High-moisture extrusion processing of walnut meal waste: Mechanism of fibrous formation and enhancement of characteristics

The formation mechanism of fibrosis in walnut meal protein (WMP) was investigated using high-moisture extrusion technology, and also explored the improved texture and color properties of the extruded product by mixing with soybean protein isolate (SPI) and wheat gluten (WG) in various proportions. The results indicated that significant changes occurred in the protein molecules during the extrusion process, and the die and cooling zone outside the barrel were the key regions for the development of fibrosis in WMP extrudate. The hydrogen bonds and disulfide bonds interactions were essential in maintaining the extrudate fibrous structure, with the protein secondary structure being β-turn > β-sheet > α-helix > random coil. High-water extrusion enhanced the free amino acid content of WMP. When the ratio of WMP, SPI, and WG was set at 8:1:1, the texturization degree of the excluded compound proteins was 1.92, and the texture of the extruded WMP complex was comparable to that of chicken breast. This work provides a basis for the comprehensive utilization of walnut by-products and contributes to the enrichment of resources in plant protein-based products.