Direct expanded snacks from sorghum

Abstract

Food type white sorghum (ATx631xRTx436) grown in College Station, 2001 was used to produce direct expanded snacks. Corn meal was used as reference. Sorghum grains were analyzed for their density, hardness, weight, and size. Sorghum was decorticated to remove 0 (whole) and 20% of its initial weight. Both whole (WS) and decorticated sorghums (DS) were milled and sifted into coarse and fine meals. Meals were analyzed for chemical composition and physical properties. All meals were extruded with a single screw cooking-extruder (Wenger X-20) using optimum extrusion conditions for coarse corn meal. The extrudates were analyzed for physical and sensory properties. Particle size distributions of coarse meals from WS and DS were adjusted to equal the particle size of corn meal. Decortication reduced fat, protein and fiber contents and lighten the color of the sorghum grains. Fine meals had higher pasting viscosities than coarse meals. Extrudates from coarse DS meal had the highest expansion ratio among sorghum extrudates. The environmental scanning electron microscope showed that extrudates from fine DS meal had thick cell walls probably due to the starch being overcooked and the extrudate structure collapsing after expansion. Extrudates from both DS meals were white with a bland taste. Particle size was important to produce good snacks but the composition, especially fat content, had more effect than the particle size. Extrudates from both WS meals had low expansion due to the higher fat and fiber and reduced starch contents. Fat and fiber act as lubricants during extrusion. Extrudates from WS were very hard and off-white with a mild after-taste. The extrusion conditions for WS and DS milled products would require adjustments to produce expanded snacks with properties similar to those of coarse corn meal. Sorghum can be used as raw material alone for direct expanded snacks. Extrudates from DS meals had excellent characteristics that were similar to extrudates from corn and other commercial extruded snacks. The mild flavor and light color suggests that sorghum can compete with rice in extruded snacks. The WS extrudates can be used to produce whole grain high fiber snacks.