A comparative study of different drying methods respect to the content of phenols and flavonoids in dry leaves of Citrus aurantium L.

Abstract

Citrus Aurantium leaves contain compounds such as phenols and flavonoids that give it antioxidant properties. These properties can be affected by using any conservation method, such as drying. This study was carried out to determine the effects of different technologies of thermal drying on total phenols content (TPC) and the total flavonoids content (TFC) from the leaves of bitter orange (Citrus aurantium L.).  Solar drying was carried out under the open-air sun conditions and using two direct solar dryers; one with natural convection and the other with forced convection. TFC and TPC in equivalents of gallic acid (EGA) and quercetin (Q), respectively, of the ethanolic extracts of C. Aurantium were determined by using spectrophotometric techniques. The results showed maximum values of phenols for direct natural convection solar dryer (161.4 mg EGA/g MS) and minimum for shade drying (61.43 mg EAG/g MS). Regarding flavonoids, the highest values were obtained in the direct forced convection solar dryer (32.22 ± 1.6 mg QE/g MS), while in the open-air sun the lowest values were observed (11.72 mg QE/g MS). It is concluded, that the direct solar dryers are effective technologies to maintain the TPC and the TFC in the dry leaves of C. aurantium.