An explanation for the combined effect of xylanase-glucose oxidase in dough systems

In the bakery industry, glucose oxidase is usually used in combination with xylanase. Although many theories exist on the mechanism of action of each enzyme, the positive effect of combining the two is as yet unexplained. In this paper we studied a possible basis for this synergy by focusing on the involvement of arabinoxylans. Water-extractable arabinoxylans and water-unextractable solids were studied in dough with or without glucose oxidase. Addition of glucose oxidase led to a stiffer and less extensible dough. Addition of arabinoxylans caused a further decrease in dough extensibility. Addition of xylanase could correct for this decrease. The role of arabinoxylans was further investigated by studying modified water-extractable arabinoxylans and the effect of agents affecting arabinoxylan crosslinking (ferulic acid). Water-extractable arabinoxylan was modified with xylanase to generate a low-molecular-weight fraction (WEAX(XYL)). Alternatively, it was modified with NaOH to prepare a fraction with a decreased ferulic acid content (WEAX(OH)). Addition of modified arabinoxylans diminished the effect of glucose oxidase. Glutenin macropolymer and water-extractable arabinoxylan viscosity experiments were performed to obtain further detail on the role of arabinoxylans (AX). These results give rise to a new theory explaining the contribution of xylanase in its synergy with glucose oxidase. In this theory glucose oxidase not only catalyses the formation of protein disulfide bonds, but also of AX-AX crosslinks. The latter negatively affect bread quality. Xylanase corrects for this latter effect by cleaving arabinoxylan complexes and generating small ferulic acid-containing arabinoxylan fragments interfering with the crosslinking of high-molecular weight arabinoxylans.