Inhibition of growth of butter cultures in naturally ripened cream after neutralization

Abstract

Growth of Streptococcus diacetilactis cultures was slower and diacetyl production lower in bulk factory cream after neutralization than in low-acid cream.
Growth and diacetyl production in some individual samples of ripened cream after neutralization was similar to that in low-acid cream, but in other samples growth was inhibited. Approximately 50 per cent. of the samples of high-acid cream as received at the butter factory were inhibitory to the growth of the starter culture.
This inhibition was found to be due to the presence of inhibitory streptococci, which were strains of S. lactis. Such inhibitory organisms were also found in fairly large numbers in creams which were not inhibitory.
When acid production took place normally in a ripened cream, the rate and amount of diacetyl production were the same as in a low-acid cream.