Glycosyltransferases improve breadmaking quality by altering multiscale structure in gluten-free bread

Abstract

In gluten-free bread (GFB), starch and its interplay with structural agents were vital for product quality due to the absence of gluten. During breadmaking, amylolytic enzymes modified starch in situ , and their reaction modes determined starch structure and hence how interactions occurred. Herein, based on the matrices of rice protein and hydroxypropyl methylcellulose (HPMC), α-amylase and multifunctional enzymes of glucan branching enzyme (GBE) and cyclodextrin glycosyltransferases (CGTase) were adopted, aiming to understand the mechanism of these enzymes on breadmaking quality of fresh bread from the multiscale structure of GFB. Results demonstrated that all enzymes, especially CGTase and GBE, markedly increased GFB specific volume to 107%–134% of Control. Compared with α-amylase, CGTase and GBE more depended on the structural changes rather than fermentation to improve GFB volume. Considering the texture, CGTase and GBE reduced crumb stickiness and still maintained a relatively softness and springiness crumb, while α-amylase induced a stick and less elastic crumb. Starch molecular changes enhanced the entanglement of starch and HPMC to form extended and bold fibril bundles and finally improved strength and pore size of gel network structure. Moreover, the starch structure modifications and specific enzymatic products of CGTase and GBE altered the microstructure and thus facilitated the even distribution of rice protein, which further improved GFB texture properties. Amylolytic enzymes, that acted both hydrolysis and glycosyl transfer, moderately hydrolyzed starch and generated specific enzymatic products, were more suitable to enhance GFB structure and eliminate the weak crumb texture. • α-amylase (α-Amy) and glycosyltransferases (GTases) were included. • Breadmaking quality of gluten-free bread (GFB) with α-Amy and GTases was compared. • GFB with GTases performed better in crumb structure and texture. • GTases depended more on structure rather than gas to improve volume. • Interactions of enzymatic starch and structural agents was crucial for GFB quality.