Understanding the influence of the arabinoxylan-rich psyllium (Plantago ovata) husk on dough elasticity and bread staling: Interplay between biopolymer and water dynamics

Abstract

Bread staling is a complex phenomenon in which multiple interconnected mechanisms involving water operate, including the formation of amylopectin crystallites sequestering water, crumb-to-crust moisture migration, and the escalating immobilization of water reducing gluten plasticization. Considering the pivotal role of water-gluten-starch interactions, the integration of the highly-soluble, water-avid, arabinoxylan-rich psyllium husk (PSY) into a wheat dough/bread system was explored, to understand the impact of PSY on the water and biopolymer dynamics that could lead to lower staling. With the addition of PSY, optimal dough development required more water (from 68.0 to 119.5 % in control and 10 % wheat flour replacement with PSY, respectively). LF-NMR showed a parallel increase in the proton population attributed to free water entrapped by the continuous network of biopolymers surrounding granular starch (A23), and its relaxation time (T23). PSY resulted in freshly baked bread with similar specific volume, porosity and starch gelatinization than the control, but with a much higher proportion of intergranular free water (A23). Importantly, PSY did not affect amylopectin retrogradation nor shortened the relaxation time of water protons in exchange with gluten, suggesting that PSY did not withdraw plasticizing water from starch or gluten, respectively. During storage, PSY resulted in a dose-dependent delay of both crumb hardening (correlated to T23, r = −0.76, p < 0.05) and loss of cohesiveness (correlated to T23, r = 0.71, p < 0.05 and A23, r = 0.74, p < 0.05). PSY also resulted in greater crumb resilience, which was related to the self-assembly of PSY molecules and its impact on dough elasticity (with up to two-fold increase in recovery strain).