Research on the physicochemical and digestive properties of Pleurotus eryngii protein

The physicochemical and digestive properties of Pleurotus eryngiiprotein and the effects of heat treatment and ultrasound treatment on the properties were investigated. The physicochemical property results showed that the shear stress and viscosity increased as the protein concentration increased from 3 to 9 g/100 g raw materials and decreased as the temperature increased from 25°C to 45°C. The pH value from 2.0 to 7.0 significantly affected the state of protein because of the change of the disulfide bond and sulfhydryl bond content. The protein might be held closer with higher sulfhydryl bond at pH 7.0 and be less coacervation with higher disulfide bonds at pH 3.5. The addition of calcium from 0.01 to 0.05 mol/L into the protein system could increase the rheology property of the protein. Based on the results of Fourier-transform infrared spectroscopy, the content of α-helix increased after heat treatment and ultrasound treatment, while the content of β-sheet decreased, indicating the change of spatial conformation of protein. The result of differential scanning calorimetry of protein manifested that ultrasound treatment significantly enhanced the protein thermal stability (P < 0.05). The digestive property results indicated that heat treatment and ultrasound treatment increased the available amino groups (DH) and vitro digestibility of protein digestive juice and reduced the content of peptides. There were more kinds of amino acids of protein digestion with ultrasound treatment than non-treatment and heat treatment. In addition, the protein after ultrasound treatment exhibited excellent antioxidant properties in in vitro digestion.