Defined Single Strains of Lactic Streptococci in Bulk Culture for Cheddar and Monterey Cheese Manufacture

Acid production and Cheddar cheese quality were improved at three cheese plants when undefined commercial blends of'-lactic cultures were removed and replaced with phage insensitive, single strains propagated either in pairs or in one multiple blend of five or six strains. The paired strain program worked in one plant for over 12 mo with only six strains used during the last 7 mo. Two mutants replaced parent strains. The multiple blend worked for 6 mo in two plants with only one mutant replacing a parent strain. Careful phage-activity monitoring and strain selection were necessary to assure optimal success of the programs. A refrigerated reserve culture was used to provide back-up for the primary blend in the plant using the paired strain program. Make time and final cheese pH were more uniform than when undefined culture blends were used.