Microbiological and biochemical properties of Canestrato Pugliese hard cheese supplemented with bifidobacteria

Canestrato Pugliese cheeses from ewe milk were produced according to a trad itional protocol and by adding 7.0 log(10) cfu of fresh cells per gram of B ifidobacterium bifidum Bb02, Bifidobacterium longum Bb46, or both species; The traditional technology was modified slightly to favor the survival of p robiotic microorganisms. After 56 d of ripening, the survival of B. bifidum Bb02 and B. longum Bb46 was 6.0 and 5.0 log(10) cfu/g, respectively After 19 d cheeses contained ca. 7.0 log(10) cfu/g of bifidobacteria. Compared to traditional cheese, the addition of bifidobacteria seemed to support the g rowth and survival of mesophilic lactobacilli and Streptococcus thermophilu s, used as starter, during ripening. No significant differences were observ ed in the main chemical composition, and only a slightly higher concentrati on of acetic aci d was found in cheeses with bifidobacteria added. On the c ontrary, alpha- and beta -galactosidase activities were markedly more prono unced in the presence of bifidobacteria, especially with B. bifidum Bb02. I n contrast with traditional cheese, the lactose was completely hydrolyzed i n cheeses made with bifidobacteria. Urea-PACE electrophoresis of the pH 4.6 -soluble and pH 4.6-insoluble N fractions did not show appreciable variatio ns. Only the reversed-phase-HPLC analysis:of the pH 4.6-soluble N showed a slightly more complex profile in the presence of bifidobacteria. This findi ng was in agreement with the higher value of the pH 4.6-soluble N/total N r atio and with the more pronounced amino-, imino-, and dipeptidase activitie s found in all the cheeses with the bifidobacteria added, especially B. bif idum Bb02. 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 si gnificant differences, and Canestrato Pugliese cheeses were characterized b y small and uniformly distributed eyes, were pale yellow, had an elastic co nsistency and a Pecorino-like smell, were very salty, and tended to be mode rately piquant.