Estimating equilibrium moisture content from relatively short sorption experiments
2020
Tejada-Ortigoza, Viridiana | Welti-Chanes, Jorge | Campanella, Osvaldo H. | Peleg, Micha
Experimental determination of the equilibrium moisture (ME) content of food, especially by the static method at high water activities (aw's) or relative humidities (RH's), can be an issue. Here, we proposed a mathematical method for estimating the ME value at a given aw or RH from data obtained at shorter exposure times than those needed to reach constant weight (or equilibrium). The method, based on a flexible empirical sorption model, requires the initial and two subsequent moisture content determinations. Its applicability has been tested with published moisture sorption data on cassava flour film, casein, freeze-dried apple puree and plantain flour. Moisture contents after 24 h predicted with the model from data obtained in 3–12 h agreed with the reported experimental ones within ≈2%. This suggests that ME content estimates can be obtained from static data in 24 h or less, depending on the aw or RH. The procedure has been automated and posted online as a freely downloadable interactive Wolfram Demonstration. The concept and method can also be implemented in dynamic methods to shorten their cycle, and/or improve their estimates whenever reaching constant weight is uncertain. It is also shown that, in principle, the method can be used for ME's estimation in desorption.
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