Secagem em camada de espuma da polpa de cajá.

Abstract

The cajá pulp was dryed using foam-mat drying process and results were analyzed using the experimental factorial design. Were prepared formulations of cajá pulp with three different concentrations of the emulsifier Emustab® (1, 2 and 3%) and fixed concentration Super Liga Neutra (2%) additive; this mixture was stirred during 15 minutes until the foam formation. AH samples at the end were analyzed for its chemical, physical and physico-chemical properties. The Formulations 1, 2 and 3% were dried in a stove with air circulation at 60, 70 and 80 °C and thickness 0.5; 1.0 and 1.5 cm. The Page, Henderson & Pabis and Cavalcanti Mata models were used to fit the experimental data. The moisture content, °Brix, pH, acidity, sugars (reducing, total and non-reducing sugars), ascorbic acid, ashes, color, water activity and yield of the powder pulp was determined to study the effect of the drying temperature, foam layer thickness and the emulsifier concentration. From these results, the best sample was selected to study the moisture adsorption isotherm at 25 °C, fitting data by the GAB, Oswin and Peleg models. According the results it can be concluded that the whole cajá pulp is acid and could have its applications as a vitamin C source; furthermore is classified as pseudoplastic fluid, whereby its experimental data was best fítted by the Herschel Bulkley model. It can be stated that the density, volumetric expansion and stability of the foam of the three different formulations were in agreement with the drying standards of foam layers. There was an effect of the additives on the properties of the whole pulp as well as on the different formulations, whereby the formulations presented a pseudoplastic behavior, with its experimental data best fitted by the Mizrahi-Berk model. The drying curves were affected by the thickness of the layer and temperature. It was noticed that thinner layers resulted in higher drying rates with a lower final moisture content. The highest drying rate was obtained by the sample with 3% of the emulsifier. The experimental data of the drying process was best fitted by the Cavalcanti Mata model. According to the experimental factorial design the sample with the concentration of 3% of Emustab® and 2% of Super Liga Neutra, dried with a layer thickness of 0.5 cm at a temperature of 60 °C presented the best results.