Comparison of functional properties and secondary structures of defatted wheat germ proteins separated by reverse micelles and alkaline extraction and isoelectric precipitation

The functional properties and secondary structures of defatted wheat germ protein separated by reverse micelles (DWGRMPI) were investigated and compared with those of defatted wheat germ protein separated by alkaline extraction and isoelectric precipitation (DWGPI). The results showed that DWGRMPI had a higher nitrogen solubility index, fat absorption capacity, foaming capacity, foaming stability and emulsifying stability compared to DWGPI, whilst water holding capacity, surface hydrophobicity and emulsifying activity of DWGRMPI were relatively lower than those of DWGPI. DWGRMPI contained high levels of threonine, histidine, alanine, arginine, glycine, serine, cysteine, proline and especially lysine compared to DWGPI. The denaturation temperature and denaturation enthalpy of DWGPI were both lower than those of DWGRMPI, and DWGPI contained more random coil and less α-helix than DWGRMPI, which suggested that DWGPI has lost its ordered secondary structure. This may possibly due to the conditions the used in protein extraction.