Transforming Vegetable Waste: Insect Flour Quality through Tenebrio molitor Larvae Supplementation

Insect farming presents a viable solution to transform vegetable waste generated by the food industry into valuable products such as insect flours. Vegetable waste is rich in bioactive compounds and essential nutrients, which can potentially enhance the quality of insect flours. This study aims to investigate the impact of adding vegetable waste to the diets of Tenebrio molitor larvae on the quality of the generated flours during long-term storage.

The iets of T. molitor larvae consisted of supplementing (1:1) wheat bran with cucumber or tomato wastes for 6 weeks. Post-supplementation, the larvae were dried using a pilot infrared oven at 68°C for 4 hours, and then ground into flour. The quality attributes (moisture, color, lipid oxidation, and microbial load) of these insect flours were assessed over a 12-month storage period at room temperature.

During storage, moisture was around 5-7% in all flours, which is essential for avoiding microorganism growth. Thus, the presence of Salmonella spp., Escherichia coli, and Listeria monocytogenes was below the legislation limit. The color parameters ​​of L*, a*, b*, and C* progressively decreased in all flours; this reduction was more pronounced in flours from larvae fed only with wheat bran. All flours darkened during storage, especially those from supplemented larvae. These results are consistent with the results of nutritional composition and lipid oxidation since flours from larvae fed with vegetable wastes have a higher proportion of unsaturated fatty acids (35% in supplemented versus 25% in control), and are more prone to oxidation, which provides a darker color. Lipid oxidation was stable until 3 months of storage.

Therefore, using tomato and cucumber wastes as supplements for T. molitor diet is a sustainable strategy to revalorize vegetable waste and produce flours that maintain acceptable quality attributes for at least 3 months of storage at room temperature.