Technical parameters affecting the physicochemical, phenolic, antioxidant and sensory properties of watermelon (Citrullus vulgaris L.) kefir

Abstract

Watermelon contains a rich source of valuable constituents that could be utilized as substrate for lactic and alcoholic fermentation. Fruit kefir beverages are really appreciated due to its unique acidic taste, refreshing, low carbonated, adequate alcoholic and acceptable acetic content. It’s necessary to process watermelon fruit into value-added product to resolve the unmarketable congestion at harvesting season. This research was conducted at STNanotech Laboratory in 2021 to demonstrate different technical parameters such as fermentation temperature (28-31oC), fermentation time (12-60 hrs), kefir grain ratio (3-5% w/v) to the physicochemical, phenolic, antioxidant and sensory attributes of watermelon kefir. Results showed that fermentation resulted on a significant degradation of total soluble solid, total phenolic content and DPPH free radical scavenging, a great improvement of total titratable acidity and ethanol. Meanwhile, there was no clear difference on viscosity during fermentation. Watermelon juice fermented at 30oC for 36 hrs with 4% kefir grain showed the best overall acceptance (8.86±0.01 score) with adequate ethanol content (4.28±0.02 % v/v) and total titratable acidity (2.56±0.01 g/L citric acid). Watermelon kefir with a pleasant alcoholic flavor would be one favorite beverage in daily consumption.