Solar drying of Tenebrio molitor L: Impact of covering materials on the physical and chemical properties of yellow mealworms

Abstract The investigation evaluated the impact of different covering materials in solar dryers on the physical and chemical properties of yellow mealworms ( Tenebrio molitor L.). Five solar dryers were constructed using different cover materials, including transparent polycarbonate, glass, acrylic, dark polycarbonate and aluminium coated with titanium oxide. Their performance was compared to an electric stove at 50 °C. The yellow mealworms dried in the glass cover dryer achieved the lowest moisture content (1.39%) in the shortest time (240 min), due to its high internal temperature (72.56 °C) and ability to transmit over 90% of solar irradiance. The drying process increased the concentration of nutrients, including total proteins content, fats, fibre, carbohydrates, and ash content, due to water removal. The total protein content increased significantly in all dried samples. However, changes in colour parameters were observed, with a decrease in lightness and variations in hue angle and chroma. The smallest total colour difference between fresh and dried samples ( ) was recorded using the electric stove (11.43), followed by the titanium oxide dryer (12.8). The study carried out suggest that the use of solar dryers with specific covering materials can preserve the nutritional and colour properties of yellow mealworms, with the titanium oxide dryer being a promising option due to its ability to retain heat and eliminated Ultra Violet radiation (UV) exposure. Also it was possible to conclude that edible insects, such as yellow mealworms, represent a promising alternative protein source to address global food security challenges due to their high nutritional value.