Optimization of a cryoprotective medium for infant formula probiotic applications using response surface methodology

摘要

The paper focuses on the development of a cryoprotective drying medium suitable for the application of probiotics in infant formulae. Response surface methodology was used to optimize the concentrations of skim milk and prebiotics for maximizing the survival of the probiotic Bifidobacterium lactis DSM 10140 during freeze-drying. The optimal combination was found to be 15.0% skim milk blended with 3.4% prebiotics, which protected viability in 62.16% of cells. There was no significant difference (p?>?0.05) between the experimental and predicted values, thereby verifying the model adequacy. The stability of the freeze-dried cells in the optimal combination of drying medium was examined under different conditions of rehydration and storage and in a simulated gastrointestinal tract model. The results showed that optimized drying medium could increase the viability of freeze-dried stationary phase cells by 1.34 log (CFU/ml) as compared to phosphate buffer after 120?days of storage at 4°C. However, with increasing temperature to 25°C, the protective effect of the optimized medium was more obvious. The optimized drying medium was also able to reduce the mortality rate of cells after sequential incubation under simulated infantile gastrointestinal conditions, including gastric conditions (pH 3.0 and 4.0, 90?min) and intestinal conditions (pH 7.5, 5?h) by 1.24 and 0.57 log (CFU/ml), respectively, compared to the control.