Secagem por aspersão da polpa do mandacaru.

Abstract

The aim o f this study was to obtain a product in powder form from mandacaru fruit pulp, using spray dryer, assess it and monitor it during 50 days of storage under controlled conditions of relative humidity (57.7%) and temperature(25 °C), at different dextrose equivalent values (DE = 10 and DE = 14), and concentration of 10% maltodextrin. Spray drying was conducted to select the best formulations prepared with the pulp and different concentrations of maltodextrin (10, 15 and 20%) and dextrose equivalent values (DE = 1 0 and 14), at drying temperature of 170 °C, pneumatic nipple (1.2 mm), peristaltic pump flow rate of 0.5 L/h and compressed air flow rate o f 0.3 L/min. The rheological behavior of the pulp and formulations was then analyzed, in the temperature of 10 °C, and the Ostwald-de-Waelle, Herschel-Bulkley and Casson were fit to experimental data. Mandacaru fruit pulp, its formulations and the pulp samples obtained after drying were submitted to chemical, physical and physicochemical characterization, using analysis of pH, soluble solids, ascorbic acid, total solids, moisture content, total titratable acidity, total sugars (reducing and non-reducing), ashes, color (luminosity, redness and yellowness) and water activity and density for the pulp and formulations, in order to determine the influence o f dextrose equivalent values and their corresponding concentrations. Properties related to the instantaneity of the powder product were also assessed, indicating possible differences between the additives and concentrations used in terms of solubility, wettability and reconstitution time. Moisture adsorption isotherms were determined in the temperatures of 20, 30 and 40 °C in the powder products prepared with 10% maltodextrin, and DE o f 10 and 14; all the samples were fit to the GAB, Peleg and Oswin models. The mandacaru fruit pulp was considered acidic, with low ascorbic acid content, and pseudoplastic behavior, where the Herschel-Bulkley model proved to be better at predicting the experimental data. The formulations exhibited the same rheological and pseudoplastic behavior; however, the addition o f different concentrations of maltodextrin and different dextrose equivalent values modified the initial characteristics of the whole pulp. Pulp samples with DE o f 10 and 14 displayed similar traits. During storage the differences were more marked at DE = 14, even though the flexible laminated packaging did not prevent an increase in moisture content and yellowness or a decrease in ascorbic acid, at the two de values. The moisture adsorption isotherms of the 10% maltodextrin samples were classified as type I I , in the temperatures of 30 and 40 °C, and type I I I , in the temperature of 20 °C, while the Peleg model best fit the experimental data.