Reducing Agents Aid in the Texturization of Pea Protein Isolate During High Moisture Extrusion

One of the leading hypotheses of plant protein texturization during extrusion is the formation of disulfide bonds during the extrusion process. This study aimed to gain a deeper understanding of the role of disulfide bonds during the texturization of plant protein high moisture meat analogs. Pea protein was blended with three reducing agents, sodium metabisulfite, cysteine, and glutathione, at varying levels of inclusion. The blends were extruded using a co-rotating twin-screw extruder at two different temperature settings of 130°C and 150°C. The feed rate (60 g/min), screw speed (100 rpm), and moisture content (60% w.b.) were kept constant. The extrudates were evaluated for polymeric protein size exclusion, disulfide, and thiol bond quantification, integrity index analysis, and anisotropic index. The reducing agents cleaved disulfide bonds and significantly affected the structure, texture, and integrity index of the extrudates. The reducing agents also had varying effects on the extrudate and the flow of the melt, with the best product obtained with 0.05% glutathione inclusion extruded at 150°C. Although the reducing agents had a relatively small impact on the disulfide bonds, they had a major impact on the physical characteristics of the product and the crosslinking of proteins.