In-line salt solution injection as an ionic modulation strategy in high-moisture extursion of plant-based meat alternatives: Effects on fibrous structuring

Plant-based meat alternatives require controllable structuring strategies to replicate meat-like fibrous structures. We hypothesized that adding salt during processing would enhance intermolecular cross-linking among plant proteins and thereby promote the formation of meat-like fibrous networks. Accordingly, we examined how the ionic environment modulates fiber formation during high-moisture extrusion of a pea protein isolate–vital wheat gluten–corn starch blend by replacing process water with sodium chloride (NaCl) or potassium chloride (KCl) solutions (0.4–1.6 %, w/w) delivered in-line to the extruder barrel. We evaluated specific mechanical energy (SME), moisture content, water- and oil-holding capacities (WHC and OHC), macro- and microstructure, cutting forces, degree of texturization, free sulfhydryl (–SH) content, and nitrogen solubility index. Relative to the no-salt control, both salts reduced SME, indicating ionic plasticization and improved melt flow. Moisture content, WHC, and OHC generally declined with increasing salt; at equal mass fractions, NaCl samples retained more water than their KCl counterparts, consistent with higher ionic strength and ion-specific effects. Moderate salt levels maximized fibrous features: 1.2 % NaCl and 0.8 % KCl yielded the highest texturization and the lowest free –SH in their respective series. The reduction in free –SH reflects increased disulfide cross-linking, which tightens and stabilizes the aligned protein network and thereby increases the degree of texturization. Macro- and microstructural images supported dense, well-aligned fibers under these conditions. These results support the existence of an optimal ionic-strength range that balances melt plasticization with interchain bonding and demonstrate that in-line injection of salt solutions is an effective lever to steer fibrous structuring during high-moisture extrusion.