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Appl Environ Microbiol. 1969 June; 17(6): 805-810
Copyright © 1969 American Society for Microbiology. All Rights Reserved.

Preparation of Concentrated Lactic Streptococcus Starters¹

^a Department of Food Science, North Carolina State University, Raleigh, North Carolina 27607

ABSTRACT

Single-strain cultures of Streptococcus cremoris were grown in a semisynthetic medium with automatic pH control. After centrifugation, the cells were resuspended in sterile nonfat milk (2% of the original volume). There was no significant difference in the maximum population attained when cultures were grown at pH values of 5.5, 6.0, or 6.5 with sodium hydroxide as the neutralizer. With ammonium hydroxide as the neutralizer, maximum populations obtained were increased about twofold. In most cases, the acid-producing ability of the culture concentrates was comparable to that of fresh-milk cultures. There was some variation among strains of S. cremoris with respect to the effects of different neutralizers and levels of pH control on the biological activity of the culture concentrates. The culture concentrates were stored in liquid nitrogen for as long as 231 days without significant loss in biological activity.

¹ Paper number 2850 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, N.C.