Microbiological and biochemical characteristics of Canestrato Pugliese cheese made from raw milk, pasteurized milk or by heating the curd in hot whey

Canestrato Pugliese cheeses were produced from raw ewes' milk (R and R-II c heeses), pasteurized ewes' milk (P cheese) and by heating the curd in hot w hey according to a traditional protocol (T cheese). R-II differed from R ch eese mainly by having been produced from raw milk with a higher number of s omatic cells, 950.000 vs. 750.000 ml(-1), respectively. Compared to P and T cheeses, R and R-II cheeses had a higher concentration tone or two orders of magnitude) of cheese-related bacteria such as adventitious mesophilic la ctobacilli, enterococci and staphylococci. At the end of ripening, all chee ses contained less than 1.0 log cfu g(-1) of total and fecal coliforms, and Escherichia coli and Staphylococcus aureus were not detected. As shown by phenotypic identification and RAPD-PCR, R cheese contained the largest numb er of mesophilic lactobacilli species and the greatest diversity of strains within the Lactobacillus plantarum species. Primary proteolysis did not di ffer appreciably among the cheeses. On the contrary, both urea-PAGE and the RP-HPLC analyses of the water-soluble N fractions showed the more complex profiles in cheeses produced by raw milks. R and R-II cheeses had the highe st values of water-soluble N/total N (ca. 30%) and the highest concentratio n of total free amino acids (ca. 40 mg g-l) which approached or exceeded th ose reported for Italian cheeses with very high level of proteolysis during ripening. The main differences between R-R-II and P-T cheeses were the con centrations of aspartic acid, proline, alanine, isoleucine, histidine and l ysine. The water-soluble extracts of R and R-II cheeses contained levels of amino-, imino- and di-peptidase activities, which were about twice those f ound in P and T cheeses. Cheeses differed slightly in the concentration of total free fatty acids that ranged between 1673 and 1651 mg kg(-1) in R and R-II cheeses, and 1397 and 1334 mg kg(-1) in P and T cheeses. Butyric, cap roic, capric, palmitic, oleic and linoleic acids were found at the highest concentrations. (C) 2001 Elsevier Science B.V. All rights reserved.