Natural Exopolysaccharides Enhance Survival of Lactic Acid Bacteria in Frozen Dairy Desserts

¹ Department of Food Science, University of Missouri, Columbia 65211

Viable lactic acid-producing bacteria in frozen dairy desserts can be a source of ß-galactosidase for persons who absorb lactose insufficiently. However, freezing kills many of the cells, causing loss of enzymatic activity. Cultures selected for high ß-galactosidase activities and high survival rates in the presence of bile were examined for survivability during freezing in reduced-fat ice cream. Encapsulated S. thermophilus strains survived better than their nonencapsulated mutants in reduced-fat ice cream after freezing and frozen storage at –29°C for 16 d (28 vs. 19%). However, a small nonencapsulated strain of Lactobacillus delbrueckii sp. bulgaricus survived better than the large encapsulated strain in reduced-fat ice cream. Factors that improved survival of encapsulated S. thermophilus 1068 in ice cream were 1) harvest of cells in the late-log phase of growth at 37°C rather than at 40, 42.5, or 45°C; 2) overrun at 50% rather than 100%; and 3) storage at –17°C rather than –23 or –29°C. Survival of strain ST1068 was unaffected by 1) neutralization of acid during growth or 2) substitution of nitrogen for air in building overrun.

Key Words: capsule • freezing • survival • ßbeta;-galactosidase

Submitted on July 7, 2000
Accepted on January 25, 2001

This article has been cited by other articles:

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