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

Probiotic fermented ice-cream was produced from milk containing different sugar concentrations (15, 18 and 21%) with or without inulin addition (11 and 2 %). After heat treatment mixes were inoculated probiotic yogurt culture and incubated at 37 degrees C until pH 5.5 was attained. Bacterial counts were determined immediately after fermentation of mix, after ripening of mix, after freezing and at days 7, 30, 60 and 90 of storage at -18 degrees C. Physical, chemical and sensory analyses were carried out 1 week after production. Increasing sugar concentration stimulated physical and sensorial properties. The addition of inulin improved viscosity, first dripping and complete melting times, however, had no effect on the sensory properties. In spite of decreasing by 1.5-3.0 log unit in viable numbers in ice-cream at the end of the storage, they were found to be above the threshold for therapeutic minimum (10(6)-10(7) cfu g(-1)). Increasing sugar concentration at first stimulated viable bacteria numbers and then caused reduction of them. Initial counts of the bacteria and their subsequent survival were better in the products supplemented with inulin. The results suggested that the addition of inulin stimulates the growth of L. acidophilus and B. lactis which results in improved viability of these organisms.