Effects of rapeseed protein addition on soybean protein-based textured protein produced by low-moisture extrusion: Changes in physicochemical attributes, structural properties and barrel flow behaviors

This study investigated the potential of rapeseed protein as a novel alternative protein source in meat analogs produced by extrusion cooking technology. To study the substitutability of rapeseed protein to soybean protein, the addition ratios of rapeseed protein to soybean protein in the extrusion experiment were 0:50, 10:40, 20:30, 30:20, 40:10 and 50:0 (w/w), respectively. The results showed that adding 0–20% rapeseed protein not only decreased the specific mechanical energy and mass flow rate of the mixture during extrusion, but also enhanced the hardness and chewiness of the extrudates while reducing their elasticity and resilience. In addition, increasing the amount of rapeseed protein may lead to decreased expansion characteristics, internal pore structure, and water absorption rate of the extrudates, as well as a decrease in brightness and an increase in redness on the surface. Weibull model could well describe the rehydration behavior for dynamic fitting of the extrusion rehydration process. Moreover, with the increase of rapeseed protein substitution, the content of disulfide bonds, and the proportion of relatively ordered protein secondary structures with high stability increased, and the degree of protein denaturation decreased. Besides, the degree of starch gelatinization reduced and the thermal stability of extrudates improved. Interaction analysis indicated that disulfide bonds are the primary force maintaining protein-mediated interactions in the extrudates. The incorporation of rapeseed protein shortened the mean residence time of molten feedstock and shifted the flow state to plug flow. Overall, our investigation suggests that within low levels of addition (≤20%, w/w), rapeseed protein has the potential to partially substitute for the soybean protein-based textured proteins. High substitution levels or complete substitution are not feasible due to the relatively low expansion and rehydration rates.