Lipoxygenase (LOX) is thought to play an important role in the formation of desirable or undesirable
flavor and aroma in many plant products. In rice seeds, LOX activity is localized in the bran fraction
and LOX-3 is the major isozyme component. We used gas chromatography-mass spectrometry to
determine whether the degree of staleness in the flavor of stored brown rice was related to the
presence of LOX-3. We found that the amount of hexanal, pentanal, and pentanol in normal raw
LOX-3 rice markedly increased during storage at 35 °C. That in LOX-3-less rice increased slightly
but was a third to a fifth that of normal LOX-3 rice. In cooked rice, the amount of these components
from glutinous rice exceeded that in nonglutinous rice, and that in normal LOX-3 rice exceeded
that in LOX-3-less rice. These results indicate that the stale flavor production in LOX-3-less rice