Effect of Paraprobiotic Strain K-1 on the Chemical, Physicochemical and Antioxidant Properties of Kombucha Produced from Different Type of Tea Leaves and Sugars

Lau, Yee Lin (2024) Effect of Paraprobiotic Strain K-1 on the Chemical, Physicochemical and Antioxidant Properties of Kombucha Produced from Different Type of Tea Leaves and Sugars. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Kombucha is an ancestral beverage that is made by the fermentation of sweetened tea, involving symbiosis of acetic acid bacteria and yeast species. Paraprobiotic is defined as a non-viable microorganism that confers health benefits to consumers. The objective of this study is to determine the effects of tea leaves type, sugar type and the addition of paraprobiotic on the physicochemical, chemical and antioxidant activity of kombucha. The tea leaves used for kombucha fermentation were black tea and green tea, whereas the sugars used were table sugar, molasses, and coconut palm sugar (Gula Melaka). The substrate (black tea and green tea) contains 5% (w/v) of sugar, and 1% (v/v) of starter tea was fermented using SCOBY at room temperature in the dark for seven days, then proceeding to second stage fermentation for another seven days. To investigate the effect of paraprobiotic on kombucha fermentation, about 0.2% (w/v) of paraprobiotic K-1 was added to the seven-day fermented kombucha and proceeded to second fermentation under the same condition. The physicochemical (pH, titratable acidity, total soluble solid content), chemical (total sugar content, total phenolic content (TPC), total flavonoid content (TFC)), and antioxidant activity (ABTS, DPPH, FRAP) of all kombuchas were compared. The results demonstrated a significant increase (p<0.05) in TPC after fermentation, with the tea containing molasses contained the highest TPC. However, fermentation did not cause significant changes in ABTS and DPPH of both teas. Besides, the kombucha added with paraprobiotic shown no significant change in pH, titratable acidity and total soluble solid content, but there was significant decrease in TPC, except green tea kombucha with Gula Melaka. The addition of paraprobiotic K1 significantly increased DPPH of black tea kombucha with Gula Melaka, but significantly reduced ABTS of black tea kombucha with table sugar and green tea kombucha with molasses, and FRAP of black tea kombucha with molasses and Gula Melaka and green tea kombucha with Gula Melaka. This finding reveals that tea type, sugar type and the presence of paraprobiotic K1 exert significant effects on the antioxidant activity of the kombucha end product. Furthermore, the result of the 9-point hedonic test showed that the sweetness, sourness, color and overall acceptability of the green tea kombucha with table sugar (GTTS) had no significant difference with the commercial kombucha. However, the commercial kombucha ranked the first in terms of its sweetness, sourness and fizziness compared to the experiment samples. Although GTTS did not exhibit the highest antioxidant activity, it received the highest preference among the samples. Further study is needed to boost the antioxidant activity of green tea kombucha. In view of paraprobiotic K1 did not synergistically enhance the antioxidant activity of kombucha, it will be omitted from the investigation of future study.