Cow's Milk Cheese Research Articles

Innovation in the development of fermented dairy drink with cow's milk and goat cheese whey

The fermented dairy drink is an important form of utilization of whey because of its high acceptance. Passion fruit and bee honey are regional products with features that can be exploited in the development of the drink, as acidity and its functional potential, respectively. The objective of this research is to study the various relationships of mixing milk and whey in the preparation of a dairy drink flavored with passion fruit and sweetened with honey of Africanized bees, as well as to characterize this drink according to its physicochemical, microbiological and sensory aspects and to evaluate its stability and purchase intent. There was no difference in the sensory aspects among adults about the content of pulp and the goat whey that were tested. Regarding the acceptance test with children, 88% of the participants said they liked the drink. Regarding the stability of the product, there was a decrease in the pH from 4.6 to 3.8 during the first seven days, but it remained stable during the storage. In the five evaluated times, there was no significant difference among the sensory aspects, except because of one flavor that decreased until the 14th day of storage, and after that a slight growth was observed, returning to the acceptance level found on the 7th day of storage. The passion fruit flavored drink showed considerable values for purchase intent, suggesting to be a food with market potential.

Nutrient Contents and Sensory Quality Assessment of Home-Prepared Cheese and Yoghurt from Fresh Cow Milk

Objective: This study was designed to assess the nutrient contents and acceptability of local cheese (‘wara’) and yoghurt. Materials and Methods: Fresh cow milk was collected from Ijaye dairy farm, Oyo State, Nigeria. It was collected in three sterile containers of 2.5 litres each. Fresh cow milk and home-prepared cheese and yogurt were analyzed chemically using standard methods of AOAC, Atomic Absorption Spectrometry and Spectrophotometry. Data obtained were subjected to statistical analysis: means and standard deviation, analysis of variance (ANOVA) and means separated using Duncan’s Multiple Range Test. Results: Protein and fat contents of local cheese and yoghurt were higher than that of fresh milk. The values of the protein content of fresh milk were 4.25±0.01g/100g while that of local cheese and yoghurt were 4.70±0.06g/100g and 4.82±0.02g/100g, respectively. The values of phosphorous and magnesium of local cheese and yoghurt were also found to be higher than that of fresh milk. Phosphorous in fresh milk, local cheese and yoghurt were 0.37±0.01mg/100g, 1.04±0.03mg/100g and 1.06±0.04mg/100g while magnesium contents of fresh milk, cheese and yogurt were 0.23±0.01mg/100g, 1.04±0.02mg/100g and 1.06±0.03mg/100g respectively. The sensory analysis revealed that both cheese and yogurt were well accepted. Conclusion: Local cheese (‘wara’) and yoghurt produced locally should be introduced into Nigerian market to improve nutritional status of consumers and also could serve as complementary food. Local cheese and yoghurt have nutritional benefits beyond fresh cow milk.Key words: Cheese, Yoghurt, Home-prepared, Cow milk, Dairy products

Microbial dynamics during the ripening of a mixed cow and goat milk cheese manufactured using frozen goat milk curd

To overcome the seasonal shortage of goat milk in mixed milk cheese manufacture, pasteurized goat milk curd and high-pressure-treated raw goat milk curd manufactured in the spring were held at −24°C for 4 mo, thawed, and mixed with fresh cow milk curd for the manufacture of experimental cheeses. Control cheeses were made from a mixture of pasteurized cow and goat milk. The microbiota of experimental and control cheeses was studied using culture-dependent and culture-independent techniques. Bacterial enumeration by classical methods showed lactic acid bacteria to be the dominant population in both control and experimental cheeses. In total, 681 isolates were grouped by partial amplified rDNA restriction analysis (ARDRA) into 4 groups and identified by 16S rRNA gene sequencing as Lactococcus lactis ssp. lactis (563 isolates), Leuconostoc pseudomesenteroides (72 isolates), Lactobacillus spp. (34 isolates), and Lc. lactis ssp. cremoris (12 isolates). Temporal temperature gradient gel electrophoresis (TTGE) analysis of cheese showed (1) the predominance of Lc. lactis in all cheeses; (2) the presence of Leu. pseudomesenteroides population in all cheeses from d 15 onward; (3) the presence of a Lactobacillus plantarum population in control cheese until d 15 and in experimental cheeses throughout the ripening period. Due to the most diverse and complete set of peptidases present in the genus Lactobacillus, the prevalence of this population in experimental cheeses could give rise to differences in cheese flavor between experimental and control cheeses.

Occurrence of foodborne pathogens and characterization of Staphylococcus aureus in cheese produced on farm-dairies

The objective of this study was to address knowledge gaps identified in an earlier risk assessment of Staphylococcus aureus and raw milk cheese. A survey of fresh and short-time ripened cheeses produced on farm-dairies in Sweden was conducted to investigate the occurrence and levels of S. aureus, Listeria monocytogenes and Escherichia coli, to characterize S. aureus isolates with special emphasis on enterotoxin genes, antibiotic resistance, bio-typing and genetic variation, and to collect information related to production practices. In general, the hygienic quality of farm-dairy cheeses appeared to be of an acceptable microbiological quality, e.g. L. monocytogenes and staphylococcal enterotoxin were not detected in cheese samples. However, E. coli and enterotoxigenic S. aureus were frequently found in raw milk cheeses and sometimes at levels that are of concern, especially in fresh cheese. Interestingly, levels in raw milk fresh cheese were significantly lower when starter cultures were used. Up to five S. aureus colonies per cheese, if possible, were characterized and about 70% of isolates carried one or more enterotoxin genes, most common were sec and sea. The Ovine biotype (73%) was most common among isolates from goat milk cheese and the Human biotype (60%) from cow milk cheese. Of all isolates, 39% showed decreased susceptibility to penicillin, but the proportion of isolates from cows' cheese (66%) compared to isolates from goats' cheese (27%) was significantly higher. S. aureus isolates with different properties were detected in cheese from the same farm and, sometimes even the same cheese. Isolates with the same pulsed-field gel electrophoresis (PFGE)-pattern were detected on geographically distant dairies. This indicates that multiple sources and routes of contamination are important. To improve the safety of these products efforts to raise awareness of the importance of hygiene barriers and raw milk quality as well as improved process control can be suggested, e.g. use of starter cultures and monitoring of fermentation with a pH-meter. For future safety assessments, a better understanding of factors determining toxin production in these cheeses is needed.

Chemical and biochemical study of industrially produced San Simón da Costa smoked semi-hard cow's milk cheeses: Effects of storage under vacuum and different modified atmospheres

Two batches of smoked, semi-hard (ripened for 45 d) San Simón da Costa cow's milk cheeses with Protected Designation of Origin were used to investigate the chemical, biochemical, and sensorial parameters that may be affected by modified-atmosphere packaging. Cheeses were packaged for 45 d as follows: vacuum packaging, packaging in 100% N2, packaging in a gas mixture of 20% CO2/80% N2, and packaging in a gas mixture of 50% CO2/50% N2. The San Simón da Costa cheeses were characterized by high contents of lactic, oxalic, and citric organic acids. The main free amino acids found were isoleucine, phenylalanine, serine, valine, lysine, and glutamic acid, and the most abundant volatile compounds included ethanol, diacetyl, 2-butanol, isopropyl alcohol, furfural, acetaldehyde, 2-butanone, acetone, and 2-methylfuran. Modified atmospheres appeared to alter the ripening processes by affecting lipolysis, as indicated by the lower concentrations of butyric and propionic acids compared with control cheeses. In addition, modified-atmosphere packaging altered the proteolysis processes, yielding higher amounts of branched-chain alcohols. The results revealed that storage under modified atmosphere contributes to the accumulation of several compounds probably derived from smoke, including aldehydes such as 2-furancarboxaldehyde (furfural), alcohols such as 2-methoxyphenol (guaiacol), ketones such as 2-cyclopenten-1-one, and esters such as methyl furancarboxylate, which were negatively correlated with flavor. Vacuum packaging was the most useful technique in terms of preserving the sensory quality of San Simón da Costa Protected Designation of Origin cheeses. Considering the current demands for packaged portions of food at the distribution and retail levels and the potential health risks associated with some smoke-derived compounds usually present in some smoked foods, the results obtained in this study may be of special interest to the cheese industry.

Mööhrenlaibchen: How the Carrot Got into the Cheese

At first glance the small, round cow's milk cheese seems decidedly unexciting, one of the mild, semi-hard, ‘‘children’’ cheeses Germans apparently favor for their unobtrusiveness, the very opposite of the characterful, often pungent varieties their French neighbors like to make and eat. However, the intense orange color is unusual and the flavor special enough to find out more about it. Indeed, the Mööhrenlaibchen, literally ‘‘small carrot round‘‘, is a modern classic of the new German artisanal cheese scene. Its origin is at the Dottenfelder Hof near Frankfurt am Main, a renowned Demeter estate where the ideals of the anthroposophist Rudolf Steiner are put to practice. But Mööhrenlaibchen also taps into German history: a long tradition of coloring cheeses (for various reasons), as well as vegetarianism and the Lebensreform movement that formed as a countertrend to the heavy and rapid industrialization and urbanization at the end of the 19th century. The article explores the complex role the carrots play in this modern German artisanal cheese.

Antibiotic Resistance in Lactic Acid Bacteria and Micrococcaceae/Staphylococcaceae Isolates from Artisanal Raw Milk Cheeses, and Potential Implications on Cheese Making

Antibiotic susceptibility against 19 antimicrobial agents was evaluated in isolates of the genera Lactococcus (46 isolates), Leuconostoc (22), Lactobacillus (19), Staphylococcus (8), Enterococcus (7), and Microccoccus/Kocuria (5) obtained from the predominant microflora of nonrecent and recent types of artisanal raw cow's milk cheeses. Beta-lactams showed broad activity against all genera, although leuconostocs and lactobacilli were highly resistant to oxacillin (80% to 95.5%). Resistance to aminoglycosides was frequent for lactococci and enterococci (particularly for streptomycin), whereas lower rates of resistance were detected for lactobacilli and leuconostocs. Technologically interesting traits for the food industry were distributed among isolates that showed different degrees of resistance to common antibiotics. However, isolates showing resistance to less than 2 antibiotics were mainly those with properties of greatest technological interest (acidifying activity, proteolytic/lipolytic activities, or diacetyl production).

Analysis of the lactic acid bacteria microflora in traditional Caucasus cow's milk cheeses

A total of 157 lactic acid bacteria (LAB) were isolated from three hand-made cheeses taken from different households in the region of the Caucasus Mountains. The cheeses were manufactured from cow's milk without the addition of a starter culture. The isolates of LAB were characterized by subjecting them to phenotypic and genotypic tests. The results of identification of LAB indicate that the examined cheeses contained 10 species, viz., Lactobacillus plantarum, Lactobacillus paraplantarum, Lactobacillus arizonensis, Lactobacillus farciminis, Lactobacillus brevis, Lactococcus lactis subsp. lactis, Leuconostoc mesenteroides subsp. mesenteroides, Leuconostoc pseudomesenteroides, Enterococcus faecium, and Enterococcus faecalis. The strains within the species L. plantarum, L. arizonensis, L. paraplantarum, L. farciminis, and L. pseudomesenteroides showed good proteolytic activity.

Dominant lactic acid bacteria in artisanal Pirot cheeses of different ripening period

In this study two raw cow's milk cheeses of a different ripening period were examined. The cheeses were taken from a country household in the region of mountain Stara Planina and manufactured without adding of starter culture. A total 106 lactic acid bacteria (LAB) strains were isolated from both cheeses. They are tested by classical physiological tests as well as by API 50 CH tests. Proteolytic and antimicrobial activities were done too. Identification of LAB isolates was done by repetitive extragenic palindromic-polimerase chain reaction (rep-PCR) with (GTG)5 primer. The LAB isolates from cheese BGPT9 (four days old) belonged to the eight species of LAB (Lactobacillus plantarum, Lactobacillus paracasei subsp. paracasei, Lactobacillus delbrueckii, Lactobacillus brevis, Enterococcus faecium, Enterococcus faecalis, Enterococcus durans and Leuconostoc garlicum), while in the BGPT10 cheese (eight months old) only two species were present (Lactobacillus plantarum and Enterococcus faecium). Proteolytic activity showed 30 LAB from BGPT9 cheese, mainly enterococci. From BGPT10 cheese only one isolate (which belonged to the Lactobacillus plantarum species) possessed partial ability to hydrolyze ?-casein. Seven enterococci from BGPT9 cheese and four enterococci from BGPT10 cheese produced antimicrobial compounds.

Relationships between animal species (cow versus goat) and some nutritional constituents in raw milk farmhouse cheeses

The objective of this study was to specify the relationships between animal species (cow versus goat) and the contents of fat-soluble constituents (fatty acids, carotenoids, retinol and α-tocopherol) in raw milk farmhouse cheeses. Four hundred and thirty-two farmhouse cheeses (74 farms × 6–7 cheeses), including 306 cow's milk cheeses and 126 goat's milk cheeses, produced in real herd management conditions throughout the year, were collected. The conditions of milk production were identified beforehand by means of surveys. In order to limit the confounding effects related to the management practices specific to each animal species, the effect of animal species was studied only within cheeses associated with conditions of milk production common to both animal species. Except for C8:0, C10:0 and β-carotene, and to a lesser extent C4:0, the levels of which in cheese clearly differed according to the animal species, the variability within species was higher than the variability between species. Caprine milk fat was on average richer ( P < 0.001) in C8:0, C10:0, C18:2 n − 6, retinol and α-tocopherol (>30% richer) and to a lesser extent C6:0, C12:0 and C18:0 (from 8 to 25% higher) than bovine milk fat. On the other hand, bovine milk fat was richer ( P < 0.001) in C4:0, trans-11 C18:1, cis-9, trans-11 C18:2, xanthophylls and β-carotene (>30% richer) and to a lesser extent C14:0, C16:0 and C18:3 n − 3 (from 16 to 23% richer). Caprine milk fat was completely devoid of β-carotene. In conclusion, the results of this work indicate that, under real herd management conditions, the animal species (cow versus goat) is a strong influencing factor of the nutritional composition of cheese.

Occurrence and persistence of Listeria spp. in the environment of ewe and cow's milk cheese dairies in Portugal unveiled by an integrated analysis of identification, typing and spatial–temporal mapping along production cycle

Eight dairies, located in two distant geographic regions of Portugal, were screened along the production cycle in order to evaluate the presence and distribution of Listeria spp. in their environment. Three dairies in each region were positive for the presence of listeriae and 213 isolates were obtained. Based on an integrated analysis of RAPD fingerprints with three primers, molecular identification and genomic typing of isolates was performed followed by spatial and temporal mapping on dairy plants. The occurrence of Listeria species by region was noticeable different. Listeria monocytogenes prevailed in South Portugal dairies and L. innocua presented the highest occurrence in Azores, whereas L. seeligeri and L. ivanovii were detected in distinct regions. Dairies were at risk of contamination, from more than one source, whatever the stage in the production cycle and the surface materials used. For the three prevalent species, most of the genomic types were dairy and sampling time specific. Nonetheless, more than one type could be found in each dairy at a particular site and, in a few cases, even for different species. Some dairies also shared types, mainly for L. innocua and usually at the same stage of the production cycle. For L. monocytogenes, PCR serotyping was applied and 52% of genomic types were serotype 4b. An equal frequency of genomic types (24%) was found for serotypes 1/2b or 3b and 1/2a or 3a. The global pattern of types within a dairy is not constant, suggesting cycles of elimination and recontamination along the production cycle.

Verocytotoxin-producing Escherichia coli O157 in minced beef and dairy products in Italy

A total of 3879 samples of foodstuffs were examined for the presence of Verocytotoxin-producing Escherichia coli O157 (VTEC O157). The survey was conducted by 9 of the 10 Italian Veterinary Public Health Laboratories. Samples were collected between May 2000 and September 2001 in 14 regions and comprised 931 minced beef specimens and 2948 dairy products (DP) with less than 60 days of ripening. The DP included 657 pasteurised and 811 unpasteurised bovine DP, 477 pasteurised and 502 unpasteurised ovine DP, and 501 water-buffalo's milk mozzarella cheese. Samples were collected at retail level, from plants processing minced beef and dairy plants and from farms directly manufacturing cheeses. All the samples were tested using a sensitive procedure based on ISO/DIS 16654:1999 (later ISO 16654:2001), which includes an immunomagnetic separation step. A preliminary inter-laboratory trial was organised with artificially contaminated samples to assess the ability of all the participating laboratories to isolate E. coli O157 by the established procedure. VTEC O157 was isolated from four (0.43%) of the minced beef samples, collected in four different regions and during different months, but was not detected in any of the dairy products. E. coli O157 VT −eae + was isolated from one raw cow's milk cheese. This survey provided national data on the presence of VTEC O157 in foodstuffs, demonstrating a low prevalence of the organism. The survey also encouraged updating of knowledge and procedures on VTEC O157 in laboratories with official responsibility for microbiological testing of foods of animal origin.

Verocytotoxin-producing Escherichia coli O157 in minced beef and dairy products in Italy

A total of 3879 samples of foodstuffs were examined for the presence of Verocytotoxin-producing Escherichia coli O157 (VTEC O157). The survey was conducted by 9 of the 10 Italian Veterinary Public Health Laboratories. Samples were collected between May 2000 and September 2001 in 14 regions and comprised 931 minced beef specimens and 2948 dairy products (DP) with less than 60 days of ripening. The DP included 657 pasteurised and 811 unpasteurised bovine DP, 477 pasteurised and 502 unpasteurised ovine DP, and 501 water-buffalo's milk mozzarella cheese. Samples were collected at retail level, from plants processing minced beef and dairy plants and from farms directly manufacturing cheeses. All the samples were tested using a sensitive procedure based on ISO/DIS 16654:1999 (later ISO 16654:2001), which includes an immunomagnetic separation step. A preliminary inter-laboratory trial was organised with artificially contaminated samples to assess the ability of all the participating laboratories to isolate E. coli O157 by the established procedure. VTEC O157 was isolated from four (0.43%) of the minced beef samples, collected in four different regions and during different months, but was not detected in any of the dairy products. E. coli O157 VT − eae + was isolated from one raw cow's milk cheese. This survey provided national data on the presence of VTEC O157 in foodstuffs, demonstrating a low prevalence of the organism. The survey also encouraged updating of knowledge and procedures on VTEC O157 in laboratories with official responsibility for microbiological testing of foods of animal origin.

Effect of ripening time and type of rennet (farmhouse rennet from kid or commercial calf) on proteolysis during the ripening of León cow milk cheese

Classical nitrogen fractions, caseins and their degradation products, and free amino acids were determined during ripening of six batches of León raw cow milk cheese. Three batches were made using commercial calf rennet (average 1/8342 strength and 76% of chymosin) and three were made using farmhouse rennet obtained from kid abomasum (average 1/857 strength and 34% of chymosin). The pH 4.6-soluble nitrogen and the 12% TCA-soluble nitrogen contents increased moderately during ripening, reaching significantly ( P<0.05) higher average final values in the cheeses made using commercial rennet (18.0 and 11.0% of TN, respectively) than in the cheeses made using farmhouse rennet (8.3 and 5.1% of TN, respectively). The greater extent and intensity of proteolysis registered in the cheeses made using commercial rennet, especially after 15 days of ripening, became clear again on quantifying the caseins and their degradation products. β-Casein did not undergo any appreciable degradation during ripening. In the cheeses made using commercial rennet, 20% of the αs-caseins were degraded during ripening, whilst in those made using farmhouse rennet only 10% of the αs-caseins were degraded. These results show that this cheese undergoes a slight proteolysis and that the rennet plays a preponderant role in protein degradation. The content of total free amino acids increases progressively during ripening. In the batches made using commercial rennet, the final values were double those found in the batches made using farmhouse rennet. In the mature cheeses, the major free amino acid was lysine, followed by leucine, glutamic acid, tryptophan, valine, and phenylalanine. The type of rennet used during manufacture made no difference to the free amino acid profile at maturity.

Compositional and Physico-chemical Modifications during the Manufacture and Ripening of León Raw Cow's Milk Cheese

The gross and mineral composition and the most relevant physico-chemical parameters were determined in five batches of León cow's milk cheese throughout ripening and in the milk used in their manufacture. The milk used in the manufacture of this cheese is characterized by having high values of fat and total solids; the mineral composition and the values of pH do not differ significantly from those observed in cow's milk from different origins. During ripening, León cow's milk cheese undergoes a very intense dehydration, due to this, the final values of moisture and A w are among the lowest observed in cow's milk cheese. The fat contents in this cheese are placed in the higher extreme of the range of values observed in other cheeses. The presence of residual lactose in cheese after 90 days (end of ripening) is exceptional. During curdling a very intense acidification takes place as a consequence of which very low values of pH are reached in the curd (around 4.6) and remain during ripening with minimum variation, with the final values of pH being among the lowest found in cow's milk cheese. As a consequence of acidification during curdling, the minerals for the most part bound to the micelle of casein (Ca, P, Mg and Zn) underwent a solubilization and were lost in significant amounts in the whey. The contents of these minerals and of total ash at the end of ripening are clearly lower than those observed in other similar cow's milk cheeses.

Proteolytic and lipolytic changes during the ripening of León raw cow's milk cheese, a Spanish traditional variety

Proteolytic and lipolytic changes were studied throughout ripening of five batches of León cow's milk cheese, a traditional variety made in the north of Spain. Total soluble nitrogen, non‐protein nitrogen, oligopeptides nitrogen, amino nitrogen and ammonia nitrogen fractions increased slightly during the ripening process. The final values of these nitrogen fractions indicate that this cheese undergoes a very slight proteolysis as much in extent as in depth. This weak protein degradation is corroborated when the caseins and their degradation products were quantified by electrophoresis. β‐Casein stayed practically intact throughout the ripening process and only 10% of αs‐casein became degraded. The content of total free amino acids increased progressively but in a slightly increased way during ripening, reaching final average values of 592 mg (100 g)−1 of total solids. The most abundant free amino acid at the end of ripening was lysine, followed by leucine, glutamic acid, tryptophan, valine and phenylalanine. The acidity index of the fat values increased during ripening by a factor of 4.39. The final values of this parameter are in the range of those observed in other cow's milk cheeses ripened by bacteria. The content in total free fatty acids underwent an increase throughout ripening reaching final average values of 6669 ppm. The most abundant free fatty acid at the end of ripening was oleic acid followed by butyric and palmitic acids. The high content of short‐chain fatty acids is outstanding, specially that of butyric acid.

Characterization of Prato cheese, a Brazilian semi-hard cow variety: evolution of physico-chemical parameters and mineral composition during ripening

The evolution followed by the overall chemical composition, physico-chemical parameters and the main mineral and trace elements during the ripening of 18 batches of artisanal Prato cheese was studied. This cheese is characterised for its high total solids values (69.15±3.79 g/100 g), as well as low NaCl values (1.03±0.56 g/100 g) which were lower than those described for the majority of other cow's milk cheeses studied. Its lactose content disappeared after the first month of ripening, without observing any significant variations in pH values during ripening. The Ca, P, Zn and Mn contents showed a significant decrease ( p<0.05) during ripening. The contents of Fe and Cu showed variations in the different batches studied although the final values were lower than those described for other cheeses with similar characteristics.

Proteolysis and Lipolysis of Goat Milk Cheese

Numerous varieties of goat milk cheeses are produced worldwide. Maturation or ripening of goat and other species milk cheeses is governed by interplay of many different factors. Proteolysis and lipolysis are two major biochemical processes in the multifaceted phenomenon of cheese aging, which involves a variety of chemical, physical, and microbiological changes under controlled environmental conditions. Proteolysis of cheeses in general is influenced by several factors including plasmin, chymosin, protease from starter and nonstarter bacteria, pH and moisture levels of the curds, storage temperature and time, salt content, salt-to-moisture ratio, and humidity. Primary factors affecting lipolysis in cheeses are fatty acid composition, lipolytic enzymes, lipolytic microorganisms, moisture, temperature, storage time, oxygen, and surface area, etc. Several analytical techniques have been used to measure proteolysis of goat and (or) cow milk cheeses during ripening, such as solubility of peptides and amino acids in various solvents or precipitants, liberation of reactive functional groups, various forms of chromatography, and different forms of electrophoresis. Lipolysis of goat milk cheeses has been estimated by acid degree value (ADV), acid value, and free fatty acid concentration, while lipid oxidation of dairy goat products can be determined by peroxide value, thiobarbuturic acid value (TBA). Recent reports have shown that goat cheeses had greater rates of protein degradation than cow counterparts, and that aging time and temperature synergistically elevated most of proteolytic and lipolytic indices in goat cheeses. This paper will further discuss proteolytic and lipolytic characteristics of goat milk cheeses.

A survey of the prevalence of Escherichia coli O157 in raw meats, raw cow's milk and raw-milk cheeses in south-east Scotland

2429 samples of foodstuffs were examined for the presence of verocytotoxigenic Escherichia coli O157 (VTEC O157) by means of immunomagnetic separation (IMS) over a 2-year period commencing April 1997. Specimens comprised 1190 raw meats, 500 raw milks and 739 raw-milk cheeses. The meat and cheese samples were purchased from retail premises in south-east Scotland; raw milk samples were obtained directly from farms. In addition, total E. coli counts were performed on milk and cheese samples, and the pH of cheese specimens measured. The water activity ( A w) was also measured for a representative sample of each cheese type, and for all of the samples with high levels of E. coli. VTEC O157 was isolated from two samples of beef burger, both manufactured on the premises of the same butchers shop. Control studies with artificially inoculated foodstuffs demonstrated a sensitivity of detection of <5 organisms 25 g −1. These findings, which contrast with the results of similar studies elsewhere in the UK, suggest that other sources of infection may be important in explaining the high rates of infection with this organism in south-east Scotland.

Microbiological, chemical and biochemical characteristics of ‘Tetilla’ raw cows-milk cheese

The microbiological, chemical and biochemical characteristics of Tetilla raw cow's-milk cheese produced in Galicia (NW Spain) were studied. The identification of the main microbial groups of technological interest was carried out. Mean log mesophilic counts, lactic acid bacteria on M17, citrate-utilizing bacteria and enterococci in 24 cheese samples were 10·60, 10·34, 9·35 and 7·30, respectively. High mean log counts of total coliforms (6·09),Micrococcaceae (5·68) and yeasts (4·44) were also measured. On the other hand, moulds (<2·60),Staphylococcus aureus (<1·79) and Escherichia coli (<1·72) counts were low. Listeria monocytogenes was detected in two samples. None of the samples yielded Salmonella spp. Isolates of technological-interest bacteria were characterized as enterococci (39·8%), lactococci (19·0%), lactobacilli (12·3%) and leuconostocs (7·6%). Micrococci (8·0%) were also isolated.Enterococcus faecalis and Lactococcus lactis subsp. lactis were the species most frequently found. In accordance with the results of pH and chemical composition, only nine samples fulfil the specifications of the Appellation of Origin. β -casein content was higher than αs 1-casein content for all cheeses analysed and a low peptide αs 1-I/αs 1-casein ratio and nitrogen soluble fraction content were found. High volatile free fatty acid and long chain free fatty acid contents were measured, which can be attributed to the action of native lipase. A high level of diacetyl-acetoin was also determined.