Effects of different emulsion gels and extrusion temperature on structural properties of meat substitutes processed by high-moisture extrusion of soybean protein

In order to develop a new type of plant-based meat substitute, and investigate the effects of different emulsion gels on improving the structural characteristics and quality of plant-based meat substitutes, this study investigates the structural properties of meat substitutes produced via high-moisture extrusion using soybean protein (SP) and three types of emulsion gels: polysaccharide-based (PB), protein–polysaccharide composite-based (PPCB), and gelled double emulsion-based (GDEB) gels. The effects of processing temperature (130–170°C) and soybean protein/emulsion gel (50%:50%, 45%:55%, 40%:60%) on protein aggregation were evaluated. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) revealed that SP:GDEB formulations exhibited the most compact and stable protein networks, particularly at a 45%:55% ratio, whereas SP:PB showed network fragmentation at high temperatures. Fourier transform infrared spectroscopy (FTIR) analysis indicated that SP:GDEB provided the highest thermal stability under different processing temperatures and emulsion gel concentrations, the integral intensity of the amide I band did not change significantly. Fluorescence spectroscopy demonstrated that SP:GDEB maintained stable tertiary protein structures across all temperatures, with little fluctuation in fluorescence intensity, whereas SP:PB and SP:PPCB were more susceptible to temperature fluctuations. Protein solubility analysis showed that SP:PB had the highest solubility, while SP:GDEB exhibited the lowest due to extensive hydrophobic interactions. Disulfide bond formation increased with temperature in SP:PB and SP:PPCB. However, SP:GDEB retained a higher sulfhydryl content, indicating superior thermal resistance. Degree of texturization studies revealed that SP:PB achieved optimal texturization at 140–150°C, whereas SP:GDEB maintained stable texturization across a broader temperature range.