Processing and properties of extruded flaxseed-corn puff

The effects of flaxseed meal (0, 5, 10 and 15%) in flaxseed meal/corn meal blend and processing variables, including moisture content (16, 18 and 20%), and screw speed (200, 300 and 400 rpm), on extrudate chemical property (lignan residue) and physical properties (specific volume, hardness and color) were studied. The lignan compounds in the flaxseed and corn meals were 2.27 and 0 mg/g, respectively, before extrusion. A higher flaxseed meal level and a higher screw speed favored the retention of lignan compounds, but higher feed moisture showed the opposite effect. About 25-52% lignan compounds were lost after extrusion. Increasing flaxseed meal level, increasing feed moisture or decreasing screw speed significantly reduced the expansion and resulted in harder extrudate that was darker, more reddish and less yellow.