Microencapsulation of Lactobacillus casei LK-1 by spray drying related to its stability and in vitro digestion

- Skim milk was an effective vehicle for L. casei LK-1 during production, storage and digestion.
- The temperature and water activity had a significantly influence on the viability of L. casei LK-1 during storage.
- The glass state was necessary but the Tg was not absolute threshold for high storage viability and low storage viability of L. casei LK-1.

Bacterial viability is a requirement for probiotics in food applications, and retaining a high viability rate is important to ensure its beneficial effects. The study aimed to determine the protective effects of different matrices on microencapsulated Lactobacillus casei LK-1 during spray drying, storage and in vitro digestion. Skim milk, trehalose and maltodextrin were used as protective agents to form different bacterial microcapsules by spray drying. Viability of bacteria in capsules stored at different temperatures (−20, 4, 25 and 37 °C) and in capsules with different water activities were studied. The results showed that both storage temperature and water activity had significant influence on viability of L. casei LK-1 and the glass state was necessary but not absolute factors for storage stability. All matrix showed the highest viability when stored at −20 °C and with water activity of 0.11. It was found that skim milk endowed L. casei LK-1 high viability in either gastric or intestinal juice. In general, skim milk protected L. casei LK-1 better than trehalose and maltodextrin during spray drying, storage and simulated digestion. This study demonstrated that it is important to choose appropriate protective agent to achieve high viability in probiotic application.