A STUDY OF BARLEY PROTEIN COMPOSITION DURING BEER BREWING PROCESS USING SE-HPLC

The aims of this project were to examine how proteins in barley are degraded during the beer brewing process and if the protein content in the final beer product differ if the barley is sown in different locations and with different amount of nitrogen in fertilization. The proteins extractability was also followed through the beer brewing process. The beers were brewed in a pilot brewery and were analyzed with SE-HPLC. Certain beer proteins have been shown to influence the beer foam and haze formation and since consumers rely much on their visual impression it is important for the breweries that the beer has a stable foam and no haze formation. Two albumins in beer have been associated with beer foam formation; protein Z and lipid transfer protein 1 (LTP1), while it is proline-rich proteins which has been shown to influence the beer haze formation. The results showed that all the polymeric proteins were degraded into monomeric proteins during the brewing process; in the final beer product 70 % of the proteins were small monomeric proteins and the rest was large monomeric proteins. The unextractable proteins were transformed extractable to some extent during malting and mashing and the unextractable proteins left in the wort after mashing were removed during lautering. The most of the proteins were degraded into small monomeric proteins somewhere after the protein rest during mashing and before fermentation. Different location and amount of nitrogen added to the soil resulted in a significant difference, both in total protein content and protein composition in the final beer product. Since it could not be shown which specific proteins that differed, further research is required before any conclusions can be drawn about how the parameters influence the beer quality