Kefir fermented fruit by-products: anti-Alicyclobacillus spp. activity, and antioxidant activity

Abstract

This study aimed to investigate the antimicrobial activity of kefir fermented fruit by-products against strains of Alicyclobacillus spp., and determine their chemical characterization and antioxidant activity. According to the results, extracts fermented for a longer period (72 h) showed greater inhibition, and the extract of acerola by-product fermented for 72 h achieved the best results. For all strains, the Minimal Inhibitory Concentration (MIC) was 0.78%, except for A. acidocaldarius subsp. rittmannii, (1.56%). The same applies to the Minimal Bactericidal Concentration (MBC), in which 1.56% of the extract was capable of inactivating A. cycloheptanicus and A. acidocaldarius. In addition, damages to the structure of the microorganisms caused by the extracts were detected by Scanning Electron Microscopy. Metabolite identification through liquid chromatography (UHPLC-Qtof-MS) showed that the fermented extracts had a greater number of compounds compared to the non-fermented ones, such as glucuronic, succinic and glutaric acids. In conclusion, the extracts of fruit by-products showed to have bioactive properties, such as antibacterial potential and antioxidant activity against the Alicyclobacillus strains tested in this study, not to mention the value added by the use of a food by-product.