The Physicochemical characterization, Sensory acceptability and Shelf-life stability of extruded composite flour enriched with long-horned grasshopper (Ruspolia differens)

Abstract

In Tanzania, chronic malnutrition rates remain high, with 32 per cent of children under the age of 5 being stunted. The high cost of dietary protein sources is a contributing factor to the deterioration of the nutritional status of most children. Edible insects are suggested to provide an alternative source of protein in enriching the nutritional composition of foods. However, there is limited current knowledge on the potential use of long-horned grasshopper (Ruspolia differens) to enhance extruded composite flour nutritional properties. This study intended to develop an extruded composite flour enriched with the long-horned grasshopper and further evaluate its proximate composition, mineral properties, antinutritional composition, functional properties, sensory acceptability and shelf-life stability. Four blends were formulated using a twin-screw extruder with a mixing (%wt.) ratios of 100:0 (ECF 0), 95:5 (ECF 5), 85:15 (ECF 15), 75:25 (ECF 25) for blended flour (cassava, millet, sorghum) and edible grasshopper pellets, respectively. Feed moisture content and barrel temperature were adjusted from 15 to 16% and 128 to 142 ⁰C for Zone I, and 105 to 114 ⁰C for Zone II, respectively. The findings show that inclusion of grasshopper meal in the extruded composite flour significantly increased the moisture, crude fibre, crude ash, crude protein and crude fat and mineral contents of Fe and Zn while significantly decreasing the carbohydrate contents at (p<0.001), and Mg contents at (p=0.0089). The phytate contents between ECF 0 and extruded composite flour treatments enriched with grasshopper did not differ significantly (p<0.141). All treatments, ECF 5 (0.007 mg CE/g), ECF 15 (0.012 mg CE/g) and ECF 25 (0.011 mg CE/g) showed a significant higher tannin content when compared to values in control (0.004 mg CE/g). There was significant difference at a 5% confidence level on the sensory properties between ECF 0 and ECF 15 and ECF 25, these two treatments had higher score for colour and lower score for aroma and taste attributes when compared to ECF 0. Although all the treatments (ECF 5, ECF 15, ECF 25) showed significantly higher peroxide value (3.52 to 5.32 mEq/Kg) than those in the control sample (2.80 to 3.33 mEq/Kg). In conclusion, the enrichment of edible grasshopper meal in the composite flour significantly increased the proximate composition, Zn and Fe of extruded composite flour.