Application of principal component analysis to chemical characteristics of Mahon cheese

 The chemical composition of the seven existing types of Mahon cheese, manufactured under the “Mahon” cheese Appellation of Origin, were studied. Of the cheeses, four were industrial (fresh, half-ripened, ripened and old-ripened) and three were traditionally manufactured (half-ripened, ripened and old-ripened). The chemical parameters were evaluated using ANOVA, Tukey’s multiple range test and principal component (PCA) analyses. Significant differences were found between Mahon cheeses ripened for different times in terms of moisture and non-protein nitrogen (NPN) contents (p <0.001); these differences were found to be independent of the manufacturing methodology, i.e. industrial or traditional. The ash and fat contents of industrially manufactured cheeses were significantly different from those in traditionally manufactured cheeses (p <0.001). PCA reduced chemical variables to two independent components: the first principal component was high in moisture, NPN content and water activity; the second, in NaCl, ash and fat contents. These results indicate that the seven types of Mahon cheese described by the “Mahon” cheese Appellation of Origin can be differentiated by their chemical characteristics. Received: 4 April 1997 / Revised version: 4 July 1997     

Differentiation and grouping of chemical characteristics of Mahon cheese

 Cluster analysis of cases (CAC) and variables (CAV) and stepwise discriminant analysis (SDA) were applied to estimate the usefulness of various chemical determinations for the characterization and differentiation of the seven types of Mahon cheese, four industrially manufactured (fresh, half-ripened, ripened and old-ripened cheeses) and three traditionally manufactured (half-ripened, ripened and old-ripened cheeses). CAV showed that, on the one hand, moisture, non-proteic nitrogen (NPN) and water activity measurements, and on the other ash, NaCl and fat measurements are very similar variables. Using SDA, it was possible to differentiate between industrially and traditionally manufactured cheeses by measuring NaCl and fat contents, and also between the four stages of ripening suggested by the "Mahon" cheese Appellation of Origin according to the moisture and NPN variables. Using classification functions obtained by SDA, 94.1% of cheese samples were correctly classified into traditional or industrial groups, and 89.7% of samples into fresh, half-ripened, ripened and old-ripened groups (jackknife validation). Received: 15 July 1997 / Revised version: 2 February 1998     

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 Penicillium roqueforti and incorporation of whey cheese on volatile profiles and sensory characteristics of mould‐ripened Civil cheese

In this study, four different types of mould‐ripened Civil cheese were manufactured. A defined (nontoxigenic) strain of a Penicillium roqueforti (SC 509) was used as secondary starter for the manufacture of mould‐ripened Civil cheese with and without addition of the whey cheese Lor; in parallel, secondary starter‐free counterparts were manufactured. A total of 83 compounds were identified. Ketones, alcohols and esters were the principal classes of volatile components. Principal component analysis of the headspace volatiles grouped cheeses by age and type. P. roqueforti inoculated cheese was clearly separated from the other cheeses at 180 days of ripening, and these cheeses were characterised with high levels of ketones (e.g., 2‐butanone, 2‐heptanone). Differences in the panel scores between the cheese samples were not significant during the first stage of ripening (up to 60 days); as ripening proceeded, these differences were become evident and P. roqueforti inoculated cheeses received higher scores than others. Addition of Lor in the manufacture of mould‐ripened Civil cheese caused lower points by the sensory panel, and the cheese inoculated with P. roqueforti and Lor‐free was the best type of mould‐ripened Civil cheese. The results showed that the use of P. roqueforti in the manufacture of mould‐ripened Civil cheese has significant impact on the volatile profiles and sensory attributes.     

Proteolysis of Mahon cheese as affected by acoustic-assisted brining

 Mahon cheeses were brined in the presence of an ultrasonic field and ripened during 75 days at 12  °C and 85% RH. Secondary proteolysis (water-soluble N, non-protein N, and free amino acids) was measured and compared to that obtained for cheeses conventionally brined. There were no differences in water-soluble and non-protein N attributable to the brining treatment. However, cheeses acoustically brined exhibited higher concentrations of free amino acids. The release of total free amino acids was more pronounced during the first 15 days of ripening for both types of brining treatments. The changes in proteolysis (free amino acids) during cheese ripening caused by acoustic-assisted brining are indicative of a higher extent of proteolysis and may also improve cheese flavor. Received: 13 March 2000     

Monitoring the molecular changes by front face fluorescence spectroscopy throughout ripening of a semi-hard cheese

Twenty four semi-hard cheeses produced during autumn (n = 12) and summer (n = 12) periods were manufactured and ripened at an industrial scale. Tryptophan and vitamin A fluorescence spectra were scanned on the 24 cheeses at 2, 30 and 60 days of ripening. Principal component analysis (PCA) and factorial discriminant analysis (FDA) were applied on the spectral data sets. The first five principal components (PCs) of the PCA extracted from each data set (tryptophan or vitamin A) of cheeses produced during autumn or summer period were pooled into a single matrix and analysed by FDA. Regarding cheeses produced during the autumn period, the percentage of samples correctly classified was 95.8% and 86.1% for the calibration and validation samples, respectively. Similar results were obtained from cheeses produced during the summer period. Finally, concatenation technique was applied to the tryptophan and vitamin A spectra recorded on cheeses independently of their production seasons. Correct classification was observed for 87.5% and 80.6% for the calibration and validation samples, respectively. Although this statistical technique did not allow 100% correct classification for all groups, the results obtained were promising considering the significant effect of the season on the cheese characteristics.     

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).     

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.     

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     

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     

Biogenic Amines Content of Four Types of “Pecorino” Cheese Manufactured in Tuscany

Biogenic amines content of four types of Tuscan ewes’ milk “pecorino” cheese was evaluated using HPLC-UV analysis. All cheeses were manufactured in the same dairy factory with different combinations of milk (raw or pasteurized) and type of ripening. Total biogenic amines and tyramine levels of a raw milk “pecorino” ripened five months, partly in a traditional cave, were significantly higher than those of a pasteurized milk “pecorino” with a similar ripening; and of a two months raw milk “pecorino” ripened in the dairy plant. No statistical significant difference was found when comparing total biogenic amines and tyramine contents of the same five month ripened raw milk “pecorino” with a pasteurized milk “pecorino” ripened six months, partly in a traditional “fossa.” In raw milk cave-ripened and “fossa”-ripened cheeses, total biogenic amines exceeded 1000 mg/kg. In cheeses manufactured with raw milk and/or in particular ripening environments, specific hygienic cares are needed to limit biogenic amines formation.     

The effect of natural cheddar cheese ripening on the functional and textural properties of the processed cheese manufactured therefrom

ABSTRACT:  Cheddar cheese ripened at 8 °C was sampled at 7, 14, 28, 56, 112, and 168 d and subsequently used for the manufacture of processed cheese. The cheddar cheese samples were analyzed throughout ripening for proteolysis while the textural and rheological properties of the processed cheeses (PCs) were studied. The rate of proteolysis was the greatest in the first 28 d of cheddar cheese ripening but began to slow down as ripening progressed from 28 to 168 d. A similar trend was observed in changes to the texture of the PC samples, with the greatest decrease in hardness and increase in flowability being in the first 28 d of ripening. Confocal scanning laser microscopy showed that the degree of emulsification in the PC samples increased as the maturity of the cheddar cheese ingredient increased from 7 to 168 d. This increased emulsification resulted in a reduction in the rate of softening in the PC in samples manufactured from cheddar cheese bases at later ripening times. Multivariate data analysis was performed to summarize the relationships between proteolysis in the cheddar cheese bases and textural properties of the PC made therefrom. The proportion of α _{s 1}-casein (CN) in the cheddar cheese base was strongly correlated with hardness, adhesiveness, fracturability, springiness, and storage modulus values for the corresponding PC. Degradation of α _{s 1}-CN was the proteolytic event with the strongest correlation to the softening of PC samples, particularly those manufactured from cheddar cheese in the first 28 d of ripening.     

The effects of some starter cultures on the properties of Turkish White cheese

White cheese samples were manufactured from bovine milk using three different commercial direct vat starter cultures (DVS-1, -2 and -3) and a lyophilized culture, and ripened at 4 ± 1°C for 90 days. The composition, titratable acidity and ripening indices of the cheese samples were determined on the 2nd, 30th, 60th and 90th days of ripening. The ratios of total solids, protein and fat were higher for cheeses manufactured using DVS-2 and lyophilized cultures but the titratable acidity in cheese produced using DVS-3 and lyophilized cultures was higher (P < 0.01). The mean value of the ripening indices of the cheese produced using the lyophilized culture was lower than the cheeses produced with added DVS cultures (P < 0.05). The total solids, ash, salt ratios, titratable acidity and ripening indices values increased for all types of white cheeses during ripening (P < 0.05).     

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.     

Simultaneous Quantification of Fat and Water Content in Cheese by TD-NMR

The usefulness of a one-step time domain nuclear magnetic resonance (TD-NMR) method for the simultaneous quantification of fat and water content in cheese has been evaluated. The proposed method consists of a combined relaxation analysis, where the magnetization at a certain time is determined by both the longitudinal (T ₁) and the transverse (T ₂) NMR relaxation processes. Calibration models for fat and water quantification in cheese were constructed using partial least square regression in the whole spectral region, evaluated by cross-validation and subsequently tested with external samples. The results were compared with fat and water values determined by means of IDF standard norms 5A (IDF 1969) and 4A (IDF 1982). The proposed TD-NMR methodology allowed a satisfactory determination of fat and water content in cheese samples (root mean square errors ≤1 % and determination coefficients ≥0.98) of different origins (Mallorca and Menorca), cheese makers, milk treatments (raw and pasteurized), and ripening stages (fresh, half-ripened, ripened, and old-ripened).     

Secondary proteolysis in Serra cheese during ripening and throughout the cheese-making season

 Experimental Serra cheeses were manufactured from raw ewe’s milk and thistle flowers following a two-way factorial design. The content of nitrogen soluble in water (WSN), in 2% trichloroacetic acid (2% TCA-N), in 12% TCA (TCA-N) and in 5% phosphotungstic acid (5% PTA-N), and the pH and salt-in-moisture concentration were measured throughout the ripening period (sampling at 0, 7, 21 and 35 days) and the cheese-making season (sampling in November, February and May). Proteolysis in 35-day-old Serra cheese was quantitatively high [average values of 34.6% and 11.9% for WSN/TN (total nitrogen) and 2% TCA-N/TN, respectively], but qualitatively low (average values of 5.8% and 1.2% for 12% TCA-N/TN and 5% PTA-N/TN, respectively). The ratios WSN/TN and 2% TCA-N/TN were lowest for cheeses ripened in February, whereas the ratio 12% TCA-N/TN was highest for cheeses ripened in November. By 35 days of ripening, the average pH and salt-in-moisture concentration values were 5.2 and 4.8%, respectively. No correlation was found to occur between the measured pH or salt-in-moisture concentration and the values of soluble nitrogen fractions throughout the cheese-making season. Received: 14 February 1996/Revised version: 4 June 1996     

Mycotoxin-forming ability of two Penicillium roqueforti strains in blue moldy tulum cheese ripened at various temperatures

Isolated and identified toxigenic and nontoxigenic Penicillium roqueforti (PR) strains from moldy tulum cheeses were inoculated into tulum cheeses made in the laboratory and ripened at 5 and 12 degrees C. Mycotoxin (patulin, penicillic acid, PR toxin, and roquefortine) formation in the control and mold-inoculated cheeses were detected by thin-layer chromatography on the first through fourth months of ripening. Patulin, penicillic acid, and PR toxin were not detected in the experimental cheeses. Only roquefortine was detected in cheese inoculated with the toxigenic strain of the mold and ripened at 5 and 12 degrees C on the third and first months of ripening, respectively. Toxin in cheeses ripened at 5 and 12 degrees C was 2.1 to 2.4 and 2.1 to 3.8 mg/kg cheese, respectively.