Effect of thermal treatments on the phenolic composition and antioxidant retention in Celastrus hindsii leaf

Abstract

Celastrus hindsii has been well known as a useful herbal medicine with a great anticancer property. In order to exploit this phytochemical plant source as a functional food drink, Celastrus hindsii leaf could be processed into dried herbal tea. During tea production, they must be blanched to inactivate enzyme and retain green color; dehydrated to low moisture content for long stability. However, these thermal treatments could seriously affect to bioactive components. It's very important to find out the optimal parameters in the blanching and drying steps so that the most phenolic content and antioxidant capacitycould be preserved. This research was conducted during 2020 at STNanotech laboratory, Vietnam to evaluate the impact of various conditions in blanching (100/15, 95/30, 90/45, 85/60, 80/75, °C/seconds) and drying (35/20, 40/18,45/16, 50/ 14, 55/12, °C/hours) on the phenolic composition and the antioxidant capacity of Celastrus hindsii leaf.The total phenolic content was determined by the Folin-Cicalteau method. Aluminum chloride colorimetric method was used for quantification of total flavonoid content. DPPH free radical scavenging activity and ABTS radical scavenging activity wasexamined by using 2,2-diphenyl-2-picrylhydrazyl and 2,2̍-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) assays. Results revealed that both hot water blanching at 90°C within 45 seconds, convective drying at 45oC within 16 hours greatly retained the total phenolic content(161.25±0.21 mg GAE/100 g), flavonoid content (103.19±0.14 mg QE/100 g), DPPH free radical scavenging (297.41±0.17 μg/mL), ABTS radical scavenging activity (1.640.02 mM TE/g) of the dried leaves. Through thermal treatment, the raw Celastrus hindsii leaf would beconverted into dehydratedform. Therefore, consumers had more chance to improve their health via daily consumption of this herbal tea.