[Trials of cheese-making using concentrated bacterial starters]

Studies about cheese preparation with frozen and concentrated bacterial starters have been carried out. The Pategras cheeses were obtained from raw milk. The starters were prepared with a selected strain of Streptococcus lactis, concentrated until reaching a value of 3.10(9) colony forming units/ml and resuspended in milk previously supplemented with 8% of yeast extract. These concentrates were frozen at -40 degrees C and kept at -20 degrees C for 60 days. Three kinds of starters were tested: one thawed by placing the flask in a 40 degrees C water bath, another added to the cheese vat without previous thawing and a control sample prepared in steamed reconstituted milk. In order to evaluate the convenience of each technique several chemical and microbiological analysis were performed during the preparation (Table 1 and 2) and the ripening of the cheese (Table 3). The results have showed that the direct use of thawed frozen concentrates in the cheese vat allows the obtaining of high quality cheese. On the other hand, the technique based on thawing through a water bath did not lead to good results.