Characterization of the free fatty acids profile of Pategrás cheese during ripening

This work compares the free fatty acids (FFA) profiles of Pategrás cheeses manufactured on the pilot scale, with and without the addition of probiotics. Total and FFA in milks and cheeses, respectively, were similar, indicating a nonselective release during ripening. Lipolysis was lo for control cheeses, but somewhat higher for those made in summer, probably because of an elevated psychrotrophic bacterial development. Probiotic bacteria remained highly viable during ripening and had an influence on FFA profiles. A simple sensory profiling of the cheeses showed no differences in flavour and taste and little evidence of treatment effects was found using univariate analysis. Nevertheless, multivariate analysis showed clear differences between probiotic and control products.     

Proteolysis during ripening of Manchego cheese made from raw or pasteurized ewes' milk. Seasonal variation

Changes in nitrogen compounds during ripening of 40 batches of Manchego cheese made from raw milk (24 batches) or pasteurized milk (16 batches) at five different dairies throughout the year were investigated. After ripening for six months, degradation of p-kappa- and beta-caseins was more intense in raw milk cheese and degradation of alpha(s2)-casein in pasteurized milk cheese. Milk pasteurization had no significant effect on breakdown of alpha(s1)-casein. Hydrophobic peptide content did not differ between raw and pasteurized milk cheese, whereas hydrophilic peptide content was higher in raw milk cheese. There were no significant differences between seasons for residual caseins, but hydrophobic peptides were at a higher level in cheese made in autumn and winter and hydrophilic peptides in cheese made in winter and spring. Raw milk cheese had a higher content of total free amino acids and of most individual free amino acids than pasteurized milk cheese. The relative percentages of the individual free amino acids were significantly different for raw milk and pasteurized milk cheeses. The relative percentages of Lys and lie increased, while those of Val, Leu and Phe decreased during ripening. There were also seasonal variations within the relative percentages of free amino acids. In raw milk cheeses, Asp and Cys were relatively more abundant in those made in autumn, Glu and Arg in cheeses made in winter, and Lys and Ile in cheeses made in spring and summer. Biogenic amines were detected only in raw milk cheese, with the highest levels of histamine, tryptamine and tyramine in cheeses made in spring, winter and spring, respectively.     

Proteolysis and texture of hard ewes' milk cheese during ripening as affected by somatic cell counts

Ewes' milk samples with low (<500,000 ml(-1)), medium (1,000,000-1,500,000 ml(-1)) and high (> 2,500,000 ml(-1)) somatic cell counts (SCC) were used to manufacture hard ewes' cheese using the Zamorano cheese manufacturing protocol. Cheeses that had been ripened for 1, 2 and 3 months were used to obtain isoelectric ovine casein that was analysed by capillary electrophoresis. The texture of the cheeses during ripening was determined instrumentally using the Warner-Bratzler maximum shear force and assessed for sensory qualities by consumers using hedonic tests. The study revealed that the pH value and the lactose content of the milk were affected by high SCC and that the coagulation properties were dependent on the somatic cell content. The protein and moisture contents of the cheeses were unaffected by SCC but a significant increase of pH with ripening time were observed in high-SCC cheeses. The results also pointed to a significant increase in proteolysis related to SCC levels, showing that intact casein, both alphas1 and beta-casein, decreased as the SCC of milk increased, and that the proteolytic fragments, mainly I-alphas1, increased with SCC levels. Significant differences in texture were found among the samples, the cheeses made with high levels of SCC being significantly less compact at each ripening time. The differences in texture were detected by the consumers, who reported defects in cheeses made with high levels of SCC. Indeed, high SCC cheeses were significantly less well accepted.     

Effects of high pressure treatment on volatile profile during ripening of ewe milk cheese

The effect of high-pressure treatment on the volatile profile of ewe milk cheeses was investigated. Cheeses were submitted to 200, 300, 400 and 500 MPa at 2 stages of ripening (after 1 and 15 d of manufacturing) and volatile compounds were assayed at 15 and 60 d of ripening. High-pressure treatment altered the balance of volatile profile of cheeses, limiting the formation of acids, alcohols, ketones, aldehydes, and sulfur compounds and enhancing the formation of 2,3-butanedione. In general, cheeses pressurized at 15 d of ripening were more similar to untreated cheeses than those treated at 1 d. Cheeses treated at 300 MPa after 1 d of manufacturing were characterized by higher levels of free amino acids, ethanol, ethyl esters, and branched-chain aldehydes, whereas cheeses treated at 500 MPa after 1 d of manufacturing had lower microbial populations, showed the highest abundance of 2,3-butanedione, pyruvaldehyde, and methyl ketones, and the lowest abundance of alcohols.     

Changes in the major free fatty acids in Serra cheese throughout ripening

Changes in the concentrations of the free fatty acids (FFA) containing an even number of carbon atoms in Serra cheese were monitored using a two-way factorial design over a ripening period of 35 days throughout the cheesemaking season. Both time variables had statistically significant effects at the 5% level on the concentrations of FFA. The concentration of stearic acid increased significantly to 351 mg kg⁻¹ (fat basis) only during the first week of ripening. Concentrations of palmitic and oleic acids increased significantly during all stages of ripening and approximately doubled during the 35-day ripening period to reach levels of 425 and 453 mg kg⁻¹, respectively. Concentrations of butyric, caprylic, lauric and myristic acids were approximately constant during the first week and increased significantly thereafter up to 285, 17, 94 and 59 mg kg⁻¹, respectively, at 35 days. The concentrations of caprylic and myristic acids increased five-fold in 35 days, the concentration of butyric acid increased three-fold, and the concentration of lauric acid almost doubled during the same period. The concentrations of caproic, capric, linoleic and linolenic acids increased significantly to 48, 121, 188 and 126 mg kg⁻¹, respectively, only after 21 days of ripening. The concentration of linoleic acid doubled in that time period, while increases in the concentrations of caproic, capric and linolenic acids were much smaller. The concentrations of butyric, caproic and palmitic acids in cheeses manufactured in February were statistically lower than those in cheeses manufactured in May. The principal FFAs throughout ripening were, according to chain length and degree of saturation, butyric (short-chain), capric (medium-chain), palmitic and stearic acids (saturated long-chain), and oleic (unsaturated long-chain). Saturated and unsaturated long-chain FFA were present at the highest concentration at all stages of ripening. It is concluded that lipolysis in Serra cheese proceeds slowly to total FFA concentration of 2167 mg kg⁻¹ (fat basis) by 35 days of ripening.     

Influence of selected lab cultures on the evolution of free amino acids, free fatty acids and Fiore Sardo cheese microflora during the ripening

Fiore Sardo Protected Denomination of Origin is a traditional Sardinian (Italy) hard cheese produced exclusively from whole raw ovine milk and coagulated with lamb rennet paste. Currently, Fiore Sardo is still produced by shepherds at the farmhouse level without the addition of any starter culture and the cheese-making process is characterized by significant waste. The first objective of the present work was to investigate the autochthonous microflora present in milk and Fiore Sardo cheese in order to select lactic acid bacterial (LAB) cultures with suitable cheese-making attributes and, possibly reduce the production waste. Secondly, the ability of selected cultures to guarantee cheese healthiness and quality was tested in experimental cheese-making trials. In this study, we show that the typical lactic microflora of raw ewe's milk and Fiore Sardo cheese is mostly composed of mesophilic LAB such as Lactococcus lactis subsp. lactis, Lactobacillus plantarum and Lactobacillus casei subsp. casei. Moreover, strains belonging to the species were selected for cheese-making attributes and used in experimental cheese-making trials carried out in different farms producing Fiore Sardo. The evolution of the cheese microflora, free amino acids and free fatty acids during the ripening showed that the experimental cheeses were characterized by a balanced ratio of the chemical constituents, by a reduced number of spoilage microorganisms and, remarkably, by the absence of production waste that were significant for the control cheeses.     

Amino acids evolution during ripening of goats' milk cheese manufactured with different coagulants

Powdered plant coagulant obtained from the cardoon flowers ( Cynara cardunculus ) was compared with calf rennet for the manufacture of traditional raw goats' milk cheese, by determining differences in the profiles of the amino acids throughout the ripening period. Derivatisation with o -phtaldialdehyde and a C₁₈ column were used for chromatographic separations. In order to establish the relationships between the different variables and to detect the most important causes of variability, principal component analysis was applied to the free amino acids data, which reduced to two dimensions where cheese samples from 2 to 60 days and cheeses from 90 to 120 days were distributed dependently of ripening time and coagulant used. Leu, Val, Lys, Gly, Tyr and Asp were correlated with PC1, which separated the samples according to their ripening time. Arg, His, Trp, Ser and Thr were correlated with PC2, which separated the samples according to the coagulant used.     

Effects of heating milk and accelerating ripening of low fat Ras cheese on biogenic amines and free amino acids development

Two experiments were conducted to study the effects of heating milk and, consequently, incorporation of whey proteins into cheese curd, fat content, accelerating cheese ripening by attenuated lactobacilli, species of bacteria and method of attenuation on formation of biogenic amines and liberation of free amino acids. Total biogenic amines and total free amino acids increased as ripening period progressed in all cheese treatments. Total biogenic amines and total free amino acids decreased as the fat content was decreased. Heating of 3% fat milk up to 70°C caused a significant (p<0.05) increase in total biogenic amines and total free amino acid concentrations, while raising the temperature of heat treatment up to 75 and 80°C decreased them. However, heating of 2% fat milk up to 75°C caused a definite (p<0.05) increase in total biogenic arnines and total free amino acids; conversely raising heat treatment temperature to 80°C decreased them. These results indicate that there is a positive correlation between total biogenic amines and total free amino acids; moisture and salt contents affected the formation of biogenic amines, while incorporation of whey proteins had no significant effect on biogenic amines development. In a second experiment, addition of attenuated lactobacilli as adjunct bacteria caused a pronounced (p<0.05) increase in free amino acids and biogenic amines. Addition of either freeze- or heat-shocked Lactobacillus helviticus was more effective in promoting the build-up of biogenic amines and free amino acids in the resultant cheeses than in cheeses made with addition of freeze- or heat-shocked Lactobacillus casei, respectively. There was a positive correlation between free amino acids and biogenic amine contents. The type of bacteria and prolongation of ripening period significantly affected the development of biogenic amines. Tyramine was the highest biogenic amine followed by histamine, while spermidine was the lowest.     

The evolution of free fatty acids during the ripening of Idiazábal cheese: influence of rennet type

 The object of the present study was to determine the influence of the rennet type on the free fatty acid (FFA) content of Idiazábal cheese. Varying this parameter during cheese-making resulted in significant differences in FFA content in the cheeses during ripening. The main FFAs in both cheese batches were caproic acid (C6 : 0) and capric acid (C10 : 0). The differences between the extreme values for the lipolysis rate were around 45%, which emphasizes the importance of the cheese-making procedure employed on lipolysis in this type of cheese. The use of locally made rennet in the preparation of Idiazábal cheese increased the level of lipolysis in the cheese. Received: 4 December 1998 / Revised version: 18 March 1999     

Specific effect of high-pressure treatment of milk on cheese proteolysis

The extent of primary and secondary proteolysis of cheeses made from raw (RA), pasteurized (PA, 72 degrees C, 15 s) or pressure-treated (PR, 500 MPa, 15 min, 20 degrees C) goats' milk was assessed. Modifications in cheese-making technology were introduced to obtain cheeses with the same moisture content, and thus studied per se the effect of milk treatment on cheese proteolysis.The PR milk cheese samples were differentiated from RA and PA milk cheeses by their elevated beta-lg content, and by the faster degradation of alphas1-, alphas2- and beta-CN throughout ripening. Non-significant differences were found in either pH 4.6 soluble-nitrogen or trichloracetic acid soluble-nitrogen contents of cheeses. However, the pasteurization of milk decreased the free amino acid production in cheese. The RA milk cheeses had the highest amount of proline and the lowest concentrations of serine, tyrosine, arginine and alpha-aminobutyric acid, whereas PR milk cheese showed higher levels of arginine.     

Ultrafiltration of cheese milk: Effect on plasmin activity and proteolysis during cheese ripening

Havarti 45+ cheese was manufactured from milk concentrated 1.8–4.6-fold by ultrafiltration (UF) and from normal milk, and the effect of concentration factor on plasmin activity and subsequent proteolysis in cheese during ripening was examined. There was decreased plasmin activity and a reduced rate of proteolysis of α_S2-casein and β-casein in the UF-cheeses, compared with the corresponding controls, independent of concentration factor. The decreased plasmin activity and slower breakdown of α_S2-casein and β-casein in UF-cheeses compared with traditional cheeses can be partly explained by the inclusion of an increased amount of plasmin inhibitors into the UF-cheeses. However, it is suggested that the differences in plasmin activity and proteolysis arise mainly as a result of inactivation of the plasminogen activation system during UF-concentration, due to a combination of time, temperature and the presence of air in the UF-equipment. The effect of milk treatment on the plasminogen activation system should be further investigated.     

Microstructure,free amino acids and free fatty acids in Ras cheese

The physical state of the protein in Ras cheese has been followed by TEM and SEM in parallel with the chemical changes during maturation. The microstructure of young Ras cheese, by TEM, consists of casein micelles joined to form an open network, with some clustering of the micelles that appear, by SEM, as thin fibres aggregated into cross-linked elongated strands. At higher magnification, the casein fibres appear folded to include cavities.With further maturation to 4 months, the cheese matrix changed considerably by dissociation of the casein micelles to form a more homogeneous structure of sub-micelles, as seen by TEM, whilst SEM micrographs indicated that some protein fibres still existed.The protein breakdown, the accumulation of free amino acids and the liberation of free fatty acids in Ras cheese increased during maturation by decomposition of paracasein and cheese fat.Ras cheese is characterized as a compact body but can be viewed as an extensive inter-connection between the casein sheets in a cheese matrix and by a sharp flavour attributed to free glutamic acid and the presence of butyric, caprylic and caproic (free volatile) fatty acids.     

Seasonal variations in the free fatty acid composition of Manchego cheese and changes during ripening

 This paper examines the evolution of the free fatty acid concentration in Manchego cheese during ripening (up to 150 days) and in two different cheesemaking seasons (autumn and winter). Factorial analysis of the principal components showed that short-chain fatty acids were the variables that best correlated (81% of the total variance explained) with the samples when distributed according to ripening time. These fatty acids likewise differentiated autumn and winter samples. Received: 30 April 1999 / Revised version: 5 July 1999     

Influence of starter cultures on the free fatty acids during ripening in Tea sausages

The influence of starter cultures on the free fatty acids content during ripening of Tea sausages, typical dry sausages produced in the south of Croatia, was studied. Three batches of Tea sausages were produced using different starter mixtures (Staphylococcus xylosus S81 and Lactobacillus sakei G20; Staphylococcus xylosus S142 and Lactobacillus sakei G20; Staphylococcus xylosus S206 and Lactobacillus sakei G20), while the control batch was produced without a starter. The amounts of free fatty acids present in the samples at the end of the ripening period were not significantly different, suggesting that the lipolytic enzymes naturally occurring in meat could play a predominant role in the free fatty acids release. Oleic and linoleic acids were present in the highest concentrations, while only small quantities of short-chain fatty acids were detected, with acetic acid being the most representative one.     

Indirect ELISA for detection of goats' milk in ewes' milk and cheese

An indirect ELISA (enzyme-linked immunosorbent assay) has been developed successfully for the detection of defined amounts of goats' milk (1–25%) in ewes' milk and cheese. The assay uses polyclonal antibodies raised in rabbits against goats' caseins (GC). The anti-GC antibodies were recovered from the crude antiserum by immunoadsorption and elution from a column containing immobilized goats' caseins. The anti-GC antibodies were biotinylated and rendered goats' milk specific by mixing them with lyophilized bovine and ovine caseins. The assay was developed in a non-competitive ELISA format and it comprised coating plates with extracts from samples. ExtrAvidin-peroxidase was used to detect the biotinylated anti-GC antibodies bound to goats' caseins immobilized on 96-well plates. The colour developed by the subsequent enzymic conversion of the substrate resulted in discernible differences in optical densities when assaying mixtures of ewes' milk and cheese containing variable amounts of goats' milk.     

The use of near infrared spectroscopy to predict selected free amino acids during cheese ripening

The correlation between near-infrared (NIR) spectra of grated cheese and the development of selected free amino acids during cheese ripening of rindless Norvegia and Präst cheese was evaluated. Both the age of cheese and the respective NIR spectra, with the NIR spectra being superior, were shown to give good predictive ability for the free amino acids aspartate , serine (Ser), methionine , threonine , glutamate , valine and the total amount of free amino acids in grated cheese. No single partial least squares (PLS) factor from the NIR spectra could be identified as predominant in the estimation of Ser. Ten PLS factors were needed to provide the minimum prediction error for Ser.     

Increase on free fatty acids during ripening of anchovies (Engraulis anchoíta)

The changes of free fatty acids (FFA) during the ripening of salted anchovy was studied. In the course of the curing process, the content of free fatty acids (FFA) in the muscle increased fifteen-fold, mostly in the first 100 days of the process. Each sample was subjected to sensory evaluations. A high correlation between FFA contents and sensory scores was found. Therefore the determination of FFA is proposed as an objective index to assess the ripening of salted anchovies.     

混合型大豆干酪成熟特性的研究

对混合型大豆干酪的成熟特性进行了研究。检测了混合型大豆干酪成熟过程中游离脂肪酸和氨基酸含量的变化,在扫描电镜下观察了不同成熟条件下干酪的微观结构。结果表明,成熟温度对游离脂肪酸含量影响不显著,对游离氨基酸含量影响显著;随着成熟时间的延长,饱和脂肪酸与不饱和脂肪酸含量之比下降,游离氨基酸含量变化较为显著;成熟对混合型大豆干酪的微观结构影响很大,使得干酪质地越来越致密均匀。     

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.