Lipoxygenase in Sweet Corn Germ: Isolation and Physicochemical Properties

Off‐flavor and off‐aroma development, which may be catalyzed by lipoxygenase (LPO), are common in frozen stored sweet corn. Lipoxygenase activity in the germ fraction of sweet com (Z ea nruys L. cv. Jubilee) was determined and compared with that in the degermed fraction. Lipoxygenase activity/g germ was about three times greater than that of the degermed fraction, Optimized procedures for isolation of lipoxygenase from the germ fraction were developed. Lipoxygenase was isolated by preparation as an acetone powder, extraction with 0.2M TrisHCI, pH 8.0 (4°C), fractionation with 40–60% saturated ammonium sulfate and dialysis. Optimum pH was 6–7 and temperature 50°C for activity of partially purified lipoxygenase. The enzyme appeared stable at pH 5–8 and ∼90% of original activity was inactivated after heating in pH 7 buffer at 70°C for 3 min.