Secagem contínua e intermitente de fatias de pera para elaboração de barra de cereal

Abstract

The study of different methods for drying agricultural products is necessary, both to verify the quality of the finished product and the viability of the process. In this sense, the objective of this work was to carry out continuous and intermittent drying kinetics (with an intermittency ratio of 2/3) on circular pear slices to obtain flour for the production of cereal bars. The pears were cut into circular slices, 5 mm thick, subjected to temperatures of 50 and 70°C. Mathematical and diffusive models were used to describe the continuous and intermittent drying process, using infinite wall geometry and boundary conditions of the first and third types. Page's model was the best fit to the experimental data. For the analytical solution of the diffusion equation, the Convective Adsorption software was used for third- type boundary conditions, enabling the determination of the Biot number, effective diffusivity and convective mass transfer coefficient. The Prescribed Adsorption software was used for the first type boundary condition, with the third type boundary condition being the one that best described the pear drying processes and the effective mass diffusivity increased with intermittent drying. The comparison between continuous and intermittent drying kinetics showed a reduction in drying time with the application of intermittency, providing greater energy savings. The results state that not only the intermittency ratio is important for reducing drying time, but also the tempering period. The flour obtained through intermittence of 10 min at 70°C demonstrated desirable characteristics, as it stood out in terms of higher protein, crude fiber, ascorbic acid, flavonoids and relatively high content of phenolic compounds; which justified its selection among the others obtained for processing cereal bars. The results of the microbiological analyzes of the cereal bars indicated that all analyzed samples presented satisfactory microbiological quality and were considered suitable for human consumption. The sample most accepted by consumers for the attributes color, appearance, odor and flavor was F4, followed by F2. Regarding purchase intention, the majority would buy sample F4, which suggested that the increase in pear flour promoted greater acceptability of the bars.