Distributions of isoflavones in soybeans treated with oven-drying, roasting, or explosive puffing were
analysed using high-performance liquid chromatography (HPLC). As oven-drying time increased from
0 to 120 min at 100 C, concentration (lmol/g) of malonyl derivatives of isoflavones decreased and b-glucosides
increased significantly with over 0.99 coefficient of determination (R2) (P < 0.05). Roasting at
200 C for 7, 14, and 21 min and explosive puffing at 490, 588, and 686 kPa decreased malonyl derivatives
significantly and increased acetyl-b-glucosides and b-glucosides significantly (P < 0.05). Total isoflavones
(TI) in 21 min roasted and 686 kPa puffed soybeans decreased by 25.46% and 10.42%, respectively, while
TI in 120 min oven-dried soybeans was not significantly different (P > 0.05) compared to untreated samples.
Regression analysis showed that malonyl-b-genistin had higher slopes of decreases (lmol/g/min)
than malonyl-b-daidzin in oven-dried soybeans. This is the first report on the effects of explosive puffing
and the changes of isoflavone profiles in soybeans.