Effects of inulin and sugar levels on the viability of yogurt and probiotic bacteria and the physical and sensory characteristics in probiotic ice-cream

Ice-cream containing probiotic bacteria was produced by mixing fortified milk fermented with probiotic strains with ice-cream mixes with different sugar concentrations (15, 18, 21% (w/w)). Cultures were grown (37 °C, 12 h) in UHT skimmed milk supplemented with or without inulin addition (1% and 2%). The fermented milk was added to the ice-cream mix to a level of 10% w/w.Increasing sugar concentration stimulated physical and sensory properties. The addition of inulin improve viscosity, first dripping and complete melting times; however, it had no effect on the sensory properties. Viable bacteria numbers were highest at 18% sugar concentration. Streptococcus thermophilus was most stable in all the samples of probiotic ice-cream with >107 cfu g−1 throughout the storage period. The count of Lactobacillus delbrueckii ssp. bulgaricus was reduced by 1.5 log cycles. The counts of Lactobacillus acidophilus and Bifidobacterium lactis decreased to 105 cfu g−1 in the control samples, whereas the counts were 106 cfu g−1 in the samples supplemented with inulin. The results suggested that the addition of inulin stimulated the growth of L. acidophilus and B. lactis, which resulted in an improved viability of these organisms.