This test allows the quantitative detection of Saccharomyces cerevisiae var. diastaticus which is a variety of the typical top fermenting brewing yeast Saccharomyces cerevisiae. Both are equal in their morphological appearance and only distinguishable by the capability of diastaticus to further break down long chain polysaccharides in finished beer. 

S. cerevisiae var. diastaticus belongs to the superattenuating yeasts and can grow in finished beer, producing carbon dioxide. It is used in sour beer production, but is regarded as a spoiler in conventional beers. It often takes months until spoilage suddenly occurs in finished products. The taste of contaminated beer is sour and often described as a loss of body and dry mouthfeel. The pressure caused by high carbon dioxide production can grow up to causing explosion of packaged units.