The influence of ripening temperature and sampling site on the lipolysis in Reggianito Argentino cheese

The effect of ripening temperature elevation and sampling site on lipolysis in Reggianito Argentino cheese was evaluated. Cheeses ripened at 12 or 18 °C and 85% relative humidity were assayed at 2, 4 and 6 months at two sampling zones (central and external). Samples were analysed to determine physicochemical parameters and the concentration of nine free fatty acids (FFAs) (C_6:0–C_18:2). Myristic, palmitic, stearic and oleic acids were found in higher concentration. While ripening time and temperature significantly affected the concentrations of the nine FFAs analysed, sampling zone significantly affected only two FFAs. Ripening temperature increased the lipolytic process, but it seems to have no effect on the pathways of lipolysis in Reggianito Argentino cheese.     

Acceleration of cheese ripening at elevated temperature. An estimation of the optimal ripening time of a traditional Argentinean hard cheese

The effect of elevated ripening temperature on physicochemical, biochemical and sensory characteristics in Reggianito Argentino cheese was evaluated to determine the optimal time for cheese ripening at 18 °C that ensures typical cheese characteristics. Cheeses ripened at 12 or 18 °C and 85% relative humidity were analysed at 2, 4 and 6 months. Seventy-eight variables (as determined by urea-PAGE, RP-HPLC of the water-soluble at pH 4.6 fraction, free amino acids, free fatty acids and sensory analysis) were considered for the principal component analysis. The statistical analysis allowed determination of the optimal time for ripening Reggianito Argentino cheese at 18 °C, which was ranged between 2 and 3 months. In conclusion, the results obtained were not only useful in characterising the ripening of an Argentinean hard cheese, but also in evaluating the effect of an increase of ripening temperature on the main physicochemical, biochemical and sensory changes of Reggianito Argentino cheese.     

Substitution of natural whey starter by mixed strains of Lactobacillus helveticus in the production of Reggianito Argentino cheese

Reggianito Argentino cheeses were manufactured with mixed strains of Lactobacillus helveticus cultured in free viable bacteria whey. As controls, cheeses with natural whey starter were made. Gross composition of cheeses did not differ significantly. The number of total termophilic lactic acid bacteria at the end of ripening was near 10⁷ CFU/g, but when the strain Lh 209 was present in the mixture, this number was 10⁶ CFU/g. Soluble nitrogen at pH 4.6 did not differ between control and experimental cheeses, but soluble nitrogen in tricloroacetic acid 12% and phosphotungstic acid 2.5% showed significant differences at the end of ripening, being higher the values when the strain Lh 209 was present in the mixture. Electrophoretic profiles for control and experimental cheeses were very similar at 0, 90 and 180 days of ripening. An increase in the acid degree value of fat during ripening was noticeable indicating a lipolytic activity in the cheese matrix that was similar for the different strains mixtures. Results from sensory analysis did not show differences among the cheeses of these tests. Despite some differences in the production tricloroacetic and phosphotungstic acid soluble nitrogen were observed for mixtures in which Lh 209 was present, all cheeses were good quality Reggianito Argentino cheeses. These results open and interesting prospective for the use of selected strains culture in whey in substitution of natural whey.     

Proteolysis on Reggianito Argentino cheeses manufactured with natural whey cultures and selected strains of Lactobacillus helveticus

Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter.     

Influence of ripening on proteolysis and lipolysis of Murcia al Vino cheese

The aim of this study was to evaluate the influence of five different manufacturers and two ripening periods on the proteolysis and lipolysis patterns of Murcia al Vino goat cheese. The manufacturers significantly affected the water activity (a_w), pH, dry matter and fat content, several nitrogen fractions: water soluble nitrogen (WSN), trichloroacetic acid (12% w/v) soluble nitrogen (TCASN) and phosphotungstic acid (5% w/v) soluble nitrogen (PTASN); also the free amino acid (FAA) and free fatty acid (FFA) contents, with the exception of C_4:0, C_16:0 and C_18:0. Different ripening periods significantly affected the dry matter content, WSN and PTASN and all FAA, except serine.     

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     

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     

Study of the chemical composition,proteolysis, lipolysis and volatile compounds profile of commercial Reggianito Argentino cheese: Characterization of Reggianito Argentino cheese

Reggianito is a typical variety of grana-type hard cheese produced in Argentina. It is the most exported and due to its organoleptic characteristics is very appreciated by the consumers. The objective of this study was to characterise the global composition, lipolysis, proteolysis and volatile compound profiles of commercial Reggianito cheeses from different dairy plants.Statistical differences (P ? 0.05) in some physicochemical parameters, nitrogen fractions and FFA levels among commercial brands were detected. The volatile profiles were studied by SPME–GC–MS/FID. A total of 53 compounds were identified, the majority belonging to the groups of ketones, alcohols, acids, esters and aldehydes. All these compounds have been reported in Italian grana-type cheeses. Visualization of the analytical results was performed by principal component analysis. This analysis clustered cheese samples according to dairy plants. This fact could be, among other factors, consequences of differences in technologies and ripening time of different manufacturers.     

Effect of activating lactoperoxidase system in cheese milk on the quality of Saint‐Paulin cheese

Saint‐Paulin cheese was made from cow’s milk refrigerated at 4 °C for 72 h and preserved by the lactoperoxidase (LP) system. The effect of the LP system on the microbiological, physicochemical and biochemical properties of cheese over a ripening period of 23 days was investigated, using a control (C0), refrigerated LP‐inactivated cow’s milk (C1) and refrigerated LP‐activated cow’s milk (LPA). The LPA treatment showed the least contamination in flora count, particularly salt‐tolerant bacteria at the end of the ripening period. LPA cheese had significantly lower coliform, yeasts and mould counts (P < 0.05) than the other cheeses; this demonstrated the bacteriostatic effect of the LP system. The proteolysis results showed the least value for LPA cheese as compared with the two other samples, as determined by using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis of casein fractions extracted from the three samples. The findings indicated that the preservation of cow’s cheese milk by the LP system can be used to improve the microbiological quality, inhibit psychotropic germs, correct the losses of soluble nitrogen fractions in the whey and conserve the cheese yield affected by refrigeration.     

Microbiological quality of Port Salut Argentino cheese stored at two temperature treatments

Microbiological quality of Port Salut Argentino cheese was studied during 10 days (after ripening) at two storage temperature treatments: (a) 4°C and (b) a temperature combination of both 4 and 20°C (4/20°C), which implied 12 h at 4°C and 12 h at 20°C. Total coliforms were not higher than 10³ cfu/g among samples. E. coli was detected at both treatments. Thirty three percent of the cheese contained Staphylococcus aureus. Listeria spp. and Salmonella spp. were not detected in any treatment. Bacillus spp. incidence was 50% of the cheese, being B. cereus, B. cereus variety mycoides and B. pumilus. Bacillus cereus and Staphylococcus aureus grew at 4/20°C. Mesophilic aerobic bacteria were between 10⁴ and 10⁷ cfu/g. At 4/20°C counts decreased. At 4°C the behaviour was variable. Moulds were lower than 10⁴ cfu/g and yeasts were between 10⁴ and 10⁵ cfu/g. pH, moisture content and tritatable acidity ranges of samples were 5.5-6, 51-52.3% and 1.215-1.935 g/100 g of lactic acid, respectively. Manufacturing of this cheese includes a short heat treatment and starter culture addition; consequently, our results indicate that this processing may be insufficient for achieving hygienic cheese production. The storage at refrigeration temperature will not always guarantee the cheese safety and quality.     

Proteolysis in ultra-filtered and conventional Iranian white cheese during ripening

Conventional and ultra-filtered (UF) Iranian white cheeses were made with almost identical gross chemical composition and the extent and characteristics of proteolysis were studied during ripening. UF cheeses exhibited a lower rate of development of pH 4.6-soluble nitrogen than conventional cheeses. The rates of degradation of α_s1-casein and particularly β-casein were lower in UF cheeses than in conventional cheeses. Plasmin activity was lower in UF cheeses than that in conventional cheese, whereas coagulant activity was higher in the former. Noticeable qualitative and quantitative differences were observed in reverse-phase high performance liquid chromatography (RP-HPLC) peptide profiles between UF and conventional white cheeses and chemometric analysis of peak height data distributed the cheeses into two separate groups. The levels of free amino acids in UF cheeses were lower than in conventional cheeses. Lower peptide degradation and production of amino acids suggested slower ripening, which may have been associated with the weak aroma development characteristic of UF cheeses.     

Biochemistry of cheese ripening

Rennet-coagulated cheeses are ripened for periods ranging from about two weeks to two or more years depending on variety. During ripening, microbiological and biochemical changes occur that result in the development of the flavour and texture characteristic of the variety. Biochemical changes in cheese during ripening may be grouped into primary (lipolysis, proteolysis and metabolism of residual lactose and of lactate and citrate) or secondary (metabolism of fatty acids and of amino acids) events. Residual lactose is metabolized rapidly to lactate during the early stages of ripening. Lactate is an important precursor for a series of reactions including racemization, oxidation or microbial metabolism. Citrate metabolism is of great importance in certain varieties. Lipolysis in cheese is catalysed by lipases from various source, particularly the milk and cheese microflora, and, in varieties where this coagulant is used, by enzymes from rennet paste. Proteolysis is the most complex biochemical event that occurs during ripening and is catalysed by enzymes from residual coagulant, the milk (particularly plasmin) and proteinases and peptidases from lactic acid bacteria and, in certain varieties, other microorganisms that are encouraged to grow in or on the cheese. Secondary reactions lead to the production of volatile flavour compounds and pathways for the production of flavour compounds from fatty acids and amino acids are also reviewed.     

Use of mass spectrometry to characterize proteolysis in cheese

A rapid method for characterizing proteolysis in different cheese varieties was developed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS). pH 4.6-soluble extracts of different cheese varieties were sub-fractionated using ethanol and 70% ethanol-soluble extracts were analyzed using MALDI-ToF-MS. Sample analysis time was ∼3 min compared to ∼100 min for reversed-phase HPLC; moreover, the method yielded accurate molecular masses of peptides originating as a result of proteolysis. Small peptides (<3500 m/z) were monitored and data for relative intensities of peptides were analyzed using multidimensional scaling (MDS) to demonstrate the similarity between profiles obtained from different cheese varieties. The similarities between the profiles of MALDI-ToF mass spectra were demonstrated in a two-dimensional space by performing MDS on the similarity matrix. Use of MALDI-ToF-MS is thus a fast and effective method for monitoring small peptides produced in cheese as a result of proteolysis.     

Behaviour of Listeria monocytogenes in Lighvan cheese following artificial contamination during making,ripening and storage in different conditions

This study investigated the behaviour and fate of Listeria monocytogenes at different ripening temperatures and NaCl concentrations in traditional Lighvan cheese. L. monocytogenes was added to raw sheep's milk. After producing the cheese, they were stored in 8%, 12% and 15% NaCl at 4, 9 and 14 °C. Sampling was performed for 150 days. Different temperature and NaCl concentrations had a significant effect on the survival of L. monocytogenes (P < 0.001). The lowest growth and survival rates of L. monocytogenes were in 15% NaCl at 14 °C and 12% NaCl at 14 °C, respectively. Also, the highest growth and survival rates of the bacterium were in 8% NaCl at 4 °C.     

Changes in physicochemical and organoleptic properties of traditional Iranian cheese Lighvan during ripening

Lighvan cheese was studied to determine the physicochemical and biochemical changes over 90 days of ripening in brine. Acidity, pH, dry matter, fat values, lipolysis level, water‐soluble nitrogen (WSN), total nitrogen (TN), ripening index (RI), trichloroacetic acid‐soluble nitrogen (TCA‐SN) and organoleptic assessments were analysed. Dry matter and fat values decreased during ripening. Lipolysis level, RI, TCA‐SN values and salt content increased continuously until the end of the ripening period, but total nitrogen decreased throughout a 90‐day storage period. The ripening stage was the main factor affecting the cheese’s sensory properties.     

Role of salt in Iranian ultrafiltered Feta cheese: Some textural and physicochemical changes during ripening

The effect of NaCl (0–4%) on the ripening of Iranian ultrafiltered (UF)‐Feta cheese was assessed over 120 days of ripening at 4 °C. Whey percentage, whey salt, whey pH, cheese pH and textural properties of hardness and cohesiveness were monitored, and experimental modelling performed using response surface methodology. Texture, pH and whey percentage were significantly affected by NaCl and ripening. The maximum whey of 22% was recorded at the end of ripening period. Texture of this cheese becomes harder during ripening confirming cheese pH and whey percentage being the major determining factors. Cheese samples were more elastic than viscous with cohesiveness values of 0.6–0.9.     

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     

Presence of biogenic amines in a traditional salted Italian cheese

Asino cheese is a traditional Italian cheese ripened in a special dilute brine (salmuerie), mixed with whey, milk and milk cream. The aim of this work was to ascertain whether this processing technology can influence amine production. The study demonstrated that biogenic amine content increased gradually in the Asino cheese during the soaking phase in brine. Moreover, the biogenic amine content of the salmuerie was very high and the salmuerie and the Asino cheese had a similar relative profile in amine content. These results suggested that the biogenic amines migrate from the brine into the cheese as a result of the concentration differential existing between the two systems.