Characteristics of crude lipoxygenase from commercially de-oiled lupin flakes for different types of lupins (Lupinus albus, Lupinus angustifolius)

To use effectively lupin protein products in food formulations, the two mainly cultivated and processed sweet lupins (Lupinus albus, Lupinus angustifolius) were investigated related to lipoxygenase activity. Optimum pH of purified lupin lipoxygenase was reported at 6.0, however, optimum pH of crude lipoxygenase from L. angustifolius and L. albus was found to be 7.5 and 8.0, respectively. This crude extract showed 10 times of total activity of purified lipoxygenase. Lipoxygenase from L. angustifolius showed higher thermal stability up to 80 °C than L. albus. Soybean crude lipoxygenase showed 9–12 times activity of lupin lipoxygenase both at pH 7.5 and 8.0. Our results indicate that research on crude extract is useful to know the changes of lupin lipoxygenase activity and thermostability of lipoxygenase in the food applications.