Study of microbiological, biochemical and organoleptic properties in the probiotic soy yoghurt

Worldwide, the demand for consumption of functional foods is growing rapidly due to the increased awareness of the consumers from the impact of food on healthProduction of soy based probiotic yoghurt will improve the functional potential. The aim of this study was to assess the effect of cow’s milk to soymilk proportion and type of probiotic starins on qualitative aspects of soy based probiotic yoghurt.

proportions of cow's milk to soymilk (100:0, 75:25, 50:50, 75:25, 0:100) were prepared using reconstituted skim milk powder, and two type of mix starter culture (ABY-1 and ABY-2 that contains Lactobacillus acidophilus LA-5 and bifidobacterium Lactis Bb-12 and traditional yoghurt starter culture) were inoculated. pH, titratable acidity and redox potential parameters, amounts of lactic acid and acetic acid and viability of probiotics and sensory attributes of samples were analysed.

probiotic bacteria in starter culture ABY-1 in proportion of (50:50) had the highest viability (p<0.05). The greatest sensory properties were related to the treatments which had the highest proportion of cow's milk and then it was treatment of cultured with starter culture ABY-1 and proportion of 50% of cow's milk to 50% of soymilk (50:50-ABY-1) which was set in third grade in total acceptance manner (p<0.05).

The equal proportion of cow's milk to soymilk represented the highest biochemical changes, and with adding amount of soymilk, viability of probiotics increased probably due to the presence of prebiotics ingredients of soy and proteolitic activity decline of yoghurt starter cultures.