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Abstract

Mixtures of defatted soy flour and sweet potatoes were extruded at 0:100, 25:75, 50:50, 75:25 and 100:0 ratios in an Insta-Pro 600 single screw extruder operated at 180, 200, 220 rpm. Oil (3-5%) was added into the mix before extrusion. A 5 x 32 fractional factorial central composite response surface design was adopted for investigating the variables: feed composition, % oil, and screw rotation speed (RPM). Percent oil and screw speed were randomly investigated at three levels, while feed composition was randomly investigated at five levels. Effect of extrusion cooking on functional properties: bulk density, expansion ratio, water absorption and solubility indices and trypsin inhibitor were assessed. Results showed that feed composition and screw speed had strong influences on the process. The effect of adding oil, into defatted soybean significantly (p < 0.05) affected only trypsin inhibitor content. High extrusion temperature (> 130 degrees C), and accompanying high shear, were the result of the non-pasting nature of the extrudate. Therefore the products may have limited uses.

Comparison of the Physicochemical Properties and Pasting Characteristics of Flour and Starch from Red and White Sweet Potato Cultivars

“…Extending the use of SP starch is primarily determined by its physicochemical and functional properties. So far, sweet potatoes have been processed or incorporated into different products and the effect of some processing methods on functional properties determined ( , ). To date, there is no information on physical properties of SP cultivars in Western Africa.…”