Key volatile off-flavor compounds in peas (Pisum sativum L.) and their relations with the endogenous precursors and enzymes using soybean (Glycine max) as a reference.

The dominant volatile off-flavor compounds of pea and soy milk were investigated by gas chromatography-olfactometry-mass spectrometry (GC-O-MS), sensory evaluation, and odor-activity values (OAVs), which led to the identification of their differences. We identified 11 aroma compounds as important odorants with OAVs greater than 1 in pea and soy milk. OAVs contribution rate demonstrated that 6 compounds contributed most to the characteristic off-flavor of pea milk, among which 2-methoxy-3-isopropyl-(5 or 6)-methyl pyrazine, hexanal, (E,E)-2,4-nonadienal, and (E,E)-2,4-decadienal contributed more than others. For soy milk, 1-octen-3-one, hexanal, (E,E)-2,4-nonadienal, and (E,E)-2,4-decadienal showed more important contributions. These odor-active compounds were divided into non-lipoxygenase (non-LOX) and LOX pathways based on their synthesis. Several endogenous enzymes that are important to the LOX pathway were identified by liquid chromatography tandem mass spectrometry (LC-MS/MS), and the contents of key off-flavor compounds were found to be related to the enzyme activities, while the lipid content was not an important factor.