Concentrated cultures of Leuconostoc citrovorum.

Two single-strain cultures of Leuconostoc citrovorum were grown in a broth medium with automatic pH control. Culture concentrates were prepared by centrifugally harvesting the cells and resuspending them in 1/50th the original volume in 10% nonfat milk solids. The concentrates were stored in liquid nitrogen until analyzed. The maximum population attainable was approximately equal when cultures were grown at pH 6.0, 6.5, or 7.0 with sodium hydroxide or ammonium hydroxide as the neutralizer. Citrate was required in the growth medium for the cultures to be able to produce diacetyl subsequently in milk. At pH 6.0, the cells reached maximum population and ability to produce diacetyl. Organoleptic analysis by an experienced flavor panel showed a preference for cottage cheese creamed with a creaming mixture prepared with a culture concentrate rather than a normal culture. The culture concentrates maintained their viability and ability to produce diacetyl for at least 30 days when stored in liquid nitrogen.