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Dynamic vapour sorption isotherms and isosteric heats of sorption of two edible insects (Cirina forda and Rhyncophorus ferrugineus)

par Bukamba Tshanga, Célestin ;Malumba, Paul;Kambashi, Bienvenu;Bindelle, Jérôme;Debaste, Frédéric
Référence IFW 2022 Insects to feed to world (4: 12-16 juin 2022: Quebec City)
Publication Non publié, 2022-06-16

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Résumé :

Cirina forda (Cf) and Rhyncophorus ferrugineus (Rf) are widely consumed insects in tropical Africa. Drying is one of the main conservation techniques to improve their availability for distant markets and outside their harvest seasons. The main goal of this study was to investigate thee sorption isotherms of these insects and estimate their shelf-life. Sorption isotherms of these two insects were determined at 25, 30, 40 and 50°C using a Dynamic Vapor Sorption (DVS) device. Five isothermal sorption models were fitted to the experimental data, and Peleg equation was found to give the best fit for both insects. Both insects exhibited sorption isotherm of type III indicating monolayer-multilayer behavior with limited hysteresis. Amplitude of hysteresis was higher for Rf than for Cf. According to the sorption isotherms to ensure a safe storage at 25 and 30°C the Rf larvae must be dried at 8.8 % and 8 % respectively. Cf caterpillars must be dried to 9.5 and 9.4 % for respective storage at 25 and 30°C. Based on Kinshasa climate data when these two insects are left in contact with ambient air, their equilibrium moisture content can evolve to values higher than values guaranteeing a safe storage. This suggests that for better preservation the dried insects should be packed in airtight packages. Using Heiss-Eichner model, dry base moisture contents of 6.9 % and 8.5 % respectively for Rf and Cf were predicted to ensure the expected shelf-life of 12 months at 30°C when insects are packaged in polyethylene films.