Citrate utilization in milk byLeuconostoc cremorisandStreptococcus diacetilactis

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Abstract
Summary: Citrate utilization and diacetyl, acetoin and acetaldehyde production by 2 strains each ofLeuconostoc cremorisandStreptococcus diacetilactisin milk were studied. With the leuconostoc bacteria no growth and little citrate utilization occurred unless a stimulant (yeast extract) was present, when complete utilization of citrate without concomitant production of diacetyl or acetoin was obtained. The addition of Mn2+stimulated growth and citrate utilization in the presence of yeast extract. Addition of citric acid after 65-h growth resulted in diacetyl and acetoin production. Destruction of diacetyl and acetoin occurred when the citric acid level fell toc. 1000 and 600 μg/g in the case ofLeuc. cremorisFR8-1 and CAF1, respectively. Only strain FR8-1 produced acetaldehyde. In contrast,Str. diacetilactisproduced diacetyl, acetoin and acetaldehyde concomitant with citrate utilization.