Dietary contribution of grasshoppers (Ruspolia nitidula) and white ants (Macrotermes bellicosus) and influence of processing methods on their nutrient composition
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Edible insects are a common source of food in Africa. In Uganda, grasshoppers (Ruspolia nitidula) and white ants (Macrotermes bellicosus) commonly known as ensenene and enswa in Luganda, respectively form a common source of food. This study assessed the consumption, source and nutritional contribution of white ants and grasshoppers to the diets of the people of Kampala. The study also determined the effect of common traditional processing methods on the nutritional quality of grasshoppers and white ants. Nutritional contribution of edible insects was assessed using seven day recall questionnaires. Grasshoppers and white ants were subjected to common processing methods namely; dry pan frying, boiling, and boiling followed by sun drying. Proximate composition, protein digestibility, fatty acid profiles and selected minerals of unprocessed and processed samples were determined following standard biochemical procedures. The survey results showed that grasshoppers and white ants consumed in Kampala were mainly purchased or received as gifts by respondents. Grasshoppers contributed about 16,100 kcal and 513g of protein per person per annum. The results further showed that grasshopper and white ants are an expensive source of proteins. On dry basis, grasshoppers contained about 32% protein and 54% fat whereas white ants contained about 31% proteins and 65% fat. Processing methods affected crude fibre, energy in grasshoppers. Crude fibre in grasshoppers reduced (p≤0.05) from 9.1% in the unprocessed to 6.4% in boiled plus sun dried samples. Dry pan frying and boiling followed with sun drying reduced (p≤0.05) the energy content in grasshoppers. In white ants; ash, fat and energy reduced (p≤0.05) after processing. Ash reduced from 6.1% in unprocessed white ants to 4.2% in boiled white ants. Fat reduced from 64.8% in the unprocessed to 44.8% in the boiled white ants. Energy reduced from 1016.4 kcal/100g in the unprocessed to 738.4 Kcal/100g in the dry pan fried white ants. Protein digestibility varied between 34%-67% in grasshoppers and 46%-63% in white ants. Processing did not affect (p≥0.05) protein digestibility in the white ants. However, protein digestibility in grasshoppers decreased (p≤0.05). Boiling alone reduced protein digestibility from 67% in unprocessed grasshoppers to 34% whereas boiling followed with sun drying reduced protein digestibility in grasshoppers to 44%. Fatty acid analysis showed that grasshopper and white ant lipids were predominantly unsaturated, with 59.6% and 56.7% unsaturated fatty acids, respectively. The most dominant unsaturated fatty acids were oleic (MUFA) and linoleic (PUFA) acid in both insects. Saturated fatty acids accounted for 40.5% in grasshoppers and 43.3% in white ants. The most predominant saturated fatty acid in both insects was palmitic acid 31.8% in grasshoppers and 33.3% white ants. Processing methods had no effect (p≥0.05) on the fatty acid composition in grasshoppers and white ants. In both insects the fatty acid profiles after processing were similar to those before processing. These results suggest that grasshoppers and white ants are a good dietary source of animal protein and essential fatty acids, their costs and availability notwithstanding. Common processing methods did not adversely affect the nutritional composition of grasshoppers and white ants. This would contribute to improved health, food and nutrition security hence fight malnutrition in Uganda.