Innovating Polyphenol‐Rich Kombucha as a Superfood Beverage: Leveraging Untapped Agricultural Byproducts as Sustainable Substrates to Enhance Antioxidant Activity and Sensory Appeal

ABSTRACT The expanding kombucha market drives demand for diverse functional products. This study explored underexplored commodity crop byproducts, including Melicope pteleifolia leaves, oil palm ( Elaeis guineensis ) leaves, mango ( Mangifera indica ) leaves, kenaf ( Hibiscus cannabinus ) leaves, coffee ( Coffea spp.) leaves, and cocoa ( Theobroma cacao ) rind as alternative sustainable fermentation substrates. The aim was to optimize fermentation conditions and comprehensively evaluate the physicochemical, nutritional, antioxidant, and sensory properties of these kombuchas. Utilizing a single factor experimental design approach, fermentation was optimized for sugar concentration, temperature, and residue presence, with analyses covering key quality attributes including pH, ethanol, total phenolic content (TPC), total flavonoid content (TFC), DPPH free radical scavenging activity, and sensory properties. Optimal conditions were 37°C, 5% (w/v) sugar, and fermentation without residues for 6–8 days. All optimized kombuchas exhibited safe pH and low ethanol profile. Coffee leaves kombucha yielded the highest TPC, while mango leaves kombucha had the highest TFC. Melicope pteleifolia kombucha showed superior antioxidant activity (DPPH IC 50 529.2 mg/mL) and achieved the best overall consumer acceptability (5.8/7). This research successfully developed novel, safe, and functional kombucha beverages. Melicope pteleifolia kombucha holds particular promise as a functional drink, offering a valuable alternative and valorizing plant resources. Future pilot‐scale studies are essential for commercialization.