Optimization of fermentation conditions and evaluation of qualitative characteristics of almond-soy milk beverage fermented with kefir starter

Almond and soy milk, due to unsaturated fatty acids phytosterols and antioxidant Compounds are important among functional Drinks. Fermentation of these products using probiotic microorganisms of kefir grains increases the functional properties. Therefore, in this study, we investigated the physicochemical properties (acidity, antioxidant and viscosity), microbial (number of bacteria of lactic acid and yeast) and sensory of fermented almond / soybean milk using kefir starter. For this purpose, different conditions of fermentation processes including different concentrations of sugar (1-5%), and inoculum (0/04-0/1%), and fermentation temperature (20-30 °C) were investigated using response surface methodology (RSM) in Central Composite Design (CCD). The results showed by increasing the sugar concentration and inoculum, the acidity and antioxidant activity of the samples were increased. Effect of sugar concentration, inoculation and fermentation time had a significant effect on the number of lactic bacteria and yeasts (p<0.01). Sensory evaluation results of the samples showed that with increasing the percentage of inoculum, overall acceptance of samples were increased. Based on the results of the optimization of the conditions of the beverage production process, it can be stated that for the production of beverages with appropriate physico-chemical and organoleptic properties was 3.51% sugar concentration, 0.1% inoculation and 23.50 °C. fermentation temperature. In this condition, maximum antioxidation powerful, number of probiotics (acid lactic bacteria and yeasts), apparent viscosity was 47.19%, 48×106 cfu/ml and 28×106 cfu/ml, 165.17CP respectively with a maximum score for sensory assessments.