Abstract: Soybean proteins were prepared from the model systems consisting of lipid-reduced soybean proteins and different levels of linoleic acid(LA) and lipoxygenase.The interactions of soybean proteins and oxidizing linoleic acid catalyzed by lipoxygenase were assayed by fluorescence spectroscopy and soluble protein hydrophobicity.The fluorescence of the oxidized samples showed excitation and emission maxima at 350nm and 440 nm respectively.The fluorescent compounds were partially soluble in the organic layer of the chloroform-methanol(2:1,V/V).The solution fluorescence showed an excitation maximum at 350 nm and an emission maximum at 430 nm,and the intensity increased with reaction time.The interactions of soybean proteins and oxidizing linoleic acid catalyzed by lipoxygenase also resulted in decreases of soluble protein hydrophobicity.With an antioxidant(BHT) addition,the changes in fluorescence and soluble protein hydrophobicity were inhibited.

Key words: soybean protein, fluorescence spectroscopy, lipoxygenase, linoleic acid, oxidation