In this study, the response surface methodology was used to optimize the cryoprotective agent (skimmed milk powder, lactose and sucrose) formulation for enhancing the viability of Lactobacillus curvatus N19 during freeze-drying and storage stability of cells freeze-dried by using optimum formulation was evaluated. Our results showed that the most significant cryoprotective agent influencing the viability of L. curvatus N19 to freezing and freeze-drying was sucrose and skim milk, respectively. The optimal formulation of cryoprotective agents was 20 g/100 mL skim milk, 3.57 g/100 mL lactose and 10 g/100 mL sucrose. Using the optimum formulation during freeze-drying, the cell survival was found more than 98%. Under the optimal conditions, although only storage of the cells at 4 °C for 6 month retained the maximum stability (8.85 log cfu/g), the employed protectant matrix showed promising results at 25 °C (7.89 log cfu/g). The storage stability of cells under optimized conditions was predicted by accelerated storage test, which was demonstrated that the inactivation rate constant of the freeze-dried L. curvatus N19 powder was 9.74 × 10-6 1/d for 4 °C and 2.08 × 10-3 1/d for 25 °C. The loss of specific acidification activity after the storage at 4 and 25 °C was determined.

中文翻译：

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优化冷冻保护剂配方下冻干曲乳杆菌N19的储存稳定性和酸化动力学

本研究采用响应面法优化冷冻保护剂（脱脂奶粉、乳糖和蔗糖）配方，以提高曲乳杆菌 N19 在冻干过程中的活力和使用最佳配方冻干细胞的储存稳定性。评估。我们的结果表明，影响 L.curvatus N19 冷冻和冷冻干燥活力的最重要的冷冻保护剂分别是蔗糖和脱脂牛奶。冷冻保护剂的最佳配方为 20 g/100 mL 脱脂牛奶、3.57 g/100 mL 乳糖和 10 g/100 mL 蔗糖。在冻干过程中使用最佳配方，发现细胞存活率超过 98%。在最佳条件下，尽管细胞仅在 4°C 下储存 6 个月才能保持最大稳定性（8.85 log cfu/g），所采用的保护剂基质在 25 °C (7.89 log cfu/g) 下显示出令人满意的结果。通过加速贮藏试验预测优化条件下细胞的贮藏稳定性，结果表明，冻干的 L.curvatus N19 粉末的灭活速率常数为 9.74 × 10-6 1/d for 4 °C 和 2.08 × 10 -3 1/d 25 °C。测定在 4 和 25 °C 下储存后特定酸化活性的损失。