Electrophoretic and HPLC methods for comparative study of the protein fractions of malts, worts and beers produced from Scarlett and Prestige barley ( Hordeum vulgare L.) varieties

Abstract

Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC) methods were used for studying the protein fractions (hordeins; albumins and other soluble proteins) of Scarlett and Prestige barley malts and to follow changes of the protein profile of worts and beers from these two malt varieties. Similar industrial brewing conditions were applied for both varieties. Statistical analyses of RP-HPLC data showed that hordeins were exposed to a proteolytic process during germination, which reduced its content and originated less hydrophobic peptides. In contrast, albumins and other soluble proteins increased during the germination process. Some malt water-soluble proteins result from the hordein proteolysis. Quantitative differences were observed between the protein fractions of the two malt varieties. SDS-PAGE patterns indicate that most of the components present in the worts were also detectable in final beers. However, chemometric analysis of the HPLC data showed quantitative differences between Scarlett and Prestige worts quantitative protein profiles. Scarlett wort contained more protein than Prestige worts. However, final beer samples presented a quantitative protein profile more similar than the respective worts. The optimized methodologies can be successfully used to compare the protein fractions of malts produced from two barley varieties, to follow the evolution of protein fraction during germination and the evolution of protein fraction content of worts and beers.