Effect of watermelon seed flour quantity on the density and expansion ratio of extrudates

Watermelon (Citrullus vulgaris) seeds which are considered as waste have a high nutritional value due to the high content of proteins, minerals and unsaturated fatty acids and for that reason they are suitable for production of functional extruded products. Therefore the focus of this experiment is to investigate the effect of watermelon seed flour content, temperature of the matrix and moisture content on the density and expansion ratio of extrudates from corn grits. A single screw extruder Brabender 20 DN was used for the extrusion cooking. A full factorial experiment 23 with independent parameters watermelon seed flour content (3 % and 10 %), temperature of the matrix (160 °C and 180 °C) and moisture content (14 % and 18 %) was applied. The expansion ratio varies between 1.76 and 2.56 while the density change from 0.103 g/cm3 to 0.159 g/cm3 respectively. The statistical analysis showed that the expansion ratio decrease with the increase of the moisture content and watermelon seed flour content while the density increase.