Chemical Characterization of White Lupin (Lupinus albus) Flour Treated by Extrusion Cooking and Aqueous Debittering Processes.

Lupin is a very nutritious legume with high levels of protein and fiber, but it also contains quinolizidine alkaloids which, depending on the species, can accumulate to toxic levels. The objective of this work was to evaluate the white lupin chemical composition, due to the effects of different processes (aqueous debittering, extrusion cooking, and reactive extrusion), aiming at reducing total alkaloids, preserving fibers, and increasing in vitro protein digestibility. Regarding raw material, the aqueous process reduced significantly total alkaloids (-93.87%), increased dietary fiber (+22.03%), and increased protein digestibility (+6.73%), whereas the extrusion processes were inefficient to reduce alkaloids (< -3.70%) and reduced the dietary fiber content, the reduction being more severe during reactive extrusion (-75.36%). Protein digestibility was improved by extrusion cooking (+3.07%), while the reactive extrusion reduced digestibility (-12.50%). Electrophoresis and quantification of soluble proteins and aromatic amino acids confirmed the high digestibility index, staying only the γ-conglutin fraction in the digested samples evaluated by SDS-PAGE. The aqueous process proved to be the best option, as it reduces the alkaloid content to safe levels and improves the protein digestion of white lupin flour.