Enzyme activity in Spanish goat's cheeses

Specific enzyme activity has been studied in Spanish goat's cheese. Neutral protease, aminopeptidase, and carboxypeptidase activity was analysed during the ripening of two Spanish goat's cheeses. One cheese was Majorero cheese from the island of Fuerteventura; the other was a soft cheese mould-ripened by P. candidum on the surface. The trend in neutral protease activity was rather similar in both cheeses over the ripening period. Protease activity was higher in Majorero cheese and higher on the surface than inside the mould-ripened cheese.Aminopeptidase activity also increased in both cheeses over the entire ripening period, but it was higher in the mould-ripened cheese than in the Majorero cheese.Carboxypeptidase activity was not recorded in either the Majorero or the soft cheese.     

Proteolysis in goat cheese made from raw,pasteurized or pressure-treated milk

Primary and secondary proteolysis of goat cheese made from raw (RA), pasteurized (PA; 72 °C, 15 s) and pressure-treated milk (PR; 500 MPa, 15 min, 20 °C) were examined by capillary electrophoresis, nitrogen fractionation and HPLC peptide profiles. PA milk cheese showed a more important hydrolysis (P<0.05) of α_s1-casein than RA milk cheese at the first stages of ripening (15 days), while PR milk cheese had a level between those seen in PA and RA milk cheeses. Degradation of β-casein was more important (P<0.05) in PA and PR than in RA milk cheeses at 15 days of ripening. However, from thereon β-casein in PR and RA milk cheeses was hydrolyzed at essentially similar rates, but at lower rates (P<0.05) than in PA milk cheeses. Pressure treatment could induce proteolysis of β-casein in a way, which is different from that produced by heat treatment. There was an increase in 4.6-soluble nitrogen (WSN) and in trichloroacetic acid (TCASN) throughout ripening in cheeses, but higher contents (P<0.05) in PA and PR milk cheeses at the end of ripening were observed. PR milk cheeses contained considerably higher content (P<0.05) of free amino acids than RA or PA milk cheeses. In general, heat and pressure treatments had no significant effect on the levels of hydrophobic and hydrophilic peptides.     

Compositional,biochemical and textural changes during ripening of Tulum cheese made with different coagulants

In the present study, biochemical, chemical and texture changes in Tulum cheeses made using calf rennet and microbial rennets (Aspergillus niger protease and Rhizomucor miehei protease) were compared during ripening for up to 90 days. A total of 15 free fatty acids (FFAs) were detected in the cheese samples. The peroxide values (PV) of the cheeses increased significantly (P < 0.05) during ripening and the cheese made with calf rennet had the highest PV. Proteolysis in the cheeses increased as the ripening time increased. α_s1‐casein and β‐casein degradation was higher in cheeses manufactured with R. miehei protease. Cheeses made with calf rennet were significantly (P < 0.05) harder, more adhesive, more cohesive and more resilient than those made with microbial rennet.     

The effect of varying casein/fat ratio on physicochemical and sensory qualities of Feta‐type cheese made using buffalo milk

The Feta‐type cheese was prepared with different casein/fat (C/F) ratios of buffalo milk using microbial rennet. The manufactured Feta cheeses were subjected to physicochemical and sensory quality at 15‐day interval up to 60 days of ripening. Sensory analysis discriminated the different level of C/F ratio of buffalo milk cheeses predominantly by age. There was no significant difference (P < 0.01) observed in cheese made from C/F ratio of 0.6–0.7 in terms of flavour. The titratable acidity (TA), soluble protein and free fatty acid appear to be age‐dependent and increased throughout the ripening in all experimental cheeses.     

Alternatives for improving physical, chemical, and sensory characteristics of goat cheeses: the use of arid-land forages in the diet

To establish the effect of an alternative diet on the quality of Majorero cheese, the basic physicochemical parameters, fatty acid profile, and sensory characteristics were studied. Two groups of 20 Majorero goats were fed 2 different diets: a forage diet (DF), which had a high ratio of long fiber to concentrates (65:35), and a concentrate diet (DC), with a low ratio of long fiber to concentrates (35:65). The DF dietary fiber was supplied by native forages adapted to arid land. A total of 42 Majorero goat cheeses were used for this study: 21 in the DF group and 21 in the DC group. Seven cheeses from each group were tested after 2, 15, and 60 d of ripening. The milk produced by goats fed the DF diet had a higher fat concentration. No significant differences were observed in the milk fatty acid profile. The diet affected the chemical composition of the cheese in pH and fat content, and fat was significantly higher in cheeses made from DF milk than those from DC milk. Dietary characteristics had important effects on the medium-chain fatty acid composition (C₆ to C₁₄) of the cheese fat, giving DF cheeses the specific goat's milk flavor that is sought after for this type of cheese. The fatty acid composition (%) differed substantially among different ripening times. The DF cheeses were more appreciated by the panelists, as they had a greater variety of odors and flavors than the DC cheeses. The DF hard cheeses were described as having vegetable and fruity tones as well as tones of hay and dried fruit.     

The Effect of Yeast Species from Raw Milk in China on Proteolysis and Aroma Compound Formation in Camembert-Type Cheese

The influence of selected yeast strains (Pichia fermentans, Issatchenkia orientalis, Yarrowia lipolytica) on Camembert-type cheeses has been investigated by monitoring their microbial and compositional changes. During the ripening period from day 1 to day 15, the yeast strains grew exponentially and then slowed to a moderate growth rate. Our results indicated that the selected strains did not significantly affect the general characteristics of cheese but rather the content and ratio of individual free amino acids (P < 0.05). In the cheese with added I. orientalis, a greater amount of small peptides and a higher concentration of non-protein nitrogen and NH₃ were found. Meanwhile, the presence of adjunct yeasts did not enhance the lipolysis activity in cheese. A principal component analysis of 30 free fatty acids and volatile compounds differentiated five cheeses out of eight according to the content of specific free fatty acids and volatile compounds. In terms of the ripening period, two groups of cheeses at 15 and 45 days were distinguished.     

Effect of nitrate/nitrite on the quality of sausage (sucuk) during ripening and storage

The effects of nitrate/nitrite on the microbial and chemical properties and sensory quality of Turkish‐style sausage (sucuk) were investigated during 15 days of ripening and 45 days of storage. Aerobic plate count, mould and yeast count, pH, 2‐thiobarbituric acid value, residual nitrite level, nitrosomyoglobin conversion and sensory characteristics (flavour, colour and cutting scores) were monitored. Aerobic plate count increased (P < 0.05) during the first 8 days of ripening and decreased (P < 0.05) during further ripening and storage. Mould and yeast count increased (P < 0.05) during the first 4 days of ripening and decreased (P < 0.05) during further ripening and storage. Overall sensory quality increased (P < 0.05) during the first 12 days of ripening and decreased (P < 0.05) during further ripening and storage. Increasing the nitrate/nitrite concentration increased (P < 0.05) the overall sensory quality. During the first 4 days of ripening, the pH of all sausages decreased (P < 0.05) from 5.98 to 4.53–4.81, owing to the action of lactic acid bacteria. Residual nitrite level decreased (P < 0.05) sharply during the first 8 days of ripening, from 150 to about 2 mg kg^?1 in sausage samples B3 (prepared with 150 mg kg^?1 nitrite, 300 mg kg^?1 nitrate and starter culture) and from 75 to about 1 mg kg^?1 in samples B2 (prepared with 75 mg kg^?1 nitrite, 150 mg kg^?1 nitrate and starter culture). The conversion of haem pigments to nitrosomyoglobin increased (P < 0.05) during the first 12 days of ripening and decreased (P < 0.05) during further ripening and storage. Copyright © 2004 Society of Chemical Industry     

Utilization of interesterified fat in the production of Turkish white cheese

The chemical, physicochemical, proteolysis, sensory, and texture characteristics of white cheeses made from interesterified fat were examined throughout ripening for 90 days. The water-soluble nitrogen based ripening indexes of cheeses increased throughout the ripening period. However, there were not large quantitative differences between the peptide profiles of the all cheese samples. Cheeses produced by using fully interesterified fat had higher values for hardness, chewiness, and gumminess than that of control cheese (p<0.05). The polyunsaturated to saturated fatty acid ratios of cheeses were increased due to the presence of interesterified fat. The cholesterol values of cheeses decreased at the rate of between 58.83–89.04% depending on interesterified fat addition. In the sensory analysis, similar scores were obtained for both the control cheese and the other cheeses. The results showed that interesterified fat in cheese production could be used to fully or partially replace the milk fat in cheese.     

Effect of a hygienized rennet paste and a defined strain starter on proteolysis,texture and sensory properties of semi-hard goat cheese

A hygienized rennet paste (HRP) and a defined strain starter culture, including Lactobacillus casei subsp. casei IFPL as adjunct, were considered for manufacturing Majorero cheese, a Spanish traditional variety made from goat milk. Influence of both factors on physicochemical characteristics, proteolysis, rheological and sensory properties, was evaluated throughout the ripening. Cheeses produced either industrially (IL) or in artisanal manner (AL) were compared with the experimental lot (EL), which included HRP and IFPL starter in its manufacture. Results showed a low level of primary proteolysis, expressed by a low content of non-casein nitrogen (NCN), in experimental cheeses. Despite the slightly poor texture (hard and crumbly) related to the high TS and salt contents, a good general acceptability was attained for EL, with the best scores for aroma and flavour intensities achieved at 30 ripening days. In fact, the sensory panel detected the “piquant” flavour (typical of the artisanal cheese variety) in EL after 15 days of ripening.     

Effect of a nisin-producing lactococcal starter on the late blowing defect of cheese caused by Clostridium tyrobutyricum

Clostridium tyrobutyricum causes swelling, cracks and off-flavours of cheeses (late blowing defect, LBD) due to butyric acid fermentation. To control this spoilage bacterium, we investigated the use of nisinogenic Lactococcus lactis subsp. lactis INIA 415 as starter in cheeses contaminated with C. tyrobutyricum spores. Control cheese made with spores showed LBD after 14 days of ripening. However, in cheese made with the bacteriocin producer and spores, in which (unlike control cheese) bacteriocin activity was detected throughout ripening, LBD occurred after 21 days. At this stage, level of lactic acid was 1.22-fold higher (P < 0.01) and concentrations of propionic and butyric acids were 2.15- and 2.32-fold, respectively, lower (P < 0.01) in cheese made with the nisin producer than in control cheese, according to the less pronounced spoilage symptoms showed by the former cheese. The bacteriocin producer delayed the appearance of LBD, although it cannot arrest completely C. tyrobutyricum growth.     

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.     

Microbiological and biochemical changes in herby cheese during ripening

The aim of this study was to determine and compare the microbiological, biochemical and sensory characteristics of herby cheese made with two different methods. In the first method (M1), milk and herbs were pasteurized at 65°C for 30 min, and Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris were added as starter culture at an inoculum ratio of 1.5%. In the second method (M2), the conventional cheesemaking was applied. Microbiological and biochemical changes were monitored throughout the ripening period of 90 days. Samples were taken from cheeses on days 1, 15, 30, 60, and 90. At the end of ripening, sensory characteristics of cheeses manufactured with both methods were evaluated. The obtained results suggested that most changes in pH, titratable acidity, and dry matter contents of cheese varieties were not found to differ statistically significant, but the difference in salt content was significant (P < 0.01). Total aerobic count, lactic acid bacteria, Staphylococcus aureus, coliforms, moulds, yeasts, proteolytic and lipolytic microorganism counts were lower in M1 cheese samples than those of M2 cheese samples (P < 0.01). The numbers of psychrotrophic microorganism in both cheese types were not found to differ significantly. Moreover, the results suggested that there were significant differences (P < 0.01) in the degrees of proteolysis and lipolysis of the cheese varieties. High proteolysis and lipolysis rates were monitored in the traditional cheese samples. However, there were no significant differences between the sensory characteristics of cheese samples.     

Use of changes in triacylglycerols during ripening of cheeses with high lipolysis levels for detection of milk fat authenticity

The triacylglycerol (TAG) compositions by carbon number during ripening of two Protected Designation of Origin (PDO) cheeses were analysed using short capillary column gas chromatography. Lipolysis levels were high in the Cabrales (blue cheese produced from cows’ milk or from blends of cows’ with goats’ milk) and Majorero goats’ milk cheeses at the end of ripening, with free fatty acid (FFA) levels of around 24 000 ppm and significant changes in the TAG composition. The level of lipolysis in an industrial blue cheese made from ewes’ milk was low, with an FFA value of around 6000 ppm and no significant changes in the TAG composition during ripening. The TAG values recorded for each cheese sample were substituted into the multiple regression equations that have been proposed for use in detecting foreign fats in milk fat. The values thus obtained were within the established ranges in early ripening. In the cheeses with high lipolysis levels during ripening, some of the values obtained fell outside the established ranges. These equations can be potentially useful for detecting foreign fats in these cheeses, when employed early in the ripening period. Furthermore, it is important to take into account that before coming to a conclusion about cheese authenticity, several individual samples should be analysed.     

Proteolysis,texture and colour of a raw goat milk cheese throughout the maturation

Changes on chemical and textural parameters were studied throughout maturation of PDO Ibores cheese. NCN/TN (non-casein nitrogen/total nitrogen) values were significantly modified (P < 0.001) throughout maturation, and significantly, lower values were observed at day 1 than at day 30, 60 and 90. Non-protein nitrogen/total nitrogen (NPN/TN) was not significantly changed during the ripening process (P > 0.05). Therefore, proteolysis extent (casein degradation and ‘ripening depth’) took place at initial stage and was limited throughout Ibores cheese maturation. In addition, since casein nitrogen decreased during the first month of ripening without a simultaneous increase in NPN/TN, this likely indicates that the large fragments of caseins liberated during this period are not further degraded into smaller products. Primary proteolysis (resulting from the action of endoproteases on caseins) is thus far more important than secondary proteolysis during this period. Moreover, secondary proteolysis remains limited along the 90 days. Polypeptide nitrogen significantly increased at day 30 from casein degradation compared to day 1, while free amino acids (FAA) content significantly increased during maturation process. In addition, hardness and adhesiveness values significantly increased, but cohesiveness and springiness significantly decreased up to day 60. Variables such as dry matter, NCN/TN and polypeptide nitrogen showed high correlations with textural parameters. Principal component analysis (PCA) of variables divided the Ibores cheeses according to their ripening: early, middle or late ripening.     

Use of principal component analysis to evaluate the physical properties of Mahon cheese

 The texture, colour and water activity of the seven existing types of Mahon cheese, manufactured under the Mahon cheese Appellation of Origin, were studied using eight physical variables. Four of the types are industrially manufactured [fresh (less than 10 days of ripening), half-ripened (2–5 months of ripening), ripened (5–10 months of ripening) and old-ripened (more than 10 months of ripening)] and three are traditionally manufactured (half-ripened, ripened and old-ripened). ANOVA, Tukey's multiple range test and principal component analysis (PCA) were used. Mahon cheeses from different ripening periods exhibited significant differences in water activity and yellowness values (P<0.001). PCA reduced the eight physical variables to two independent components, which accounted for 84.4% of the total variance. The first principal component (PC1) separated cheeses characterised by high water activity, high springiness values and slight yellowness from those with high hardness and puncture force; PC1 therefore distinguished among samples from different ripening periods. Cohesiveness, chewiness and gumminess were highly correlated in the second principal component, which could be interpreted as an index of cohesiveness. Received: 8 February 1999     

The effect of three different ripening/storage conditions on the distribution of selected parameters in individual parts of Dutch‐type cheese

The aim of the study was (i) to detect changes of dry matter, NaCl and twenty‐two free amino acids contents, pH and levels of selected microorganisms in four layers of cheese (from edge to core) during ripening and storage period and (ii) to describe the changes of the above‐mentioned parameters caused by early relocation of cheese from optimum ripening conditions to refrigeration temperatures. The number of mesophilic aerobic and facultative anaerobic bacteria and lactic acid bacteria differed significantly (P < 0.05) during the experiment dependent on the analysed layer and ripening/storage conditions. The free amino acid content differed significantly in individual analysed layers of cheese and also according to individual ripening/storage conditions. The highest content of free amino acids was found in samples stored at optimal ripening temperatures. Cheese hardness was also analysed and the lowest one was detected in samples ripened under optimal temperatures for the whole period. Early release of cheeses into storage rooms with lower temperature significantly affected properties of these products.     

Phenolic compounds in persimmon during maturation and on-tree ripening

Changes in weight, Brixº, moisture and phenolic substances, extractable with water, methanol and aqueous methanolic solution, were determined during maturation and on-tree ripening (120 days) of persimmon. Fruit weight increased during maturation (40 to 169 g/fruit) and then decreased to an average value of 145 g/fruit on ripening. Brixº increased throughout from 15 to 20 while moisture content exhibited irregular trend. Maturation time and extracting solvents significantly influenced the polyphenolic compounds (P < 0.05). The concentration of sinapine, catechin and procyanidine in relation to different extractants showed an overall decreasing pattern during maturation and ripening. However, total phenolics exhibited an upsurge after 60 days while leucoanthocyanidine values increased between 15–75 days followed by reduction with each solvent. An overall significant linear correlation (r = ?0.811 to ?0.916) was found between the loss of polyphenols except leucoanthocyanidine and maturation/ripening time (P < 0.05).     

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.     

The effects of using a starter culture,lipase, and protease enzymes on ripening of Mihalic cheese

The purpose of this study was to determine the effects of fungal lipase from Mucor miehei and a bacterial neutral protease from Bacillus subtilis alone and combined with a starter culture on ripening properties of traditional Turkish Mihalic cheese. The use of protease with lipase (Cult + Prot + Lip) resulted in better flavour and texture with accelerated ripening. The obtained results pointed out that the gross compositions of the cheeses were changed by the type of enzymes and ripening time (P < 0.01). The acid degree value (ADV) of all cheeses showed a linear increase with ripening. The highest lipolysis rate was noted in lipase‐added cheese batch (as 5.56 ADV) with highest γ‐CN ratio and β‐CN degradation. At the end of ripening time, it was observed that αs‐CN ratios decreased in starter‐added (Cult), starter + protease–added (Cult + Prot), and protease‐added (Prot) cheese batches. The use of protease with lipase (Cult + Prot + Lip) resulted in better flavour and texture with accelerated ripening. Protease‐added cheeses, which were characterized by bitterness and crumbly textural properties owing to the intense breakdown of β‐casein, scored lower than lipase‐added cheeses. It was determined that the use of mesophilic aromatic starter culture with lipase and protease could be used to accelerate ripening of Mihalic cheese made from pasteurised milk.     

Effect of the addition of nitrate to milk on the formation of volatile N-nitrosamines and apparent total N-nitroso compounds

 Saint-Paulin, a French semihard cheese, was manufactured from milk with and without added NO₃ ^–. Reference and experimental cheeses were analysed at different stages of ripening for the presence of apparent total N-nitroso compounds (ATNC) by chemical denitrosation and chemiluminescence detection (thermal energy analyser). The fate of NO₃ ^– and NO₂ ^–was also scrutinized. The levels of ATNC and of volatile N-nitrosamines were followed during ripening. After 60 days of ripening, ATNC were detected at concentrations of 27 μg NO-N/kg and 64 μg NO-N/kg in the cheeses obtained from milk with and without added NO₃ ^–, respectively. The NO₃ ^– contents of both cheeses were nearly the same, and below 5 mg/kg. The occurrence of NO₂ ^–was not observed. No relationship was found between the NO₃ ^– contents and the contamination of the cheeses by volatile N-nitrosamines. At the beginning of ripening, the cheeses manufactured with added NO₃ ^- showed high levels of ATNC (mean value 5800 μg N-NO/kg with large variations of 570–15210 μg NO-N/kg). These ATNC contents rapidly decreased during the first days of ripening (96%), but decreased much more slowly during the following days. An hypothetical mechanism, attempting to explain the disappearance of ATNC, involving the formation of alkylated species in the cheese was proposed. Received: 30 March 1998 / Revised version: 7 October 1998