Antioxidant activity optimisation of young Robusta coffee leaf kombucha by modifying fermentation time and withering pre-treatment

Kombucha is a fermented drink made from liquid tea. The fermentation is involving bacteria and yeast called Symbiotic Culture of Bacteria and Yeast (SCOBY) The current study aims to investigate the possibility of young Robusta coffee leaf tea as a raw material for kombucha, by optimizing its antioxidant activity and applying withering pre-treatment. The Response Surface Methodology (RSM) was applied to design the observation up to 21 days. Within the duration of fermentation, the optimum IC₅₀ was observed on the third days of fermentation. The results showed that withering treatment significantly affect the pH values, total sugar, total phenolic content, and IC₅₀ of young coffee leaf kombucha. The sensory quality also shows that 5 out of 19 attributes, including brown color, sour taste, bitter taste, alcoholic aroma, sour aroma were also affected by the treatment (p-value<0.05). Regardless the chemical and sensory qualities, the kombucha was still significantly accepted (p-value<0.05) by the respondents.