A Rapid Detection Of Spoilages In Top-fermented Wheat Beers

In this paper, a rapid detection of spoilages in top-fermented wheat beer wasstudied. Firstly, the characteristics of bacteria contamination in top-fermented wheatbeer were described. The wheat beer-spoilage bacteria were classified. And thedistribution of the harmful bacteria was determined. Then the reason thattop-fermented wheat beer was more susceptible to be contaminated was researched.Secondly, beer spoilage bacteria were detected using traditional selective medium.Samples were from pilot-scale brewing tests of2tons in China–Germany brewingtechnical center of Shandong Polytechnic University, including yeast, wort, fermentedbeer and finished beer. NBB medium was used to detect anaerobic bacteria, and E. coliwas determined by ox bile medium.In order to improve the sensitivity and stability of PCR detection, a enrichedmedium of top-fermented wheat beer was optimized. Response surface methodologywas used to optimize the component of CNFF-A medium. Sodium acetate, honey andfolic acid were chosen as influencing factors, and the number of lactic acid bacteriacolonies was response. The optimum component of CNFF-A medium was as follows:Peptone10.0g/L, honey1.12g/L, beef extract7.0g/L, yeast extract5.0g/L, arginine1.0g/L, folic acid3.87g/L and sodium acetate2.85g/L. The largest number of lacticacid bacteria colonies (72.43/0.1mL) was achieved under this optimal condition.Finally, PCR method was used for rapid detection of lactic acid bacteria oftop-fermented wheat beer. This detection was based on the universal primers of thepartial sequences of16S rDNA. Comparing the obtained sequences, lactic acid bacteriaSK007were confirmed. The result showed that PCR method was more rapid andsensitive than traditional detection method.