Co-fermentation of Xuxiang kiwifruit juice by Lacticaseibacillus paracasei with other lactic acid bacteria: impacts on quality properties, nutrients, volatiles, and in vitro antioxidant activities

This study addressed kiwifruit's postharvest perishability and nutrient loss during juicing by co-fermenting <i>Xuxiang</i> kiwifruit juice with <i>Lacticaseibacillus paracasei</i> and five other LAB strains. We evaluated fermentation performance, nutrition, volatiles, sensory attributes, and antioxidant changes during digestion to develop a high-nutrition functional beverage. Co-fermentation significantly increased total phenolics, flavonoids, amino acids, and organic acids while boosting antioxidant activities (DPPH/ABTS, SOD). Volatile profiles strongly correlated with sensory attributes, and specific co-fermentation combinations produced complex aromas and a smooth mouthfeel preferred by consumers. Strain-specific metabolic activities created distinct flavors, such as creamy, or apple-citrus notes. <i>L. paracasei</i>:<i>L. fermentum</i> produced 3-methyl-1-butanol (13.70 ± 0.11 %), enhancing fruity notes. Fermented samples maintained high SOD activity and ABTS scavenging after <i>in vitro</i> digestion, the <i>L. paracasei</i>:<i>L. acidophilus</i> combination showed the highest ABTS radical scavenging activity (51.88 ± 0.06 %) and SOD activity (135,300 U/mL). LAB co-fermentation is a sustainable strategy to simultaneously improve kiwifruit juice's nutritional and sensory quality.