Effects of extrusion parameters on the structure of soybean meal proteins

The relations between structure of soybean meal protein and extrusion parameters including the moisture of material, expanding temperature, the die length, the length of section δ and the rotate speed of screw were studied. The protein structure has been characterized independently by free sulfhydryl groups content and surface hydrophobicity. A mathematical model was developed to quantitatively analyze the free sulfhydryl groups content of soy meals protein at different extrusion conditions. Results show that the lower moisture of meals, the lower expanding temperature and the shorter die length have greater benefit for soy meals protein with increasing conformational stability. On the contrary, meal proteins that have higher amount of exposed hydrophobic surfaces and disulfide cross-links are more susceptible under the conditions of high temperature and high moisture. Furthermore, compared with the traditional processing of solvent extraction pre-treatments, it is benefit for the structural stability of soybean meal protein based on the development processing of extruding-expelling pre-treatment.