Effects of Roselle (Hibiscus Sabdariffa L.) and Sugar Source Variation on Physicochemical and Antioxidant Properties of Kombucha during Fermentation

Koh, Lai Jing (2020) Effects of Roselle (Hibiscus Sabdariffa L.) and Sugar Source Variation on Physicochemical and Antioxidant Properties of Kombucha during Fermentation. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Kombucha beverage is a fermented beverage traditionally prepared from black tea and white sugar with the addition of previous brew and starter culture, Scoby. It is commonly known that kombucha has strong antioxidant activity besides provides various health benefits include antimicrobial, antioxidant, anti-carcinogenic and anti-hyperlipidemic characteristics. In this study, roselle was used as an alternative to black tea in traditional kombucha while sugar sources used in the fermentation of kombucha were white sugar and coconut palm sugar. Effects of different substrates and sugar sources on physicochemical and antioxidant activity of kombucha were studied while their changes along the fermentation period of 12 days were compared. In this study, the physicochemical analysis showed that fermentation resulted in the decline of pH along with the increase in titratable acidity, reached final pH between 2.83 ± 0.02 and 2.91 ± 0.00 and final titratable acidity of 0.98 ± 0.02 % acidity and 1.22 ± 0.06 % acidity. Roselle kombucha demonstrated lower pH and titratable acidity as compared to black tea kombucha after the fermentation process while the effects of sugar sources were not consistent. An overall decline in Brix values was observed in all kombucha samples analyzed, with a larger difference identified in kombucha prepared from white sugar. Other than that, colour analysis on kombucha samples demonstrated a larger colour change in black tea kombucha compared to roselle kombucha. Fluctuation in changes of phenolic compounds and flavonoid content were observed along the fermentation process while roselle kombucha illustrated decreasing total anthocyanin content. Antioxidant activity of kombucha samples was evaluated based on FRAP and DPPH assay with results demonstrated inconsistent changes throughout the fermentation process. Effects of substrates and sugar sources used in kombucha fermentation demonstrated a significant influence on its physicochemical and antioxidant activity. In overall, kombucha prepared from black tea served to provide higher antioxidant activity while the effects of sugar sources varied.