Reducing Biogenic Amines In Huangjiu By Recycling The Lactobacillus Enhanced Rice Soaking Water

Biogenic amines（BAs）were generally detected in Huangjiu,an appropriate concentration of BAs are important in the regulation of natural physiological processes,but the intake of large amounts of BAs can cause dizziness,vomiting and other adverse effects.A large number of BAs can be formed in the rice soaking process,which can increase the BAs in Huangjiu,however,the influence of rice soaking process on the BAs of Huangjiu has not been studied.And the shortcomings of rice soaking technology（long soaking time,huge wastewater emissions）need to be improved.In this study,the influence of the rice soaking process on BAs in Huangjiu was studied.And based on analysing the source of BAs in rice soaking process and screening of the Lactobacillus degrading BAs,the screened Lactobacillus were inoculated in the rice soaking process and recycling the rice soaking water.Further,the recycling the Lactobacillus enhanced rice soaking water technology was developed and applied,which reduced the content of BAs in Huangjiu and improved the traditional rice soaking technology.The main work and results were as following:1.The main source of BAs in Huangjiu fermentation mash is rice soaking process.A high concentration of BAs was detected in the soaking rice（135.16 mg/kg）,and during the process of the Huangjiu fermentation,the BAs concentration increased sharply within 24 hours（142.6mg/L）,then decreased slightly in the subsequent fermentation process（125.26 mg/L）.Further,the concentration of BAs in fermented mash was positively correlated with the rice soaking water and the soaking rice（R² was 0.83 and 0.92 respectively）by analyzing the 25 batches of Huangjiu brewing process.Moreover,the total BAs contribution rate of soaking rice to fermented mash was 71.15%.2.The mechanism of BAs formation in the rice soaking process was analyzed by studying the changes of physicochemical indexes and the microbial community structure of rice soaking water.The rice was saturated with water within 120 minutes,and the total acid in soaking water was increased up to 16 g/L（14 d）.And the BAs in the soaking rice were up to 237.95 mg/kg,which can increase the BAs in Huangjiu.And,it is also difficult to treat the rice soaking water because the concentration of COD and BOD₅ was high（10⁴ mg/L）.Further,analyzing the microbial community structure in rice soaking water by high-throughput sequencing technology,a microflora dominated by Lactobacillus,Lactococcus,Weissella were formed,and the accumulation of BAs may be related to the lactic acid bacteria with the potential to produce BAs existed in the rice soaking water.3.The Lactobacillus degrading BAs was screened.Based on analysing the characteristics of BA metabolism,growth and acid production and pH tolerance,the Lactobacillus plantarum14-2-1 was screened from 43 isolates,which has strong growth and acid production ability,can not produce BAs and degrade 21.89%of BAs in the medium.4.Development of the recycling the Lactobacillus enhanced rice soaking water technology.The L.plantarum 14-2-1 was inoculated to rice soaking process at the optimal inoculation ratio of 7.5%,a microflora dominated by L.plantarum was formed in rice soaking water and the BAs decreased by 93.84%compared with the traditional rice soaking technology.Further,during the process of recycling the rice soaking water,the initial acidity of rice soaking water was≥4.23 g/L,the L.plantarum was the most dominant bacterium（>96%）and the concentration of BAs was<2 mg/L in the soaking water.It was also found that the BAs in Huangjiu brewed by the recycling rice soaking water technology were as much as nearly 12times lower than traditional rice soaking technology.5.Application of the recycling the Lactobacillus enhanced rice soaking water technology.Applicating the recycling the Lactobacillus enhanced rice soaking water technology in the Huangjiu factory,the initial acidity of the rice soaking water can affect the content of BAs by affecting microbial community structure in rice soaking water.Further,the initial acidity of rice soaking water is 4.63 g/L～5.38 g/L when the rice soaking water was completely recycled,and the BAs in the soaking rice and fermented mash decreased by 75.99%and 79.27%respectively without affecting the Huangjiu brewing.In conclusion,this study found that the rice soaking process is the main source of BAs in Huangjiu.Further,the mechanism of BAs formation in the rice soaking process was analyzed.And the target L.plantarum 14-2-1 was screened,which can be applied to rice soaking process.Based on this,the recycling the Lactobacillus enhanced rice soaking water technology was developed and preliminary applied to factory,which effectively improved the problems of traditional rice soaking technology（high BAs,long soaking time,wastewater discharge）and reduced the concentration of BAs in Huangjiu without affecting the brewing of Huangjiu.