Impact of debittering and fermentation processes on the antinutritional and antioxidant compounds in Lupinus mutabilis sweet

Abstract

Lupin is a nutritive grain, but its use is limited due to its high content of bitter alkaloids and other antinutritional factors, such as phytic acid, tannins, nitrates and trypsin inhibitors (TI), that have undesirable physiological effects. There is increasing interest in finding appropriate methods for reducing the antinutritional compounds in lupin. The objective of this research was to assess the efficacy of a biotechnological process, namely, fungal fermentation, as a debittering process relative to that of conventional aqueous thermal treatment (ATT). We evaluated the effects of these processes on the reduction of antinutritional compounds as well as their potential impacts on enhancing the beneficial antioxidant properties of lupin. Three varieties (INIAP-450, INIAP-451 and Criollo) of the Lupinus mutabilis species were studied. The application of ATT and fermentation with Rhizopus oligosporus caused decreases in the following antinutrients: nitrates (94.59%), tannins (82.10%), alkaloids (94%), urease activity (93.75%), phytic acid (70.06%) and trypsin inhibitors (76.76%). Ascorbic acid also decreased (79.72%). All values corresponded to the average in the three varieties evaluated. While the contents of phenols, carotenoids and the antioxidant capacity decreased by 96.83, 49.42 and 96.13%, respectively, due to the debittering process, solid fermentation promoted increases in these compounds and properties in the debittered grain.