Functional and conformational characterisation of walnut protein obtained through AOT reverse micelles

Summary Walnut protein was extracted from defatted walnut flour by bis (2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micellar system and alkali solution with isoelectric precipitation. The functional and conformational characteristics of two proteins were investigated and compared. Walnut protein obtained through AOT reverse micelles was found to have higher extraction yield, solubility, emulsifying activity, foam capacities, water- and oil-holding capacity compared to the protein from alkali solution along with isoelectric precipitation, while the surface hydrophobicity (H0), contents of disulphide bond (SS) and sulfhydryl group (SH) were relatively lower. The differences of H0, SS and SH contents could be due to the conformational changes of walnut proteins using two extraction methods. FTIR spectra and data showed that the reverse micelles caused the decrease in α-helix, β-sheet, random and β-turn of walnut protein, the increase in the side-chain structure content, which could be responsible for the modification of functional properties.