Sheep Milk Cheese Research Articles

Correlation Between DNA Base Composition and Routine Tests for the Identification of Micrococcaceae Isolated from Sheep's Milk Cheese

Summary Fifty-three strains of Gram-positive, catalase-positive cocci, isolated from sheep's milk cheese, were used to test the reliability of some simple classification procedures (acid production during anaerobic fermentation of glucose, Evans and Kloos' test, Schleifer and Kloos' scheme and lysostaphin sensitivity). On the basis of these tests, only 16 isolates could be identified. All of them belonged to the genus Staphylococcus . The remaining strains were finally identified according to the mol % G+C of their DNA. The Micrococcaceae studied showed poor correlation between acid production during anaerobic fermentation of glucose, Evans and Kloos' test, Schleifer and Kloos' scheme, and the G+C content characteristic of the genera Micrococcus and Staphylococcus . The lysostaphin sensitivity test was more satisfactory. However, it did not allow the identification of 14 of the isolates which showed a low sensitivity to this enzyme.

Microbiological quality and composition of two types of Spanish sheep's milk cheeses (Manchego and Burgos varieties)

SummaryThirty six samples of Manchego and 36 of Burgos cheese from retail outlets were examined. The mean log microbiological counts/g in Manchego cheese were 2·6 coliforms, 3·76 enterococci, 7·07 lactic acid bacteria, 8·02 mesophiles, 3·84 psychrotrophs 4·47 yeasts and moulds and 4·11 staphylococci, and in Burgos cheese were 7·17, 3·45, 7·25, 8·89, 8·18, 5·09 and 5·12 respectively. Coagulase-positive staphylococci were detected only in three samples of Manchego cheese, one of these isolates producing enterotoxin A. Staphylococcal thermonuclease was detected in eight samples of Manchego and 12 of Burgos cheese, the mean values of enzyme detected being 0·29 and 0·32 ng/g cheese respectively. Staphylococcal enterotoxins were not detected in any of the cheeses tested. Possible relationships between microbial counts and physicochemical characteristics were investigated by regression analysis.

Viscosity and heat capacity of whey retentates from sheep's milk cheese

SummaryDifferent concentrates from sheep's milk cheese whey, with up to 26·5% solids, were prepared in the laboratory by reverse osmosis, and their viscosities and heat capacities determined over the temperature range 5–80 °C. These products behaved like other liquid milk concentrates previously studied, so that similar analytical expressions could be used to predict these physical properties in cheese whey as a function of the temperature and solid content. A nomogram is also given for an easier computation of each property. The water in liquid dairy products and their concentrates up to 40% solid content appears to behave as pure, free water with respect to its partial contribution to the heat capacity of these products, its apparent heat capacity being 4·208±0·016 kJ. kg-1°C-1.

Classification of Citrate Fermenting Lactobacilli Isolated from Lamb Stomach, Sheep Milk and Pecorino Romano Cheese

Summary Three hundred and thirty strains of citrate-fermenting lactobacilli were isolated from lamb stomach, lamb rennet paste, sheep milk and Pecorino Romano cheese. Fifty-two representative strains belonging to four physiological groups were checked for their genetic relationship using the DNA-DNA hybridization test. Most of the hetero-fermentative strains, isolated from lamb stomach and lamb rennet paste belonged to Lactobacillus reuteri , while the others were found to be related to L. fermentum . The homofermentative citrate-fermenting lactobacilli, isolated mainly from Pecorino Romano cheese, shared high levels of genetic homology with L. plantarum . Only one strain was found to be similar to L. casei .

Sheep's milk cheeses

Sheep's milk cheeses