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

Abstract

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.