title: The influence of barley malt protein modification on beer foam stability and their relationship to the barley dimeric alpha-amylase inhibitor-I (BDAI-I) as a possible foam-promoting protein.
abstract: The foam stability of beer is one of the important key factors in evaluating the quality of beer. The purpose of this study was to investigate the relationship between the level of malt modification (degradation of protein, starch, and so on) and the beer foam stability. This was achieved by examining foam-promoting proteins using two-dimensional gel electrophoresis (2DE). We found that the foam stability of beer samples brewed from the barley malts of cultivars B and C decreased as the level of malt modification increased; however, the foam stability of cultivar A did not change. To identify the property providing the increased foam stability of cultivar A, we analyzed beer proteins using 2DE. We analyzed three fractions that could contain beer foam-promoting proteins, namely, beer whole proteins, salt-precipitated proteins, and the proteins concentrated from beer foam. As a result, we found that in cultivar A, some protein spots did not change in any of these three protein fractions even when the level of malt modification increased, although the corresponding protein spots in cultivars B and C decreased. We analyzed these protein spots by peptide mass finger printing using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. As a result, all of these spots were identified as barley dimeric alpha-amylase inhibitor-I (BDAI-I). These results suggest that BDAI-I is an important contributor to beer foam stability.
authors.affiliation: Bioresources Research and Development Department, Sapporo Breweries Ltd., 37-1, Nittakizaki, Ota, Gunma 370-0393, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okada
authors.forename: Takashi
authors.initials: T
authors.lastname: Iimure
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takoi
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kaneko
authors.forename: Makoto
authors.initials: M
authors.lastname: Kihara
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Hayashi
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Ito
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sato
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Takeda
mesh_terms: D001515:Beer / Q000032:analysis / Q000592:standards*; D015180:Electrophoresis, Gel, Two-Dimensional; D001467:Hordeum / Q000737:chemistry / Q000235:genetics; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry*; D011489:Protein Denaturation; D013045:Species Specificity; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
chemical_list: D010940:Plant Proteins; D000516:alpha-Amylases