Sensory Changes During Ripening of Raw Ewes' Milk Cheese Manufactured With and Without the Addition of a Starter Culture

ABSTRACT: This study characterizes and compares the sensory aspects of raw ewes' milk cheeses manufactured with and without the addition of a starter culture using specifically developed sensory terminology. Furthermore, overall organoleptic quality was assessed at each ripening stage. Two different raw ovine milk cheese batches were manufactured with and without the addition of a freeze-dried starter. Sensory differences in odor, flavor, and texture were related to starter and raw milk flora activities during manufacturing and ripening. Cheeses made with the addition of a starter culture were scored higher by quality experts. Cheeses manufactured without a starter culture received higher scores for dirty and animal attributes, such as rennet, butyric, sharp, pungent, and brine, possibly related to lower quality scores. Conclusions reached in the present study coincide with previous ones; however, by using a sensory lexicon specifically developed for ewes' milk cheeses, it has been possible to describe slight and specific differences in the cheeses.     

Effect of mesophilic lactobacilli and enterococci adjunct cultures on the final characteristics of a microfiltered milk Swiss-type cheese

The effect of four associations of adjunct cultures composed of mesophilic lactobacilli and enterococci, either solely or combined, on the microbiological, biochemical and sensory characteristics of Swiss-type cheese made using microfiltered cows’ milk and supplemented with propionibacteria was studied. The global pattern of growth was similar to that generally observed in raw milk cheese and interactions between microflora were highlighted during ripening. Enterococci, which negatively affected the survival of streptococci starters, seemed to play a limited role in the formation of volatile compounds, probably due to their low levels throughout ripening. On the contrary, mesophilic lactobacilli, which affected the evolution of propionibacteria, enterococci and L. delbrueckii subsp. lactis starter counts, modified free amino acid content, production of volatile compounds and organoleptic properties of mature cheese. This population appeared to be of major importance in the formation of cheese flavor as it was positively related to numerous potential flavor compounds such as alcohols and their corresponding esters, acetaldehyde and 4-methyl-4-heptanone. The original mesophilic lactobacilli present in milk could play an important role in the sensorial diversity of raw milk Swiss-type cheeses such as Comte.     

Microbiological changes throughout ripening of goat cheese made from raw,pasteurized and high-pressure-treated milk

The bacteriological quality during ripening of raw (RA), pasteurized (PA; 72°C, 15 s) and pressure-treated (PR; 500 MPa, 20°C, 15 min) goat milk assessed by enumeration of total bacteria, psychrotrophic bacteria, Enterobacteriaceae, lactobacilli, enterococci, Micrococcaceae and lactococci was evaluated. The high pressure treatment applied was as efficient as pasteurization in reducing the bacterial population of milk. Experimental cheeses were made from RA, PA and PR milks to study the microbial population during ripening. Lactobacilli and lactococci were the predominant microbiota present during ripening in all the cheeses. There were no differences in numbers of starter bacteria during ripening. However, lactobacilli counts for RA milk cheese were significantly higher than for PA and PR cheeses in all the ripening stages studied. Micrococcaceae and enterococci remained at a secondary level, and no differences were observed between cheeses at the end of ripening. On the other hand, the number of Enterobacteriaceae decreased during ripening, but faster in PR milk cheese than in PA and RA milk cheeses. The results of this study suggest that goat cheese made from PR milk had similar microbiological characteristics to PA milk cheeses.     

Changes of composition and free fatty acid contents of Urfa cheeses (a white-brined Turkish cheese) during ripening: Effects of heat treatments and starter cultures

The influences of heat treatments (at 65 °C for 20 min or 72 °C for 5 min) applied to the milk and addition of mesophilic or thermophilic starter cultures, prior to cheese-making, on the composition and free fatty acid contents of Urfa cheeses were evaluated throughout the ripening period. Sensory evaluation of cheese samples was also performed on 90th day. The basic composition of ripened cheese samples was not significantly affected by the heat treatments and starter cultures. Heat treatments adversely affected the lipolysis and sensory properties of Urfa cheeses, particularly at 72 °C. The FFA contents of cheeses made from mesophilic and thermophilic cultures were similar. Cheese made from raw milk had a higher level of lipolysis than the cheeses made from milk inoculated with mesophilic or thermophilic lactic starters (p < 0.05).     

Influence of pasteurised milk, raw milk and different ripening cultures on biogenic amine concentrations in semi-soft cheeses during ripening

In semi-soft cheeses, produced with pasteurised milk, raw milk and different starter cultures, the concentrations of cadaverine, histamine, phenylethylamine, putrescine and tyramine were investigated. The cultures (pasteurised milk cultures, raw milk cultures and starter cultures) strongly influenced the biogenic amine concentrations in the cheeses ripened for 5 months. Two cheeses made with identical pasteurised milk, but different ripening cultures, differed greatly in their total biogenic amine concentrations (51 vs 371?mg/kg). In general, the biogenic amine concentrations increased markedly between month 2 and month 3 of cheese ripening. The high content of enterococci and Enterobacteriaceae yielded the biogenic amine concentrations. In contrast, Lactobacilli did not seem to be important. However, unspecified bacteria have to be considered, since cheeses with comparable microbiological profiles differed enormously in their biogenic amine concentrations. Semi-soft cheeses produced from pasteurised milk showed remarkably lower total biogenic amine concentrations compared to semi-soft cheeses produced from raw milk (51–1096?mg/kg vs 1011–3133?mg/kg, depending also on the ripening cultures). The highest total biogenic amine concentration (4817?mg/kg) was detected in a cheese produced from raw milk that had been stored for 36?h. In this cheese, the concentrations of cadaverine, phenylethylamine, putrescine and tyramine were higher than in all other cheeses. The highest histamine concentration was found to be in another raw milk cheese (573?mg/kg).     

Accelerated ripening of low fat Ras cheese by attenuated lactobacilli cells

Thirteen Ras cheese were made from 4% fat raw milk; 3% raw and heat treated; 2% raw and heat treated milks in order to study the effect of freeze-shocked or heat-shocked L. casei NIH 334 or L. helveticus CNRZ 53 on the quality of the resultant cheeses. The soluble nitrogen, soluble tyrosine, soluble tryptophan, total volatile fatty acids, titratable acidity and organoleptic evaluation scores increased as ripening period progressed, while moisture decreased. Neither strain nor the heated lactobacilli had significant effects on moisture content of cheeses, while increasing their acidity. Cheeses with freeze-shocked L. casei or L. helveticus had higher titratable acidity than cheeses in which heat-shocked cells were added. However, cheeses added L. helveticus had higher acidity than those with L. casei. Ripening indices (soluble nitrogen, soluble tyrosine, soluble tryptophan and total volatile fatty acids) and organoleptic evaluation scores had similar trends. Cheeses with attenuated lactobacilli had higher ripening indices and cheese scores than cheeses without lactobacilli. Addition of either freeze-shocked L. casei or L. helveticus yielded cheeses having higher ripening indices and organoleptic scores than cheeses made with heat-shocked lactobacilli. The best cheeses were made from 3% fat milk heated to 70 °C, and containing freeze-shocked L. helveticus followed by cheeses made from 2% fat milk heated to 75 °C and containing freeze-shocked L. helveticus.     

Effect of some technological parameters on microbiological, chemical and sensory qualities of Civil cheese during ripening

The objective of this research was to determine the effects of different ripening methods [brine salting, dry salting, incorporating with Lor cheese (LR) and vacuum packaging] of Civil cheeses on its microbiological, chemical and sensory properties. Civil cheeses were analysed on the 2nd, 30th, 60th and 90th day of ripening. Chemical compositions of the cheeses were significantly different. While the highest dry matter and titratable acidity values were determined on dry salted cheeses, the highest fat and fat in dry matter contents were found in Civil cheese ripened together with LR. The water-soluble nitrogen and ripening index values were lower in cheese ripened incorporating with LR. Excessive proteolysis was not seen in any of cheese samples. The ripening in different methods affected microbiological and sensory properties of Civil cheese. Panellists preferred vacuum packaging and dry-salting cheeses compared to the other samples on the 90th day of ripening.     

Effect of pasteurization of Ewe's milk and use of a native starter culture on the volatile components and sensory characteristics of roncal cheese.

The effect of pasteurization of milk and use of a native starter culture on the volatile components and sensory characteristics of a Spanish ewe's-milk cheese were examined. Three cheese batches were made, one from raw milk, another from pasteurized milk, and a third from pasteurized milk with an added native starter culture in addition to the commercial starter. Cheeses were analyzed at 1, 120, and 240 d of ripening. Analysis of the volatile components was by purge and trap connected to a gas chromatograph with a mass spectrometer and disclosed a total of 76 components belonging to the following chemical families: hydrocarbons, fatty acids, esters, sulfur and carbonyl compounds, and, in particular, alcohols. Pasteurization lowered the levels of certain volatile components, especially alcohols, aldehydes, and ketones. The cheeses made from pasteurized milk showed lower scores for attributes of characteristic taste and aftertaste, as well as a characteristic aroma at 240 d of ripening. These results suggest that the components present in higher concentrations in the cheeses made from the raw milk were necessary for development of characteristic Roncal cheese aroma. The new native starter culture tested did not exert a significant effect on any of the parameters considered, with the exception of certain isolated components, for which higher or lower quantities were recorded in the cheeses made with that starter culture, although the differences did not have a definite effect on the sensory characteristics of the cheeses.     

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.     

Hygienic quality of ewes' milk cheeses manufactured with artisan-produced lamb rennet pastes

The use of artisan-produced lamb rennet pastes, but not any of the other commercial animal rennets, imparts a characteristic flavour to the cheese, so most Mediterranean ewes' milk cheeses are coagulated with this kind of rennet paste. In contrast to the advantages of using lamb or kid rennet pastes from the sensory point of view, questions are still raised as to their hygienic quality. The goal was to examine the microbiological and enzymic quality of lamb rennet pastes prepared by cheese manufacturers for their own use, and evaluate the hygienic quality of raw sheeps' milk cheeses made with them, using Idiazabal cheese as a model. Lamb rennet pastes prepared by artisan cheese makers from the Basque region of Spain (27), and Italy (8) were evaluated. For cheese making experiments 5 different lamb rennet pastes were selected among the 27 samples from the Basque Country region of Spain. Microbiological analyses were carried out on samples from rennet pastes, rennet extracts, milks and cheeses during ripening. Enzymic activities studied in rennet paste were: total coagulating strength and lipase. Analysis of variance and Student's t-tests was performed. The results show that the artisan-produced rennet pastes contain high levels of a variety of microorganisms. After 60 ripening days, which is the minimum ripening period required for Idiazabal cheese prior to its commercialization, no Eschericia coli, Clostridium, Salmonella spp. or Listeria monocytogenes were detected, and levels for the rest of the microorganisms were below the limits of the European legislative standards for cheese manufactured with raw milk. We can conclude that the use of artisan-produced lamb rennet pastes of questionable hygienic quality for the manufacture of raw milk hard cheeses yields products of good hygienic quality.     

Selection, application and monitoring of Lactobacillus paracasei strains as adjunct cultures in the production of Gouda-type cheeses

Raw milk cheeses have more intense flavours than cheeses made from pasteurized milk and harbour strains with potential adjunct properties. Two Lactobacillus paracasei strains, R-40926 and R-40937, were selected as potential adjunct cultures from a total of 734 isolates from good quality artisan raw milk Gouda-type cheeses on the basis of their prevalence in different cheese types and/or over several production batches, safety and technological parameters. Conventional culturing, isolation and identification and a combined PCR-DGGE approach using total cheese DNA extracts and DNA extracts obtained from culturable fractions were employed to monitor viability of the introduced adjuncts and their effect on the cheese microbiota. The control cheese made without adjuncts was dominated by members of the starter, i.e. Lactococcus lactis and Leuconostoc pseudomesenteroides. In the cheeses containing either R-40926 or R-40937, the respective adjuncts increased in number as ripening progressed indicating that both strains are well adapted to the cheese environment and can survive in a competitive environment in the presence of a commercial starter culture. Principal component analysis of cheese volatiles determined by steam distillation-extraction and gas chromatography-mass spectrometry could differentiate cheeses made with different concentrations of adjunct R-40926 from the control cheese, and these differences could be correlated to the proteolytic and lipolytic properties of this strain. Collectively, results from microbiological and metabolic analyses indicate that the screening procedure followed throughout this study was successful in delivering potential adjunct candidates to enrich or extend the flavour palette of artisan Gouda-type cheeses under more controlled conditions.     

Employment of autochthonous microflora in Pecorino Sardo cheese manufacturing and evolution of physicochemical parameters during ripening

The isolation and identification of lactic acid bacteria (LAB) from raw ewes’ milk and traditional Pecorino Sardo cheese made from this milk without the addition of starter culture was carried out to define the autochthonous lactic microflora present in milk and the evolution of LAB during cheese ripening. Isolation of 275 strains belonging to different Lactococcus, Lactobacillus, Streptococcus and Enterococcus species was achieved. Coccal-shaped LAB were found to predominate during cheese fermentation, while lactobacilli were preponderate during the latter phase of ripening. The technological selection of a total of 174 LAB strains belonging to the species Lactococcus lactis, Streptococcus thermophilus, Lactobacillus helveticus and Lb. casei allowed an experimental starter to be prepared, in which a potentially probiotic species, Lb. casei was used. The suitability of the autochthonous starter culture was tested in cheese-making trials, using thermised ewes’ milk, by comparing experimental Pecorino Sardo cheese with a control cheese produced at industrial scale using a whey starter culture from previous batches of manufacture. In particular, microbiological and physicochemical parameters were determined over 210 days of cheese ripening. Although sensory evaluation did not show any significant difference between experimental and control Pecorino Sardo cheeses, the use of the selected autochthonous starter allowed the production of experimental cheese with a significantly higher level of free amino acids, in particular essential amino acids, in comparison with the Pecorino Sardo control cheeses.     

Preliminary observations on proteolysis in Manchego cheese made with a defined-strain starter culture and adjunct starter (Lactobacillus plantarum) or a commercial starter

Different authors have demonstrated the potential of adding lactobacilli as adjunct cultures to pasteurized milk used in cheese manufacture. The aim of this work was to observe the effect of the use of a defined-strain starter culture and the addition of an adjunct culture (Lactobacillus plantarum) to cheesemilk in order to determine their effect on the ripening of Manchego cheese. Manchego cheeses were manufactured using one of the following starter culture systems: a defined starter consisting of Lactococcus lactis ssp. lactis and Leuconostoc mesenteroides ssp. dextranicum; a defined starter, as described above, and Lb. plantarum, which were isolated from a good quality Manchego cheese made from raw milk, or a commercial starter comprised of two strains of Lc. lactis. The cheeses were sampled at 15, 45, 90 and 150 d of ripening. Principal component analysis of peak heights of reversed-phase HPLC chromatograms of 70% (v/v) ethanol-insoluble and -soluble fractions distributed the samples according to the starter used in their manufacture. Quantitative differences in several peptides were evident between the three cheeses. Cheeses made with the defined-strain starters received higher scores for the flavour quality and intensity and for overall impression than the cheeses made with the commercial starter.     

Effect of soy protein supplementation on the quality of ripening Cheddar-type cheese

The impact of soy protein isolate on the proteolysis and organoleptic properties of Cheddar-type cheese during ripening was studied. Cheese was prepared from cow's milk (control) and cow's milk plus soy protein isolate by using a starter culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp . bulgaricus, and then ripened at 12  ±  1°C for 3 and 5 months. The molecular weight range and peptide fraction in the cheeses were determined by high-performance liquid chromatography (HPLC), and the microstructure was observed by scanning electron microscopy (SEM). Sensory evaluation was used to compare the flavour, body, texture and appearance of the cheeses. The results show that the molecular weight range (9924–9966  Da) in the control cheese was larger than that (6954–6957   Da) in the soy protein-treated cheese and the microstructure in the latter was less compact than in the control cheese. In the sensory evaluation, higher scores were given for some experimental cheese than the control cheese. After 5 months of ripening, the organoleptic properties of the cheese had markedly improved and no bitter off-flavour was detected in the treated cheeses. It was concluded that soy protein could be used to improve the quality of cheese and the addition of 5% soy protein isolate could be recommended for improving the flavour and texture of Cheddar-type soy supplemented cheese.     

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).     

The effect of heat treatment and starter culture on colour intensity and sensory properties of Kulek cheese

The effect of the heat treatment on colour intensity and sensory properties of Kulek cheese made from raw milk with (RS) or without starter culture (R) and heated milk with starter culture (HS) was investigated during ripening. Colour L, a and b values of Kulek cheeses were determined for both interior and surface. The values for cheese R were 82.4 and 74.5 for L, ?5.2 and ?5.5 for a, 31.0 and 34.7 for b interior and surface respectively. The equivalents for RS cheese were 82.8 and 75.7 for L, ?4.8 and ?5.0 for a, 31.0 and 34.0 for b. The values for HS cheese were 88.9 and 88.4 for L and ?3.3 and ?3.3 for a, 22.8 and 24.2 for b. L values (lightness) were the highest in cheeses made from heated milk while b and negative a values were the highest in cheeses made from raw milk. Aroma scores of raw and heat‐treated milk cheeses made with starter were not significantly different. The panelists scored cheeses made from raw milk without starter as the best in body and texture.     

THE CONTRIBUTION OF HERBS TO THE ACCUMULATION OF HISTAMINE IN "OTLU" CHEESE

The aim of this study was to determine the effect of herbs and the use of raw milk on histamine accumulation in “Otlu” (Herby) cheese during ripening. Cow's milk was used for the cheese production. The milk was divided into two main groups: one was used raw and the other was pasteurized at 65C for 30 min. Each group was further divided into two subparts, one of which was used as control (without herbs), while 2% (w/v) of the herbs were added into the other to produce Herby cheese. All cheeses were ripened at 7C for 90 days. The cheese samples were analyzed in terms of histamine content, titratable acidity, dry matter, salt and degree of ripening on days 5, 30, 60 and 90. Total mesophilic aerobic bacteria (MAB) were also counted during ripening. The use of raw milk and the addition of herb both increased histamine formation in Otlu cheeses (P < 0.05). Moreover, higher water‐soluble nitrogen values, as degree of ripening, were obtained from both raw milk and herb‐added cheeses. The number of MAB was higher in raw cheeses (P < 0.05) and also herb‐added cheeses. The study suggests that the addition of herbs may facilitate histamine formation in Herby cheese.     

Utilization of microfiltration or lactoperoxidase system or both for manufacture of Cheddar cheese from raw milk

The objective of the present study was to determine if application of microfiltration (MF) or raw milk lactoperoxidase system (LP) could reduce the risk of foodborne illness from Escherichia coli in raw milk cheeses, without adversely affecting the overall sensory acceptability of the cheeses. Escherichia coli K12 was added to raw milk to study its survival as a non-pathogenic surrogate organism for pathogenic E. coli. Five replications of 6 treatments of Cheddar cheese were manufactured. The 6 treatments included cheeses made from pasteurized milk (PM), raw milk (RM), raw milk inoculated with E. coli K12 (RME), raw milk inoculated with E. coli K12 + LP activation (RMELP), raw milk inoculated with E. coli K12 + MF (MFE), and raw milk inoculated with E. coli K12 + MF + LP activation (MFELP). The population of E. coli K12 was enumerated in the cheese milks, in whey/curds during cheese manufacture, and in final Cheddar cheeses during ripening. Application of LP, MF, and a combination of MF and LP led to an average percentage reduction of E. coli K12 counts in cheese milk by 72, 88, and 96%, respectively. However, E. coli K12 populations significantly increased during the manufacture of Cheddar cheese for the reasons not related to contamination. The number of E. coli K12, however, decreased by 1.5 to 2 log cycles during 120 d of ripening, irrespective of the treatments. The results suggest that MF with or without LP significantly lowers E. coli count in raw milk. Hence, if reactivation of E. coli during cheese making could be prevented, MF with or without LP would be an effective technique for reducing the counts of E. coli in raw milk cheeses. The cheeses were also analyzed for proteolysis, starter and nonstarter lactic acid bacteria (NSLAB), and sensory characteristics during ripening. The concentration of pH 4.6 soluble nitrogen at 120 d was greater in PM cheese compared with the other treatments. The level of 12% trichloroacetic acid-soluble nitrogen at 120 d was greater in RM, RME, and RMELP cheeses compared with PM, MFE, and MFELP cheeses. This could be related to the fact that cheeses made from raw milk with or without LP (RM, RME, and RMELP) had greater levels of NSLAB compared with PM, MFE, and MFELP cheeses. Cheeses at 60 d, as evaluated by 8 trained panelists, did not differ in bitterness, pastiness, or curdiness attributes. Cheeses at 120 d showed no differences in acid-taste, bitterness, or curdiness attributes. Sensory analysis at 60 d showed that PM and MFELP cheeses had greater overall sensory acceptability than RM and RME cheeses. The overall sensory acceptability of the cheeses at 120 d showed that PM, MFE, and MFELP cheeses were more acceptable than RM and RME cheeses.     

Effect of high pressure treatment applied on starter culture or on semi-ripened cheese in the quality and ripening of cheese in brine

Cheese ripening acceleration is of continuous interest for the industry. High-pressure (HP) treatment of starter cultures used in cheese-manufacturing offers the potential to accelerate ripening by increasing the activity of their intracellular peptidases that contribute in the development of desired cheese organoleptic characteristics.The objective of the present research was the investigation of the effect of HP treatment (200 MPa-20 °C - 20 min) directly on white brined cheese or on the starter culture used for its manufacture (Str. thermophilus:L. lactis:L. bugaricus 2:1:1). For this purpose, the microbial, textural, physicochemical and organoleptic characteristics and proteolysis were assessed during the 2nd stage of ripening in cold stores. Control cheese without any treatment was also studied.Cheeses made with HP-treated starters had increased secondary proteolysis. Organoleptic scoring of these cheeses was higher during the whole storage period compared to control and HP-treated cheese. Their superiority was evident even at the early stages of ripening in cold stores, since no bitterness was detected. On the contrary, although HP treated cheeses showed the highest increase in aminopeptidases activities, this was not correlated with the studied ripening indices or the organoleptic characteristics.According to the results, HP-treated starter culture can accelerate proteolysis and potentially the ripening of cheese-in-brine.Industrial relevanceThe data obtained from this work suggest that application of HP treatment under optimized conditions on cheeses in brine starter cultures or on whole cheeses can be effectively used for the production of products with reduced ripening time. This is of great importance for the cheese industries, since the storage period for ripening is long (higher than two months), while applying HP treatment as suggested in this study, this time may be reduced to less than one month, producing cheeses of superior quality.     

Afuega’l Pitu Cheese Quality: Carbon Dioxide Addition to Refrigerated Milk in Acid-coagulated Cheesemaking

The suitability of milk preserved by refrigeration and CO₂ addition for the manufacture of Afuega’l Pitu, a Spanish acid-coagulated short-ripened cheese, was evaluated at pilot scale using an autochthonous cheese starter. Cheeses manufactured, after milk pasteurisation, from vacuum degasified refrigerated CO₂-treated samples (pH 6.2) were compared with two different control cheeses made from pasteurised milk either fresh or refrigerated. The multiplication and acidification capacity of lactic acid bacteria as well as the production of volatile compounds during cheesemaking and ripening were not affected by the previous refrigeration and CO₂-treatment of raw milk nor by the residual CO₂ still present in pasteurised milk after degasification and pasteurisation. Residual CO₂ retarded the proteolysis although no differences on proteolysis and sensory properties were detected at the optimum time of consumption (15 days) between cheeses made from CO₂-treated milk and those made from untreated control milk. CO₂-treatment effectively prevents the decrease in cheese yield caused by the microorganisms present in raw milk of poor microbial quality. These results support the interest of the CO₂-addition in preservation of milk for cheesemaking, specially when it has a high initial microbial load; the method can be satisfactorily used in the manufacture of Afuega’l Pitu cheese and may be extended to the production of other acid-coagulated cheeses.