Moisture Adsorption Isotherms, Thermodynamic Properties and Estimated Maximum Storage Time of Flours of Rhynchophorus Phoenicis and Imbrasia Truncata Larvae

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2024年5月27日

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Aymar Rodrigue FOGANG MBA,
Germain KANSCI,
Catherine LOISEL,
Claude GENOT

摘要

To evaluate the storage stability of flours from Rhynchophorus phoenicis and Imbrasia truncata larvae obtained by freeze-drying, their moisture adsorption isotherms have been determined at 20, 30 and 40 °C and their thermal properties explored by differential scanning calorimetry (DSC). DSC evidenced reversible transitions attributed to lipid melting/crystallization between − 60 and 90 °C. The GAB model was chosen to model adsorption isotherms. It evidenced 2 and 3 water compartments in R. phoenicis and I. truncata flours, respectively. Adsorption isotherm of R. phoenicis is type III at 20 and 30 °C, while that of I. truncata is type II at 20, 30 and 40 °C. GAB model also allowed calculating flour monolayer moisture contents (Mo ≤ 5.6 g/100 g dry matter (DM)). Net isosteric heat (qst) was evaluated. q_st decreases with increase of water content and was higher for the flour of I. truncata larvae (from 8571 to 503 J/mol; 2,5 to 20 g/100 g DM) than that of R. phoenicis larvae (from 1750 to 124 J/mol; 5 to 30 g/100 g DM). Finally, the maximum storage times of the insect flours under typical packaging and storage conditions were estimated according to the Heiss and Eichner model. Highest for the flour of I. truncata, q_st remained however moderate indicating that the insects can be dried without important energy supply. The estimated storage time of R. phoenicis larvae and I. truncata flours (3 g/100 g DM), stored at 20 °C in polyethylene bags, could reach 263 (8 months and 19 days) and 116 days (3 months and 24 days), respectively. These results provide valuable insights into the stability and potential applications insect flour in the food processing industry. This information could help in determining suitable packaging methods and storage conditions to maintain the quality and shelf life of products containing these flours to set safety and quality standards for such products.