engleski

Resistance of sourdough starter cultures to freezing

The aim of this study was to examine tolerance of lactic acid bacteria and yeast strains usually included in sourdough fermentation to blast and vacuum freezing. Freezing was conducted in water suspensions of microorganisms and rye flour (10% m/m), with or without addition of trehalose (1% m/m) as a cryoprotectant, and CFU was determined before and after freezing. This study included strains L. fermentum, L. parabrevis, L. plantarum, L. reuteri, L. sanfranciscensis, W. cibaria, S. cerevisiae, and commercial starter cultures Saff Levain LV1 (L. brevis, L. casei, S. cerevisiae) and LV4 (L. brevis, S. chevalieri). Results showed that influence of applied freezing methods and trehalose addition on microorganism survival was strain specific. Single strain cultures showed to be more resistant to freezing than commercial starter cultures. LV4 S. chevalieri was the most sensitive with 5-log CFU reduction after vacuum freezing without trehalose addition. With trehalose addition there was no CFU reduction of LV4 S. chevalieri yeast and that was the only case of significant positive effect of trehalose. According to the results, L. reuteri and W. cibaria appeared as the most suitable for freezing with at least 50% survival and the lowest variability of survival depending on freezing conditions. These results of microbial survival need confirmation in sourdough freezing environment.

lactic acid bacteria ; yeast Saccharomyces cerevisiae ; vacuum freezing ; sourdough starter cultures ; trehalose

Rad je financiran od strane Hrvatske zaklade za znanost u sklopu projekta "Primjena vakuumskog hlađenja u proizvodnji hrane produljene trajnosti i svježine" (09.01/279).