Study on the Interaction Mechanism Between Soybean Protein Isolates and Lemon Flavor: Isomerization and Degradation of Citral

By headspace solid-phase microextraction/gas chromatography–mass spectrometry, the effects of 1% (w/v) alcohol denatured soybean protein isolates (L-SPI), native soybean protein isolates (N-SPI), as well as the thermal denaturation of soybean protein isolates (H-SPI) on low concentration (24 μmol/L) of citral was studied in aqueous. The results shows that the SPI could catalyze citral isomerization and yield methyl heptenone and acetaldehyde by inverse aldol condensation degradation. 3-Hydroxycitronelloal was formed as an intermediate in this reaction. The catalytic efficiency of the L-SPI was higher than that of N-SPI, whereas the catalytic efficiency of H-SPI was the lowest. Additionally, it shows that the catalytic efficiency increased as the pH increased. The catalytic efficiency of 7S (Soybean β-Conglycinin) was greater than that of 11S (Soy bean Proglycinin).