Viability of Lactobacillus acidophilus in yoghurt containing inulin or oligofructose during refrigerated storage

Viability of Lactobacillusacidophilus in yoghurt containing inulin or oligofructose, during refrigerated storage, was studied, which showed significantly (p < 0.05) better growth on oligofructose compared to inulin. During storage, all yoghurt samples showed a stable decrease in the counts of L. acidophilus. Throughout the storage period, the viability of L. acidophilus was lower for the control yoghurt as compared to other yoghurts. The content of L. acidophilus decreased on average by 1 log unit in the control yoghurt; in the presence of inulin or oligofructose by 0.4 and 0.3 log units, respectively. High viable numbers of L. acidophilus between 10(7) and 10(8) per g were found in yoghurt containing 2 to 5% inulin and 1 to 5% oligofructose. The effectiveness of the prebiotic ingredient depends on its concentration in the food. The optimal quantity of added prebiotic ingredient, to ensure adequate numbers of L. acidophilus in yoghurts up to the end of shelf life period, was 1%.