Descrição do processo de secagem e caracterização físico-química de cascas de maracujá amarelo (Passiflora edulis f. flavicarpa o. deg.).

Abstract

The present research aimed to describe and optimize the drying process of passion fruit peels, dried at 60 and 70 °C, submitted and not submitted to bleaching pre-treatment, as well as to analyze the physical-chemical parameters of dry content (flours) and products prepared from it (mignon biscuits). To describe the drying kinetics of passion fruit peels, empirical models and a numerical solution were used for the diffusion equation (assuming the geometry of an infinite wall, as well as, considering that the effective diffusivity of mass and thickness of the product could vary), through two softwares called Lab Fit and Infinite Slab Numerical. After convective drying, the samples were crushed until flours were obtained, which were characterized for the parameters of moisture, water activity (aa

), acidity, lipid and ash. The flour that presented the best physical-chemical characteristics, as well as shorter processing time, was used for the preparation of mignon biscuits. The biscuits were characterized by moisture,

, lipid and ash analyses. According to the results obtained, it was possible to verify that the equilibrium moisture content was influenced by bleaching pre-treatment for both samples (60 and 70 °C), while the drying temperature only influenced the moisture content of the bleached samples. In relation to drying time, a reduction of 105 minutes was noted in the total process period for dry treatment at 70 °C with bleaching. A significant influence of temperature and bleaching on drying rates was observed. Among the empirical models, Page was chosen the model that best fit the data of the drying. The diffusive model adjusted satisfactorily to the experimental data, and was even considered the one that was more effectively adapted to the data. Regarding the convective mass transfer coefficient, temperature influence was noted (as the drying temperature increased the coefficient also increased). On drying kinetics, it was possible to notice that there was a greater influence of temperature when compared to bleaching pretreatment. Regarding the effective diffusivity of mass, there was a significant difference in these diffusivity at the beginning of the process. All flours obtained presented satisfactory physical-chemical characteristics (values according to current legislation). The flour chosen for the preparation of mignon biscuits was that derived from bleached samples dried at 70 °C, because it presented shorter processing time. The biscuits were also considered physical-chemically adequate, presenting themselves as promising products from the biotechnological point of view, with wide insertion capacity in the food industry. In general, it was noticed that the models used to describe the drying kinetics (empirical models and a number solution for diffusion equation) were satisfactorily adjusted to the experimental data, as well as, both the flours of passion fruit bark, and the

mignon biscuits presented good physicochemical characteristics, presenting themselves as promising products from the biotechnological point of view.