Hygroscopicity and Sorption Isotherms of Acerola Pulp Powder Produced by Foam-Mat Drying

Abstract

Acerola is a tropical fruit rich in vitamin C and other bioactive compounds, but its high perishability limits storage and distribution. This study evaluated the hygroscopic behavior and storage stability of acerola pulp powder produced by foam-mat drying. The pulp was foamed with Emustab and dried at 60 °C. Fresh pulp and powder were analyzed for water activity, total titratable acidity, reducing sugars, vitamin C, carotenoids, total phenolic compounds, and antioxidant activity. Powder adsorption isotherms, hygroscopicity, caking, and solubility were evaluated at 10 and 25 °C under relative humidities of 20, 50, 70, and 90%. Drying increased the reducing sugar concentration from 5.24% to 45.49%. The Oswin model best described the Type II sigmoidal isotherms, with R2 values of 0.9921 and 0.9974 and mean relative errors of 4.61% and 3.27% at 10 and 25 °C, respectively. Equilibrium moisture content was higher at 25 °C, an atypical behavior associated with the high concentration of low-molecular-weight sugars. Hygroscopicity ranged from 8.77 ± 0.72% to 53.39 ± 0.51%. Although the powder has potential as a functional ingredient, its high hygroscopicity and limited physical stability require moisture-barrier packaging and formulation strategies to improve storage and industrial applicability.