八公山腐乳酿制过程中毛霉和根霉的前期发酵比较研究

Comparative Study of Pre-fermentation with Mucor racemosus and Rhizopus oryzae in Bagongshan Sufu during Fermentation

八公山腐乳前期发酵工艺对其总体风味具有重要影响,围绕腐乳酿制中常用的总状毛霉（Mucor racemosus）和米根霉（Rhizopus oryzae）开展工艺探索具有重要意义。在单因素试验的基础上,选取发酵时间、发酵温度和接种量为影响因子,以蛋白酶活力为评价指标,采用响应面法优化总状毛霉和米根霉发酵腐乳的前期发酵条件,比较最优条件下二者前期发酵分泌酶系和氨基酸。研究结果表明总状毛霉的前期发酵条件为：发酵时间60 h、发酵温度24℃、接种量1.0×10^5 CFU/mL,此时分泌产蛋白酶活力为42.79μg/mL;米根霉的前期发酵条件为：发酵时间50 h、发酵温度32℃、接种量1.0×10^5 CFU/mL,此时分泌产蛋白酶活力为33.51μg/mL。通过对二者前期发酵的情况比较分析可知：总状毛霉发酵前期产物中蛋白酶活力高于米根霉,而淀粉酶、糖化酶、脂肪酶活力低于米根霉。总状毛霉发酵产物的氨基酸总量高于米根霉,但其中呈味氨基酸和疏水氨基酸差别不大。两种菌的前期发酵互有优势,为协同作用提供了一定的理论依据。

Since the pre-fermentation of Bagongshan sufu has an important impact on its overall nutritional quality and flavor and the exploration of its fermentation process with two common strains（Mucor racemosus or Rhizopus oryzae） is of great significance for practical production. The conditions for pre-fermentation of either strain were optimized by the combined use of one-factor-at-a-time method and response surface methodology. Fermentation time, temperature and inoculum amount were selected as independent variables while protease activity was selected as response variable. This study also compared the enzyme systems and amino acids produced by the two stains under optimized fermentation conditions. Results showed that the optimal fermentation conditions of Mucor racemosus were found to be fermentation for 60 h at 24 ℃ with an inoculum amount of 1.0 × 10^5 CFU/mL. Under these conditions, the activity of protease was 42.79 μg/mL. The optimal fermentation conditions of Rhizopus oryzae were determined as 50 h, 32 ℃ and 1.0 × 10^5 CFU/mL, respectively. Under these conditions, the activity of protease was 33.51 μg/mL. Comparative investigations indicated that the activity of protease in Mucor racemosus was higher than that in Rhizopus oryzae, while α-amylase, glucoamylase and lipase from Mucor racemosus were lower than from Rhizopus oryzae. The content of total amino acids in sufu fermented by Mucor racemosus was higher than that in sufu fermented by Rhizopus oryzae while there was no obvious difference in flavor amino acids or hydrophobic amino acids. Both Mucor racemosus and Rhizopus oryzae had their own advantages for the pre-fermentation of Bagongshan sufu, which may lay a theoretical foundation for synergistic fermentation.