title: Evaluation of lactic acid Streptococci for the preparation of frozen concentrated starter cultures.
abstract: Eight strains of Streptococcus diacetilactis and Streptococcus lactis were examined for viability, growth rate, lactic acid and diacetyl production in milk and proteolytic activity before and after freezing at --30 degrees C. Concentrations of yeast autolysate, peptone, lactose and citrate as well as the usefulness of milk and whey culture media for active biomass production were investigated. After freezing and storage at --30 degrees C, with the use of non-fat milk as a cryoprotective agent, high survival and endocellular proteolytic activity of the frozen concentrate was achieved. S. diacetilactis sp. and S. lactis 115 were shown to be more biologically active than other strains. Their physiological properties remained unaffected by freezing.
mesh_terms: D000818:Animals; D002364:Caseins / Q000378:metabolism; D002951:Citrates / Q000494:pharmacology; D003451:Cryoprotective Agents; D003470:Culture Media; D046508:Culture Techniques / Q000379:methods; D003931:Diacetyl / Q000096:biosynthesis; D005615:Freezing; D007773:Lactates / Q000096:biosynthesis; D013294:Lactococcus lactis / Q000502:physiology*; D007785:Lactose / Q000494:pharmacology; D008892:Milk; D010461:Peptones / Q000494:pharmacology
chemical_list: D002364:Caseins; D002951:Citrates; D003451:Cryoprotective Agents; D003470:Culture Media; D007773:Lactates; D010461:Peptones; D007785:Lactose; D003931:Diacetyl