Synergistic effects of Ultrasound-Assisted Ultra-High pressure on quality attributes and flavor profile of lactic acid Bacteria-Fermented fresh jujube juice

Non-thermal processing technologies have emerged as promising alternatives to preserve bioactive compounds in fruit-based beverages. However, the synergistic effects of ultrasound-assisted ultra-high pressure (US-UHP) combined with lactic acid bacteria fermentation on jujube juice quality remain poorly understood. This study systematically investigated the effects of US-UHP pretreatment on physicochemical properties, bioactive compounds, volatile profiles, and sensory characteristics of fermented jujube juice (FJJ). Results demonstrated that US-UHP pretreated samples exhibited superior quality attributes. At 24'h fermentation, total phenolic content reached 2.32 mg/mL, ABTS and DPPH radical scavenging activities were 87.30% and 74.86%, respectively, and ascorbic acid content was significantly higher than other groups. After 40 h fermentation, reducing sugar consumption rate reached 54.69%. Notably, US-UHP treatment significantly improved colloidal stability, with particle size maintained at 33.41-53.21 d.nm compared to 1597.67 d.nm in untreated samples, accompanied by lower polydispersity index values. Gas Chromatography-Ion Mobility Spectrometry and Headspace Solid-Phase Microextraction Gas Chromatography-Mass Spectrometry analyses revealed that US-UHP treatment effectively reduced undesirable flavor compounds (butyric acid, hexanal, acetaldehyde) while promoting the accumulation of floral and fruity scent-related ketones. Principal component analysis of electronic nose data confirmed distinct flavor differentiation among treatments, and sensory evaluation demonstrated that US-UHP pretreated samples achieved the highest overall acceptability scores. Correlation analysis indicated significant positive relationships between total phenolic/flavonoid contents and overall acceptance (r > 0.92). These findings demonstrate that US-UHP pretreatment synergistically enhances microbial inactivation, bioactive compound release, and metabolic efficiency, providing theoretical insights and technical guidance for high-quality FJJ development.