A Novel Method for the Preparation of Template DNA for PCR from Beer to Detect Materials and to Develop DNA Markers to Evaluate the Quality of Beer

We developed a method for the preparation of template DNAs for polymerase chain reaction (PCR) from beer. We improved the method by (i) lyophilizing and pulverizing the beer to concentrate DNAs, (ii) decomposition of polysaccharides and proteins so as not to inhibit DNA extraction by the use of heat-resistant amylase and proteinase K, (iii) separation of template DNA by purification using 70% EtOH extraction and isopropyl alcohol precipitation, and (iv) the use of magnetic beads to purify DNA. We developed suitable 7 STS (sequence-tagged site) primers related to beer quality for PCR, and it proved possible to identify 16 dominant malting barley cultivars and 22 kinds of beers. To digitize the results of PCR, discriminative DNA bands were binarized as 0 (disappeared) or 1 (appeared) and subjected to multiple regression analysis. Estimation formulae for the quality of beer were developed using the above-mentioned independent variables based on the results of PCR against dependent variables related to the qualities of beer, including foam stability, bitterness, sourness and astringency. These equations showed multiple regression coefficients of 0.93, 0.82, 0.87, and 0.87 for calibration.