Transformation of high moisture extrusion on pea protein isolate in melting zone during: From the aspects of the rheological property, physicochemical attributes and modification mechanism

Abstract

Plant-based meat analogs are emerging products mainly produced by extruder. To reveal the “black box” processing mechanism of extrusion, the physicochemical and rheological properties of pea protein isolate (PPI) were evaluated at different extrusion temperatures (90 °C, 100 °C, 110 °C, 120 °C and 130 °C) and moisture contents (65% and 70%) by using rheological simulation and stop-operation. The results showed a gel-like PPI paste, which presented shear thinning gel-like behavior and strong elastic characteristics. The weaken strain overshoot behavior of the PPI paste transformed to a strong strain overshoot with temperature increased under large amplitude oscillation. The PPI molecules transformed from a spherical structure to a tangled fibrous network, the absolute zeta potential value increased, and the total SH decreased. The native-like secondary structures of PPI were lost, and the relatively rigid protein structure was broken with increasing temperature. The tertiary structure of the raw material is gradually lost, and the Trp residue is transferred from the spherical structure interior to the surface of the protein molecule. The protein subunits were not decomposed during the extrusion process, and although the thermal stability of the PPI was reduced, new cross-links of higher bond energy could be formed at higher temperatures. Moreover, a higher extrusion temperature and proper moisture content can result in partial unfolding and realignment of extruded PPI.