The mechanism of low-level pressure coupled with heat treatment on water migration and gel properties of Nemipterus virgatus surimi

Abstract

The effects of high-pressure processing (HPP) at different levels (0.1–600 MPa) and pressure coupled with two-stage heat treatment on the gel properties and water migration of Nemipterus virgatus surimi were studied. The gel prepared by HPP at 100 or 200 MPa for 15 min, followed by a two-stage heating, namely 100 P H and 200 P H respectively, showed the improved the gel strength, water-holding capacity (WHC) and whiteness (P < 0.05). The gel strength of the 100 P H sample was higher than that of the two-stage heated gel sample and the optimal HPP sample (300 MPa/15 min), increased by 124.14% and 131.43%, respectively. Under 100 MPa, HPP induced increased β-sheet and the exposure of reactive sulfhydryl groups, while the endogenous transglutaminase (TGase) of surimi maintained high activity. The subsequent heat treatment promoted the cross-linking induced by the endogenous TGase, the formation of protein-protein disulfide bonds and hydrophobic-hydrophobic interactions, forming a dense three-dimensional network. In addition, the enhanced interaction of protein-water restricted the migration of immobile water to free water. These ultimately rendered better gel properties. However, excessively high levels of pressures (300–600 MPa) coupled with heat treatment resulted in disordered gel structure, causing less immobile water with higher free water, leading to weak gels.