Abstract: To investigate the protective effects of the novel nanomaterial whey protein isolated fibrils (WPIF) and typical antioxidants against oxidative stress in probiotics during ambient storage, spray-dried probiotic powders were prepared using whey protein isolate (WPI) or WPIF as wall material alone or in combination with different concentrations of epigallocatechin gallate (EGCG) or glutathione (GSH) in this study. The experimental results suggested that the viability of probiotics during ambient storage decreased in the following order: WPIF ≈ WPI > WPI + 0.5 mg/mL EGCG > WPI + 0.5 mg/mL GSH > WPI + 5.0 mg/mL EGCG > WPI + 5.0 mg/mL GSH. There was no significant difference in the probiotic survival between the WPI and WPIF groups, which may be because the high temperature during spray drying allowed the fibrils to break down and aggregate. Interestingly, EGCG and GSH concentration-dependently accelerated the death of probiotics during ambient storage, which might be related to the antimicrobial activity or the cytotoxicity of the oxidative products of EGCG and GSH.

Key words: whey protein isolate fibrils; antioxidant; epigallocatechin gallate; glutathione; oxidative stress; probiotics