We here report on the use of water as a ‘green’ extraction solvent for the isolation of isoflavones from
okara, a by-product of soymilk production. At a low liquid-to-solid ratio of 20 to 1 and 20 C, 47% of
the isoflavones that can be extracted with 70% aqueous ethanol were extracted. The malonyl-glucosides
were fully recovered with a ratio of 20 to 1, while b-glucosides were recovered with an increased
liquid-to-solid ratio of 40 to 1. The extraction of aglycones was better at higher ratios, but leveled off
before reaching a 100% yield. Temperature hardly affected the total amount of isoflavones. At a 20 to 1
ratio, 20 C, and pH 10, there was no significant difference (p > 0.05) between isoflavone extraction in
water and in 70% aqueous ethanol. The results suggest that water may be used as a green alternative
for separation of isoflavones from okara.