Effects of seasonal variation and geographical location on the nutritional composition of mopane worm (Gonimbrasia belina)

Abstract

Mopane worm (Gonimbrasia belina) consumption contributes to the sustainable supply of protein and several other nutrients for low socio-economic communities. However, mopane worm are bivoltine, producing two generations per rainy season which is postulated to affect their nutritional value. This research investigated the effect of emergence season and geolocation on the nutritional composition of mopane worms. Proximate, mineral composition and fatty acid profile were analysed on degutted mopane worm samples collected over three mopane worm emergence seasons (November-December 2020, April-May 2021, and November-December 2021) from three locations in Gwanda district, Zimbabwe. Crude protein and crude fat ranged between 52.5-58.8 and 12.0-18.6% DM respectively. Potassium (1,195.3-1,759.9), magnesium (104.6-225.5) and calcium (51.2-145.5) were the most abundant macroelements (mg/100 g DM) whilst iron (10.6-21.6) and zinc (13.8-17.9) were the most abundant microelements (mg/100 g DM). Using an attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), mopane worm fat was found to be highly saturated with oleic (ω-9), linoleic (ω-6) and palmitoleic (ω-7) fatty acids. Furthermore, the results revealed a significant (Bonferroni-correction α<0.002) influence of geolocation (sampling location) on mineral content of mopane worms whilst emergence season had a significant influence on fat, protein, ash crude fibre and mineral content. These findings indicate that mopane worm due to their high content of both macro- and micronutrients could contribute significantly to the alleviation of protein, zinc, and iron deficiencies in target communities. More so, the findings on nutritional variation due to emergence season and geolocation provide information that is key in domestication of the mopane worm for realisation of its optimum nutrient content.