Effect of 60Co γ-rays on dried figs adsorption isotherms and thermodynamic properties

Ahmed Irchad; Rachid Razouk; Rachida Ouaabou; Mohamed Mouhib; Lahcen Hssaini

doi:10.3389/fnut.2022.940111

Effect of ⁶⁰Co γ-rays on dried figs adsorption isotherms and thermodynamic properties

Front Nutr. 2022 Oct 11:9:940111. doi: 10.3389/fnut.2022.940111. eCollection 2022.

Authors

Ahmed Irchad¹, Rachid Razouk², Rachida Ouaabou³, Mohamed Mouhib², Lahcen Hssaini²

Affiliations

¹ Faculty of Sciences and Technics, University of Comoros, Moroni, Comoros.
² National Institute of Agricultural Research (INRA), Rabat, Morocco.
³ Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakesh, Morocco.

Abstract

Irradiation is one of the promising food preservation techniques, but few are known about its impact on foods' water vapor change. In this research, the impact of gamma irradiation on moisture adsorption isotherms of dried figs, one of the most emblematic foods of the Mediterranean diet, at increasing doses (0, 1, 1.5, and 2 kGy) was investigated. The isotherms data of equilibrium points displayed a sigmoid-shaped curve of the type II pattern for both controlled and irradiated dried figs, with a notable effect of irradiation on equilibrium moisture content, which revealed a decreasing pattern as irradiation dose and temperature increase. This effect was also seen in data fitting, where GAB model showed the best prediction statistics for control samples, while Peleg model displayed the most suitable samples irradiated at 1 and 1.5 kGy, then the Enderby model for those treated with 2 kGy. Results of Net isosteric heat of adsorption suggested that high irradiation dose increases the spontaneity of moisture adsorption. Hence, gamma irradiation exhibited a significant effect on the water-specific surface area of which the magnitude was proportional to the increasingly applied doses. This effect was also visibly significant on the optimum water activity [a_w (op)] for proper dried fig storage. Indeed, a_w was about 0.4243 for control samples, which is much higher compared to irradiated ones (a_w = 0.2). Information from this research suggests that gamma irradiation at a dose up to 2 kGy extended the dried figs' shelf life. Since many aspects related to the impact of gamma irradiation on the moisture adsorption isotherms and thermodynamic properties of dried figs as well as in other foods have yet to be further investigated, this study provides interesting results that may be a useful reference for future research direction.

Keywords: Cobalt radioisotopic source; Ficus carica L.; adsorption isotherms; gamma irradiation; post-harvest storage; thermodynamic properties.