Exploring the Effects and Mechanisms of Epigallocatechin Gallate and Ascorbic Acid as Antioxidative Components in Producing Lacticaseibacillus rhamnosus GG Powder via Spray Drying

In producing active probiotic powder, the encapsulant impacts the viability and functionality of dehydrated bacteria through various mechanisms, which may exhibit synergistic or antagonistic effects. This study investigated the effects of supplementing a water-soluble antioxidant to non-fermentable disaccharide lactose or fermentable disaccharide trehalose as encapsulants for producing Lacticaseibacillus rhamnosus GG (LGG) powders via spray drying. LGG powders prepared with pure sugar encapsulants exhibited inactivations of 0.68–1.02 log, whereas incorporating 0.5 wt% antioxidants significantly increased viability loss, with inactivation levels reaching 1.08–1.71 logs for epigallocatechin gallate (EGCg) and 4.03–4.52 logs for ascorbic acid (AA). More intensive inactivation was observed for trehalose-based powders than for lactose-based powders. The powders showed minimal changes in antioxidant capacity, indicating neutralized oxidative stress during spray drying. The particle morphology and the thermal and hygroscopic properties of LGG-encapsulating powders were minorly affected by the antioxidants. However, LGG cells in antioxidant-supplemented powders bore substantial injuries on growth capability, membrane integrity, and cellular shape. Incubating LGG with each antioxidant confirmed their antibacterial effects in sugar solutions, with EGCg being more inhibitory than AA. ¹H NMR revealed the electron-donating behavior of EGCg when interacting with LGG, potentially disrupting the bacteria’s metabolic system. AA caused a shift in three out of seven LGG signal peaks toward the low field, and it might induce additional acid stress during dehydration. The findings elucidated the multiple pathways that antioxidative agents interact with LAB during dehydration, including altering the intensity of dehydration-associated stresses, modifying the physicochemical properties of particles, and interfering with cellular activities.