Microbiological and Biochemical Properties of Canestrato Pugliese Hard Cheese Supplemented with Bifidobacteria

Canestrato Pugliese cheeses from ewe milk were produced according to a traditional protocol and by adding 7.0 log10cfu of fresh cells per gram of Bifidobacterium bifidumBb02, Bifidobacterium longumBb46, or both species. The traditional technology was modified slightly to favor the survival of probiotic microorganisms. After 56 d of ripening, the survival of B. bifidumBb02 and B. longumBb46 was 6.0 and 5.0 log10cfu/g, respectively. After 19 d cheeses contained ca. 7.0 log10cfu/g of bifidobacteria. Compared to traditional cheese, the addition of bifidobacteria seemed to support the growth and survival of mesophilic lactobacilli and Streptococcus thermophilus, used as starter, during ripening. No significant differences were observed in the main chemical composition, and only a slightly higher concentration of acetic acid was found in cheeses with bifidobacteria added. On the contrary, α- and &szligbeta;-galactosidase activities were markedly more pronounced in the presence of bifidobacteria, especially with B. bifidumBb02. In contrast with traditional cheese, the lactose was completely hydrolyzed in cheeses made with bifidobacteria. Urea-PAGE electrophoresis of the pH 4.6-soluble and pH 4.6-insoluble N fractions did not show appreciable variations. Only the reversed-phase-HPLC analysis of the pH 4.6-soluble N showed a slightly more complex profile in the presence of bifido-bacteria. This finding was in agreement with the higher value of the pH 4.6-soluble N/total N ratio and with the more pronounced amino-, imino-, and dipeptidase activities found in all the cheeses with the bifidobacteria added, especially B. bifidumBb02. No differences were found in the free amino acid and free fatty acid contents. The amino acids glutamic acid, valine, proline, leucine, and lysine and the fatty acids butyric, caproic, capric, and oleic acids were found at the highest concentrations. The sensory evaluation did not show significant differences, and Canestrato Pugliese cheeses were characterized by small and uniformly distributed eyes, were pale yellow, had an elastic consistency and a Pecorino-like smell, were very salty, andtended to be moderately piquant.