Influence of starter culture ratios and warm room treatment on free fatty acid and amino acid in Swiss cheese

Quantification of water-soluble volatile free fatty acids (FFA) and free amino acids (FAA) was performed as a ripening index and an indirect measure of flavor development in Swiss-type cheeses. The objective of this research was to assess the effect of warm room treatment (WRT) and usage ratio of starter cultures, Streptococcus thermophilus and Lactobacillus helveticus vs. propionibacteria, on the concentration of FFA and FAA in pilot plant-scale Swiss cheese. A capillary gas chromatograph equipped with a flame ionization detector was used for the analysis of FFA in Swiss cheese. Free amino acids were analyzed by the Cd-ninhydrin method. Starter culture ratios did not affect development of FAA during the cheese ripening. However, duration of WRT had an effect on the concentration of FAA in the Swiss cheese. Free amino acids increased considerably during WRT. A continuous increase in FAA was shown during 70-d ripening time after WRT. The concentrations of C2:0 and C3:0 fatty acids were affected by starter culture ratios after 2-wk WRT, but these differences had mostly disappeared after 3-wk WRT. Similar concentrations of FFA and FAA reported in previous studies were developed in Swiss cheese with a 3-wk WRT and a 0.33:1 ratio of Streptococcus thermophilus and Lactobacillus helveticus to propionibacteria.     

快速成熟契达干酪成熟期间的理化特性变化

对天然契达(Cheddar)干酪快速成熟期间理化特性进行了研究,结果表明,在21 d内,pH值呈下降趋势(P<0.05),在21 d到35 d的成熟中,pH值缓慢增加(P>0.05);Cheddar干酪快速成熟过程中由于蛋白酶和脂肪酶的作用使蛋白发生水解,pH值为4.6醋酸溶液—水溶性氮质量分数、质量分数为12%的三氯乙酸—可溶性氮和游离氨基酸(FAA)的质量分数都呈明显增加趋势(P<0.05);成熟过程中TPA各项指标均有不同程度的变化,硬度和凝聚性呈先下降后增加的趋势,弹性和咀嚼性呈先上升后下降的趋势。     

Free amino acid profile during ripening of ewe's milk cheese from the Croatian island Krk

The aim of this study was to determine the content of free amino acids (FAA) and their ratio in ewe's milk cheese from the island Krk during its ripening. FAA content was determined by reversed phase HPLC (RP‐HPLC) of cheese aqueous/ethanol extracts after FAA were transformed into their 6‐aminoquinolyl‐N‐hydroxysuccinimidyl carbamate derivatives. Their concentration increased during ripening, reaching the value of 5% in cheese dry matter. The dominant FAA were glutamic acid>leucine>valine>aspartic acid>phenylalanine>serine>proline, and higher content of nonessential vs essential FAA was revealed. Krk cheese has, in relation to other cheeses, higher values for glutamic acid/leucine, glutamic acid/phenylalanine, glutamic acid/proline and smaller values for leucine/aspartic acid, valine/aspartic acid, phenylalanine/aspartic acid ratios, while other ratios are comparable to those of other hard ovine cheeses.     

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。     

Lipolysis,proteolysis and sensory properties of ewe’s raw milk cheese (Idiazabal) made with lipase addition

In this paper, we describe the effect of the addition of pregastric lipase on the composition and sensory properties of Idiazabal cheese. Free fatty acids (FFA), partial glycerides, free amino acids (FAA), gross composition and sensory characteristics were determined at different ripening times in cheeses manufactured with three different amounts of commercial animal lipase or with lipase-containing artisanal lamb rennet paste. The addition of lipase increased the content of total FFA, particularly of short-chain FFA, and that of total partial glycerides in cheeses. Unexpectedly, lipase utilization significantly affected total FAA concentration, which decreased in cheeses elaborated with high lipase amount. In general, Val, Glu and Leu were the major FAA, and their concentrations depended, mainly, on ripening time. Lipase addition had significant influence on the sensory characteristics of the cheeses, increasing scores for most of the flavour and odour attributes of the cheese. Principal component analysis (PCA) was done including dry matter, FFA, FAA, partial glycerides and odour and flavour attributes of the cheeses. It indicated that aroma and flavour parameters of Idiazabal cheese and the content of short-chain FFA and diglycerides were highly correlated to first principal component (PC1), while texture parameters, compositional variables and FAA were correlated to the second principal component (PC2).     

Evolution of free amino acid content during ripening of Mahon cheese

Evolution of free amino acids (FAA) during ripening (10–300 days) of five batches of Mahon cheese was studied; three batches were made from raw milk and two from pasteurized milk. Major FAA were GLU, VAL, LEU, LYS and PHE (43–67% of total FAA). Relative THR, SER, GLU and GLY contents significantly increased during ripening whereas LEU, PHE and ORN decreased. GLU, ILE, SER, THR, GLY and PHE varied during ripening according to a zero order reaction (r² > 0.99). Principal component analysis showed that the first principal component could be considered representative of the ripening time. The most ripened cheeses showed high GLU, GLY, SER and THR contents and the less ripened cheeses presented high ORN, LEU, PHE and ALA contents. The second component distinguished between cheeses made with pasteurized milk (with high ASN and GLN contents) and raw milk. Indigenous microflora of raw milk showed a strong influence on the proteolytic activity in Mahon cheese.     

Effect of freeze–dried kefir culture on proteolysis in feta-type and whey-cheeses

The effect of freeze–dried kefir culture on the proteolysis of feta-type and whey-cheese was investigated. All nitrogen fractions increased during ripening. Although no significant differences were observed in total nitrogen (TN), the levels of water-soluble nitrogen (WSN), pH 4.4-soluble nitrogen (SN), 12% trichloroacetic acid-soluble nitrogen (TCA-SN) and phosphotungstic acid-soluble nitrogen (PTA-SN) were significantly higher in cheeses produced by freeze–dried kefir culture during the later stages of ripening. Content of total free amino acids (FAA) was significantly affected by freeze–dried kefir starter culture and it was continuously increased in kefir-cheese while, in rennet-cheese it was increased up to 30 days of ripening and then slightly decreased. On the other hand, FAA content continuously decreased in kefir-whey-cheese whereas it increased in whey-cheese. The cheese samples produced by freeze–dried kefir as starter culture were characterised as high-quality products during the preliminary sensory evaluation and they were accepted by the panel. Overall, the use of freeze–dried kefir suggested acceleration of cheese ripening and resulted in improved sensory characteristics.     

Evolution of free amino acids during ripening of Caciocavallo cheeses made with different milks

The evolution of free amino acids (FAA) in Caciocavallo cheeses, made with cow milk (CC) and cow milk mixed with ewe (CE) and goat (CG) milk, was studied throughout ripening. In all Caciocavallo cheeses produced, the total free amino acid (TFAA) content increased during ripening. In general, the highest TFAA content was found in cow cheeses, and the lowest in CG cheeses, whereas CE cheeses ranged over an intermediate level. In all the analyzed samples, during ripening, the content of the individual FAA increased with the exception of arginine. Tyrosine and histidine were found only in CE samples from the middle to the end of ripening. The major FAA found throughout the whole ripening period, in all types of cheese, were leucine, phenylalanine, lysine, valine, asparagine, γ-aminobutyric acid, and ornithine. The TFAA and several AA showed significant differences in ripening time, whereas tyrosine and histidine showed significant differences in kinds of milk.     

不同包装方式对半硬质干酪成熟期间蛋白质降解的影响

对真空包装和涂蜡包装的半硬质干酪成熟过程中蛋白降解进行了研究。结果表明:2种包装的干酪在成熟过程中pH 4.6SN含量和12%TCA-SN含量都随着时间的延长逐渐增大,且2组数据之间差异显著(P<0.05);2种包装的干酪中游离氨基酸总量随成熟时间的延长而逐渐增加,各种氨基酸含量变化的显著性不同;SDS-PAGE电泳图谱显示2种干酪在成熟期内蛋白质都发生了明显的降解,且涂蜡包装的干酪蛋白降解程度较真空包装的深,在成熟45 d后较为明显。     

Ripening time estimation of Kariesh cheese

Kariesh cheese is a popular cheese in Egypt produced by acid coagulation of milk. It can be consumed fresh or after ripening. Proteolysis in cheese was measured by determining soluble nitrogen (SN), amino acid nitrogen (AAN), total amino acids (TAA) and free amino acids (FAA). SN, AAN and FAA increased during ripening. Free amino acids profile revealed in total 16 amino acids and the same distribution of free amino acids. Cheese ripening was influenced by the type of milk and the method of production. The mildly acid sweet flavour was attributed to the concentration of glutamic acid, aspartic acid, proline and valine. Linear regression analysis was carried out to estimate the ripening time of this cheese. A positive correlation between the accumulation of amino acid and ripening time was established. The highest coefficient of determination near one resulted from glutamic acid (R² = 0.99) followed by lysine (R² = 0.97–0.99), then aspartic acid (0.90–0.98). From the linear regression equation for glutamic acid, lysine, aspartic acid or proline, the ripening time of Kariesh cheese in weeks was determined as follows: Time of ripening [weeks] = mg amino acid 100 g cheese-a/b where b = slope and a = intercept of regression straight line at 0 time.     

Impact of chymosin- and plasmin-mediated primary proteolysis on the growth and biochemical activities of lactobacilli in miniature Cheddar-type cheeses

Strongly proteolytic starters seem to improve the growth of nonstarter lactobacilli during cheese ripening, but no information is available on the impact of the nonmicrobial proteases usually active in cheese on their development. In the current study, the influence of chymosin- and plasmin-mediated proteolysis on the growth and biochemical activities of lactobacilli during ripening of miniature Cheddar-type cheeses, manufactured under controlled microbiological conditions, was studied. Two experiments were performed; in the first, residual chymosin activity was inhibited by the addition of pepstatin, and in the second, plasmin activity was increased by adding more enzyme, obtained in vitro through the activation of plasminogen induced by urokinase. Cheeses with or without a Lactobacillus plantarum I91 adjunct culture and with or without added pepstatin or plasmin solution were manufactured and ripened for 60 d. The addition of the adjunct culture resulted in enhancement of secondary proteolysis, evidenced by an increase in the total content of free amino acids (FAA) and modifications of the individual FAA profiles. Reduction in residual chymosin activity caused a decrease in primary and secondary proteolysis, characterized by the absence of α_s1-casein hydrolysis and reduced production of peptides and FAA, respectively. The increase in plasmin activity accelerated primary proteolysis but no enhancement of secondary proteolysis was observed. Chymosin- and plasmin-mediated proteolysis did not influence the growth and biochemical activities of adventitious or adjunct lactobacilli, indicating that it is not a limiting factor for the development and proteolytic-peptidolytic activities of lactobacilli in the cheese model studied.     

How milk type,coagulant, salting procedure and ripening time affect the profile of free amino acids in Picante da Beira Baixa cheese

The concentration of total free amino acids (FAA) in Picante cheese increased with ripening time irrespective of the particular protocol used for manufacture (ie ratio of caprine to ovine milks, animal or plant rennet and number of salting steps). The experimental cheeses manufactured with 20% (v/v) caprine milk, coagulated with animal rennet and salted only once exhibited the highest content of total FAA by 120 days of ripening. All four manufacture parameters were statistically significant on the 0.5% level of significance in terms of total concentration of FAA. The dominating free amino acids present in the various experimental cheeses throughout the ripening period were valine, leucine and phenylalanine, each one representing more than 10% (w/w) of the total concentration of FAA. All four manufacture parameters were, in general, statistically significant with respect to the content of every single FAA, with particular emphasis on salting and ripening time. © 1999 Society of Chemical Industry     

Effect of Free or Encapsulated Recombinant Aminopeptidase of Lactobacillus rhamnosus S93 on Acceleration of Cheddar Cheese Ripening

The use of recombinant aminopeptidase (PepN) from Lactobacillus rhamnosus S93 in free or encapsulated form was investigated to shorten the duration of Cheddar cheese ripening. Proteolysis was determined by measuring the soluble nitrogen as phosphotungstic acid (PTA-N) derivatives and free amino acids (FAA) over a 6-month period. The experimental cheeses received higher scores for sensory properties than the control cheese. The amounts of PTA-N and total FAA in the cheese with the encapsulated enzyme after 2 months of ripening were close to those of the control cheese after 6 months, suggesting the acceleration in proteolysis by about 4 months.     

Amino acid and soluble nitrogen evolution throughout ripening of Serra da Estrela cheese

Four batches of Serra da Estrela cheese originating from as many dairy farms were sampled throughout the ripening period, and assayed for the evolution of free amino acid (FAA) content, total nitrogen content (TN), water-soluble nitrogen content (WSN), trichloroacetic acid-soluble nitrogen content (TCASN) and phosphotungstic acid-soluble nitrogen content (PTASN). The WSN content increased from 1% (on the day of manufacture) up to 43% of TN by 180 d of ripening, thus reflecting the intense proteolytic activity of the enzymes contributed by the plant coagulant utilized. The TCASN was also found to be high in this cheese by the end of ripening (16–20%), which suggests a high extent of FAA release throughout maturation. The major FAA by 180 d of ripening were Glu, Val, Leu and Lys, representing 56–70% of the total in all four dairies sampled. Cheeses produced from refrigerated milk possessed higher amounts of γ-amino-n-butyric acid (Gaba) and lower amounts of Glu when compared with those manufactured with non-refrigerated milk.     

Proteolysis,texture and colour of a raw goat milk cheese throughout the maturation

Changes on chemical and textural parameters were studied throughout maturation of PDO Ibores cheese. NCN/TN (non-casein nitrogen/total nitrogen) values were significantly modified (P < 0.001) throughout maturation, and significantly, lower values were observed at day 1 than at day 30, 60 and 90. Non-protein nitrogen/total nitrogen (NPN/TN) was not significantly changed during the ripening process (P > 0.05). Therefore, proteolysis extent (casein degradation and ‘ripening depth’) took place at initial stage and was limited throughout Ibores cheese maturation. In addition, since casein nitrogen decreased during the first month of ripening without a simultaneous increase in NPN/TN, this likely indicates that the large fragments of caseins liberated during this period are not further degraded into smaller products. Primary proteolysis (resulting from the action of endoproteases on caseins) is thus far more important than secondary proteolysis during this period. Moreover, secondary proteolysis remains limited along the 90 days. Polypeptide nitrogen significantly increased at day 30 from casein degradation compared to day 1, while free amino acids (FAA) content significantly increased during maturation process. In addition, hardness and adhesiveness values significantly increased, but cohesiveness and springiness significantly decreased up to day 60. Variables such as dry matter, NCN/TN and polypeptide nitrogen showed high correlations with textural parameters. Principal component analysis (PCA) of variables divided the Ibores cheeses according to their ripening: early, middle or late ripening.     

Accelerating cheese proteolysis by enriching Lactococcus lactis proteolytic system with lactobacilli peptidases

The knowledge available on the genetics and proteolytic system of lactic acid bacteria makes it possible to genetically engineer starters with increased proteolytic properties. Our objective was to identify the best available strains capable of accelerating or modulating casein proteolysis during cheese ripening.To attain this goal, we used Lactococcus lactis strains expressing 5 different Lactobacillus peptidases to ripen a cheese model. At the end of ripening, free amino acids were quantitatively and qualitatively analysed.We identified the mixture of prolidase, PepQ, and X-prolyl dipeptidyl peptidase, PepX, as well as the peptidase PepW as the most efficient peptidases to increase, up to 3-fold, the overall level of amino acids at the end of ripening. The levels of threonine, asparagine, glycine, methionine, valine, glutamine, isoleucine and proline in particular increased (more than 3.5 fold). Grouping the amino acids produced according to the specific aroma compounds that each may give rise to following an enzymatic or chemical conversion, revealed that expression of PepW or PepX and PepQ increased the amounts of all groups of amino acids while expression of PepQ or PepN increased more especially those of aromatic amino acids/proline and glutamic acid, respectively.The combination of increased proteolysis and conversion of amino acids into aroma compounds now needs to be tested. In addition, the role of proline and its derived compounds in the overall flavour of cheese should be investigated.     

干酪成熟过程发酵剂的作用及快速成熟的研究进展

干酪的成熟过程,是在添加酶及各种微生物的协同作用下完成的.干酪中的微生物作用也包括人为添加发酵剂的作用.本文综述了干酪生产过程中发酵剂的使用和成熟过程所起的作用,主要有酸化、改善质构、形成风味物质.此外,本文也讨论了干酪的成熟机制,综述了目前用于促进干酪成熟所使用的一些方法和技术以及对它们的最新研究进展.     

热烫拉伸温度对Mozzarella干酪蛋白降解及质构特性的影响

不同的热烫拉伸温度对Mozzarella干酪的组织结构、凝块中微生物以及酶的活性有很重要的影响,进而会影响其成熟过程中蛋白质的降解以及最终品质的形成,该研究对不同热烫拉伸温度的Mozzarella干酪成熟过程中的蛋白降解及质构特性指标进行测定。结果表明,同一成熟期内,随着热烫温度（对照、70 ℃、90 ℃）的提高,干酪的pH 4.6可溶性氮（SN）显著下降（P＜0.05）,12%三氯乙酸-可溶性氮（TCA-SN）有所下降（P＞0.05）,而干酪的硬度、咀嚼性均显著增大（P＜0.05）,弹性增大而黏附性有所下降（P＞0.05）,融化性、油脂析出性均显著下降（P＜0.05）。因而采取70 ℃的热烫拉伸温度更有利于干酪成熟后形成良好的质构特性及充分的蛋白降解。     

THE CONTRIBUTION OF HERBS TO THE ACCUMULATION OF HISTAMINE IN "OTLU" CHEESE

The aim of this study was to determine the effect of herbs and the use of raw milk on histamine accumulation in “Otlu” (Herby) cheese during ripening. Cow's milk was used for the cheese production. The milk was divided into two main groups: one was used raw and the other was pasteurized at 65C for 30 min. Each group was further divided into two subparts, one of which was used as control (without herbs), while 2% (w/v) of the herbs were added into the other to produce Herby cheese. All cheeses were ripened at 7C for 90 days. The cheese samples were analyzed in terms of histamine content, titratable acidity, dry matter, salt and degree of ripening on days 5, 30, 60 and 90. Total mesophilic aerobic bacteria (MAB) were also counted during ripening. The use of raw milk and the addition of herb both increased histamine formation in Otlu cheeses (P < 0.05). Moreover, higher water‐soluble nitrogen values, as degree of ripening, were obtained from both raw milk and herb‐added cheeses. The number of MAB was higher in raw cheeses (P < 0.05) and also herb‐added cheeses. The study suggests that the addition of herbs may facilitate histamine formation in Herby cheese.