牛霉菌奶酪成熟过程中品质的影响,并确定其在成熟过程中的最佳相对湿度和成熟时间,本实验以牦牛霉菌奶酪为试验材料,将其分别置于相对湿度为30%、50%、70%条件下成熟,测定其在成熟过程中感官品质、质构、pH、营养成分、蛋白质和脂肪分解指标以及挥发性风味物质的变化。结果表明:相对湿度为50%,成熟6 d时,奶酪的感官评分最高且质构较佳。随着成熟时间的延长,三个实验组的水分、蛋白质和脂肪含量呈下降趋势,灰分逐渐上升;pH呈先下降后保持不变或上升。除成熟第0和8 d外,在同一成熟时间点,相对湿度为30%的水分含量均显著低于其他两组(P<0.05);灰分、蛋白质和脂肪含量变化不明显;相对湿度为50%的pH下降速度最快。pH4.6醋酸盐缓冲液可溶性氮含量、12%三氯乙酸可溶性氮含量、酸价和硫代巴比妥酸值均在奶酪成熟过程中不断升高,且相对湿度为50%时值最高。对牦牛毛霉霉菌奶酪挥发性风味物质检测发现,相对湿度为50%,成熟第6 d时,奶酪的风味物质含量较高。因此,牦牛霉菌奶酪在相对湿度为50%,成熟6 d时,其品质最佳。     

非发酵剂乳酸菌A-3和D-3对半硬质山羊奶干酪成熟的影响

目的获得加速半硬质山羊奶干酪成熟的非发酵剂乳酸菌菌株(non-starterlacticacidbacteria,NSLAB)。方法以前期分离自地中海地区山羊奶干酪中的2株优良NSLAB菌株为研究对象,测定其对干酪成熟过程中组成成分、微生物菌群、蛋白质水解和质构的影响。结果添加NSLAB菌株对干酪组成成分没有显著影响, NSLAB菌株没有影响乳球菌生长,在干酪成熟期间pH 4.6-SN和12%TCA-SN逐渐增加,且添加NSLAB的干酪在成熟30 d后显著增加了pH 4.6-SN和12%TCA-SN含量, 5%PTASN/TN的增加主要是由于乳酸菌中肽酶作用的结果, SDS-PAGE电泳结果说明添加NSLAB菌株的干酪中小分子多肽含量明显比对照干酪多,RP-HPLC分析得出干酪水溶性中肽的数量随着成熟时间增加。添加NSLAB菌株A-3没有改变干酪的硬度,使干酪的弹性增加。结论添加菌株A-3作为NSLAB的干酪样品中微生物自溶率高,蛋白水解程度强,质构性能良好,具有加速干酪成熟的潜力,是山羊奶干酪工业化生产的优良NSLAB。     

The effect of exposure to pressure of 50 MPa on Cheddar cheese ripening

The possibility of acceleration of commercial Cheddar cheese ripening by exposure to a high pressure (HP) treatment of 50 MPa for 3 days at 25°C at different stages of ripening was investigated. Proteolysis was examined in the treated and untreated cheeses by measurement of pH 4.6 water soluble nitrogen, expressed as g/100 g total N (pH 4.6 SN/TN), urea-PAGE, reverse phase (RP) HPLC, analysis of molecular mass distribution by gel permeation and measurement of free amino acids (FAA) in the pH 4.6 SN. There was an immediate increase in pH 4.6 SN/TN and FAA in cheese HP-treated at 2 days of age, although this effect decreased with cheese age. Urea-PAGE analysis of cheese samples indicated that HP treatment accelerated degradation of α_s1-casein and accumulation of α_s1-I-casein (f 24-199). RP-HPLC profiles indicated quantitative but not qualitative differences between treated and non-treated samples. Confocal laser scanning microscopy did not indicate any gross structural changes in the cheese matrix as a result of exposure to 50 MPa for 3 days at 25°C. It was concluded that the enhancement of proteolysis observed may be attributed to a combination of the temperature and pressure used in the treatment.     

地衣芽孢杆菌凝乳酶对切达干酪成熟过程中蛋白水解的影响

利用地衣芽孢杆菌凝乳酶制作切达干酪和切达干酪类似物,分析干酪成熟过程中各蛋白水解指标的变化规律,以揭示地衣芽孢杆菌凝乳酶对切达干酪成熟过程中蛋白水解的影响。结果表明,CDF组（添加地衣芽孢杆菌D3.11凝乳酶所制切达干酪）、CD3组（添加地衣芽孢杆菌D3.11凝乳酶但未添加发酵剂制成的干酪类似物）和CCF组（添加商品凝乳酶所制切达干酪）干酪蛋白含量、pH 4.6-可溶性氮、12%三氯乙酸-可溶性氮、5%磷钨酸-可溶性氮、总游离氨基酸含量均随着成熟时间延长呈显著增加趋势,并且成熟期间CDF组干酪均显著高于CCF组干酪（P＜0.05）;十二烷基硫酸钠-聚丙烯酰氨凝胶电泳分析表明,CDF组干酪α-酪蛋白水解程度较大;pH 4.6-可溶性肽段分析表明,随着干酪的成熟,总肽含量呈先增加后下降趋势,但疏水性肽与亲水性肽的比值呈持续下降趋势,在成熟第6个月时,CDF组、CD3组和CCF组干酪疏水性肽与亲水性肽比值分别为2.668、2.822、3.788。主成分分析表明,3 组干酪的蛋白水解程度与成熟度呈正相关,与疏水性肽和亲水性肽的比值呈负相关。以上结果表明,利用地衣芽孢杆菌凝乳酶制作的干酪蛋白水解度更高,但其疏水性肽比例较小,研究结果可为地衣芽孢杆菌凝乳酶在干酪生产中的应用提供理论依据。     

豆奶干酪成熟过程中蛋白水解的研究

本文主要研究了豆奶干酪成熟过程中蛋白水解的变化,并与纯牛乳干酪进行比较。结果表明:豆奶干酪中pH4.6 SN 和12%TCA SN随着时间的延长逐渐增高,而且pH4.6 SN的增长速度比12%TCA SN快,这与纯牛乳干酪是一致的,但豆奶干酪的可溶性氮低于同一时期的纯牛乳干酪。     

成熟温度和时间对半硬质干酪成熟特性影响研究

研究成熟温度和时间对半硬质干酪成熟特性的影响。将干酪分别在4、10、16℃条件下成熟,测定其在90d 内品质变化规律。结果表明,在90d 成熟期内,pH 值先下降后升高,最后趋于稳定;pH4.6 可溶性氮含量和12% 三氯乙酸可溶性氮含量逐渐升高;乳酸菌总数逐渐下降。成熟温度对干酪的感官品质、pH 值、蛋白质的降解和乳酸菌总数影响显著。4℃成熟的干酪,在第90 天时,感官品质达到最好;10℃成熟的干酪,在第45天时,感官品质达到最好;16℃成熟的干酪,感官品质较差。根据感官品质和其他参数的变化规律,确定半硬质干酪的最佳成熟温度为10℃,最佳成熟时间为45d。     

Effect of pH and calcium concentration on proteolysis in mozzarella cheese

Low-moisture Mozzarella cheeses (LMMC), varying in calcium content and pH, were made using a starter culture (control; CL) or direct acidification (DA) with lactic acid or lactic acid and glucono-delta-lactone. The pH and calcium concentration significantly affected the type and extent of proteolysis in Mozzarella cheese during the 70-d storage period at 4 degrees C. For cheeses with a similar pH, reducing the calcium-to-casein ratio from -29 to 22 mg/g of protein resulted in marked increases in moisture content and in primary and secondary proteolysis, as indicated by polyacrylamide gel electrophoresis and higher levels of pH 4.6- and 5%-PTA-soluble N. Increasing the pH of DA cheeses of similar moisture content, from approximately 5.5 to 5.9, while maintaining the calcium-to-casein ratio almost constant at approximately 29 mg/g, resulted in a decrease in primary proteolysis but had no effect on secondary proteolysis. Comparison of CL and DA cheeses with a similar composition showed that the CL cheese had higher levels of alpha(s1)-CN degradation, pH 4.6- and 5%-PTA-soluble N. Analysis of pH 4.6-soluble N extracts by reverse-phase HPLC showed that the CL cheese had higher concentrations of compounds with low retention times, suggesting higher concentrations of low molecular mass peptides and free amino acids.     

干酪介电特性与成熟期及成熟度相关性分析

以半硬质契达干酪为研究对象,对同一加工样品在9℃贮存成熟,分别对成熟期0、15、30、45、60、90、120、150、180 d的干酪样品进行了介电特性和成熟度指标的测定,包括干酪样品总氮(total nitrogen,TN)含量、p H 4.6可溶性氮(soluble nitrogen,SN)含量及三氯乙酸(trichloroacetic acid,TCA)溶液中SN含量的测定。测试频率选定为500、915、1 500、2 000 MHz,对测试结果进行了统计分析,建立了干酪介电特性与成熟度指标之间的相关性。结果表明:随着成熟期的延长,干酪水分含量略有减少、水分活度明显降低、p H值先降低后升高、成熟度指数p H 4.6-SN/TN和12%TCA-SN/TN均随成熟期延长而增大;介电常数ε’在所选的测试频率下与成熟期和成熟度指数的变化均呈线性相关关系;介电损耗因数ε’’在所选测试频率范围内,随成熟期的延长和成熟度的增大呈现总体下降趋势,与成熟期和成熟度在500 MHz和915 MHz频率条件下线性相关性极显著(P0.01),而在高频1 500 MHz和2 000 MHz条件下线性相关性不显著;损耗角正切值变化不明显,表明在测试频率范围介电常数ε’和介电损耗因数ε’’的变化方向一致,同时变化幅度相近。     

Accelerated ripening of Cheddar cheese at elevated temperatures

Blocks (20 kg) of Cheddar cheese from a single vat were obtained from a local factory. Half the cheeses were cooled rapidly (15 h) to ripening temperature (8, 12 or 16 °C) and half were cooled slowly over 8 days to the same ripening temperatures. Cheeses were ripened for 9 months at 7 different time/temperature combinations. Ripening temperature had little influence on the number of non-starter lactic acid bacteria in the cheeses after 9 months, although rapid cooling to and ripening at 8 °C drastically reduced the growth rate of these adventitious bacteria. Proteolysis (as determined by urea-polyacrylamide gel electrophoresis; increases in water-soluble N; increases in phosphotungstic acid-soluble N; Cd ninhydrin-reactive amino groups; and reverse-phase HPLC) and lipolysis were accelerated by increasing the ripening temperature and by slow cooling of the cheeses. The rate of ripening was increased or decreased by changing the temperature. Cheeses ripened at 16 °C generally received the highest flavour scores, particularly early during ripening. However, the texture of these cheeses deteriorated after prolonged ripening at 16 °C. Maturation at 12 °C was considered to be optimal for the commercial acceleration of Cheddar cheese ripening.     

Proteolysis in Manchego-type cheese salted by brine vacuum impregnation

A new salting procedure based on the brine vacuum impregnation of porous products was tested on Manchego-type cheese and compared with conventional brine immersion. Its effect on cheese proteolysis throughout a 90-d ripening period was determined. Three cheese regions were evaluated (the rind, the middle, and the internal regions). The parameters analyzed were total N, water-soluble N, soluble N in trichloroacetic acid and soluble N in phosphotungstic acid by using the Kjeldahl method, casein profile by urea-PAGE, and peptide profile of the water soluble nitrogen extract by reverse-phase HPLC. Free amino acid formation was monitored with a spectrophotometric method by using a Cd-ninhydrin reagent. Globally, proteolysis was significantly affected by ripening stage (increasing throughout all the maturation period studied) and cheese region (rind showed a proteolysis pattern different from the middle and internal regions). The salting procedure only affected cheese proteolysis in the rind, whereas conventional brine-salted cheeses showed lower proteolysis than vacuum-impregnated cheeses.     

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on cheddar cheese quality: pH changes during ripening

The pH of cheese is an important attribute that influences its quality. Substantial changes in cheese pH are often observed during ripening. A combined effect of calcium, phosphorus, residual lactose, and salt-to-moisture ratio (S/M) of the cheese on the changes in cheese pH during ripening was investigated. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. All the cheeses were salted at a pH of 5.4, pressed for 5 h, and then ripened at 6 to 8°C. The pH of the salted curds before pressing and the cheeses during 48 wk of ripening was measured. Also, cheeses were analyzed for water-soluble Ca and P, organic P, and bound inorganic P during ripening. Changes in organic acids’ concentration and shifts in the distribution of Ca and P between different forms were studied in relation to changes in pH. Cheeses with low S/M exhibited a larger increase in acid production during ripening compared with high S/M cheeses. Cheeses with the highest concentration of bound inorganic P exhibited the highest pH, whereas cheeses with the lowest concentration of bound inorganic P exhibited the lowest pH among the 8 treatments. Although conversion of lactose to short-chain, water-soluble organic acids decreased cheese pH, bound inorganic phosphate buffered the changes in cheese pH. Production of acid in excess of the buffering capacity (which was the case in low Ca and P and low S/M treatments) led to a low pH, whereas solubilization of bound inorganic P in excess to acid production (which was the case in high Ca and P and high S/M treatments) led to an increase in pH. However, for cheeses with high Ca and P and low S/M, changes in cheese pH were influenced by the level of residual lactose. Hence, pH changes in Cheddar cheese can be modulated by a concomitant control on the amount and state of Ca and P, level of residual lactose, and S/M of the cheese.     

Rheological and calcium equilibrium changes during the ripening of Cheddar cheese

The small deformation rheological properties and the calcium (Ca) equilibrium of Cheddar cheese were investigated as a function of ripening time. The proportion of insoluble Ca as a percentage of the total Ca decreased from ∼72 to 57% between 3 days and 9 months; most changes occurred within the first 4 weeks. During ripening, the storage modulus (G′) of the cheese increased at low temperature, but decreased rapidly at high temperature. At temperatures >40 °C, the loss tangent increased to reach a maximum at a temperature of ∼70 °C in young cheese and there was a steady decline in this temperature during ripening. The maximum loss tangent values increased substantially during the first 4 weeks and then showed little change. Changes in the insoluble Ca content significantly correlated with pH 4.6 soluble nitrogen (pH 4.6 SN). Partial correlation analysis indicated that the insoluble Ca content was more significantly correlated with the rheological properties than was pH 4.6 SN.