Changes of lactose, lactic acid, and acetic acid contents in Serra cheese during ripening

 Changes in the quantities of lactose, lactic acid and acetic acid in Serra cheese were monitored using a triplicate two-way factorial design over a ripening period of 35 days (sampling at 0, 7, 21 and 35 days) throughout the cheesemaking season (sampling in November, February and June). The amount of lactose in total solids of cheese (TS) decreased slowly from 6.17% to 0.21% (w/w_TS) as ripening time elapsed. As a result of sugar metabolism, the lactic acid content increased from 0.07% at day 0 to 2.10% (w/w_TS) by 35 days, whereas the acetic acid content increased from 0.00% to 0.24% (w/w_TS) during the first week. The lactose content was statistically correlated with the lactic acid content but not with the acetic acid content. Received: 18 November 1996     

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.     

Electrophoretic ripening index for the evaluation of proteolysis and the deduction of the age of Parmesan cheese

We have established an electrophoretic method to evaluate proteolysis in Parmesan cheese by means of an objective ripening index. The separation of caseins by alkaline polyacrylamide gel electrophoresis (PAGE) (12% T, 2.6% C, pH 8.9, 5 M urea) is followed by the densitometric analysis of the- and-casein fractions. The relationship between the resulting coefficients (-Cn/-Cn) and the age of reference samples of Original Italian Grana Padano (6–22 months) was linear up to 15 months, allowing an evaluation of the extent of proteolysis and therefore a deduction of the age of the Parmesan samples analysed. Based on this calibration we propose to use a threshold level of 1.3 (-Cn/-Cn) to verify the required age, i.e. 12 months, of Parmesan cheese, retailed as a loaf or prepacked slices. Commercially grated Parmesan samples may contain 20% cheese rind, which has a very low degree of casein breakdown. So a threshold level of 0.8 (-Cn/-Cn) is proposed for all grated Parmesan products. The preparation of reference solutions with defined coefficients (-Cn/-Cn), corresponding to the proteolysis indices of reference samples of different aged Grana Padano is described. The coefficients (-Cn/-Cn) as well as the-casein content of two additional series of reference samples and of 49 commercial Parmesan samples taken from retail outlets in Austria and Italy are presented.     

Caprine cheese with probiotic strains: the effects of ripening temperature and relative humidity on proteolysis and lipolysis

 The effects of ripening temperature, relative humidity and time on chemical and textural characteristics of a 'probiotic' goat's milk cheese were examined. The experimental layout followed a 2³ factorial design, with all possible combinations of 5  °C and 10  °C (ripening temperature), 85% and 95% (ripening relative humidity) and 1 day and 70 days (ripening time). All proteolytic indices measured (water-soluble nitrogen, trichloroacetic acid-soluble nitrogen and phosphotungstic acid-soluble nitrogen) were enhanced with increased ripening temperature to a greater extent than with increased ripening relative humidity; the increase in phosphotungstic acid-soluble nitrogen was the most significant. Free fatty acid concentrations in cheeses were not influenced by ripening relative humidity but increased with ripening temperature and time. A higher ripening temperature and a lower relative humidity gave rise to firmer cheeses. Postulated empirical models have provided a good fit to the experimental data set generated; such models were able to predict a decrease of 25 days in ripening time with no impairment of either proteolytic or lipolytic indices if a cheese were to be ripened at 10  °C (rather than 5  °C) and 95% relative humidity. Received: 23 March 1998     

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.     

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     

Changes in microbial populations, kinds of lactic acid bacteria and biochemical characteristics of Greek traditional feta cheese during ripening

Three batches of feta cheese manufactured from raw (R) and thermized (TS) milk with yogurt as a starter were studied. Enterobacteriaceae and coliforms underwent a more accelerated decrease in TS cheese. Nonstarter lactic acid bacteria (NSLAB) were counted at higher levels in R than in TS cheese throughout ripening and predominated over the other microbial groups. The composition of NSLAB in the fresh cheese was similar for both cheese types. Proteolysis products (noncasein nitrogen soluble in 12% trichloroacetic acid, nitrogen soluble in 5% phosphotungstic acid /100 total nitrogen) were higher in R than TS cheese. Degradation of αs-casein was in R > TS, while a small reduction of β-casein during storage was recorded only for TS cheese.     

The effect of refrigerated storage of raw milk on the physicochemical and microbiological quality of Tunisian semihard Gouda‐type cheese during ripening

A Tunisian semihard Gouda‐type cheese made from milk kept at 4 °C for 24, 48, 72 and 96 h was monitored during 45 days of ripening. The effect of milk refrigeration on the evolution of physicochemical parameters in relation to the quantitative variation of the microbial population during ripening of Gouda‐type cheese was investigated. Microbiological and physicochemical analyses were performed on raw milk and cheese samples after curding, 2, 9, 16, 23, 30, 37 and 45 days of ripening time. The raw milk kept under refrigeration at 4 °C for 96 h showed the highest microbial count and proteolysis level. The duration of storage significantly reduced the cheese yield as a result of important solubilisation casein in proteoses‐peptones. Results of different nitrogenous fractions by Kjeldahl method showed enzymatic hydrolysis products of casein whose intensity depended on the maturing stage as well as the refrigeration time. Besides the evident action of the plasmin, original milk protease, on the hydrolysis of casein in soluble fractions, the proteolysis of cheese caseins is also initiated by proteolytic action of the chymosin and extracellular heat‐resistant proteases notably produced by the same psychrotrophic microflora. Lactic acid bacteria starters that constitute the dominant microflora of this type of cheese are also considered as aroma precursors.     

Intervarietal comparison of proteolysis in commercial cheese

 Proteolysis in different varieties of cheese, i.e. Cheddar, British, Dutch and Swiss types and Italian varieties, was compared by polyacrylamide gel electrophoresis (PAGE) and reverse-phase high-performance liquid chromatography (RP-HPLC). Urea-PAGE of the water-insoluble fraction (WISF) of cheese appeared to be unable to distinguish between Cheddar and Dutch-type cheeses, whereas it could be used to distinguish Emmental from Parmesan and both of these from Cheddar and Dutch types. Urea-PAGE of the 70%-ethanol-insoluble fraction of the water-soluble extract (WSE) showed large inter-varietal differences but there were also some intra-varietal differences. RP-HPLC of the 70%-ethanol-soluble and -insoluble fractions of the WSEs of cheeses was more effective than urea-PAGE of the WISFs or of the 70%-ethanol-insoluble fraction of the WSEs of cheeses when classifying cheese according to variety. However, analysis of a larger number of cheese samples is required to verify this result. One of the problems with using either urea-PAGE or RP-HPLC to identify cheese is that the characteristics analysed by these techniques change as ripening progresses. Received: 22 September 1997 / Revised version: 8 June 1998     

Influences of rennet and container types on proteolysis of traditional Kurdish cheese during the ripening

The effect of rennet and container types was evaluated on proteolysis of traditional Kurdish cheese during 60 days ripening. The enzymes involved were commercial chymosin and traditional rennet from lamb abomasum. Goat skin (traditional container) and plastic containers were used as storage containers. The trend of proteolysis was determined by measuring the content of nitrogen (N) in compounds soluble in water, 12% trichloroacetic acid and 5% phosphotungstic acid along with the urea–polyacrylamide gel electrophoresis method. The results showed that the nitrogen in compounds soluble in water, 12% trichloroacetic acid and 5% phosphotungstic acid was higher in ripened cheeses into plastic containers; however, the containers had no significant effect on the breakdown of α‐ and β‐caseins (P < 0.05). Using commercial rennet caused the breakdown of α‐ and β‐caseins and the level of nitrogen in compounds soluble in water to increase. Finally, however, the amount of α‐ and β‐caseins breakdown was trivial, and α‐casein was decreased more than β‐casein in all samples.     

Evolution of chemico-physical characteristics during manufacture and ripening of Castelmagno PDO cheese in wintertime

Biochemical, volatile and textural profiles during manufacture and ripening were determined in samples of Castelmagno PDO cheese obtained from three different batches in the main artisan cheese plant of Castelmagno PDO production area. At the end of manufacture, samples were characterised by a pH of 6.57% and 52.4% moisture content. The HPLC analysis of organic acids and sugars showed the exhaustion of lactose content, while Urea-PAGE indicated extensive primary proteolysis of both β-casein and α_s1-casein. During ripening, cheeses were characterised by high degradation of β-casein and α_s1-casein, due to bacterial action. RP-HPLC profiles showed a high production of peptides eluted between 20 and 30 min. In total, 92 volatile compounds were identified in cheese headspace. Texture profiles showed an increase in hardness, gumminess, chewiness and adhesiveness values, as well as a decrease in cohesiveness during ripening.     

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.     

Effects of different ripening procedures on the final characteristics of Picante cheese

 Picante da Beira Baixa (or Picante) cheese is a hard, piquant, salted traditional cheese manufactured in Portugal from raw sheep's and goat's milks. The purpose of this work was to quantitatively assess the influence of various ripening procedures on the final characteristics of Picante cheese. Two alternative ripening protocols were considered, the traditional one and another with controlled environmental conditions via use of maturation chambers set at different preselected temperatures. The experimental cheeses were characterised in terms of microbiological, physicochemical, biochemical, sensorial and textural properties. Ripening time and temperature were statistically significant parameters for all microflora. The two ripening methods led to statistically significant differences in all physicochemical and biochemical parameters, especially the moisture content and the soluble nitrogen fractions (i.e. water loss was slower and proteolysis was faster in cheeses ripened via the traditional method). Differences in microbiological, physicochemical and biochemical properties were probables implicated in differences in textural and sensorial properties, especially cheese hardness and flavour. It was concluded that the standard ripening method was closest to the traditional one in terms of final cheese characteristics when the ripening temperature was above 11.5  °C. Received: 3 February 1998     

Influence of traditional smoking on the triglyceride composition during the ripening of Idiazabal cheese

 The influence of traditional smoking on the triglyceride (TG) composition of Idiazabal cheese during ripening was studied using HPLC. The partition numbers (PNs) of the TGs ranged between 22 and 53, the groupings of TG peaks with PN values of 36, 34, and 38 being the main contributors. Statistically significant differences between the smoked and the unsmoked cheeses were recorded during the ripening period. Smoking had a significant effect on certain groups of TGs at different ripening times and no effect on others. The differences in the TG profiles of the cheeses were the result of differing levels of lipolytic activity, which was heightened by smoking. Received: 29 December 1997 / Revised version: 9 March 1998     

Influence of traditional smoking on the triglyceride composition during the ripening of Idiazabal cheese

 The influence of traditional smoking on the triglyceride (TG) composition of Idiazabal cheese during ripening was studied using HPLC. The partition numbers (PNs) of the TGs ranged between 22 and 53, the groupings of TG peaks with PN values of 36, 34, and 38 being the main contributors. Statistically significant differences between the smoked and the unsmoked cheeses were recorded during the ripening period. Smoking had a significant effect on certain groups of TGs at different ripening times and no effect on others. The differences in the TG profiles of the cheeses were the result of differing levels of lipolytic activity, which was heightened by smoking. Received: 29 December 1997 / Revised version: 9 March 1998     

Effects of different ripening procedures on the final characteristics of Picante cheese

 Picante da Beira Baixa (or Picante) cheese is a hard, piquant, salted traditional cheese manufactured in Portugal from raw sheep's and goat's milks. The purpose of this work was to quantitatively assess the influence of various ripening procedures on the final characteristics of Picante cheese. Two alternative ripening protocols were considered, the traditional one and another with controlled environmental conditions via use of maturation chambers set at different preselected temperatures. The experimental cheeses were characterised in terms of microbiological, physicochemical, biochemical, sensorial and textural properties. Ripening time and temperature were statistically significant parameters for all microflora. The two ripening methods led to statistically significant differences in all physicochemical and biochemical parameters, especially the moisture content and the soluble nitrogen fractions (i.e. water loss was slower and proteolysis was faster in cheeses ripened via the traditional method). Differences in microbiological, physicochemical and biochemical properties were probables implicated in differences in textural and sensorial properties, especially cheese hardness and flavour. It was concluded that the standard ripening method was closest to the traditional one in terms of final cheese characteristics when the ripening temperature was above 11.5  °C. Received: 3 February 1998     

Chymotrypsin and general proteolytic activities in muscle of Engraulis encrasicolus and Engraulis anchoita during the ripening process

 During fish ripening, biochemical changes occur that give rise to the organoleptic properties characteristic of the product. Enzymes play a key role in this ripening process, although it is not known exactly which enzymes are involved. We investigated the effects of the gutting method (nobbing only, or nobbing and butterflying) and addition of cathepsin C on general proteolytic activity, chymotrypsin activity, pH and organoleptic characteristics during brine ripening of fresh Engraulis encrasicolus. We also monitored these variables during brine ripening of frozen/thawed E. encrasicolus and E. anchoita. Butterflied fish ripened more rapidly than fish prepared by the traditional method (nobbing only). Inclusion of cathepsin C in the brine had a negative effect on texture (very firm, low juiciness) but a positive effect on flavour, which was more intense. Frozen/thawed fish were successfully ripened, giving a final product with fully acceptable organoleptic characteristics. In all batches except the E. anchoita batch both general proteolytic activity and chymotrypsin activity increased rapidly after immersion in brine, then dropped gradually over the ripening period. Received: 7 July 1999     

Effects of Penicillium roqueforti and whey cheese on gross composition,microbiology and proteolysis of mould‐ripened Civil cheese during ripening

Four different types of mould‐ripened Civil cheese were manufactured. A defined (nontoxigenic) strain of a Penicillium roqueforti (SC 509) was used as the secondary starter with and without addition of the whey cheese (Lor); in parallel, secondary starter‐free counterparts were manufactured. Chemical composition, microbiology and proteolysis were studied during the ripening. The incorporation of whey cheese in the manufacture of mould‐ripened Civil cheese altered the gross composition and adversely affected proteolysis in the cheeses. The inoculated P. roqueforti moulds appeared to grow slowly on those cheeses, and little proteolysis was evident in all cheese treatments during the first 90 days of ripening. However, sharp increases in the soluble nitrogen fractions were observed in all cheeses after 90 days. Microbiological analysis showed that the microbial counts in the cheeses were at high levels at the beginning of ripening, while their counts decreased approximately 1–2 log cfu/g towards the end of ripening.     

The biodiversity and evolution of lactic flora during ripening of the Iranian semisoft Lighvan cheese

Ninety‐five isolated strains of Lactic acid bacteria (LAB) were identified from Lighvan cheese. The LAB evolution showed the dominance of lactococci and lactobacilli in the first stage and substitution of these genera by enterococci at the end of ripening. The most predominant strains were Enterococcus faecium (22.44%), Lactococcus lactis ssp. lactis (20.4%), Lactobacillus plantarum (18.36%) and E. faecalis (14.28%), respectively. Eleven and 51 different carbohydrate fermentation profiles were observed according to API 20 STREP and API 50 CH, respectively. API 20 STREP dendogram showed identical fermentation profiles of some E. faecalis and E. faecium strains, indicating that these strains might be well adapted to the whole cheese manufacture.     

Prediction of the ripening times of Manchego cheese using multivariate statistical analyse: a preliminary study

 Multiple linear regression, principal component regression, and partial least squares (PLS) regression were used to calculate ripening time in standard Manchego cheeses based on water activity (Aw), pH, and other proteolysis parameters. The root mean square error of prediction by cross-validation was used to study the prediction accuracy of the models. PLS regression yielded the best predictions of ripening time and was used to predict the ripening times of eight commercial Manchego cheeses. Received: 8 October 1997 / Revised version: 20 January 1998