[关键词]
[摘要]
本研究以糙米为主要培养基并结合真空干燥(-0.1 MPa)和冷冻保藏(-80 ℃)工艺开发出一种米曲霉长期保藏技术。生产实验表明,利用该方法保藏20年的米曲霉菌种直接制备的大曲中中性蛋白酶、酸性蛋白酶、淀粉酶和葡萄糖淀粉酶的酶活分别达到1871、319、256和2110 U/g干曲。利用该大曲所生产的酱油总氮、氨基酸态氮、总糖、还原糖、无盐固形物含量及原料蛋白质利用率分别达到1.53、0.92、5.39、3.52、19.88 g/100 mL和82.20%。上述指标显著优于利用常规冻干管法保藏20年的米曲霉所制备大曲和酱油的相应指标(p<0.05),与利用常规冻干管法保藏5年的米曲霉所制备大曲和酱油的相应指标无显著差异(p>0.05)。由聚类分析可知,本方法可比冻干管法延长米曲霉保藏时间15年,在实际生产中可减少菌株复壮次数,避免传代过程中米曲霉突变和污染的几率,进而提高酱油质量稳定性。
[Key word]
[Abstract]
The long-term preservation of Aspergillus oryzae was achieved through the use of brown rice as the main culture medium and vacuum drying (-0.1 MPa) and cryopreservation (-80 ℃). Koji prepared using A. oryzae that had been preserved for 20 years by this novel method exhibited neutral protease, acidic protease, amylase, and glucoamylase activities of 1871, 319, 256, and 2110 U/g dry Koji, respectively. In soy sauce prepared using the aforementioned Koji, the contents of total nitrogen, formaldehyde nitrogen, total sugars, reducing sugars, and salt-free solids and the rate of utilization of proteins in the raw materials were 1.53, 0.92, 5.39, 3.52, and 19.88 g/100 mL and 82.20%, respectively. These indicator values were significantly superior to those of Koji and soy sauce prepared using A. oryzae preserved for 20 years by the conventional tube freeze-drying method (p<0.05) and were not significantly different from those of Koji and soy sauce prepared using A. oryzae preserved for 5 years by the conventional tube freeze-drying (p>0.05). According to the hierarchical cluster analysis results, compared with the conventional tube freeze-drying method, the novel method prolonged the preservation of A. oryzae by 15 years, reduced the number of times needed for its rejuvenation during actual production, and lowered the possibility of its mutation and contamination during passage. These attributes would enhance the quality stability of soy sauce.
[中图分类号]
[基金项目]
国基自然科学基金项目(31301538);中山市重大科技专项项目(2018A1007)