Isolation,Identification,Traceability And Control Of Gas-Producing Microorganisms In Mijiu

Mijiu is a traditional fermented wine in China,with glutinous rice as raw material and Jiuyao as a fermentation agent,Mijiu is fermented by a variety of microorganisms of Jiuyao which are fermented to Mijiu.Mijiu is rich in various amino acids,vitamins and organic acids and other nutrients,with a high nutritional value.And it boasts high sugar content and low alcohol content,which can not only quickly replenish energy but also effectively promote blood circulation.There is,however,the small family workshops and small food processing plants are still the mainly current production methods of Mijiu.This production environment contains many kinds of microorganisms that may cause secondary pollution in Mijiu with incomplete sterilization or contaminated canning process.What’s more,the gas production of Mijiu will cause tank expansion,tank explosion and liquid leakage,which will not only suffer products quality and safety,but also cause property damage.Gas-producing Mijiu is takes as this paper’s research object,by comparing the changes of main indicators of normal Mijiu and gas-producing Mijiu,isolating and identifying the microorganisms that cause gas production in Mijiu.Completing the research on the characteristics of gas-producing microorganisms and tracing the pollution source of gas-producing microorganisms in the factory,finally adopting reasonable control methods to reduce the pollution of gas-producing microorganisms,to achieve the purpose of effectively reducing the gas production of finished Mijiu.The main findings are as follows:1.By comparing the sensory,physicochemical and micrbial indexes of normal Mijiu and gas-producing Mijiu,the results show that: the color and smell of Mijiu did not change significantly after gas production,but the precipitation increased greatly and amino acid nitrogen content and the total acid content increased by 0.001~0.103g/100 m L,0.14~0.20g/100 m L respectively.On the contrary,the p H,alcohol content and total sugar content decreased by 0.46~1.72,0.48~1.45%Vol,1.0~2.2g/100 m L respectively.The total number of normal Mijiu colonies and yeast were 4.0×102CFU / m L and 2.0×102CFU / m L respectively,while the mean number of colonies and yeast in gas-producing gas Mijiu were2.2×106CFU / m L and 1.8×105CFU / m L.2.The gas-producing microorganisms were isolated and purified from gas-producing Mijiu.There were three microorganisms B1,B2,D2 which are detected by traditional identification methods and 18 Sr DNA molecular biology methods,and it was concluded thatB1 and B2 belong to the same genus and different species of Saccharomyces cerevisiae.B1 is Saccharomyces cerevisiae OM368667.1,and B2 is Saccharomyces cerevisiae OM281252.1.D2 is Wickerhamomyces anomalus JX188245.1.3.The three gas-producing microorganisms are all facultative anaerobic bacteria,which could grow up in both aerobic and anaerobic conditions.But when the alcohol content exceeds 9%vol,these three strains hardly grow.If the sugar content exceeds 0.20g/m L,which is harmful to the gas-producing microorganisms.What more,Irradiation at 30 cm under40W UV lamp for 30 min has obvious killing effect on three kinds of gas-producing microorganisms.And the sterilization rate of B1,B2,D2 can reach up to 98.67%,68.60%,99.94% respectively,when they were kept in 100℃ boiling water bath for 30 minutes.4.The different production links of the Mijiu production plants,including work places,appliances,personnel hands and work clothes all were sampled for microbial detection,ultimately the source was found that gas-producing bacteria came from Jiuyao.All three kinds of gas bacteria were identified as yeast,which plays a key role in the production of Mijiu.Therefore,when taking control measures for gas bacteria,the key to prevent the secondary pollution of gas-producing microorganisms is ensuring that the gas-producing microorganisms do not appear in the production environment after sterilization.The proposed control scheme is as follows: redesigning the factory with Auto CAD software,including rebuilding a separate koji mixing chamber,and adding the partition between the pressing room and the sterilization room.It can effectively reduce the air ventilation and control the range of microbial activity.In addition,in the clean production area of the factory,40 W UV lamps are equipped every 10 ~15 square meters,and the average distance between the installation height and the irradiation surface is less than or equal to 2 meters.Imposing strict hygiene requirements to the factory production environment and personnel operation makes the average total number of bacterial colonies and the total number of yeast in the sterilized production environment(ultra-high temperature instantaneous sterilization machine mouth,employees’ hands in canning area and employees’ work clothes)from 1.0×106CFU / m L and 2.9×105CFU / m L of the first sample respectively,down to 2.1×103CFU/ m L and 4.8×102CFU / m L of the improved sample respectively.The contamination of gas-producing microorganism was effectively controlled.