Effects of Sucrose, Skim Milk and Yeast Powder on Survival of Lactobacillus rhamnosus GG Encapsulated with Alginate during One-week Storage at room Conditions

During the manufacture and storage of probiotic products, there are always possibilities that probiotics be exposed to harmful stresses such as high temperature, low pH, various osmotic pressures and high oxygen levels, which can decrease the number of living cells. Encapsulation is one of the methods used to protect living cells such as probiotic bacteria from environmental challenges. Up-to-date, various compounds with abilities to protect bacteria during freeze-drying and to increase viability during storage have been identified. In this study, alginate with calcium chloride was used to encapsulate probiotic bacteria using extrusion method. Then, effects of sucrose and skim milk as cryoprotectants and yeast powder containing beta-glucan as prebiotic on the survival of these bacteria were investigated.

The Homogeneous solution of bacteria with alginate and cry protectants were manually extruded into a calcium chloride solution. After 30 min of agitation, shaped beads were separated. For the comparison, bacterial population were enumerated in the primary culture, after encapsulation, freeze-drying and 1 week of storage at room conditions (N0, N, NF and N1w, respectively). To assess colony-forming unit per ml of the samples, first 1 g of fresh beads was dissolved in 9 ml of trisodium citrate and then serial dilution and pour plate techniques were carried out. Plates were incubated for 24-48 h and colonies were counted.

Results showed that encapsulation of bacteria with alginate and calcium chloride alone was 51% effective while use of yeast powder and sucrose with alginate increased the encapsulation efficiency to 97 and 99%, respectively. Furthermore, use of skim milk with alginate and sucrose resulted in the highest survival rate after 1 week of storage at room conditions. Therefore, encapsulation of probiotic bacteria with alginate layer and yeast powder containing prebiotics, sucrose and skim milk can be effective in survival of these bacteria.