Influence of lyophilization on the microbiological stability of yogurt

The objective of this study was to evaluate the survival of lactic acid bacteria in yogurt before, during and after the lyophilization process with different freezing temperatures and different concentrations of sucrose. The traditional preparation of yogurt and lyophilized with sucrose concentration was 0 % and 5.0 % and if use temperatures of 5, - 25 and - 80 degrees C. The analysis of lactic acid bacteria and the calculation was performed using the dissolution technique plate, culture medium using M17 Agar Base and Lactobacillus MRS Agar, besides pH 5 with acetic acid for determination of Streptococcus thermophilus and Lactobacillus bulgaricus, respectively. The microbiological results showed that the number of UFC/g was larger than that required by legislation during and after the processing step at the two temperatures. There was not effect of sucrose concentration on the protection or maintenance of yogurt microflora. The yogurt lyophilized and rehydrated elaborated in the present study, in addition to complying with the legislation, is also an option for market due to conservation for a longer period. Microorganisms remained viable and the amount exceeding 10(7) UFC/g before, during and after lyophilization and rehydration process.