Lentil flour formulations to develop new snack-type products by extrusion processing: Phytochemicals and antioxidant capacity

Extrusion process has been generally applied to the production of cereal-based snacks. However, in recent years, extrusion process has been also used for the development of pulses-based snacks, with few studies focussing on the incorporation of these food ingredients to obtain bioactive compounds enriched snacks with acceptable quality. The effects of the extrusion processing on fiber (soluble and insoluble), total available carbohydrates, tocopherols, organic acids, total phenolics, hydroxycinnamic acids, hydroxybenzoic acids and flavonols, as well as on the antioxidant capacity of different lentil-based, fiber-enriched flours were evaluated. Total dietary fiber (TDF) in the extruded flours ranged between 7.49 and 10.22 g/100 g, with a decrease from 6 to 37% which correlated with a significant increase in the fiber soluble fraction. α-, γ- and δ-Tocopherols were characterized in all the analyzed samples, being γ-tocopherol the major isoform, before and after extrusion. Additionally, a marked decrease of 83 to 94% in total tocopherol content after extrusion processing was observed and the decrease was more significant on quinic acid content. Conversely, an increase in most polyphenolic fractions was observed, probably due to the effect of extrusion process to induce hydrolysis of polyphenols bound fiber and/or proteins moieties, changing from non-extractable to extractable polyphenols. Similar increase in antioxidant activity was also observed in most formulated lentil-based flours, measured by four different antioxidant assays. Only flavonols presented an extensive content decrease of about 62 to 82%, after extrusion treatment.