Influence of time-based hot air-drying method on total polyphenols, total antioxidants and tannins of Jatropha zeyheri tea leaves

Abstract

Phenols in tea are responsible for its antioxidant activity. The pure catechins and phenolic acids found in tea are more powerful than the antioxidant vitamins C, E and ?carotene in an in vitro lipoprotein oxidation model. The antioxidant properties have been shown to have a protective effect against several degenerative diseases. The objective of this study was to investigate effect of time-based hot air-drying method on tea phenolic compounds. Fully developed green leaves of Jatropha zeyheri were sampled randomly at Zebediela (Khureng village in Limpopo Province, South Africa). Khureng village is characterized by semi-arid climate, with rainfall of less than 400 mm per annum. The area is predominately clay with bushveld vegetation. Samples were transported to Limpopo Agro-Food Technology Station (LATS) laboratory for analysis. Four treatments, namely, 0, 24, 48 and 72 h, were arranged in completely randomized design (CRD), replicated five times. Total phenolic, total antioxidant capacity and tannin content were determined using Folin-Ciocalteu, phosphate-molybdate and Vanillin-HCl method, respectively. Total phenolic, total antioxidant capacity and tannin content were significantly increased by 63, 82 and 152%, respectively, when subjected to different drying periods.