Development of mature coconut (Cocos nucifera L.) probiotic beverage: physicochemical characteristics, microbial count, antioxidant activity, and sensory acceptance

Mature coconut (Cocos nucifera L.) water is a by-product of coconut milk and oil industries that can be transformed into value-added products as part of a sustainable and zero-waste effort. In the present work, mature coconut water was fermented using kefir grains to produce probiotic beverage, and the present work aimed to evaluate the physicochemical characteristics, microbial counts, antioxidant activities, and sensory acceptance of the developed mature coconut water kefir (MCWK) in comparison with mature coconut water (MCW) and water kefir (WK). Results showed significantly higher (p < 0.05) lactic acid and ethanol contents in MCWK relative to WK, which was attributed to the higher counts of lactic acid bacteria and yeasts. The fermentation was also apparent in MCWK, exhibiting significantly lower (p < 0.05) pH value at different fermentation days. Significantly (p < 0.05) highest total phenolic content (TPC) and antioxidant activities [DPPH radical-scavenging activity and ferric-reducing antioxidant power (FRAP)] were recorded by MCWK after three days of fermentation. Sensory acceptance test also demonstrated that fermentation of MWK with kefir grains improved the palatability and acceptance. MCWK fermented for three days resulted in significantly (p < 0.05) highest overall acceptance mean score (n = 30). In conclusion, the complex microbial consortia in kefir grains can be used to produce MCW probiotic beverage with functional properties.