Quality properties of roselle (Hibiscus sabdariffa) calyxes as affected by drying process

J.P. Ledesma-Valladolid, R. Reynoso-Camacho, G.M. Nava-Morales, M.E. Vázquez-Barrios, D. Vázquez-Celestino, M.D. Dufoo-Hurtado, E.M. Mercado-Silva
Roselle (Hibiscus sabdariffa L.) calyxes have been used worldwide in hot and cold beverages, as flavoring agent and herbal medicine as well. Traditionally, the calyxes are dried directly in the sun but this method does not allow an adequate control of the process and induces losses of quality in the product. The aim of this study was to evaluate the effect of three drying methods with two cultivars of roselle calyxes from México on the nutraceutical and physicochemical composition. Roselle calyxes from ‘Criolla’ and ‘China’ cultivars were dried using direct solar drying method, a solar oven drier, or a forced air drier (at temperatures of 45, 55 and 65°C). After the drying process, the physicochemical properties (pH, total acidity and color) and nutraceutical properties (monomeric anthocyanins, tannin-bound anthocyanins, phenolic compounds, flavonoids, and ABTS and DPPH antioxidant capacity) were evaluated. The drying kinetics was also evaluated using a 4P Gompertz model. The moisture sorption isotherm of the dry product was evaluated at 35°C and the data were fitted using the GAB model. Our results indicate that the drying process had different effects with respect to the cultivar and drying conditions. ‘China’ had higher contents of monomeric anthocyanins than ‘Criolla’. Drying in forced air at temperatures of 45 and 55°C were the best conditions to dry roselle calyxes. These treatments maintained high content of monomeric anthocyanins and better antioxidant capacity. The solar drying induced an anthocyanin loss. However, also the cultivar affected the drying process. The drying kinetics and moisture isotherm sorption was fitted satisfactorily using a 4P Gompertz and GAB model, respectively.
Ledesma-Valladolid, J.P., Reynoso-Camacho, R., Nava-Morales, G.M., Vázquez-Barrios, M.E., Vázquez-Celestino, D., Dufoo-Hurtado, M.D. and Mercado-Silva, E.M. (2020). Quality properties of roselle (Hibiscus sabdariffa) calyxes as affected by drying process. Acta Hortic. 1287, 145-152
DOI: 10.17660/ActaHortic.2020.1287.19
Hibiscus sabdariffa, drying methods, nutraceutical properties, physicochemical characteristics

Acta Horticulturae