Isolation of lactic acid bacteria from Lighvan cheese, a semihard cheese made from raw sheep milk in Iran

The lactic acid bacteria contributing to Lighvan cheese ripening during the different stages of production were investigated. Isolated strains from different culture media were identified phenotypically to species and subspecies level. In total, 413 strains were isolated from raw milk, 1-day-old cheese and fully ripened cheese. The most abundant species belonged to Enterococcus faecium (87 isolates), Lactococcus lactis ssp. lactis (68 isolates), Enterococcus faecalis (55 isolates) and Lactobacillus plantarum (48 isolates). E. faecium, Lc. lactis and Lb. plantarum were the predominantly isolated strains from ripened cheese. Therefore, they may contribute considerably to the aroma and flavour development of Lighvan cheese.     

Texture,physicochemical and sensory properties of artisanal Adobera cheese from Los Altos de Jalisco,a genuine Mexican cheese

Physicochemical and sensory properties of Adobera, a genuine, understudied Mexican raw‐milk cheese, were explored by analysing commercial samples from different manufacturers and seasons. Composition‐wise, Adobera could be considered a fresh cheese with a high moisture content (42.5%), although its relatively low water activity (0.953) and pH (5.14) and high free amino acid content (0.46 mmol/g, dry basis) could indicate otherwise. Instrumental texture corresponded to that of a semifirm cheese, while its colour was whitish‐to‐ivory. Both texture and composition were significantly affected by sampling season and cheese composition, while some attributes of sensory acceptability significantly varied with brand.     

Terpene profiles in Cantal and Saint‐Nectaire‐type cheese made from raw or pasteurised milk

Terpene profiles in cheese can be considered a ‘terroir’ fingerprint as the information contained in it should enable the pastures on which the animals were fed to be recognised. Yet a certain elasticity of the signature must be taken into account when determining authentication strategies, since products acknowledged as containing a common signature may have undergone certain procedures, such as cheese making and milk pasteurisation, that could have potentially altered their terpene profiles. In this study, Cantal and Saint‐Nectaire‐type cheeses were made from both raw and pasteurised milk from the same herd of dairy cows that had been grazed on natural grassland. Cheeses from raw and pasteurised milk were made from the same milking on the same days. Cantal and Saint‐Nectaire‐type cheeses were made on 4 different days, alternatively over four weeks. The terpenes in the cheese fat were analysed by dynamic headspace/gas chromatography/mass spectrometry. A great diversity of monoterpenes, sesquiterpenes and oxygen‐containing derivatives were identified. The major terpenes identified in most cheeses were β‐caryophyllene, α‐ and β‐pinene and limonene. Milk pasteurisation did not induce changes in the terpene profile of the cheese. Significant differences (p < 0.001) were observed between Cantal and Saint‐Nectaire cheeses: α‐pinene, β‐myrcene and β‐phellandrene were, respectively, three, five and five times more abundant in Cantal cheese, while tricyclene, α‐phellandrene and geraniol were found exclusively in Cantal cheese. In contrast, unidentified sesquiterpenes with retention indices (KI) = 1342 and 1511, α‐cubebene, longifolene and γ‐elemene were more abundant or exclusively found in Saint‐Nectaire cheese. A significant relationship with the date of milking (p < 0.01) was observed for α‐pinene and tricyclene in Cantal, for β‐myrcene, δ‐3‐carene, p‐cymene and α‐terpinene in Saint‐Nectaire cheese. Copyright © 2005 Society of Chemical Industry     

Biochemical changes during the ripening of homemade 'San Simón da Costa' raw milk cheese

'San Simón da Costa' cheese is a traditional smoked variety produced in the northwest of Spain from cow's milk. Biochemical changes were determined during its ripening. Its high calcium and phosphorus content and its low NaCl and sodium content stand out. This cheese undergoes moderate proteolysis. The most abundant free amino acid at the end of the ripening was glutamic acid, followed by tryptophan, leucine, arginine and phenylalanine. The lipolysis throughout ripening is slight; the most abundant free fatty acid being oleic, followed by palmitic and butyric acid.     

Effects of curd heating with or without previous milk pasteurisation on the microbiological quality and safety of craft‐made ‘Pasta Filata’ Kashkaval cheese curds

An empirical ‘Pasta Filata’ process used for traditional Kashkaval cheese manufacture from raw ewes’ milk improved the hygiene of fresh curd. Coagulase‐positive (RPF+) staphylococci and coliforms declined by 2.4 and 4.5 log units, respectively, and Listeria contamination was minimised. Before Pasta Filata, RPF+ staphylococci exceeded the 5‐log threshold level specified in EC Regulation 1441/2007 in raw milk curds despite the prevalence of indigenous mesophilic lactic acid bacteria. Pasta Filata favoured enterococci in raw milk curds. Pasteurisation enhanced prevalence of Streptococcus thermophilus and Lactococcus lactis starters and microbial quality and safety of pasteurised milk curds before and particularly after Pasta Filata.     

Headspace analysis of volatile flavour compounds of teleme cheese made from sheep and goat milk

The headspace compounds of teleme cheese made from sheep's milk, goats' milk or mixture of sheep's and goats' milk (50:50) were analysed during ripening by static headspace gas chromatography–mass spectrometry. A total of 21 major compounds were identified, including aldehydes (7), alcohols (5), ketones (4), and acids (2). All types of cheeses contained approximately the same volatiles at different concentrations. The total volatile compounds (TVC) increased during ripening. Cheeses made from sheep's milk showed the highest level of TVC, whereas cheeses made from goats' milk showed the lowest one.     

Microbiological and chemical characterization of Fiore Sardo, a traditional Sardinian cheese made from ewe's milk

The purpose of this study was to assess the chemical and microbial characteristics of 12 batches of artisanal Fiore Sardo, a protected designation of origin (PDO) hard cheese made from raw ewe's milk without addition of starters, during maturation. High standard deviations were observed for moisture percentage, total solids percentage and NaCl percentage content, possibly owing to differences in manufacturing processes and/or milk composition. Total mesophilic bacteria varied between 10 log₁₀ cfu/g in 48-h-old cheese samples and 3 log₁₀ cfu/g in 9-month-old samples. Total coliforms and staphylococci showed the highest counts at 48 h of ripening then decreased significantly, dropping to levels below 2 log₁₀ cfu/g at 3 months of maturation. Lactic acid bacteria and enterococci were the dominant micro-organisms throughout maturation. They were mainly represented by the species Lactococcus lactis ssp. lactis, Enterococcus faecium, Lactobacillus plantarum and Lactobacillus casei group. Low levels of yeasts were detected throughout the maturation period of the cheese. Debaryomyces hansenii and Kluyveromyces lactis var. lactis were the prevalent yeast species isolated.     

Evaluation of isolated starter lactic acid bacteria in Ras cheese ripening and flavour development

Eighteen cultures of starter lactic acid bacteria with or without added adjunct cultures, isolated from Egyptian dairy products, were evaluated in experimental Ras cheese for flavour development. Chemical composition of experimental cheeses was within the legal limit for Ras cheese in Egypt. All cultures used in this study had no effect on chemical composition of Ras cheese. Very significant variations in free amino acids, free fatty acids and sensory evaluation have been found among the cultures used in Ras cheesemaking. The levels of free amino acids and free fatty acids were correlated well with flavour development in Ras cheese. Seven of the tested cultures produced acceptable flavour and texture of Ras cheese. The highest overall score of flavour intensity, flavour and texture acceptability were in cheese made using YY47 lactic culture in addition to adjunct culture of Lactobacillus helveticus, Lactobacillus paracasei subsp. paracasei, Lactobacillus delbrueckii subsp. lactis and Enterococcus faecium. This culture can be recommended for Ras cheese manufacture using pasteurized milk.     

Changes in the microbiological and chemical characteristics of an artisanal, low-fat cheese made from raw ovine milk during ripening

Changes in the microbial flora of batzos cheese made from raw ovine milk were studied during ripening. Lactic acid bacteria and Enterobacteriaceae were the predominant groups of micro-organisms. Cheeses manufactured in summer had higher microbial counts than those made in spring, with the exception of staphylococci. Nevertheless, Enterobacteriaceae and coliforms decreased more rapidly in cheese made in summer and counts at the end of storage were lower than those in spring cheese.
Enterococci predominated in the ripened curd of cheese made in spring, whereas lactobacilli were the most abundant lactic acid bacteria in cheese made in summer. Enterococcus faecium was the predominant species in spring, and Lactobacillus paracasei ssp. paracasei predominated in cheese made in summer. The pH of the cheeses was > 5.0 throughout ripening, and NaCl-in-moisture content (> 8.0%) permitted the growth and survival of salt-tolerant micro-organisms. α_s1-Casein degraded at a faster rate than β-casein; both caseins were hydrolysed more rapidly in spring than in summer. The free amino acid content became higher in summer cheese (566.24–3460.25 µg/g of glycine equivalent) than in spring cheese because of the progress of ripening. Moreover, the milk fat of the cheese was degraded more in the summer than in the spring. The results suggest that there could be advantages to using starter cultures and improving the level of hygiene during milk and cheese production in order to eliminate undesirable micro-organisms and standardize cheese quality.     

Fate of Listeria innocua during production and ripening of smeared hard cheese made from raw milk

The fate of 2 different Listeria innocua strains was analyzed during the production and ripening of smeared raw milk Greyerzer cheese (Gruyère). These strains were used as surrogates for the pathogenic Listeria monocytogenes, as they are physiologically very similar. Bacterial cells were added to the cheese milk at levels of 10⁵ cfu/mL. During the first 24 h of cheese making, the number of the test strains decreased to a level of below 10² cfu/g. Obviously, the cooking temperature of 56°C and the subsequent slight temperature decrease to 50°C within 70 min contributed to a distinct reduction of Listeria counts. The counts in the cheese cores did not exceed 10³ cfu/g within 12 wk of cheese ripening and Listeria was not detectable after 24 wk. In contrast to the cores of the cheeses of the 4 batches in this study, their rinds always contained a high listerial load of approximately 10⁶ to 10⁸ cfu/g throughout the entire ripening period. The smeared surface showed an increase of pH to alkaline values, corresponding to smear microbiota development. Coryneforms and Staphylococcus counts were stable at >10⁷ cfu/cm² over 175 d, whereas yeast counts decreased to about 10⁵ cfu/cm² at the end of ripening. The study shows that the smear culture had no noticeable anti-listerial potential. When removing the rind or portioning such smeared cheese loaves with a cutting device, a postprocess contamination of the core might occur, thus presenting a major hygienic risk.     

Characterisation of Macedonian white‐brined cheese: Effect of raw or heat‐treated caprine milk

This research analysed the use of raw and pasteurised milk in the production of Macedonian white caprine milk cheese. Pasteurisation resulted in a considerable decrease in the nitrogen fractions, urea‐polyacrylamide gel electrophoresis of caseins, peptide profiles and volatiles during the maturation period. Forty‐five volatile components were detected, including twelve acids, fourteen esters, six ketones, three alcohols, four terpenes and six other compounds. It was deduced that pasteurisation of milk for the manufacture of artisanal white‐brined cheese delayed the evolution of volatiles, which are related to the unique flavour of the cheese.     

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).     

Volatile composition and sensory properties of industrially produced Idiazabal cheese

The volatile composition and sensory properties of industrially produced Idiazabal cheeses made from ewes’ raw milk (RM) or pasteurised milk (PM) and with addition of different starter cultures were compared. Cheeses were analysed at 90 and 180 d of ripening. Acids were the major volatile compounds in RM cheeses. Methyl ketones were the major volatile compounds in PM cheeses at 90 ripening days. However, the content of acids strongly increased with ripening whereas the content of ketones decreased in PM cheeses. The concentration of esters was higher in RM cheeses than in PM cheeses. No differences were found in the content of alcohols. Most aldehydes, hydrocarbons, terpenes and furans identified were minor volatile compounds in both RM and PM cheeses. In RM cheeses, characteristic sensory attributes for the aroma of Idiazabal cheese were present at 3 months, whereas in PM cheeses those desirable sensory attributes did not appear until 6 months of ripening.     

Effect of technological parameters on the characteristics of kasseri cheese made from raw or pasteurized ewes' milk

Two groups of kasseri cheese (pasta filata type) were manufactured from raw or pasteurized ewes' milk, without starter cultures. Cheeses of each group were divided into two subgroups: the first was ripened and stored at 4°C and packaged in plastic film; the second ripened and stored at 15°C and coated with paraffin wax. Milk pasteurization and technological parameters had a significant effect on the pH ( P  < 0.05), while only technological parameters had an effect on the total solids content. At day 120, the range of mean cfu/g counts for the mesophilic aerobic flora was 9.5 × 10⁷−1.4 × 10⁸; for the thermophilic streptococci, the range was 2.6 × 10⁷−7.6 × 10⁷; and for the thermophilic bacilli, 9.8 × 10⁶−1.7 × 10⁷. Changes in the N fractions became significant after 30 days of ripening. For mature 120-day-old cheeses, the percentage of total N soluble at pH 4.6 was 22.7%–22.9% in raw milk cheeses and 19.0%–21.7% in pasteurized milk cheeses. The percentage of total N soluble at 12% TCA was 10.1%–12.2% in raw milk cheeses and 7.3%–11.5% in pasteurized milk cheeses; the percentages of total N soluble at 5% PTA were 3.1%–4.0% and 2.6%–3.6%, respectively. The residual α_s-casein percentages at day 120 ranged between 63% and 78% of the respective area at day 1; the residual β-casein ranged between 67% and 75%. There were some characteristic differences in the reverse phase-HPLC peptide profiles of the four cheeses. In general, the effect of the different ripening conditions was more pronounced in cheeses made from pasteurized milk.     

Effect of high-pressure treatments on proteolysis and texture of ewes’ raw milk La Serena cheese

La Serena cheeses, made from Merino ewes’ raw milk, were high-pressure (HP)-treated at 300 or 400 MPa for 10 min at 10 °C, on days 2 or 50 of ripening. Cheeses treated by HP on day 2 showed higher pH values than control cheese on day 3, but cheeses treated by HP on days 2 or 50 and control cheese had similar pH values on day 60. Breakdown of caseins was delayed by HP treatment of cheeses on day 2. Cheeses treated by HP on day 2 showed higher levels of hydrophilic peptides, lower levels of hydrophobic peptides, lower hydrophobic peptides: hydrophilic peptides ratios, and higher total contents of free amino acids than those of control cheese. HP treatment of cheese on day 50 scarcely affected proteolysis of 60-day-old cheeses. Fracturability, hardness and elasticity values of cheeses treated by HP on day 2 were higher than those of control cheese and of cheeses treated on day 50. Cheeses treated at 400 MPa on day 2 received the lowest scores for quality of taste from panellists, whereas the rest of HP-treated cheeses did not differ from control cheese.     

Ripening of Camembert-type cheese made from caprine milk using calf rennet or kid rennet as coagulant

Camembert-type cheese was made from caprine milk using either calf rennet or kid 'Grandine' rennet as coagulant. The pH of all cheeses increased throughout ripening and levels of pH 4.6-soluble nitrogen increased from 8.1 to 18.2% of total nitrogen (TN) and from 6.9 to 20% TN for the cheeses made using calf rennet and kid rennet, respectively. Degradation of β-casein, measured by urea–polyacrylamide gel electrophoresis, and total and free amino acids were greater in the cheese made using kid rennet. Production of peptides, analysed by high performance liquid chromatography (HPLC), was slightly more extensive in the Camembert-type cheese made using calf rennet as coagulant. In general, a higher degree of proteolysis was found in Camembert-type cheese made from caprine milk using kid rennet than in cheese made using calf rennet as coagulant.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Raw milk and raw milk cheeses as vehicles for infection by Verocytotoxin-producing Escherichia coli

Raw milk and raw milk cheeses can be a source of food-borne pathogens, including Verocytotoxin (Shiga toxin)-producing Escherichia coli (VTEC/STEC). Outbreaks of VTEC O157: H7 infections have been attributed to the consumption of raw milk and associated dairy products. Although the general prevalence of VTEC O157 in raw milk and raw milk cheeses is low, it can be higher for non-O157 VTEC. The clinical significance of many of these VTEC is unclear, although some are associated with disease. Studies show that E. coli O157 strains can survive the various stages of the cheesemaking process and that raw milk and raw milk cheeses remain a potential vehicle for VTEC infections.     

Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurised milk

Cheddar cheeses were made from raw (R1, R8) or pasteurised (P1, P8) milk and ripened at 1°C (P1, R1) or 8°C (P8, R8). Volatile compounds were extracted from 6 month-old cheeses and analysed, identified and quantified by gas chromatography-mass-spectrometry. A detailed sensory analysis of the cheeses was performed after 4 and 6 months of ripening. The R8 cheeses had the highest and P1 the lowest concentrations of most of the volatile compounds quantified (fatty acids, ketones, aldehydes, esters, alcohols, lactones and methional). The R8 and P8 cheeses contained higher levels of most of the volatiles than R1 and P1 cheeses. Ripening temperature and type of milk influenced most of the flavour and aroma attributes. Principal component analysis (PCA) of aroma and flavour attributes showed that P1 and R1 had similar aroma and flavour profiles, while R8 had the highest aroma and flavour intensities, highest acid aroma and sour flavour. The age of cheeses influenced the perception of creamy/milky and pungent aromas. PCA of the texture attributes separated cheeses on the basis of ripening temperature. The R8 and P8 cheeses received significantly higher scores for perceived maturity than P1 and R1 cheeses. The P1 and R1 cheeses had similar values for perceived maturity. In a related study, it was found that concentrations of amino acids and fatty acids were similar in R1 and P1 during most of the ripening period, and R1 and P1 cheeses had low numbers of non-starter lactic acid bacteria (NSLAB). The panel found that ripening temperature, type of milk and age of cheeses did not influence the acceptability of cheese. It is concluded that NSLAB contribute to the formation of volatile compounds and affect the aroma and flavour profiles and the perceived maturity of Cheddar cheese.     

Proteolytic activity among psychrotrophic bacteria isolated from refrigerated raw milk

Psychrotrophic bacteria were isolated from refrigerated raw milk from a processing plant in Southern Brazil. Psychrotrophic counts were between 4.9 and 7.8 log cfu/mL, and 5.3 to 7.2 log cfu/mL, for samples collected at the truck and the milk storage silo, respectively. Among the bacterial isolates, 90% were Gram-negative. Most strains presented low proteolytic activity, but strains of Burkholderia cepacia, Klebsiella oxytoca and Aeromonas sp. showed higher than 20 U/mL on azocasein as substrate. Crude proteases from selected strains were resistant to conventional heat treatments and caused coagulation of UHT milk after 5 days storage at room temperature.