The effect of fat content in food matrix on the structure, rheological properties and digestive properties of protein

High-fat diet can induce metabolic disorders, leading to metabolic diseases such as obesity, hyperlipidemia, and diabetes. The effects of high-fat diet on the body are related to the content and composition of fat, and to changes in the structure, digestion and utilization of food protein through molecular interactions as well. The purpose of this study is to explore the influence of fat content in food system on protein properties and bioavailability. The molecular structures, system status and digestion characteristics of four proteins (casein, pork, chicken, and soy proteins) in a standard diet and a high-fat diet were studied. The results showed that high fat affected the solubility, hydrophobicity, and secondary structures of the protein. Under high-fat conditions, the solubility of protein was reduced, and the α-helix and β-sheet contents increased. The microstructure of protein systems differed with protein type, of which casein had higher emulsification and uniform dispersion, making the droplets of the system smaller. The other three proteins appeared to be aggregated. Protein digestibility was affected by protein type and fat content. Casein showed the highest protein digestibility (about 95%), and followed by soy protein (about 89%). The increasing fat content significantly improved the digestibility of pork protein (from 80% to 86%) and chicken protein (from 69% to 87%), but had no effect on casein and soy protein. This finding could provide a new insight into the structural state and digestion properties of protein in a high-fat diet.