Freezing resistance improvement of Lactobacillus reuteri by using cell immobilization.

Lactobacillus reuteri shows certain beneficial effects to human health and is recognized as a probiotic. However, its application in frozen foods is still not popular because of its low survival during freezing and frozen storage. Cell immobilization technique could effectively exert protection effects to microbial cells in order to enhance their endurance to unfavorable environmental conditions as well as to improve their viability and cell concentration. Ca-alginate and kappa-carrageenan were used to immobilize L. reuteri in this research, and the immobilized cells were exposed to different freezing temperatures, i.e. -20 degrees C, -40 degrees C, -60 degrees C, -80 degrees C, and stored at -40 degrees C and -80 degrees C for 12 weeks. The objectives were to study the protection effects of cell immobilization against the adverse conditions of freezing and frozen storage, and the effects of freezing temperatures to the immobilized cells. Cell immobilization was used to raise the survival of L. reuteri during freezing and frozen storage in order to develop frozen foods with the probiotic effects of L. reuteri. Results indicated that immobilized L. reuteri possessed better survival in both freezing and frozen storage. The survival of immobilized L. reuteri was higher than that of free cells, and the effects of lower freezing temperature were better than higher freezing temperature. The immobilization effects of Ca-alginate were found to be superior to kappa-carrageenan. Cell immobilized L. reuteri exhibits potential to be used in frozen foods.