Secagem da polpa e casca do juá em camada de espuma (foam-mat drying)

Abstract

Juazeiro (Ziziphus joazeiro Mart.), is a typical tree of Brazilian Northeastern. Its fruit, besides being sweet and rich in vitamin C, is widely used as animal feed and suitable for processing in order to obtain flours. As it is a seasonal fruit (ripening period from June to July), it prevents its spread to other regions and seasons of the year, besides the impracticability of its storage for long periods, due to the high water content of the fruit that exposes it to proliferation of microorganisms. Foam-mat drying is a simple and viable option for maintaining the physicochemical characteristics of the fruit and removing water, hindering microbial action and extending life span. Thus, the objective of this work was to obtain the pulp and peel powder from the juá by the foam-mat drying method. As the foam exerts a great influence on the drying efficiency, it was characterized by the analysis of stability, density, air incorporation, expansion and humidity. Drying was performed according to the 2³ + 3 central factorial experimental design, with the independent variables: foaming agent concentration (3, 4 and 5%); agitation time (3, 4 and 5 minutes) and drying temperature (50, 60 and 70 ° C) and evaluated the influence of these variables on the process response variables (drying time and equilibrium humidity) and on the characterization of the obtained powder by statistical analysis. The drying kinetics data produced the drying curves and the adjustment to the nonlinear mathematical models found in the literature. With the obtained results it was observed that the experiments presented a typical drying curve, represented by a constant rate followed by a decreasing rate. Foaming agent concentration and agitation time were the variables that most significantly affected foam characteristics and temperature was the only variable that influenced drying time. For the adjustment to the mathematical models, the ones that had better representativity were the ones of Page and Page Modified. The antioxidant capacity of the powders obtained in foam-mat was lower and the phenolic compounds had an increase when compared to the lyophilized powder. The analyzes performed of soluble solids, pH, solubility, water activity, ash, lipids, moisture and carotenoids obtained values close to those of the lyophilized powder of the juá pulp and peel, preserving their properties and finding that foam-mat drying is a viable technique for obtaining the fruit powder.