Freezing of Lactic Cultures

Abstract

Conditions influencing the survival of frozen single-strain and mixed-strain, multiple-type lactic cultures were studied. Rates of freezing and thawing indicated that fast freezing followed by fast thawing resulted in greatest survival. Cultures grown at 26 to 32 C had significantly greater activities after 4 wk of storage at −20 C than cultures grown at 15 or 21 C. Yeast extract, glycerol, and N-Z Amine A were superior to sucrose, dimethyl sulfoxide, egg white, and egg albumen in protecting the cells against freezing damage at −20 C. Additives, pH of cultures, and prior growth temperature had little effect upon survival of cultures stored at −196 C. Results of experiments with Cheddar cheese indicate the usefulness of freezing and storing cultures at −196 C. © 1966, American Dairy Science Association. All rights reserved.