Growing conditions and morphotypes of African palm weevil (Rhynchophorus phoenicis) larvae influence their lipophilic nutrient but not their amino acid compositions

Abstract

African palm weevil (Rhynchophorus phoenicis, Rp) larvae are a potential source of lipids and proteins of good quality for human consumption. To evaluate the influence of growing conditions on nutrient composition of larvae grown on different raffia palms, larvae (3 larvae batches per condition) were collected from the wild (yellow wild or white wild larvae) or from a breeding system (white larvae). Growing conditions influenced the morphometric parameters of the larvae and their lipid content and composition. As highlighted by principal component analysis, wild larvae exhibited greater morphometric parameters (weight, length) and higher energy, lipid, carotenoid and total fatty acid contents than larvae from breeding system. As compared to white larvae, yellow larvae contained more energy and more lipids (27.7 ± 2.3 g/100 g fresh weight vs around 19.8 g/100 g), less polyunsaturated fatty acids (0.5 ± 0.1 g/100 g vs 0.8 g/100 g) and tocopherols (2.25 ± 0.23 mg/100 g vs around 4.5 mg/100 g), and, explaining their color, more carotenoids (800 μg/100 g vs 280–390 μg/100 g). Rp larvae contained from 7.8 ± 0.3 (white wild) to 8.8 ± 0.9 (yellow wild) g/100 g proteins and high levels of indispensable amino acids, with no effect of growing conditions. Their nitrogen to protein conversion factors varied from 6.08 ± 0.3 (white wild) to 7.42 ± 0.4 (yellow wild), This work gives a new and reliable insight on nutrient content variations in palm weevil larvae.