Antioxidant activity and the survival-enhancing effect of ascorbic acid on Limosilactobacillus reuteri KUB-AC5 microencapsulated with lactose by spray drying

Highlights

• Lactose combined with ascorbic acid (AA): effective wall materials for probiotics.

• Lactose formed an amorphous glassy matrix protecting microencapsulated bacteria.

• AA concentration was a factor influencing cell survival during drying and storage.

• High AA concentration led to poor cell protection against heat and dehydration.

• High AA concentration caused a rapid cell inactivation during storage.

Abstract

To improve cell survival during spray drying and storage, an antioxidant has been exploited as a coencapsulant. In this study, ascorbic acid at various concentrations was used to complement the protective ability of lactose for encapsulation of Limosilactobacillus reuteri KUB-AC5. Ascorbic acid at 24 mg/mL had a negative impact on physicochemical properties of microcapsules. Increasing the ascorbic acid concentration reduced the glass transition temperature determined using differential scanning electron calorimetry and promoted agglomeration observed by scanning electron microscopy. After 2 months of storage at 37 °C, X-ray diffraction studies showed that the treatment with 24 mg/mL ascorbic acid had a 314.40% increase in crystallinity. Malondialdehyde before storage decreased with increasing ascorbic acid concentrations, and the highest and lowest survival was found in the samples prepared with 12 and 24 mg/mL ascorbic acid, respectively. A loss of ascorbic acid along with an increase in the half maximal inhibitory concentration was observed during storage, especially at 37 °C. An increase in malondialdehyde and a decrease in viability were found. After storage, the samples with 12 mg/mL ascorbic acid showed the highest survival. The results demonstrate the antioxidant activity of ascorbic acid by hydrogen atom transfer that promotes cell survival under stress conditions.