Co-fermentation with lactic acid bacteria and prune puree modulates volatile profile and bioactivity of Qiamagu juice

Brassica rapa L., a specialty crop from Xinjiang known as Qiamagu (QMG), has limited processing and market application due to its pungent off-flavor and perishability. This study aimed to characterize the volatile compounds responsible for the undesirable flavor in QMG processed by different methods, and to evaluate the effects of combined lactic acid bacteria (LAB) fermentation with prune puree addition on fresh QMG juice's flavor and bioactivity. Volatile compounds of five kinds of QMG products and fresh juice were analyzed using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), identifying isothiocyanates and nitriles as the primary contributors to pungency. Fresh QMG juice was fermented with Lacticaseibacillus plantarum and Lacticaseibacillus rhamnosus, combined with Xinjiang prune puree. Sensory evaluation, bioactivity assays, and storage tests were conducted to assess quality changes. Shelf life was predicted using kinetic modeling based on uric acid inhibition data. Fermentation and prune puree addition significantly reduced sulfur-containing compounds from 14,411.40 μg/L to 1089.30 μg/L, while aldehydes, esters, and alcohols increased, enhancing floral and fruity aromas. Sensory scores of fermented samples reached 74, surpassing fresh juice at 39.71. Bioactivity improved with a 39.00 % increase in uric acid inhibition rate, a 6.39 % rise in superoxide dismutase activity, and polysaccharide content elevated from 99.96 to 109.85 mg/mL. Storage at 4 °C slowed degradation of active components, with a predicted shelf life of approximately 330 days. These results demonstrate that LAB fermentation combined with prune puree addition effectively improves QMG flavor and functional properties, providing a scientific basis for its development as a functional food ingredient. By simultaneously reducing undesirable flavors and enhancing bioactivity, this strategy promotes QMG from an underutilized crop to a promising functional food ingredient with significant market potential. Furthermore, it provides a generalizable approach for optimizing flavor and functional quality in other Brassica L based foods.