Impact of Blending Ratios on Fermentation Kinetics and Bioactive Enrichment in Lychee–Pineapple Co-Fermented Functional Cider

This study investigated the development of functional ciders through lychee–pineapple co-fermentation as a strategy for juice matrix optimization. Five formulations were evaluated, ranging from 100% pineapple juice to 100% lychee juice, using Saccharomyces cerevisiae EC-1118. Fermentation kinetics were monitored by cumulative CO2 mass loss, while total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacities (DPPH and ABTS), sensory attributes, and multivariate analyses were evaluated. Lychee incorporation significantly enriched the functional profile, increasing TPC, TFC, DPPH, and ABTS by up to 49%, 117%, 69%, and 82%, respectively, compared to 100% pineapple juice. Although the lychee-rich matrix extended the fermentation lag phase, this effect was mitigated through co-fermentation. Fermentation further enhanced bioactive properties, with final ciders showing increases of up to 14% (TPC), 17% (TFC), 38% (DPPH), and 16% (ABTS) relative to their corresponding juices. Multivariate profiling differentiated lychee-dominant ciders by high bioactive density and floral notes, whereas pineapple-dominant ciders exhibited higher acidity and clarity. In conclusion, lychee–pineapple co-fermentation effectively optimizes fermentation performance, bioactive enrichment, and sensory quality without exogenous acidification.