Spectroscopic and molecular modeling investigations on heat induced behaviour of soy proteins

Abstract

Soy protein derivatives are widely used in food industry. Because structural properties of proteins vary with the environment conditions, thermal processing might be useful for modulating proteins functionality. The effect of thermal treatment at temperatures ranging from 25 to 100°C on soy proteins behaviour was tested using fluorescence spectroscopy and in silico techniques. Experimental tests were carried out at pH 4.5 and 7.0. Intrinsic fluorescence of proteins was monitored for probing the dynamics of Trp and Tyr microenvironments, such as to estimate the eventual conformation changes. Shifts of the maximum emission were recorded with pH change and temperature increase, and were associated to proteins structure alteration. Synchronous spectra indicated maximum and minimum fluorescence intensity of both chromophores at 70°C and 90°C, respectively, attributed to denaturation of the main soy proteins. Further molecular dynamics simulations, performed at single molecule level to complement the experimental results, indicated higher structural stability at 100oC of glycinin trimer compared to the β-conglycinin trimer.