Impact of different diets and starvation treatments on the microbial, chemical, and nutritional composition of tenebrio molitor

Abstract

In a world facing an environmental crisis, population growth coupled with an increasing demand for natural resources emphasizes the importance of adopting new dietary patterns more sustainable and healthier. The consumption of edible insects (e.g., Tenebrio molitor) offers an alternative to animal-based protein sources, providing a sustainable production cycle that promotes food security with minimal environmental impact. In this study, the impact of different feeding regimes (substrate supplemented with water, potatoes, carrots, and a mix of vegetables/fruits) and different starvation treatments (0 h, 24 h, 48 h, and 72 h) on the food safety of T. molitor larvae was assessed by microbiological, chemical, and nutritional analysis. Despite the variation in diets, no significant microbiological differences were observed in the mealworm larvae load. By the end of their development, the larvae microbiota was characterized by a dominance of Spiroplasma genus, along with other bacterial genera present in lower abundances, primarily belonging to the Firmicutes and Proteobacteria phyla. However, the impact of different diets was more pronounced in their metal profile, highlighting the role of feeding as the main source of principal metals, such as K, P, and Mg, as well as Zn and Fe among trace metals. On the other hand, the starvation treatment, previously described as a method for allowing the discarding of larvae gut contents, did not show significant effects on the microbial or chemical profiles of the larvae, which suggests that other factors may influence the effectiveness of this pre-treatment process. Additionally, this research contributed to clarify that the use of vegetables and fruits side streams does not pose additional biological risks (absence of Listeria monocytogenes and Salmonella spp.) or chemical risks (concentrations of heavy metals according to legislation). Furthermore, this feeding approach enables the production of mealworm larvae with similar nutritional profiles, rich in protein and fat, while also taking advantage of agricultural wastes. Ultimately, this research highlights the importance of appropriate farming methods, maintaining hygienic rearing and processing conditions, and enforcing feeding controls, among other measures, to ensure the safety of larvae of T. molitor for human consumption.

Date of Award	27 Jan 2025
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Joana Barbosa (Supervisor) & Paula Teixeira (Supervisor)