Proteolytic and lipolytic changes during the ripening of a Spanish craft goat cheese (Armada variety)

The proteolytic and lipolytic changes during the ripening process were investigated in four batches of Armada goat's milk cheese (an artisanal variety produced in the North of Spain), by determining the classical nitrogen fractions, caseins and their degradation products, free amino acids, as well as the acidity of the fat, thiobarbituric acid (TBA) number and free fatty acids. Values obtained for the nitrogen fractions and for caseins and their degradation products show that this cheese undergoes very little protein degradation. A low free amino acids content was observed throughout the ripening process with a predominance of Pro followed by Leu+Ile, Glu acid, Phe, His+Lys and Val. The lipid degrada-tion was very intense from the second month of ripening, only comparable to that reported for cheeses ripened by moulds. The average free fatty acids content increased 20-fold during ripening, reaching final values of 44·5 g kg⁻¹. All the free fatty acids increased considerably during ripening, resulting in a predominance of saturated and unsaturated long-chain acids, followed by medium-chain acids, C₁₀ principally. Short-chain fatty acid content by the end of ripening was higher than that presented in other cheese varieties with a similar high degree of lipolysis. © 1997 SCI.     

Biochemical changes during the ripening of homemade 'San Simón da Costa' raw milk cheese

'San Simón da Costa' cheese is a traditional smoked variety produced in the northwest of Spain from cow's milk. Biochemical changes were determined during its ripening. Its high calcium and phosphorus content and its low NaCl and sodium content stand out. This cheese undergoes moderate proteolysis. The most abundant free amino acid at the end of the ripening was glutamic acid, followed by tryptophan, leucine, arginine and phenylalanine. The lipolysis throughout ripening is slight; the most abundant free fatty acid being oleic, followed by palmitic and butyric acid.     

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.     

凝乳酶对牦牛乳硬质干酪成熟期间蛋白降解的影响

以新鲜牦牛乳为原料,采用小牛皱胃酶、木瓜蛋白酶和微生物凝乳酶制作硬质干酪,探讨凝乳酶种类对牦牛乳硬质干酪成熟期间蛋白质降解的影响。结果表明:三种凝乳酶牦牛乳硬质干酪成熟过程中,不同凝乳酶牦牛乳硬质干酪在成熟期间蛋白质降解能力存在较大差异,总氮（TN）、p H4.6水溶性氮（p H4.6-SN/TN）、12%的三氯乙酸氮（12%TCA-N/TN）、5%磷钨酸氮（5%PTA-N/TN）含量、游离氨基酸均随成熟时间延长不同程度的增加,蛋白氮和酪蛋白氮逐渐降低,多肽氮呈先升高后下降趋势,且微生物凝乳酶降解牦牛乳硬质干酪蛋白能力显著（p<0.05）高于木瓜蛋白酶和小牛皱胃酶。      

Lipolysis and proteolysis profiles of fresh artisanal goat cheese made with raw milk with 3 different fat contents

The objective of this study was to describe the proteolysis and lipolysis profiles in goat cheese made in the Canary Islands (Spain) using raw milk with 3 different fat contents (0.5, 1.5, and 5%) and ripened for 1, 7, 14, and 28 d. β-Casein was the most abundant protein in all cheeses and at all ripening times. Quantitative analysis showed a general decrease in caseins as ripening progressed, and degradation rates were higher for α_S1-casein than for β-casein and α_S2-casein. Furthermore, the degradation rate during the experimental time decreased with lower fat contents. The α_S2-casein and α_S1-casein levels that remained in full-fat and reduced-fat cheeses were less than those in low-fat cheese. In contrast, β-casein also showed degradation along with ripening, but differences in degradation among the 3 cheese types were not significant at 28 d. The degradation products increased with the ripening time in all cheeses, but they were higher in full-fat cheese than in reduced-fat and low-fat cheeses. The free fatty acid concentration per 100 g of cheese was higher in full-fat cheese than in reduced- and low-fat cheese; however, when the results were expressed as milligrams of free fatty acids per gram of fat in cheese, then lipolysis occurred more rapidly in low-fat cheese than in reduced- and full-fat cheeses. These results may explain the atypical texture and off-flavors found in low-fat goat cheeses, likely the main causes of non-acceptance.     

Physicochemical, microbiological and sensory changes during ripening and storage of Xinotyri, a traditional Greek cheese from raw goat's milk

Physicochemical, microbiological and sensory characteristics, evolution of lipolysis monitored by measuring acid degree value (ADV) and the main mineral elements were studied during ripening and storage of artisanal Xinotyri cheese from raw goat's milk. Cheeses were characterized by a high content in total solids (TS; 83%) and fat (59% of TS), and very low pH (4.0), water activity (0.87) and moisture (17%). Protein and salt contents at the end of storage were 31% and 2.8%, respectively. Lipolysis increased, while variations in mineral (Ca, P, Mg and Zn) content were found during ripening and storage. Cheeses were free of Salmonella and Listeria in 25 g, while enterobacteria, pseudomonads, and coagulase-positive staphylococci were < 100 cfu/g. Mesophilic lactic acid bacteria increased above 8 log cfu/g by day 6, but declined by 2–3 logs in the ripened cheese (45 days) and by 3–4 logs during cheese storage at 4°C for up to 180 days.     

Comparison of the characteristics of teleme cheese made from ewe's, goat's and cow's milk or a mixture of ewe's and goat's milk

Teleme cheeses were manufactured from ewe's, goat's and cow's milk and mixture of ewe's and goat's milk. Physicochemical and biochemical analyses of the cheeses at various stages of ripening and storage were performed. Cheeses made from goat's milk had lower moisture content than those made from other milks. No significant differences in the mean values of protein, salt and water activity (a _w ) of the different cheeses at all ages studied were found. Cheeses from goat's and cow's milk had higher contents of fat and fat in dry matter (FDM) compared to that of cheeses from ewe's milk and mixed milk. Significant differences were observed in the yield and yield on 56% moisture: cheeses from ewe's milk gave the highest yield and cheese from cow's milk the lowest. Significant differences were found in the ashes content of the different cheeses at all ages. No differences in cholesterol and cholesterol/fat contents of the four types of cheeses were found. Main and trace elements showed variability among the four cheeses.     

Changes during ripening in chemical composition,proteolysis, volatile composition and texture in Kashar cheese made using raw bovine,ovine or caprine milk

Kashar cheeses were manufactured from pure ovine (OV), bovine (BV) and caprine (CP) milk, and the chemical composition, cheese yield, proteolysis, hardness, meltability and volatile composition were studied during 90 days. Gross chemical composition, cheese yield and level of proteolysis were higher in OV cheeses than those of BV or CP cheeses. Glu, Val, Leu, Phe and Lys were the most abundant free amino acids (FAA) in the samples, and the concentrations of individual FAA were at the highest levels in OV cheeses with following BV and CP cheeses. Urea‐PAGE patterns and RP‐HPLC peptide profiles of the BV cheeses were completely different from the small ruminants’ milk cheeses (OV or CP). Higher and lower hardness and meltability values were observed in CP cheeses, respectively. OV cheeses resulted in higher levels of the major volatile compounds. In conclusion, the Kashar cheese made using OV milk can be recommended due to high meltability, proteolysis and volatiles.     

提高成熟温度加快Mozzarella干酪成熟的研究

制作2批Mozzarella干酪A和B，分别在4℃(A)和7℃(B)下成熟，观察其在成熟期间的变化及测定可溶性N的含量等指标，可知在7℃下成熟的干酪在制作后30d的蛋白水解性、功能特性等和4℃下成熟50d的干酪无显著差异，而和7℃下成熟50d的干酪有显著差异。说明成熟温度显著影响干酪的蛋白水解性。在7℃下贮藏的Mozzarella干酪成熟30d可达到4℃下贮存50d的成熟度，即将成熟温度从4℃提高到7℃，可将成熟期缩短20d左右。     

Comprehensive analysis of proteolysis during 8 months of ripening of high-cooked Old Saare cheese

We applied capillary electrophoresis, liquid chromatography coupled with tandem mass-spectrometry (MS/MS), and ultra-performance liquid chromatography to determine the composition of water-insoluble and water-soluble proteinaceous fractions of the cheese and to study in detail the degradation of caseins during 8 mo of ripening of Estonian high-temperature cooked hard cheese Old Saare. The application of high-resolution and high-accuracy MS/MS enabled identification of more than 3,000 small peptides, representing a fairly full casein peptidome containing peptides of 4 to 25 AA in length: 1,049 from β-casein (CN), 944 from α_S1-CN, 813 from α_S2-CN, and 234 from κ-CN. The majority of β-CN- and α_S1-CN-derived peptides originated from the N-terminal parts of the molecule, f6-93 and f1-124, respectively; peptides from α_S2-CN arose predominantly from the C-terminal end f100-162. At the beginning of ripening, we found a relatively high amount of peptides originating from the glycomacropeptide part of κ-CN, whereas peptides from para-κ-CN prevailed during the later stages of ripening of the cheese. The cleavage patterns of β-CN, α_S2-CN, as well as α_S1-CN, showed that primary proteolysis was started mainly by plasmin, although a low proteolytic activity of chymosin was also evident. Based on the analysis of cleavage sites, we observed a significant participation of proteolytic enzymes, including amino- and carboxypeptidases, of both mesophilic and thermophilic starter bacteria in further hydrolysis of oligopeptides during the ripening. Several new phosphopeptides were detected in the result of MS/MS data analysis. The profiles of the estimated concentrations of phosphopeptides revealed that those originating from β-CN and α_S1-CN accumulated during cheese maturation. In contrast, we did not notice any generation of phosphopeptides from the highly phosphorylated part of α_S2-CN, f25-80, presumably due to the inaccessibility of this region to the action of plasmin and chymosin. The analysis of cleavage sites and the combination of principal component and clustering analyses provided a characterization of the complex dynamics of formation and degradation of peptides during cheese maturation. We made an attempt to obtain a comprehensive picture of proteolysis during Old Saare cheese ripening on the basis of the detailed peptidomic data, including also the less abundant peptides determined by MS/MS, and complemented by the data on intact caseins and free AA and reported the results in the paper.     

Free fatty acids and oxidative changes of a raw goat milk cheese through maturation

Free fatty acids (FFA) and lipid and protein oxidation changes were studied throughout maturation process of a raw goat milk cheese with protected designation of origin. Cheeses were analyzed at 4 different times of maturation, at 1, 30, 60, and 90 d. All FFA significantly increased during maturation and the relative increase was higher for long-chain than medium- or short-chain FFA. At the end of maturation, oleic (C18:1 n9), butyric (C4:0), and palmitic (C16:0) acids were the most abundant. The higher levels of short-chain fatty acids (SCFA) regarding total FFA obtained at the end of Ibores cheese ripening compared with other raw goat milk cheeses, highlight the notable role of SCFA on the flavor of this cheese owing to their low-odor thresholds. Lipid oxidation values significantly increased during maturation process but low levels of malondialdehyde were reported; however, protein oxidation did not significantly change during ripening.     

Instron texture profile of buffalo milk cheddar cheese as influenced by composition and ripening changes

Buffalo milk Cheddar cheese samples of different ages were analysed for compositional attributes (CA), ripening indices (RI) and Instron Textural Profile (ITP). All samples were compositionally alike, except for pH and salt-in-moisture (SM) contents. RI showed significant variations. CA and RI showed highly significant correlations within themselves and with each other, except for moisture with pH, SM with moisture, MNFS, Fat and FDM and Fat with MNFS. The ITPs of cheeses showed significant variations and had highly significant intercorrelations indicating their interdependence. CA (except moisture and MNFS) and RI showed a highly significant correlationship with ITPs. Moisture content showed a highly significant correlationship with all ITPs, except cohesiveness and springiness, where it was significant. MNFS content showed significant correlations only with hardness and brittleness. Stepwise regression analysis revealed that MI was the most predominant factor influencing cheese texture, followed by pH, SM, FDM and TVFA. Knowing Ca and RI, the textural properties of cheeses can be forecast through mathematical equations. Similarly the age of cheese can also be predicted if RI and/or textural properties are known.     

Fate of Listeria innocua during production and ripening of smeared hard cheese made from raw milk

The fate of 2 different Listeria innocua strains was analyzed during the production and ripening of smeared raw milk Greyerzer cheese (Gruyère). These strains were used as surrogates for the pathogenic Listeria monocytogenes, as they are physiologically very similar. Bacterial cells were added to the cheese milk at levels of 10⁵ cfu/mL. During the first 24 h of cheese making, the number of the test strains decreased to a level of below 10² cfu/g. Obviously, the cooking temperature of 56°C and the subsequent slight temperature decrease to 50°C within 70 min contributed to a distinct reduction of Listeria counts. The counts in the cheese cores did not exceed 10³ cfu/g within 12 wk of cheese ripening and Listeria was not detectable after 24 wk. In contrast to the cores of the cheeses of the 4 batches in this study, their rinds always contained a high listerial load of approximately 10⁶ to 10⁸ cfu/g throughout the entire ripening period. The smeared surface showed an increase of pH to alkaline values, corresponding to smear microbiota development. Coryneforms and Staphylococcus counts were stable at >10⁷ cfu/cm² over 175 d, whereas yeast counts decreased to about 10⁵ cfu/cm² at the end of ripening. The study shows that the smear culture had no noticeable anti-listerial potential. When removing the rind or portioning such smeared cheese loaves with a cutting device, a postprocess contamination of the core might occur, thus presenting a major hygienic risk.     

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.     

Microstructural changes in fat during the ripening of Iranian ultrafiltered Feta cheese

In this study, fat globules in Iranian ultrafiltered Feta cheese (3 to 60 d) were directly observed during the ripening period by scanning electron microscopy. According to images of ultrafiltered Feta cheese samples obtained by scanning electron microscopy, individual fat globules and aggregates of fat were easily distinguishable on d 3 and had completely disappeared within 20 d of storage. On d 20, only the fingerprints of the fat globules and pools of free fat in the casein matrix remained. After 40 d of ripening, the texture was homogeneous and no fat globules or fat voids were detected. Chemical analysis of cheese samples showed that with an increase in the ripening period, the contents of dry matter and fat decreased significantly, whereas the pH values and salt content did not indicate any significant changes.     

黑豆豆乳添加量对Mozzarella奶酪成熟过程中品质的影响

在牛乳中添加不同的黑豆豆乳,研究不同的黑豆豆乳添加量对Mozzarella奶酪在成熟0 d、30 d、60 d、90 d时的水分活度、pH、质构、色泽、蛋白质降解等品质指标变化的影响。结果显示,随着黑豆豆乳添加量在2%～6%范围内的增大,奶酪的水分活度不断增大,pH不断降低,奶酪的硬度、弹性、粘附性、咀嚼性增加,奶酪的明亮度（L*值）下降,红度（a*值）和黄度（b*值）增加,而加入黑豆豆乳的奶酪在成熟过程中蛋白质降解与对照奶酪相似。综合各个指标,在牛乳中加入4%黑豆豆乳条件下制作的黑豆豆乳牛乳奶酪,既有独特的风味,同时奶酪具有较好的色度、质构、蛋白降解等指标特性。     

红曲水牛乳软质干酪成熟特性的研究

红曲霉(Monascus purpureus Went.)是腐乳酿造中常用的菌种,将其作为表面发酵剂喷洒在干酪表面,研究该菌种对干酪成熟期间各理化指标的影响,结果表明:随着红曲霉在干酪表面生长和干酪成熟时间的延长,其含水量呈先低后高的趋势,最终维持在42%左右,可溶性氮p H4.6 SN和12%TCA SN分别高达35.8%和33.5%,其硬度、弹性、咀嚼性均随着成熟时间的延长而下降,干酪发酵成熟25 d便可得到最佳感官品质,其Monacolin K的含量为2.13 mg/100 g。