Coffee Husk By-Product as Novel Ingredients for Cascara Kombucha Production

Abstract

Kombucha, a fermented beverage, is gaining popularity due to its numerous beneficial health effects. Various substrates such as herbs, fruits, flowers, and vegetables, have been used for kombucha fermentation in order to enhance the flavor, aroma, and nutritional composition. This study aims to investigate the potential suitability of cascara as a novel ingredient for kombucha production. Our findings suggested that cascara is a suitable substrate for kombucha production. Fermentation elevated the total phenolic and flavonoid content in cascara, which enhanced the antioxidant, antibacterial, and prebiotic characteristics of the product. Furthermore, the accumulation of acetic acid-induced the pH lowering reached 2.7 after 14 days of fermentation, which achieved the microbiological safety of the product. Moreover, 14 days of fermentation resulted in a balanced amalgamation of acidity, sweetness, and fragrance according to sensory evaluation. Our findings not only highlight the potential of cascara kombucha as a novel substrate for kombucha production but also contribute to repurposing coffee by-products, promoting environmentally friendly and sustainable agricultural development.

Keywords: Cascara; antibacterial; antioxidant; fermentation; kombucha; sustainable development.

Fig. 1. Effects of sucrose concentration on the growth of nascent pellicles SCOBYs (A) pH values (B) and acetic acid content (C) in cascara kombucha at different time intervals.

Data are presented as the means of triplicate analysis ± standard deviation. Lowercase letters (a-c) indicate statistically significant differences between groups sharing the same sugar concentration (corresponding to columns of the same color) according to fermentation time interval (p < 0.05). The superscript letters (A-C) indicate significant differences between groups with sucrose concentrations of 0, 50, 100, and 200 g/l, respectively, at each fermentation time point (p < 0.05).

Fig. 2. The total polyphenols content (TPC) / flavonoids content (TFC) in cascara kombucha fermented at sucrose concentration of 100 g/l at different time intervals.

Data are presented as the means of triplicate analysis ± standard deviation. Lowercase letters (a-c) indicate significant differences between groups over time (p < 0.05).

Fig. 3. Antioxidant activities of kombucha are expressed by DPPH free radical scavenging

(A) and ABTS free radical scavenging (B). Data are presented as the means of triplicate analysis ± standard deviation. Lowercase letters (a-c) indicate significant differences in antioxidant activities for each kind of kombucha (corresponding to columns of the same color) according to fermentation time interval (p < 0.05). Superscript letters (A-C) indicate significant differences in antioxidant activities between kombucha derived from cascara, black tea, and oolong tea, respectively, at each fermentation time point (p < 0.05).

Fig. 4. Prebiotic potential of cascara kombucha on promoting the growth of probiotics.

Data are presented as the means of triplicate analysis ± standard deviation. Lowercase letters (a-c) indicate significant differences in the growth of each probiotic strain among MRS, free-glucose MRS, and free-glucose MRS with cascara kombucha (p < 0.05).

Fig. 5

Sensory evaluation of cascara kombucha batches after 7, 14, and 21 days of fermentation.