title: Mutation analysis of barley malt protein Z4 and protein Z7 on beer foam stability.
abstract: Beer foam stability is an important characteristic. It has been suggested that isoforms of protein Z, that is, protein Z4 and protein Z7, contribute to beer foam stability. We investigated the relationship between beer foam stability and protein Z4 and protein Z7 using their deficient mutants. As a protein Z4-deficient mutant, cv. Pirkka was used. Protein Z7 deficiency was screened in 1564 barley accessions in the world collection of Okayama University, Japan. The barley samples from normal, protein Z4-deficient, protein Z7-deficient, and double-deficient were genotyped in F(2) populations and then pooled based on the DNA marker genotypes of protein Z4 and protein Z7. For a brewing trial, F(5) pooled subpopulations were used. After malting and brewing, the foam stability was determined, and the results showed that the levels of foam stability in the four samples were comparable. Two-dimensional gel electrophoresis was used to investigate the proteome in these beer samples. The results showed that low molecular weight proteins, including lipid transfer protein (LTP2), in the deficient mutants were higher than those in the normal sample. Our results suggest that the contribution of protein Z4 and protein Z7 to beer foam stability was not greater than that of other beer proteins.
authors.affiliation: Bioresources Research and Development Department, Sapporo Breweries Ltd., 37-1, Nittakizaki, Ota, Gunma 370-0393, Japan. takashi.iimure@sapporobeer.co.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Iimure
authors.forename: Tatsuji
authors.initials: T
authors.lastname: Kimura
authors.forename: Shigeki
authors.initials: S
authors.lastname: Araki
authors.forename: Makoto
authors.initials: M
authors.lastname: Kihara
authors.forename: Masahide
authors.initials: M
authors.lastname: Sato
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamada
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Shigyou
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sato
mesh_terms: D001515:Beer / Q000032:analysis*; D005511:Food Handling / Q000379:methods; D001467:Hordeum / Q000737:chemistry*; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D012639:Seeds / Q000737:chemistry; D015842:Serine Proteinase Inhibitors / Q000235:genetics* / Q000502:physiology
chemical_list: D010940:Plant Proteins; D015842:Serine Proteinase Inhibitors