Harnessing arabica and canephora coffee cascara as substrates for kombucha: Comparative study of chemical, antioxidant, antibacterial and antifungal properties

This study aimed to investigate kombuchas produced from Coffea arabica L. (KA) and Coffea canephora Pierre (KC) cascara, combined with black tea (Camellia sinensis), fermented over a 12-day period. The evaluation focused on their chemical properties, antioxidant potential, and antimicrobial activity. A decrease in pH and an increase in acidity were observed along the fermentation period. There was an increase in total phenolic content by 27.4 % in KA and 22.7 % in KC, however antioxidant activity, as determined by DPPH and FRAP assays, remained unchanged. The 5-caffeoylquinic acid (5-CQA) was the predominant phenolic acid identified, exhibiting higher concentrations in the fermented beverages compared to their respective non-fermented infusions, highlighting the impact of fermentation on its concentration. Additional phenolic acids identified included gallic, caffeic, p-coumaric, 3,4-dihydroxybenzoic, sinapic, and ferulic acids. KC exhibited higher levels of total phenolic content, 5-CQA, catechin, and caffeine compared to KA, as well as stronger antioxidant activity. Both beverages demonstrated antibacterial activity against tested strains from the 6th day of fermentation. KA exhibited bactericidal activity against Salmonella Enteritidis and fungicidal activity against Candida albicans and Candida parapsilosis on the 12th day, whereas KC showed no bactericidal or antifungal effects. As far as we know, this is the first study to report the antimicrobial properties of kombucha produced from coffee cascara. These findings suggest that arabica and canephora coffee cascara infusions are viable alternative substrates for kombucha production. The use in the development of fermented beverages with functional properties is a promising way of using by-products from coffee processing.