Stable isotope ratio analysis for the characterisation of edible insects

Entomophagy, or the act of eating insects, has been practiced since ancient times, but it started to gain more popularity, especially in Western countries, only recently. As sustainability is one of the current emerging themes, the inclusion of insects in our diet is a valid alternative that might help reduce the amount of water and land used for livestock and the associated emissions of greenhouse gasses. Moreover, insects are a source of protein, fibres, vitamins, minerals and fats. Edible insects are considered a novel food, for which no isotopic reference values are yet available. In the present work, samples of farmed edible insects (n=40) belonging to different orders (namely, Coleoptera, Hemiptera, Hymenoptera, Lepidoptera, Odonata and Orthoptera) and insect-based food items (n=4) for human consumption were analysed. The following isotopes, δ13C, δ15N, δ34S, δ18O and δ2H of the defatted samples, together with the δ13C of the fat, were investigated. The aim of the work was to provide the first reference isotopic ratios that can be used for future investigations in the food quality field. The variability of these parameters was dependent on the life stage and diet of insects, their geographical origin, and the addition of ingredients as seasoning.