The effect of soursop as fermentable substrate in formulating flavoured water kefir beverage

Water kefir is a fermented sucrose solution from fruits or vegetable juices that produces acidic fermented beverages. This study aimed to explore the usage of soursop pulp as a fermentable substrate to formulate a non-dairy fermented beverage. In this study, fruit juice from soursop was fermented with water kefir grains for 48 hrs at 24°C. The first fermentation of sugary water with water kefir grains was carried out for four days and the second fermentation of the fermented water with soursop juice was carried out for two days at room temperature. The beverage formulations based on soursop concentrations were 25, 50, 75 and 100% (v/v). Results showed that the physicochemical analyses were in the range of (pH = 3.22 to 3.34, total soluble solid (TSS) = 4.59 to 10.42°Bx, and colour with lightness (L*) of 31.17 to 56.29, red and green intensity (a*) of -0.98 to -2.76 and yellow and blue intensity (b*) of -3.06 to 2.75). The alcohol content ranged from 0.43 to 0.62%. The total phenolic content decreased significantly (p<0.05) over time for each sample. Due to the process, it had heavily influenced the panellists during the sensory tests, in which favoured sample with 50% v/v soursop in the water kefir beverage. In conclusion, the utilization of soursop juice in the production of water kefir beverages can be introduced as a newly flavoured fermented drink using water kefir grains.