STUDY ON THE CONDITIONS FOR OBTAINING THE EXTRACT FROM ROSELLE CALYX (Hibiscus sabdariffa L.) AND APPLICATION IN KOMBUCHA FERMENTATION

Abstract

Roselle (Hibiscus sabdariffa L.) calyx has an attractive dark red color, a fantastic and sour taste, and a reasonably high anthocyanin content. The objective of this study is to find out suitable conditions to obtain the extract from fresh hibiscus calyxes and apply it in kombucha fermentation. Extraction conditions were investigated with 5 ratios of fresh roselle calyxes to water (1:4 - 1:12 (g/mL), 6 levels of temperature (50 - 100 °C) and 4 levels of time (20-50 minutes). On that basis, the extract was obtained and a process of fermenting kombucha roselle was developed by determining the factors affecting the fermentation process including sugar concentration (10, 15, 20% w/v), starter concentration (5, 10, 15, 20% v/v) and fermentation time (1, 2, 3, 4, 5 days). The results showed that the material and water ratio at 1:8 (g/mL) and soaking in a water bath at 80 °C for 30 minutes were the most appropriate conditions to obtain the extract with the highest anthocyanin content. Besides, at the conditions of sugar and starter concentration of 15% w/v, fermentation of 3 days, a kombucha product was obtained with a harmonious sweet and sour taste, a special odor and color with a total acid content of 7.83 g/L and an ethanol content of 0.41% v/v.