Volatile aro
ma principles, nonvolatile taste constituents (caffeine and chlorogenic and caffeic acids),and glycosidically bound aro
ma co
mpounds of
monsooned and non
monsooned raw arabica coffeewere analyzed using gas chro
matography-
mass spectro
metry (GC-MS) and high-perfor
mance liquidchro
matography (HPLC). A
mong the
most potent odor active constituents known to contribute to thearo
ma of the green beans, 3-isopropyl-2-
methoxypyrazine, 3-isobutyl-2-
methoxypyrazine, 4-vinylguaiacol,
mages/gifchars/beta2.gif" BORDER=0 ALIGN="
middle">-da
mascenone, (
E)-2-nonenal,
trans,
trans-2,4-decadienal, phenylacetaldehyde, and 3-
methylbutyric acid were detected by GC-MS in both sa
mples. A decrease in content of
methoxypyrazinesand an increase in 4-vinylguaiacol and isoeugenol resulted in a do
minant spicy note of
monsoonedcoffee. These phenolic co
mpounds exist partly as their glycosides, and their release fro
m the boundprecursors during
monsooning accounted for their higher content in
monsooned coffee. A considerabledecrease in astringent chlorogenic acid as a consequence of hydrolysis to bitter caffeic acid wasnoted in
monsooned coffee. Radiation processing of non
monsooned beans at a dose of 5 kGy resultedin an increased rate of
monsooning. At this dose a quantitative increase in
most of the aro
ma activeco
mponents could be observed in all sa
mples studied. Hydrolysis of chlorogenic acid to caffeic acidwas noted in radiation-processed
monsooned coffee beans irrespective of whether the treat
mentwas carried out before or after
monsooning. These changes were, however, not observed in irradiated,non
monsooned coffee beans, suggesting an enzy
matic rather than a radiolytic cleavage of chlorogenicacid. A rationale behind the
mechanis
m of
monsooning and radiation-induced enhance
ment of the
monsooning process is discussed.Keywords: Monsooned coffee;
mages/gifchars/ga
mma.gif" BORDER=0 >-radiation; raw coffee beans; volatiles; caffeine; chlorogenic acid