Effects of air frying on protein digestive properties in scallop (Patinopecten yessoensis) adductor muscles and the mechanisms involved

The effects of air frying at different temperatures (140 °C, 160 °C, 180 °C, and 200 °C) on the simulated digestive properties of proteins in scallop adductor muscle (SAM) and the mechanisms involved were investigated. The results of the simulated gastrointestinal digestion showed that the 160 °C-treated SAM group had significantly higher protein digestibility than the fresh SAM group, which was reflected in higher degree of hydrolysis, more low molecular weight (<0.5 kDa) protein digestion products, and less insoluble residues, while the 140 °C-, 180 °C- and 200 °C-treated SAM groups all had opposite results. Moreover, air frying altered the solubility, secondary structure percentage and surface hydrophobicity of SAM proteins, as well as the microstructure of insoluble residues in simulated gastric juice. Correlation analysis showed that the protein digestive level of the air fried SAMs was positively correlated with the ratio of soluble proteins before digestion and the surface hydrophobicity of insoluble residues, but negatively correlated with the content of α-helix of soluble proteins dissolved in simulated gastric juice. Therefore, the highest digestibility of the 160 °C-treated SAM group can be attributed to the lowest α-helix content of soluble proteins, as well as the highest surface hydrophobicity and the largest pores size of insoluble residues. The present study provides a good basis for understanding the effects of air frying temperature on the digestion properties of aquatic muscle foods and the mechanism involved, which contributes to establish precise air frying method for aquatic muscle foods.