Natural exopolysaccharides enhance survival of lactic acid bacteria in frozen dairy desserts.
Viable lactic acid-producing bacteria in frozen dairy desserts can be a source of beta-galactosidase for persons who absorb lactose insufficiently. However, freezing kills many of the cells, causing loss of enzymatic activity. Cultures selected for high beta-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 degrees 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 degrees C rather than at 40, 42.5, or 45 degrees C; 2) overrun at 50% rather than 100%; and 3) storage at -17 degrees C rather than -23 or -29 degrees C. Survival of strain ST1068 was unaffected by 1) neutralization of acid during growth or 2) substitution of nitrogen for air in building overrun.
Hong
S H
SH
Department of Food Science, University of Missouri, Columbia 65211, USA.
Marshall
R T
RT
D000818:Animals; D002214:Capsules; D015169:Colony Count, Microbial; D003611:Dairy Products / Q000382:microbiology; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D005615:Freezing; D007054:Ice Cream / Q000382:microbiology*; D007778:Lactobacillus / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism*
D002214:Capsules; D011135:Polysaccharides, Bacterial; C085953:exopolysaccharide, Bacillus; D001616:beta-Galactosidase