title: Characterization of barley serpin Z7 that plays multiple roles in malt and beer.
abstract: Barley protein Z7 (BSZ7) is a well-known serine protease inhibitor that was regarded as a major effector of beer foam stability. Moreover, it has also been suggested to participate in haze formation and affect wort filterability. The present study purified BSZ7 from barley malt and characterized its secondary structure and modification, as well as its relationship with peroxidase, to elucidate the molecular base of BSZ7 that supports its multiple roles in malt and beer. It was found that after 30 min of heating, the secondary structure was not affected. BSZ7 has no inhibiting effect on nonspecific protease originated from malt, suggesting its negative role in wort filterability was accomplished by other means. Furthermore, the glycation of BSZ7 by the Maillard reaction may make some contribution to its survival during wort boiling. The interaction of BSZ7 with polysaccharides and polyphenols found by adding experiment may explain how it acts as a negative factor on wort filterability. Greater understanding of BSZ7 and other proteins of malts will lead to better improvements in brewing quality.
authors.affiliation: The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University , 1800 Lihu Road, Wuxi 214122, People's Republic of China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Li
authors.forename: Zhao
authors.initials: Z
authors.lastname: Jin
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.forename: Jian
authors.initials: J
authors.lastname: Lu
authors.forename: Guolin
authors.initials: G
authors.lastname: Cai
authors.forename: Jianjun
authors.initials: J
authors.lastname: Dong
authors.forename: Junhong
authors.initials: J
authors.lastname: Yu
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
mesh_terms: D001515:Beer / Q000032:analysis*; D002942:Circular Dichroism; D005511:Food Handling; D001467:Hordeum / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D015416:Maillard Reaction; D010447:Peptide Hydrolases / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry / Q000302:isolation & purification; D015842:Serine Proteinase Inhibitors / Q000378:metabolism*; D015843:Serpins / Q000378:metabolism*
chemical_list: C101795:BSZx protein, Hordeum vulgare; D010940:Plant Proteins; D011108:Polymers; D015842:Serine Proteinase Inhibitors; D015843:Serpins; C011908:melanoidin polymers; D010447:Peptide Hydrolases