Spouted bed drying of jambolão (Syzygium cumini) residue: Drying kinetics and effect on the antioxidant activity, anthocyanins and nutrients contents

This paper describes the effect of the air temperature and velocity on the drying kinetics in spouted bed of jambolão residue (peel and seeds) and the consequent changes on the antioxidant activity, anthocyanins and minerals contents in the dried products. Only the air temperature significantly influenced the drying kinetics, which presented mainly falling rate drying period. The air temperature showed a positive effect on anthocyanins degradation and their content was reduced by 60%-70% after drying. However, the antioxidant activities of dried residue still ranged from 93% to 97%, showing that drying do not decrease the free radical scavenging ability of wet residue. Besides the antioxidant activities, considering a portion of 50 g of sample, the dried product presents in average 25% of the daily recommended intake of Mg for adults, while Fe presents 8.7% and Zn and Ca, 3.2%. The photoacoustic spectroscopy was explored, showing to be sensitive to the presence of anthocyanins and other pigments before and after drying. It was observed systematic changes on the absorption spectra of the product after drying, which points out photoacoustic as an alternative method to process monitoring without the need of sample preparation.