Larvae of Tenebrio molitor as a novel food for the future: evaluation of the chemical risk factor.

Due to the rapid increase in world population, the waste of food and resources, and notsustainable food production practices, the use of alternative food sources is currently strongly promoted. In this perspective, insects may represent a valuable alternative to main animal food sources since insects grow and reproduce easily, have a high feed conversion efficiency, and can transform low value of growing substrates into high value food resource [1]. Moreover, insects have a high nutrition potential due to an interesting amino acids composition, an adequate content of minerals, vitamins and polyunsaturated fatty acids. Tenebrio molitor L. (Coleoptera: Tenebrionidae) (yellow mealworm) is particularly efficient in converting the organic substance: it can transform diet substrate with a low nutritional value in a rich protein product, and is characterized by high nutritional value [2]. Different studies highlighted how its larvae are particularly suitable for the human consumption [2], and it is a perfect candidate for rearing with the aim of producing a novel food for the future. Nevertheless, the nutritional value of edible insects is highly variable, and the differences may also depend on their feeding substrates. Moreover, there are some potential safety risks linked with insect consumption: a study on the yellow mealworm larvae, for example, showed that the insects accumulate cadmium and lead in their bodies when they feed on organic matter in soils that contain these metals [3]. In the FoodIN project (Edible insects: new frontiers in food), new feeding substrates were used for rearing T. molitor, in order to investigate the best substrate and rearing conditions and the properties of the insect-based food (i.e. flour and other processed material) so obtained. Five feeding substrates were used for rearing mealworm larvae: 100% organic wheat flour, 100% organic wheatmeal, and organic wheatmeal/organic olive pomace with different percentages: 75/25, 50/50 and 25/75, respectively. In order to assess the chemical risks possibly associated with the insect-based food produced, the determination of Cd, Pb and Hg were carried out on fresh mealworm larvae and their feeding substrates. Cd and Pb were analyzed by Atomic Absorption Spectrophotometry, after microwave digestion of the samples, whereas mercury was determined with a Direct Mercury Analyzer (DMA-1). Preliminary result showed that, in insects, heavy metals concentrations were in the range: Cd, 0.007-0-015 mg/kg ww (wet wheight), Pb, 0.07-0.09 mg/kg ww, Hg, 0.12-0.4 μg/kg ww. Insects reared with 100% organic wheatmeal showed in general higher concentration of heavy metals than insects reared with other feeding substrates. Cd concentrations were lower in insects than in their respective substrates, whereas Pb and Hg concentrations in insects were higher than that of feeding substrates. In agreement with literature data, the results of this study evidenced that heavy metals present in feeding substrates are accumulate in the body of T. molitor. Considering that the legal limit of Cd, Pb for meat, and of Hg for fish food, are 0.05, 0.10 and 0.5 mg/kg (guideline UE n. 1881/2006) respectively, insects showed metals concentrations well below the legal limits. This study demonstrate that mealworm larvae can be considered a safe food from the point of view of Cd, Pb and Hg contamination. This study was financially supported by the Università Politecnica delle Marche, Ancona, Italy, within the project “Edible insects: new frontiers in food-FOODIN”.