Evaluation of the Amount of Some Metals, Fatty Acid and Microbial Load of African Palm Weevil Larvae Rhynchophorus phoenicis (Coleoptera: Curculionidae) Collected from Ondo State, Nigeria

Edible insects are rich in protein, amino acids, fat, vitamins, and trace elements. However, they are the potential carriers of toxicants, allergenic substances, anti-nutrients, and pathogens. The present study aims to determine the proximate and nutritional, fatty acid, metal composition, and microbial load of palm weevil larvae (Rhynchophorus phoenicis Fabricius, (Coleoptera: Curculionidae)), an insect species commonly consumed in Nigeria.

Twenty five R. phoenicis were randomly collected in April, 2021 from different local farms. The insects were exterminated by freezing and thereafter defrosted at room temperature in the laboratory; with the exception of the samples for moisture analysis, they were oven dried to a constant weight at around 65 °C for 24 h, grounded, and analyzed for proximate content, fatty acids, metals, and microbial load following standard laboratory procedures.

The results show that R. phoenicis contained 45.60% crude fat, 15.79% crude fiber, and 5.25% crude protein by weight. Linoleic acid, oleic acid, and palmitic acid made up most of the fatty acid concentrations at 54.13, 23.86, and 14.19%, respectively. Iron (Fe) content was the highest metal (4.923 ppm), followed by manganese (Mn; 2.767 ppm) and zinc (Zn; 1.04 ppm). The isolated microorganisms were mold and yeast (5×10-5 Colony Forming Unit (CFU)/g), Staphylococcus sp. (33×10-5 CFU/g), and Micrococcus/Bacillus substilis sp. (5×10-5 CFU/g).

The high nutritional composition present in R. phoenicis evaluated in this study, compared to the dietary protein value obtained from other animal food sources, suggests the need for their adoption as animal protein and essential fatty acid sources in human diets.