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.

Physical Characterization of Maize Grits Expanded Snacks and Changes in the Carotenoid Profile.

The objective of this work was to evaluate the effects of feed moisture (13-17%, wb) and barrel temperature (120-160 °C) on physicochemical properties, and changes in the carotenoid profile of maize grits extruded snacks. The extrudates were obtained in a single-screw extruder, according to a 32 factorial design with two replicates. The linear coefficients of feed moisture and barrel temperature mainly affected the physicochemical properties. On the other hand, the interaction coefficient ß112 dominated the change in total carotenoids, lutein, zeaxanthin, and ß-carotene. The quadratic coefficients were also important for changes in total color (regarding feed moisture), and for ß-cryptoxanthin, specific mechanical energy, and volumetric expansion index (regarding barrel temperature). ß-cryptoxanthin and ß-carotene increased, whereas lutein and zeaxanthin decreased. The mathematical models developed from responses revealed two feasible operating regions under the domain explored. For a satisfactory process, from a technological and nutritional point of view, it is suggested to extrude at the operating conditions ranging between 13.2-13.7% feed moisture and 120-132 °C barrel temperature. Under these conditions, the specific mechanical energy input required was 410-450 kJ/kg, and extrudates with a volumetric expansion index greater than 12, a crispness work less than 0.4 N.mm, and with moderate increments in the levels of ß-carotene and ß-cryptoxanthin were produced. The use of richer cultivars in carotenoids could contribute to the production of healthier snacks.