Drying acerola residue in a spouted bed: Fluid dynamic study and functional quality analysis

Abstract

AbstractIn the fruit processing industry, a large volume of residue is generated, which is usually discarded. However, fruit residues may have appeal as functional ingredients due to the presence of bioactive compound. In this study, the drying of acerola residue in a medium‐sized conventional spouted bed was investigated. The residue was characterized; vitamin C and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) were determined to evaluate the effect of drying on bioactive compounds. To overcome the difficulty of material fluidization, a mixture composed of in natura acerola residue and acerola residue previously dried in an oven as an inert material was used. The effect of air temperature (40 and 60°C) and velocity (28 and 36 m/s) and amount of in natura residue in the mixture (20% and 30%) was evaluated during drying. As expected, higher temperatures and air velocities and lower percentages of in natura residue favored the reduction of moisture. For a mixture containing 20% in natura residue, air velocity of 36 m/s, and temperature of 60°C, it was possible to achieve a final moisture content suitable for storage (14.23% w.b.) and the highest percentage of DPPH free radical capture activity (85.31%). Moreover, a mixture containing 30% in natura residue, velocity of 28 m/s, and temperature of 40°C conserved more vitamin C (48.30 mg of ascorbic acid/100 g). Finally, spouted bed can be considered a good technique for drying acerola residue as it was able to reduce a high amount of moisture content preserving bioactive compounds during short drying periods at low temperatures.Practical ApplicationsThe acerola processing generates a residue that consists basically of the seeds, bagasse, and peels, which is rich in ascorbic acid, phenolic compounds, flavonoids, anthocyanins, and organic acids. This residue can be used to generate new food products, which reduces the environmental problem of its disposal and the loss of raw material in fruit processing. To extend the residue shelf life, it must be subjected to a drying process. In this paper, the drying of acerola residue was investigated in a medium‐sized spouted bed. The spouted bed proved effectiveness in drying the acerola residue and in conserving bioactive compounds when operating for short periods and with low temperature. Thus, it can be considered as a promising technique for drying food products. Also, the data provided in this study can contribute to the solution of the scale‐up problem in spouted beds.