Assessment of antioxidant properties, instrumental and sensory aroma profile of red and white Karkade/Roselle (Hibiscus sabdariffa L.)

The antioxidant properties of the water extract of Hibiscus sabdariffa L. as well as their aroma profile were investigated. The samples analyzed were three red (Al-Rahad, Al-Fashir, Al-Gezira) and one white varieties. Total phenolic content, total flavonoid content, total anthocyanin content, ferric reducing antioxidant power and radical scavenging activity (RSA %) were measured spectrophotometrically. The red varieties of Karkade showed better overall antioxidant properties and aroma profile compared to the white variety. Conversely, the white H. sabdariffa might also be used in antioxidants applications, as its extract exhibited the highest RSA % compared to other varieties. Nineteen volatile compounds were detected in the H. sabdariffa extracts, including aldehydes, alcohols, ketones, esters and phenol. Partial least squares regression (PLSR) was applied to determine the relationship between sensory descriptors and instrumental data. PLSR result showed a good relationship between sensory analysis and instrumental data (t1 and t2 = 94.63%). This indicated that gas chromatography-mass spectrometry (GC/MS) can be used as suitable tools to predict the aroma quality of H. sabdariffa.