Isolation, purification and structural characterization of wheat-derived beer protein

Wheat beer is known for its rich and long-lasting foam, which is largely attributed to the proteins derived from wheat. In this study, a wheat-derived protein was isolated and purified from pure wheat malt wort based on foam properties and structurally characterized. The molecular weight of this protein is 15 kDa and its foaming and foam stability were 64.11 ± 1.02 % and 64.18 ± 1.50 %, respectively. This protein has the highest match with the wheat α-amylase inhibitor protein, with 9 matched peptides scoring above the threshold and the protein cover was 96.8 %. The protein is a predominantly β-folded, less crystalline protein with a negatively charged surface. It is abundant in glutamic acid and proline, and the hydrophobic amino acids account for 49.26 % of the total amino acid content. Scanning electron microscopy showed that the protein has a lamellar structure with a tiny number of small spherical particles adhering to the surface and irregular textures and depressions on the surface. The study of functional proteins of wheat-derived can help to control the degree of degradation of wheat beer during the saccharification process.