Secagem em camada de espuma da polpa de pitaia (Hylocereus polyrhizus (Weber) Briton & Rose).

Abstract

Due to its exotic appearance, sweet taste, nutritional properties and a great use in cooking, pitaia (Hylocereus polyrhizus (Weber) Briton & Rose) has been attracting the attention of consumers and fruit growers in several regions of Brazil. Besides the great acceptability of the fruit, the pulp is rich in phenolic compounds and pigments, mainly anthocyanins and betacyanins, which may act in the body as antioxidants. The aim of this stuy was to study the drying of the pitaia pulp by the foam layer drying method. Preliminary tests were carried out with formulations containing polysorbate 80 (0,5%) and xanthan gum (0,1, 0,2 and 0,3%). To reduce the hygroscopicity of the powder obtained in these preliminary drying, maltodextrin was added to the samples at concentrations of 10, 15 and 20%. Both the whole pulp and the maltodextrin-containing formulations were characterized for chemical, physical and physico-chemical parameters. Density, over-run and foam stability were evaluated; Then these formulations were subjected to air circulation drying using rectangular trays, 1,0 cm in thickness of the foam layer, at temperatures of 50, 60 and 70ºC. The powders produced were characterized in terms of physical, chemical and physico-chemical parameters, as a way to define the best powder. In this best powdered sample the moisture adsorption isotherms were determined, at temperatures of 20, 30 and 40 ° C; Storage for 60 days under controlled temperature conditions (20, 30 and 40ºC) and relative humidity of approximately 83% with the samples packed in laminated packages; And the degradation kinetics of anthocyanins, betacyanins and red intensity for 14 days at temperatures of 20, 30 and 40°C and relative humidity of approximately 83%. The Page model was the best fit to the experimental data of the drying kinetics of the formulations with R2 values above 0,99 and DQM of less than 0,03. After drying it was found that the sample obtained at 70 ° C containing 10% maltodextrin was the best, with a water content of 5,39% b.u, acidity of 1,06% citric acid, water activity of 0,36; Red intensity of 37,41; Bulk density of 1,46 g / cm3 and Carr index less than 15%; The lowest insolubility value (18,22%), a hygroscopicity of less than 17%; Betacyanins with a value of 51,99 mg / 100g and total anthocyanins of 19,16 mg / 100g. In general the Peleg model provided the best adjustments to the experimental data of the adsorption isotherms, with R2 ≥ 0,99 and P ≤ 3,6, whose isotherm was classified as type II sigmoidal. During storage, the laminated packages were more efficient for the temperature condition of 20 ° C; With increasing temperature and during storage, a marked increase in water content, acidity, water activity, red intensity and insolubility was observed; And reduction of luminosity, intensity of blue, total betacyanins and anthocyanins. The highest degradations, for both anthocyanins and betacyanins and red intensity, occurred at the highest storage temperatures; The three degradation kinetics analyzed were well adjusted by the zero order reaction equation.