Preparation and use of apple skin polyphenol extracts in milk: enhancement of the viability and adhesion of probiotic Lactobacillus acidophilus (ATCC 1643) bacteria

This study explored the feasibility of using apple skin as a source for generating antioxidant extracts, that is ethanolic or aqueous apple skin polyphenol extract (ASPE) and examined the effects of such ASPEs and six purified polyphenols (PPs), that is rutin, epicatechin, phlorizin, cholorogenic acid, quercetin and p‐coumaric acid on the viability of probiotic bacteria (PB) Lactobacillus acidophilus in a PP‐enhanced milk drink at 4 °C and the in vitroPB adhesion to hydrophilic tissue culture microtitre plates (TCMPs) at 4 °C or 37 °C. The two ASPEs differed slightly in antioxidant activity, PP composition and total extracted PP, vitamin C and uronic acid contents. PB. had over 10× better viability in milk with added PPs than without over a 50‐day storage at 4 °C, while the aqueous extract was more effective than any of the pure PPs, except rutin. PB exhibited significantly greater potential adhesion to intestinal cells in the presence of the aqueous ASPE than the ethanolic ASPE or purified PP, while temperature (4 °C or 37 °C) had a negligible effect on adhesion. Use of apple skin as a source of PPs for enhancing PB functionality in dairy foods may offer a means of deriving value from this waste stream.