Production of extruded-cooked lentil flours at industrial level: Effect of processing conditions on starch gelatinization, dough rheological properties and techno-functional parameters

The aim of this work was to identify the effect of two different extrusion-cooking (E-C) conditions, milder and more severe, on starch gelatinization, dough rheological properties and techno-functional parameters of lentil flour (Lens culinaris Medik.). Extruded flours were obtained at 100 °C die temperature, with a screw speed of 220 rpm (EF1) and at 115 °C, 230 rpm (EF2), in an industrial plant. The E-C increased the viscoamylograph initial viscosity compared with native flour (NF), with a significantly higher value (p < 0.05) in EF1 (69.3 ± 4.1 Brabender Units, BU) than EF2 (59.1 ± 3.1 BU). The extruded flours also showed a lower degree of starch retrogradation than NF (cooling maximum viscosity = 201.3 ± 6.4 BU in EF1, 194.1 ± 9.2 BU in EF2 and 433.5 ± 8.5 BU in NF). The E-C markedly increased the Mixolab maximum consistency (with EF1 reaching 1.77 ± 0.04 Nm) compared with NF. The techno-functional parameters significantly improved, compared with NF, with an increase in water absorption index (higher in EF1 than in EF2) and oil absorption capacity (higher in EF2 than in EF1), and a decrease in bulk density. Therefore, by conveniently modulating the industrial processing conditions, lentil flour can become a valuable ingredient for several food applications.