Physico-chemical characterization, acceptability and shelf stability of extruded composite flour enriched with long-horned grasshopper (Ruspolia differens)

Abstract

In Tanzania, chronic malnutrition rates remain high, with 32 percent 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 knowledge on the potential use of long-horned grasshopper (Ruspolia differens) to enhance the nutritional properties of extruded composite flour. 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 samples of composite flour were formulated and processed using a twin-screw extruder to produce extruded composite flour (ECF) with a mixing (%wt.) ratios of 100:0 (ECF 0), 95:5 (ECF 5), 85:15 (ECF 15), 75:25 (ECF 25) for composite flour (cassava, millet, sorghum) and edible long-horned 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 the inclusion of long-horned 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 long-horned grasshopper did not differ significantly (p<0.141). All treatments showed a significant higher tannin content ECF 5 (0.007 mg CE/g), ECF 15 (0.012 mg CE/g) and ECF 25 (0.011 mg CE/g) when compared to values in control (0.004 mg CE/g). There was a significant difference at a 5% confidence level on the sensory properties between ECF 0 and ECF 15 and ECF 25; the latter two treatments had higher scores for colour and a lower score for aroma and taste attributes, respectively ECF 0. In addition, treatments (ECF 5, ECF 15, ECF 25) showed significantly higher peroxide values (3.52 to 5.32 mEq/Kg) than those in the control sample (2.80 to 3.33 mEq/Kg). In conclusion, the inclusion of edible long-horned grasshopper in the composite flour, significantly improved the quantity of crude protein, crude fat, and energy with an adequately appropriate amount of Zn and Fe to meet the needs of fast-growing infants and young children. Moreover, the functional properties of the resulted product were positively affected and its consumption is expected not to cause any harm to the human body. However, the product needs modification to improve aroma and taste attributes to increase product acceptability.