Research on the Effect of Non-Thermal Plasma on the Sterilization of Craft Beer

Abstract

The craft beer was continuously sterilized by the non-thermal plasma reactor, and its sterilization and quality were evaluated. The total count of aerobic plate, yeast and Escherichia coli were used as microbial indexes, the effects of plasma sterilization and pasteurization on the bactericidal effect of craft beer were studied. Meanwhile, the beer color, foam hold and pH were evaluated to obtain the optimum sterilization condition with the response surface. The results showed that, compared with pasteurization, the sterilization rate after plasma treatment was almost the same, but the chroma, brightness and bubble retention were better, which was closer to the original beer. The total number of colonies and Escherichia coli were almost completely killed, and the number of yeast was reduced by 97.5% with the 40 kV plasma treatment voltage, 10 s and 60 mL/min gas flow rate. According to the analysis of Design Expert software, the sterilization effect and brightness were the best when the voltage, plasma treatment times and gas flow were 40 kV, 10 s and 60 mL/min, respectively. The predicted values were consistent with the measured values. The influence of each factors were voltage > time > gas flow rate.

Keywords

• plasma
• aerobic plate count
• yeast
• e. coli
• the response surface