Clean technologies applied to the recovery of bioactive extracts from Camellia sinensis leaves agricultural wastes

Abstract

This study deals with the valorisation of tea leaves from the agricultural pruning remains using clean technologies with low environmental impact. Leaves with null commercial interest were dismissed during the pruning season, however with a sequential combination of microwave hydrodiffusion and gravity (MHG), ultrasound-assisted (US) and pressurized hot water (AH) extractions was possible to recover bioactive compounds. An initial pre-treatment was performed using MHG at selected irradiation powers to facilitate the liberation of antioxidants through the cell membrane. The solid phases were processed by three ways: i) ultrasound bath system (80°C, 80KHz, from 15 to 60min); ii) AH technology (non-isothermal treatment with maximum temperature from 140 to 200°C); and iii) a sequence of the three aforementioned technologies. Both raw material and liquors were analysed to determine fundamental physicochemical, phytochemical or biological properties. Leaves debris showed positive results in bioactive compounds with a maximum value of total phenolic around 130mg GAE/g extract in the sequential combination. Antioxidant capacity ranged from 0.3 to 0.9g Trolox/g extract. The combination of green extraction technologies guarantees an efficient recovery of bioactive compounds, creating the possibility of new products that improve the wellbeing.