GRAPE DRYING IN A FOAM BED: ANALYSIS OF KINETIC PARAMETERS AND MATHEMATICAL MODELING

Abstract

Foam-mat drying is a widely used technique for obtaining powdered food products, especially when applied to products with high sugar content, such as tropical fruits. This study aimed to analyze the foam-mat drying process of BRS Vitória grapes, evaluating foam formation, drying kinetics behavior, and the fitting of mathematical models to the experimental data. The foam was produced using formulations containing Emustab, maltodextrin, and auxiliary agents, and was characterized in terms of stability, uniformity, and suitability for drying. The drying curves showed a typical profile of hygroscopic materials, with a predominant falling-rate period, a behavior associated with the formation of a viscous surface layer that limits internal moisture diffusion. Several mathematical models were tested, with emphasis on the Page and Midilli & Kucuk models, which showed excellent performance at the three temperatures evaluated, with coefficients of determination (R²) higher than 0.997. The Page model provided the best fit under the highest temperature conditions, efficiently capturing structural changes in the matrix during the process. The results demonstrated that the selected formulation and applied conditions were suitable for producing grape powder by foam-mat drying, reinforcing the efficiency of this technique for obtaining stable products with low hygroscopicity, suitable for storage and future technological applications. This study contributes to advances in grape processing and expands knowledge on the application of mathematical models to represent drying kinetics in fruits rich in sugars.