Lutein fortification of wheat bread with marigold powder: Impact on rheology, water dynamics, and structure.

Abstract

Demands for foods conducive to eye health have been on the increase in the global healthcare sector. Marigold powder as a major source of lutein was utilized to produce lutein-fortified breads for ocular health. The physicochemical characteristics of the doughs and breads were investigated in terms of rheology, water mobility, and protein secondary structures. The incorporation of marigold powder decreased the water absorption of doughs without significantly altering thermo-mechanical properties. With a range of fortification levels (1 ~ 3%), marigold powder led to decreased storage and loss modulus of doughs by weakening their gluten network, which was supported by their T2 relaxation times. The resistances of the doughs weakened with increasing levels of marigold powder, while their extensibilities significantly incremented. FTIR spectral deconvolution revealed the changes of wheat protein structures upon marigold powder incorporation, in which the proportion of β-turn increased at the expense of β-sheet ratio. The breads with marigold powder displayed increased specific volume from 4.034 to 4.368 mL/g, accompanied by softer textures. The baking process led to heat-induced losses in lutein concentration of less than 10% within the crumbs and approximately 30% in the crusts. The use of marigold powder induced changes in protein secondary structure and extensional features of doughs, contributing to increased loaf volume and softer texture. Overall, this study provides fundamental information about the rheological and structural effects of marigold powder in a wheat bread system, consequently encouraging the food industry to utilize marigold power as a functional food ingredient. This article is protected by copyright. All rights reserved.