Tropical Red Fruit Blends: The Effect of Combination of Additives on Foaming, Drying and Thermodynamic Properties

Abstract

Blends combine advantageous characteristics of each species, resulting in products with different flavors and nutritional substances. Moreover, transforming them into powder provides numerous advantages. This work evaluated the properties of three blended foam formulations made from the pulps of tropical red fruits (acerola, guava and pitanga) to determine the foam layer drying kinetics and thermodynamic properties. The foam formulations were prepared by mixing the three pulps in equal proportions (1:1:1), all added with 6% albumin and 1% stabilizing agent. The foams were analyzed for density, volumetric expansion, stability and porosity in six mixing times. Subsequently, they were subjected to drying in an oven with forced air circulation at 4 temperatures, with a layer 0.5 cm thick. Seven mathematical models were fitted to the drying kinetics experimental data to determine the effective diffusivity and thermodynamic properties of the samples. The best mixing times were 5 min for the E2 sample and 30 min for the others. Formulation E2 presented the best results in the foam physical properties, and E3 presented the shortest drying times. All models tested were satisfactorily adjusted, but Page’s model was the most adequate to describe the process. Sample E3 showed the highest diffusivity and sample E2 the lowest activation energy. The drying temperature increase caused reductions in enthalpy and entropy, as well as an increase in Gibbs free energy, indicating an endergonic process. The combination of additives incorporated into the blend influences the drying process: formulation E2 shows greater efficiency in removing water, and formulation E1 presents the highest energy demand.