采用序贯设计对以牛乳和豆乳为原料研制混合乳开菲尔的发酵条件进行了优化。首先应用部分析因设计对影响开菲尔发酵的牛乳与豆乳比例、酵母接种量、乳酸菌接种量、蔗糖添加量、发酵温度、发酵时间6个因子进行了分析,筛选出蔗糖添加量和发酵时间为显著因子,然后通过最陡爬坡设计逼近最大响应区域,应用中心复合设计法确定蔗糖添加量(x4)和发酵时间(x6)的最佳组合,最终得到混合乳开菲尔发酵的最优发酵条件为牛乳与豆乳比例为7∶3,酵母接种量为1.00×105 CFU/mL,乳酸菌接种量为1.00×107 CFU/mL,蔗糖添加量为1.6%,发酵温度为22℃,发酵时间为22 h。

The sequential experimental design was used to optimize the fermentation conditions of kefir from milk and soymilk.Fractional factorial design was employed to evaluate the six factors,viz.the ratio of milk and soymilk,inoculum of saccharomyces cerevisiae,inoculum of lactic acid bacteria,the addition of sucrose,fermentation temperature and time.It was found that the addition of sucrose and fermentation time were the significant factors for fermentation.Then the steepest ascent design was conducted to approach the greatest response area and the optimum combinations of significant factors were confirmed via Central Composite Design(CCD).The results indicated that the optimal conditions were the ratio of milk and soymilk was 7∶ 3,the inoculum of the LAB and yeast were 1.00×107 CFU/mL and 1.00×105 CFU/mL respectively,the addition of sucrose was 1.6%,the fermentation temperature was 22℃ and the time was 22h.