Fruit peel powders as functional ingredients to improve antioxidant- properties of Kombucha-like beverages

Introduction

Kombucha is a fermented tea beverage produced by a Symbiotic Culture of Bacteria and Yeasts (SCOBY), with potential benefits for human health. In this study, we used fruit wastes to produce a kombucha-like beverage with improved antioxidant properties.

Methodology

Orange peel powder (OPP) and pomegranate peel powder (PPP) were used as supplements (1% OPP, 1% PPP, or 0.5% OPP + 0.5% PPP) for the kombucha production (traditional 7-day fermentation with SCOBY). Unsupplemented beverage (black tea) was used as control. Microbial population, antioxidant properties (DPPH, ABTS, FRAP assays), sugar metabolites production (¹H-NMR) and phenolic profile (UHPLC) were analysed.

Results

Supplementation with PPP and OPP had a positive effect on the SCOBY population. PPP significantly (p < 0.05) increased the content of phenolic compounds (e.g., gallic acid, hesperidin, epicatechin) and the antioxidant capability, while the addition of OPP increased (p < 0.05) the concentration of citric acid and flavonoids. UHPLC analysis of the samples shows the presence of ellagic acid, ellagitannins, and flavonoids in the PPP-fortified kombucha. The content of caffeine was reduced in supplemented kombucha.

Conclusions

This study demonstrated that pomegranate- or orange-peel powders affected the functional properties of Kombucha-like beverages and highlighted the potential use of fruit-processing by-products as sustainable strategy to valorise food waste and support circular economy approaches in the beverage industry.