Abstract

This study examines the desorption isotherms of starching delicious apples using the static gravimetric method at two temperatures: 25 °C and 40 °C, chosen respectively to represent ambient storage conditions and higher thermal environments influencing water desorption. Hygroscopic equilibrium was reached after 23 and 20 days, respectively. The experimental data revealed sigmoidal desorption isotherms (Type II), typical of sugar-rich fruits. As temperature increased, equilibrium moisture content decreased significantly. The sorption data were modeled using three mathematical equations: Guggenheim-Anderson-de Boer (GAB), Brunauer, Emmett and Teller (BET), and Langmuir. Among these, the BET model provided the best fit, with high correlation coefficients (r = 0.9975 at 25 °C and r = 0.9992 at 40 °C) and low standard errors (SE = 0.0426 and 0.0158, respectively). The ranges of optimal water activity for safe storage and microbiological stability were identified as 0.74 – 0.45 (at 25 °C) and 0.67 – 0.47 (at 40 °C). These results provide valuable information to optimize post-harvest handling and storage strategies for apples in controlled humidity environments.

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