Effects of Extrusion Components on the Compositional Characteristics of an Instant Gruel Produced from Millet-Pigeon Pea Flour Blend

Abstract

Extrusion cooking was used to formulate millet-pigeon pea flour blend with the aim of providing high energy, protein enriched and affordable foods for malnourished children. Five extruded samples were developed from millet-pigeon pea flour blend via extrusion cooking by loading the raw material in the feeding hopper and the screw conveys the raw materials. When the raw materials pass down the barrel, the volume is reduced and the food is compressed under pressure into a semi-solid, plasticized and form extrudates that were used for expansion index, bulk density and water absorption capacity index. Furthermore, the expansion index of 11.16, bulk density of 0.03 g/ml and swelling index of 4.10 at the screw speed of 180 to 200 rpm, feed moisture content of 15 to 25% and feed blend composition of 20 to 25% were obtained. The result of the proximate composition of the extrudates revealed that the moisture content was found to be significantly (p<0.05) higher in sample C (6.05) than values observed in sample A (3.68) as the concentration of pigeon pea decreases. In case of protein content, sample C (29.60) was observed to be statistically (p<0.05) higher among other samples. Similarly, the fat content was observed to be statistically (p<0.05) lower in sample C (2.03 g/100 g) and higher in sample A (3.53 g/100 g). The fibre content of millet-pigeon pea flour blend was observed to be significantly (p<0.05) higher in sample B than the value observed in sample A when the concentration of pigeon pea composition increased. The result of ash content indicated that sample B was significantly (p<0.05) higher than sample A. The carbohydrate content showed that sample A (68.34 g/100 g) was significantly (p<0.05) higher and lower in sample B (64.56 g/100 g). This increase in sample A could be attributed to low screw speed and high feed blend composition. The results of mineral content indicated that sodium content showed that sample A (3.01 mg/100g) was significantly higher than sample B (2.87 mg/100 g). The results of calcium content indicated that Sample B (3.56 mg/100g) was significantly higher and lower in sample C (2.86 mg/100 g). Similarly, the findings of magnesium and phosphorus content indicated that sample B was significantly (p<0.05) higher than value observed in sample D. The results of iron and zinc content of instant porridge produced from millet-pigeon pea flour blend showed that sample C was significantly (p<0.05) higher than sample A. The results of sensory properties of instant gruels produced from millet-pigeon pea flour blend indicated that sample C were statistically (p<0.05) higher in taste (8.34) and flavour (6.98) which could be attributed to higher screw speed and feed moisture content (Table 3.4). Thus, the result of texture indicated that sample B (7.92) was significantly (p<0.05) higher than value obtained in sample D (7.00). Unlike, colour rating and general acceptability of extrudates, sample C were statistically (p<0.05) higher when the feed moisture content increases. It was concluded that instant gruels were formulated from millet-pigeon pea which improved both the physical, chemical and sensory properties of the products.