INVESTIGATION OF HORDEINS DURING BREWING AND THEIR INFLUENCE ON BEER HAZE BY PROTEOME ANALYSIS

Abstract

ABSTRACT Colloidal storage haze is one of the principal indicators of beer quality. In this study, the changes of malt hordeins during the brewing process and the roles of malt hordeins in the formation of beer haze were investigated using two-dimensional electrophoresis (2-DE). It was found that most of malt hordeins disappeared during the brewing process and only the few faint hordein spots (about eight spots) were detected in beer haze. Moreover, these spots were found in wort protein and beer haze protein. The complex 2-DE patterns of malt hordein, wort and beer haze displayed a relationship with some chemical modifications during the brewing. These spots were analyzed and identified as B and γ3 hordein and storage protein (Hordeum vulgare) by mass spectrometry. Our results suggested that hordein might be minor haze-active proteins in beer but was a critical factor in the formation of beer haze. PRACTICAL APPLICATION The formation of haze is a serious quality problem that limits the storage life of beer products, an issue that has become increasingly important to brewers. It is conventionally accepted that proline-rich hordeins play a major role in the formation of haze. In this study, it was found that most of the hordeins disappeared and that small amounts of B hordein and γ3 hordein from the malt in beer haze were detected by proteomics analysis. Moreover, this study demonstrated that hordeins in beer were not a key contributor to beer haze formation. To our knowledge, to date, this result in the existing literature of similar studies has not been reported. This study laid the theoretical foundation for further investigations to determine the mechanism of the formation of beer haze. An improved understanding of the impact of brewing on hordeins could potentially provide further scope for optimizing beer quality.