Effect of fibers from bracts of maize (Zea mays) as natural additives in wheat bread-making: a technological approach

Bracts of maize ( Zea mays , L.), a large agro-industrial residue and a source of functional biopolymers, were evaluated as a source of additives in bread-making. After drying and milling, the dried powder obtained ( BP ), its alcohol insoluble residue ( AIR : ~70% yield on BP ; composed by 26% arabinoxylans, 26% cellulose, 7% lignin, 5.5% pectins), and the ferulate-crosslinked arabinoxylans ( AX-OH ) isolated by 4%-KOH treatment from AIR , were evaluated. Bread loaves were made by replacing the wheat flour in 1.5% (w/w) by each fraction, applying two elaboration methodologies: required and constant hydration. Doughs’ thermomechanical behavior during kneading showed that the rheological properties and water availability were affected within both methodologies of bread making. The major effect was noted in the formulation with the fiber enriched in arabinoxylans ( AX-OH ) when added at required hydration. The hydration percentage tended to increase with the enrichment in arabinoxylans, varying from 58.7% in the dough made without wheat flour replacement, to 62% in AX-OH dough, with the highest content of hemicellulose. Dough stability and protein weakening were the most influenced parameters, mainly owing to AX-OH fibers, suggesting that they interfered the water distribution and hence the gluten network formation. As expected, fibers’ addition decreased the specific volume of bread, while firmness analysis showed that all maize fibers also delayed bread aging at required hydration, probably by hindering the diffusion of water and, hence, leading to starch retrogradation delay. Fibers from maize bracts can be a source of biopolymers useful as natural additives in bakery products.