Abstract
Understanding sorption isotherms is crucial in food science for optimizing the drying processes, enhancing the shelf-life of food, and maintaining food quality during storage. This study investigated the isotherms of sweet cherry powder (SCP) using the static gravimetric method. The experimental water sorption curves of lyophilized sweet cherry powder were determined at 30°C, 40°C, and 50°C. The curves were then fitted to six isotherm models: Modified GAB, Halsey, Smith, Oswin, Caurie, and Kühn models. To define the energy associated with the sorption process, the isosteric sorption heat, differential entropy, and spreading pressure were derived from the isotherms. Among the six models, the Smith model is the most reliable in predicting the sorption of the cherry powder with a determination coefficient (R2) of 0.9978 and a mean relative error (MRE) ≤1.61. The values of the net isosteric heat and differential entropy for the cherry increased exponentially as the moisture content decreased. The net isosteric heat values varied from 10.63 to 90.97 kJ mol−1, while the differential entropy values varied from 27.94 to 273.39 J. mol−1K−1. Overall, the enthalpy-entropy compensation theory showed that enthalpy-controlled mechanisms could be used to regulate water adsorption in cherry powders.
Highlights
Sweet cherries (Prunus avium L.) are highly perishable fruits due to their high moisture content and respiration rate, which results in a rapid deterioration of the fruit within a few days
Sweet cherries (Prunus avium L.) of Burlat variety were harvested in June 2019 in the Meknes region in Morocco. e fruits were pitted and freeze-dried at −55°C under vacuum (4.5 Pa) for 96 h using a Freeze Dryer (ALPHA 1–4 LDplus/ALPHA 2–4 LDplus). e dried product was later crushed and sifted with a vibratory sieve shaker (Cisa/BA200 N) to obtain a fine powder with particle diameters between 50 and 125 μm. e fruit powder was kept in a sealed glass flask at 4°C
Powder samples (2 g) were first placed inside 1 L sealed glass jars containing saturated salt solutions. e water activities values of each salt solution as a function of temperature were described by Bizot and Multon [22]. e glass jars were kept in evacuated desiccators at the corresponding temperature (±1°C) and weighed periodically until equilibrium was reached
Summary
Hygroscopic Properties of Sweet Cherry Powder: Thermodynamic Properties and Microstructural Changes. E experimental water sorption curves of lyophilized sweet cherry powder were determined at 30°C, 40°C, and 50°C. e curves were fitted to six isotherm models: Modified GAB, Halsey, Smith, Oswin, Caurie, and Kuhn models. To define the energy associated with the sorption process, the isosteric sorption heat, differential entropy, and spreading pressure were derived from the isotherms. The Smith model is the most reliable in predicting the sorption of the cherry powder with a determination coefficient (R2) of 0.9978 and a mean relative error (MRE) ≤1.61. E values of the net isosteric heat and differential entropy for the cherry increased exponentially as the moisture content decreased. E net isosteric heat values varied from 10.63 to 90.97 kJ mol−1, while the differential entropy values varied from 27.94 to 273.39 J. mol−1K−1. The enthalpy-entropy compensation theory showed that enthalpy-controlled mechanisms could be used to regulate water adsorption in cherry powders
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