Structure and dilatational rheological behavior of heat-treated lotus (Nelumbo nucifera Gaertn.) seed protein

The influences of heat treatment (60, 80 and 100 degrees C, 30min) on the structure and interfacial properties (adsorption at the oil - water interface and dilatational rheology of interfacial layers) of lotus seed protein (LSP) were evaluated. Heat treatment induced an increase in average diameter and surface hydrophobicity due to partial unfolding and aggregation of LSP. Specifically, the moderate heat treatment (60 and 80 degrees C) could significantly increase the net surface potential of LSP, while heating at 100 degrees C had no effect. Additionally, the lower surface pressure at long-term adsorption and similar dynamic interfacial rheology were observed as compared to native LSP. In contrast, heat treatment led to a higher diffusion and penetration rate of protein, as observed by a faster increase of surface pressure. Nevertheless, the viscoelastic properties of the adsorbed layer of LSP after heat treatment decreased and when the interfacial pressure was greater than 18 mN/m, the interfacial modulus showed a downward trend. These findings increase our understanding of the structural dependence of protein interface behavior and the application of heat-treated proteins in emulsion preparation.