The use of durum clear flour in combination with hazelnut cake and different pomaces in the production of extruded food

The durum clear flour (8-20%), partially defatted hazelnut flour (PDHF) (5-15%), fruit waste blend (3-7%) and rice grit were blended in various ratios and then extruded using single screw extruder. Response surface methodology was used to simulate effects of process variables such as the feed moisture content (12-18%), barrel temperature (150-175oC), and screw speed (200-280 rpm) and feed composition on physical and functional properties of the produced extrudates. The product properties of extrudates were mostly affected by changes in PDHF content. Increasing PDHF content caused increase in bulk density, water solubility index (WSI), L value, total phenolic content and antioxidant activity but decrease in radial expansion ratio, porosity, hardness, water absorption index (WAI), percent starch gelatinization and starch digestibility values of the extruded products. Changing fruit waste content generally affected the texture, color and functional properties of produced extrudates. Physical and functional properties of extruded products were influenced from extrusion process conditions. Increasing moisture content and decreasing temperature increased expansion ratio and porosity whereas it decreased bulk density for most product formulations. WSI decreased at high temperature and moisture content, whereas WAI increased. Screw speed influenced values of WSI, WAI and hardness. Moisture content and temperature influenced significantly the total phenolic content, antioxidant activity, percent starch gelatinization and starch digestibility values. In extruded samples, positive correlations were determined between antioxidant activity and total phenolic matter and percent starch gelatinization and the starch digestibility values, respectively. It was observed that well expanded extruded products with acceptable sensory attributes were obtained at low PDHF content at the end of sensory evaluation of extruded samples.