High-moisture extrusion is a hot frontier technology for developing novel plant-based meat analogues with meat-like texture. In this study, a soy protein isolate (SPI)-Nemipterus virgatus surimi blend at a ratio of 80:20 (m/m) was used to investigate the effect of hydrothermal parameter combinations (moisture content 65%, 70% and 75%; extrusion temperature 125, 135 and 145 ℃ ) on the specific mechanical energy (SME) and die pressure during the high-moisture extrusion process and the quality of extrudates. Results showed that under the conditions used in this study, the surimi gel was filled as particles in the SPI-surimi mixed gel structure, which could affect the formation of the oriented gel structure. Simultaneously increasing extrusion temperature and moisture content decreased SME from 783.40 to 410.96 kJ/kg and die pressure from 7.79 to 1.60 MPa (P < 0.05). The quality of SPI-surimi mixed extrudates was affected markedly by hydrothermal parameter combinations and the effect of moisture content was more significant than that of extrusion temperature. At a moisture content of 70% and an extrusion temperature of 145 ℃ , the fiber-like structure of SPI-surimi mixed extrudates reached its maximum (2.36). Under the hydrothermal parameter combination, the SME and die pressure were nonlinearly correlated with the hardness, chewiness, gel strength, water-holding capacity and shear force of SPI-surimi mixed extrudates. This study provides a reference for the development of novel alternative protein products combining animal and plant proteins which can complement each other with their advantages.

Restructuring of plant proteins by extrusion can form plant-based meat products with similar quality characteristics to animal meat. As a beneficial complement to animal meat, plant-based meat products are of great significance to realize high-value utilization of proteins and guarantee efficient supply. However, the current plant-based meat products still have some prominent problems such as insufficient elasticity, loose structure and poor juiciness, and are mostly used in the form of minced meat in meatballs, meat patties, dumplings and other meat products, which cannot fully meet the demands of Chinese consumers yet. Enzymatic modification technology, which is safe, efficient, green and useful to modify protein structure and improve product texture and flavor, has been widely used in the research and development of meat products, and is also promising for application to plant-based meat products. This paper summarizes the differences in chemical structure and functional properties between animal and plant proteins, analyzes the mechanism and application in meat products of enzymatic modification of protein structure, and reviews the latest progress in the application of enzymatic modification combined with extrusion to plant-based meat products. We anticipate that this review will provide a reference for the development and quality improvement of new plant-based meat products in China.

Peanut protein is one type of plant protein with high nutritional value. However, it is still lacking in the high-value-added products of peanut protein. Extrusion processing can be expected to produce the peanut protein, due to the easy operation, safety, green environment, and continuous output. The puffed products of peanut protein have been produced to enhance its added value using extrusion. Nevertheless, the application of peanut protein has been confined to the low expansion effect and quality properties (texture and rehydration properties). This study aims to investigate the effects of starches on the expansion structure and quality properties of peanut protein during extrusion. Taking the peanut protein as a research object, the starches were also selected for the varying thermal and gelatinization properties. Some property parameters were measured, including the texture, color, rehydration, and rheological properties of peanut protein extrudates. In addition, a systematic analysis was then performed on the starch structure (short-range ordered and long-range ordered structure) and protein structure (protein secondary structure, sulfhydryl group content, and disulfide bond content) during extrusion. The results showed that there was a significant decrease in the parameter values of starch-protein extrudates (P<0.05). Particularly, the ΔE and b values significantly increased (P<0.05). The expansion structure, texture, and rehydration properties of peanut protein extrudates were closely related to the amylose content and thermal properties of the starch. Pea starch had a lower enthalpy (1.83 J/g), a higher amylose content (31.10%), and a lower gelatinization peak temperature (67.88 °C). Peanut protein extrudates were then formed on the porous expansion structure with high texture properties. For example, pea starch significantly increased the expansion ratio of peanut protein extrudates to 2.44, while reducing the density and hardness to 0.28 g/cm³ and 19.18 N, respectively (P<0.05). At the same time, the water-holding capacity of pea starch- peanut protein extrudate (PASE) reached the highest in the experiment group (6.05 g/g), indicating that the pea starch significantly improved the rehydration properties of peanut protein extrudates (P<0.05). In addition, the interaction between pea starch and peanut protein promoted the transformation of protein secondary structure from the order to the disorder, where the short-range ordered and crystal structure of starch was destroyed during production. The conversion of sulfhydryl groups to disulfide bonds increased the degree of protein cross-linking. Pea starch was used to raise the viscosity and elasticity of the extrudates, whereas decreased the fluidity, according to rheological investigation. Therefore, the pea starch can effectively improve the expansion and quality properties of peanut protein extrudates. The finding can provide scientific and technological support to the expansion and quality properties of the peanut protein application in extruded food.