Phage-Insensitive, Multiple-Strain Starter Approach to Cheddar Cheese Making

Abstract

Bacteriophage-insensitive Streptococcus cremoris starter strains were selected by plaquing cheese whey against a bank of potential starter strains. From those found phage insensitive, six strains were selected and characterized for use in cheese making. This six-strain mixture was used exclusively. As phage appeared, the infected strain was removed from the mixture, and cheese making continued with five strains. A phage-insensitive, fast-acid mutant of the infected strain was isolated and characterized. This mutant, possessing the same parent-strain qualities, was returned to the strain mixture. Make times (3.5 to 4.0 h), milling acidities (.47%), and cheese pH (5.1) were essentially identical for each vat of cheese produced. Plant A has used the six-strain mixture for over 23 mo to produce more than 9,400 consecutive vats of cheese. Plant B has used the culture blend for 500 days to produce 10,000 consecutive vats. Since adopting this culture system, no plants have experienced starter failure from phage attack. Total cheese production for four cheese plants using the multiple blend exclusively was over 69 million lb (31.4 million kg). These data emphasize the technological and economic advantages of this culture methodology.