Frozen Starters from Internal-pH-Control-Grown Cultures

Abstract

Frozen starters were prepared by growing and freezing unconcentrated individual Streptococcus cremoris strains in an internal-pH-control medium (PHASE 4). Frozen cultures were stored for 3 mo, with and without a cryoprotectant, and assayed monthly for cell viability and activity. Individual strains showed variations in their ability to survive storage at −20°C. Addition of glycerol helped preserve cell viability and activity at −20°C. Storage at −40 and −80°C in PHASE 4 preserved activity and viability without need of cryoprotectants. Unfrozen PHASE 4 cultures retained original activity and viability after 1 mo refrigerated storage. Frozen PHASE 4-grown starters have been used successfully in Cheddar and cottage cheese making for over 1 yr. © 1984, American Dairy Science Association. All rights reserved.