Consumption of probiotics may aid lactose digestion, control
intestinal infections, and balance the intestinal mucosal barrier.
However, most such studies were conducted with viable bacterial
preparations, and the definition of a probiotic includes viability
as an important factor (1, 18). The viability of several strains
in fermented milks is dependent on both the production method
and the strain. In one study, 5 strains of L. acidophilus and Lactobacillus
GG (ATCC 53103) were tested to determine the effect
of refrigeration on the viability of the strains in cultured buttermilk
and yogurt (19). In cultured buttermilk, 3 of the strains
showed no significant loss of viability during storage, but 2 strains
had significantly decreased viability. Results were similar in
yogurt. It is possible that cultures producing organic acids,
diacetyl, or other inhibitory compounds in the fermented milk
may influence the survival of some probiotic cultures. The baceriocins
produced by different dairy cultures were reviewed by
Ouwehand and Salminen (20). L. casei GG showed no loss of
viability during storage of any of the cultured products. Thus, the
results indicate that the production method for fermented milk
needs to be carefully evaluated to offer consumers the right
amount of viable cultures to obtain the reported health effects.