Protective effect of soybean powder as a cryoprotectant and encapsulating material on the survival of Lactobacillus fermentum SK54 during freeze drying, storage and exposure to simulated gastrointestinal conditions

Abstract

The aim of the current study was to focus on the impact of soybean powder as a cryoprotectant and microencapsulation on the survival of Lactobacillus fermentum SK54 from freeze-drying, storing and exposing to simulated gastrointestinal tract conditions. Seven cryoprotectants e.g., soybean powder, skim milk, galactooligosaccharide (GOS), inulin, sucrose, lactose and glucose were tested for their ability to protect L. fermentum SK54 during freeze-drying. Results revealed soybean powder, skim milk and GOS could highly protect L. fermentum SK54 with the survival rates 87.06-88.52% as the cryoprotectants. The optimal concentrations of soybean powder, skim milk and GOS were demonstrated to be 13% (w/v). The freeze-dried cells with soybean powder had the best survival rate from storing at 4 °C and 25 °C for 5 months. Microencapsulation of L. fermentum SK54 cells by the extrusion technique was adopted for this study. The encapsulated beads with soybean powder significantly improved the survival of the bacteria in the simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The survival rate of encapsulated cells with soybean powder stored at 4 °C and 25 °C for 5 months was markedly improved when compared with encapsulated cells without soybean powder. Soybean powder and soybean powder incorporated in encapsulated beads were the suitable cryoprotectants for L. fermentum SK54 in freeze-drying and storage processes. The results in this study indicate that soybean powder is the most suitable cryoprotectants when used alone and incorporated into encapsulated beads prepared by extrusion technique had the potential to protect probiotic cells during the manufacturing, storing processes and exposing to SGF and SIF.