Secagem por aspersão da polpa do figo-da-índia.

Abstract

This work was developed with the goal of producing a powder product from the full pulp of the cactus-pear, by spray drying method, and evaluate it using the same experimental design as well, its stability during 40 days storage under controlled humidity (83%) and temperature (25 and 40 °C). Initially, tests were preliminary to the choice of the dextrose equivalent of maltodextrin to use, the concentration of maltodextrin, the temperature of the drying air, and finally, the choice of nozzle diameter pneumatic equipment. Formulations were prepared from the pulp with the addition of 25 full, 30 and 35% maltodextrin with dextrose equivalent (DE = 10), below, these formulations were spray dried in a dryer with drying air temperature of 170, 180 and 190 °C, pneumatic nozzle diameter of 1.2 mm, flow pumping pulp made of 0.5 L / h, the air flow of 0.3 L / min. Whole pulp and the formulations were characterized for physical, chemical and physical chemists. We evaluated also the rheological behavior of slurries at temperatures of 25 °C and the experimental data were fitted by the models of Ostwald-de-Waelle, Herschel-Bulkley, Casson and Mizrahi-Berk. At the end of the drying process were collected two types of powder samples: in the drying chamber (Type A) and Cyclone (Type B), and physical-chemical analysis, by 22 factorial experimental design with three central points, with order to evaluate the influence of maltodextrin concentration and drying temperature on the parameters water content, total soluble solids, pH, total acidity, sugars (reducing, total and non-reducing), ash, color and water activity. For the selection of the best powder took into account the lower water content of the samples with that selected the dust of Experiment No. 4 (35% maltodextrin and 190 °C temperature) as the best, which was submitted to storage for 40 days under controlled humidity (83%) and temperature (25 and 40 °C). We analyzed the adsorption isotherm of water at 25 °C, the powdered sample selected and adjusted models of GAB, Oswin and Peleg the experimental data. The full pulp of the cactus-pear was considered slightly acidic and it is a pseudoplastic fluid in the Mizrahi-Berk model was the best fit to the experimental data. In addition of maltodextrin formulations to alter the characteristics of the full flesh, presenting with pseudoplastic behavior also, and the Mizrahi-Berk model that best fit the experimental data. The cactus-pear powder, collected in the drying chamber (Type A) showed different characteristics from the cactus-pear powder collected in the cyclone (type B). The empirical models of first order for the cactus-pear powder cloves Type A, obtained for water content, pH, ash and yellow intensity, and were significant predictors, while for the cactus-pear powder Type B, only the models for the water content and the intensity of yellow were significant and predictive. It was found during storage of powder samples, the laminated packaging did not prevent the absorption of water, thus increasing the water content and, consequently, the water activity during storage, the powder samples remained unchanged with respect luminosity and total acidity in the two temperatures, for the intensity of red was a decrease in temperature of 25 ° C, while the temperature of 40 °C remained constant, and the yellow intensity showed a decrease during storage, but the predominance yellow color was not affected. The adsorption isotherm of water was classified as Type III and Peleg model was the best fit to the experimental data.