Evaluation of fermentation properties, antioxidant capacity in vitro and in vivo, and metabolic profile of a fermented beverage made from apple and cantaloupe

This work is aimed at developing a fermented beverage (FB) with excellent antioxidant capacity from apple and cantaloupe using lactic acid bacteria (LAB) and yeast. The optimal fermentation process was as follows: the apple-cantaloupe juice adding 21% sugar inoculated with 9% yeast was fermented at 27 °C for 11 d, and then inoculated with 9% LAB at 36 °C for 16 d. The antioxidant activity of FB was investigated using in vitro and in vivo models. The total phenols content (TPC) and total flavonoids content (TFC), DPPH and ABTS radical scavenging activity, and Fe3+ reducing power of FB enhanced during in vitro simulated digestion. The in vivo studies indicated that 6.25% FB prolonged the lifespan of Caenorhabditis elegans, enhanced SOD and GSH-Px activity, decreased MDA content, and had significant anti-stress, but did not damage the growth, reproduction and locomotion of Caenorhabditis elegans. Untargeted metabolomics were performed to reveal the changes in metabolites of juice before and after fermentation. A total of 624 metabolites were identified. The significant differentially regulated metabolites were concentrated mainly in lipids and lipid-like molecules, organic acids and derivatives, and organic heterocyclic molecule. Thus, a bioactive food product with antioxidant properties was obtained by fermentation.