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 degrees 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 > 10(7) cfu g(-1) throughout the storage period. The count of Lactobacillus delbrueckii ssp. bulgaricus was reduced by 1.5log cycles. The counts of Lactobacillus acidophilus and Bifidobacterium lactis decreased to 10(5) cfu g(-1) in the control samples, whereas the counts were 10(6) cfu g(-1) in the samples supplemented with inulin. The results suggested that the addition of inulin stimulated the growth of L. acidophilus and R lactis, which resulted in an improved viability of these organisms. (c) 2006 Elsevier Ltd. All rights reserved.