Stability During Frozen and Subsequent Refrigerated Storage of Lactobacillus acidophilus Grown at Different Ph

Abstract

Two cultures of Lactobacillus acidophilus were evaluated for stability during frozen and refrigerated storage following growth in broth maintained at five different pH: 5.0, 5.5, 6.0, 6.5, and 7.0. Generally, significantly higher populations were obtained by both cultures during growth at either pH 5 or 5.5 than at higher pH. Freezing and frozen storage for 28 d at –196°C had no significant effect on the viability of either culture grown at any of the five different pH. However, there were significant effects on the viability of the cultures during subsequent storage at 5°C in milk. Cells of both strains grown at pH 5 did not exhibit any significant decrease in viability and population during 21 d storage at 5°C. Cells of both strains grown at all higher pH exhibited significant declines in viability during these same storage periods at 5°C.