Effects of Adding Apple Polyphenols Before and After Fermentation on the Properties of Drinking Yoghurt

Adding polyphenols (PPs) to yoghurt is a convenient way to deliver the health benefits of PPs and also the probiotic effects of starter cultures. In this study, drinking yoghurts with apple PPs (chlorogenic acid, phlorizin, or apple PP extract (APE)) added pre- or post-fermentation, and pectins (low or high methoxyl) were subjected to chemical, physical, and microbiological analyses. Results show that the type of PPs and pectin affected the total extractable PP content (TEPC), PP profiles, viscosity, storage modulus of yogurt, colony number, and morphology of the starter cultures. Adding APE before fermentation produced yoghurts with a greater TEPC and more polar PPs than adding post-fermentation. Producing drinking yoghurt enhanced with apple PPs via either approach is feasible. The pre-fermentation approach may be more beneficial in terms of increased TEPC and growth of starter culture, offering a bio-process to optimise PP profiles in drinking yoghurt.