Aggregation mechanism of soybean protein isolate for the formation of plant protein-based meat analogs during high...

The aggregation behavior and interaction mechanisms modulating the fibrous structure of plant protein-based meat analogs during high-moisture extrusion (HME) of soybean isolate protein (SPI) are critical, but limited research. Therefore, soy protein isolate (SPI)-based plant-based meat analogs were collected and analyzed at each zone of a twin-screw extruder under a moisture content of 60 % via the dead-stop operation. The results showed that HME could improve the fibrous structure of SPI extrudates through protein aggregation behavior. Within the extruder barrel, the aggregated state of protein molecules transitioned to a dispersed state, and the relative crystallinity decreased from 13.96 % to 8.55 %. Additionally, the thermal stability, as reflected by the denaturation enthalpy, decreased from 175.8 J/g to 150.5 J/g. At the die zone, SPI molecular chains initiate reorganization, with the degree of aggregation enhanced through hydrogen bonding, hydrophobic interactions, and disulfide bonding, which further promoted the formation of a distinct three-dimensional structure. In addition, the β-sheet structure was converted into α-helix, β-turn, and random coil structures, with the random coil content significantly increasing from 14.41 % to 19.48 %. Meanwhile, protein chains became intertwined, and lamellar and fibrous structures emerged owing to the more flexible molecular conformation. For the final extrudate, the turbidity slightly increased from 4.38 TU to 4.39 TU, which was attributed to the formation of stable protein molecular chain assemblies. These results provide a theoretical basis for the production and quality enhancement of high-quality plant-based meat alternatives.