Selenium bioenrichment and functional enhancement with antioxidants in Actinidia arguta juice by fermentation with selenium-enriched Tibetan kefir grains

Selenium is an essential trace element with critical roles in antioxidant defense, immune regulation, and metabolic health, yet its intake is insufficient in many populations. This study investigated the effects of fermenting Actinidia arguta juice with selenium-enriched Tibetan kefir grains to enhance its nutritional, sensory and functional. Selenium-enriched Tibetan kefir grains fermentation not only increased total Se content but also promoted the biotransformation of inorganic selenium into bioavailable organic selenium, supporting effective dietary biofortification. The fermented juice showed enhanced activities of antioxidant enzymes, including glutathione peroxidase, glutathione S-transferase, and thioredoxin reductase. Interestingly, selenium enrichment enhanced zinc bioaccumulation and co-regulation. The volatile compound analysis revealed selenium-driven shifts toward alcohols and esters, which contributed to enhanced floral, fruity, and balsamic aroma qualities. Metabolomics further revealed that selenium-enriched activated cysteine and methionine, and glutathione-related metabolism pathways. Thus, this study providing a promising approach for developing selenium-enriched functional beverages.