Effect Of The Dehydration Method Of Hibiscus Sabdariffa L Calyces On The Quality Of Their Aqueous Extracts .

Hibiscus sabdariffa L. is a plant from tropical climates, which produces, among other products, deep red calyces used to prepare refreshing drinks. The high humidity (85-87%) of the calyces at the time of harvest must be reduced to about 12% for handling and storage. The aim of the work was to evaluate the effect of the dehydration method of the calyces (sun drying, SD; hot air-drying, AD, at three temperatures: 50, 60 and 70 oC) of three varieties of Hibiscus sabdariffa L. on the quality of their aqueous extracts. The quality was measured as a function of color, and chemical variables (titratable acidity, TA, total soluble phenols, TSP; total anthocyanins content TAC, and organic acids). The varieties used were Negra Quiviquinta (NQ) with dark red calyces, UAN-9 with light red calyces, and UAN-16, with white calyces. The dehydration method affected the quality of the extracts. The SD was the one that most affected color and chemical variables. The color of the extracts was darker than that of the control while titratable acidity (TA) was reduced on average 40.6%. No effect of AD treatments was observed on these variables. On chemical composition, SD reduced TSP on average 15.3%, with UAN-16 as the most affected variety. In the varieties with red calyces, the average TAC reduction was 36.9%. Of the organic acids, malic and succinic were the most damaged. As ocurred in physical variables, AD treatments showed little negative effect on chemical composition of the calyces. Of the dehydration methods evaluated, the AD70 degrees C rendered the best quality of aqueous extract, in base of the variables evaluated.