Abstracts

Sorghum, millets and teff are important staple cropsworldwide, especially in semi-arid regions of Africa and Indiabecause of their drought tolerance. However, lack of research andother limitations have restricted their usage in food products.This study is focused on extrusion processing of low and hightannin sorghum varieties, millet and teff for high and low moistureapplications, and to investigate process characteristics such asresidence time distribution and specific mechanical energy,physico-chemical properties of resultant food products (such aspre-cooked pasta and expanded snacks) and their resistance starchcontent. Results from preliminary lab scale extrusion, includingoptimization of starch type and level for pre-cooked pasta andin-barrel moisture for expanded snacks, were used to designpilot-scale studies on a twin-screw extruder. In the firstpilot-scale experiment, decorticated white sorghum blends preparedwith addition of mono-glycerides (0.5%, 1% and1.5%) and salt (1%)were processed at three different in-barrel moisture contents 40%,44% and 48% (wet basis) for processing of precooked pasta. Theoptimum formulation containing 1% mono-glycerides and processconditions corresponding to 48% in-barrel moisture were also usedto develop precooked teff and millet pasta. The non-traditionalgrain based pastas were investigated for cooking quality, thermalcharacteristics using differential scanning calorimeter, pastingproperties using rapid visco analyzer and texture profile analysis.In general, increasing in-barrel moisture led to reduction in solidlosses (ranging from 4.0-8.2% for all treatments), indicatingimprovement in cooking quality. On the other hand, increase inmono-glycerides concertation led to higher cooking losses, and alsoaffected pasting and textural properties significantly.Sorghum-based precooked pasta was of best quality while milletpasta was poorest in cooking quality, visual and texturalattributes. Cooking loss for control pre-cooked pasta produced inthis experiment using semolina was 4.5%, and commercial semolinapasta was 3.2%. Residence time distribution in pilot-scale twinscrew extruder, during high moisture process conditions used forpre-cooked pasta, was also investigated at three differentin-barrel moistures (40%, 44% and 48%) and monoglycerides/ lipid(0.5, 1% and 1.5%) concentrations. Increase in in-barrel moisturesignificantly decreased mean residence time. For example, meanresidence time was 4.47 min at 40% moisture, 3.89 min at 44% and3.74 min at 48%. On the contrary, residence time significantlyincreased with lipid level. For example, mean residence time was3.87 min at 0.5% concentration of mono-glycerides, 4.48 min at 1%and 4.70 min 1.5%. In the second experiment focusing on lowmoisture applications, pilot-scale twin screw extrusion was used toprocess decorticated white sorghum and high tannin sumac sorghumfor expanded snacks. The addition of sumac bran decreased thespecific mechanical energy input (366-578 kJ/kg) and expansionratioAdvisors/Committee Members: Sajid Alavi.