Moisture adsorption isotherms, thermodynamics properties, and shelf-life estimation of the flour of Imbrasia epimethea larvae

This study investigates the moisture adsorption isotherms, thermodynamic properties, and estimated storage time of the flour of Imbrasia epimethea larvae, a promising protein source widely consumed in African countries. The flour of I. epimethea larvae was prepared through freeze-drying and analyzed under different water activities and temperatures (20, 30, and 40 °C). Results showed that moisture adsorption isotherms fitted the Guggenheim-Anderson-de Boer (GAB) model (R2 = 0.99; 0.37 ≤ SE ≤ 0.39), highlighting a Type II sigmoidal behavior. The M0 value decreases with the increase in temperature, from 3.17 to 2.85 g/100 g DM between 20 and 40 °C. The adsorption surface area of the flour of Imbrasia epimethea larvae was measured at 111.25, 102.33, and 100.13 m2/g DM for equilibrium temperatures of 20, 30, and 40 °C, respectively. Thermodynamic analyses revealed that moisture adsorption has an enthalpy-driven process, net isosteric heat and adsorption entropy showing a decreasing trend with increase in moisture content. Storage time predictions showed that initial moisture content and temperature significantly impact the stability of the flour of I. epimethea larvae. With an initial moisture content of 3 g/100 g, the shelf life varied from 732 days at 20 °C to 204 days at 40 °C. This research highlights the importance of moisture control and temperature management in extending the shelf life of the flour of I. epimethea larvae, emphasizing the need for tailored drying and packaging protocols. These insights can facilitate its incorporation into various food systems, reducing waste and enhancing food security while providing a sustainable protein source.