The Effect of Lipoxygenase Isoenzynes on the Odor and Taste of Soybean Sprouts during Cooking

Lipoxygenase isonzyme이 콩나물의 조리시 냄새와 맛에 미치는 영향

The present study was conducted to characterize lipoxygenase isoenzymes isolated from germinating soybean seeds to obstain pH profiles, carbonyl Production, carotene bleaching abilities, and stability to heat. The roles of these lipoxygenase isoenzymes in the generation of volatile carbonyl compounds were investigated to associate with off-flavor and odor of soybean sprouts cooked to different temperatures. Lipoxygenase isoenzymes were isolated from soybean sprouts using ammonium sulfate fractionation, gel filtration and ionexchange chromatography. Two main lipoxygenases exhibited maximum activity at pH 6.5 (lipoxygenase 2) and at pH 9.5 (lipoxygenase 1), respectively. Both lipoxygenase 1 and 2 produced 280 nm absorbing carbonlys and bleached carotene. The abilities of hydroperoxide formation, 280 nm absorbing carbonyl production and carotene bleaching of lipoxygenase isoenzymes were decreased significantly as the cooking temperature raised. Sensory evaluation data presented that raw and $50^{\circ}C$ cooked soybean sprouts showed significantly higher grassy odor than $80^{\circ}C$and $100^{\circ}C$ cooked soybean sprouts. On the other hand beany odor was significantly higher in $50^{\circ}C$ and $80^{\circ}C$ cooked soybean sprouts than in raw and $100^{\circ}C$ cooked soybean sprouts. These results indicate that lipoxygenase plays a role in the development of off-odor and flavors in soybean sprouts under the condition of chewing and inadequate heating.