Viability of Lactobacillus acidophilus in fermented milk products during refrigerated storage

The viability was studied for four L. acidophilus strains (B, V-74, CH-2 and CH-5) and their mixtures in fermented milk products under refrigeration at 7°C for 35 days. L. acidophilus B exhibited no significant loss in viability after 35 days and maintained above 10 7 cfu/mL. The viability of strains V-74 and CH-2 declined but was higher than 10 5 cfu/mL of live cell numbers following 35 days. Strain CH-5 showed the poorest survival and its viable counts at the end-point of the test were around 10 4 cfu/mL. The mixtures of L. acidophilus strains had a lower loss in viability than single-strain cultures. Their viable cell counts were over 10 7 cfu/mL, which was more than the desired therapeutic-minimum dose. Regarding the viability displayed by the 4 strains, L. acidophilus strain B is suggested to be the best culture for further use. Moreover, use of a mixed-strain culture of L. acidophilus as a starter presents a good way to improve the viability of the organism during storage.