Oxidative and proteolytic enzyme preparations as promising improvers for oat bread formulations: Rheological, biochemical and microstructural background

Commercial preparations of laccase (LAC) and glucose oxidase (GO) (0.01% and 0.1% addition levels), as well as of a protease (PR) (0.001% and 0.01% addition levels) were tested for their impact on the breadmaking performance of gluten-free oat flour. LAC 0.1%, PR 0.001% and PR 0.01% additions significantly improved oat bread quality, as they increased specific volume and decreased crumb hardness and chewiness. In contrast, GO 0.1% addition revealed detrimental effects, as it resulted in the hardest bread crumb. The improved breadmaking performances of oat breads with LAC and PR addition was explained by the increase in batter softness, deformability and elasticity which were achieved upon addition of these enzyme preparations, both containing discernible levels of endo-β-glucanase side activity. With LAC, the effect is due to prevalence of β-glucan depolymerisation over protein polymerisation while, with PR, it is due to the combined effect of protein and β-glucan degradation. Extensive protein hydrolysis during baking may have increased functionality of the soluble protein fraction. In contrast, extensive protein polymerisation was detrimental, as indicated by GO addition.