Recycling of Tea Waste: Simple and Effective Separation of Caffeine and Catechins by Microwave Assisted Extraction (MAE)

Abstract

This study was designed to develop a cost effective green extraction method to separate valuable 10 chemicals from black tea waste (BTW) and tea dust called "caffeine dust" (CD). These materials are totally 11 unwanted residue and treated as rubbish. Two extraction methods were used for extraction of waste materials 12 obtained in three collection periods. In conventional extraction method, material was subjected to hot water 13 extraction at 80 o C for 40 minutes. In microwave assisted extraction (MAE) method, different eco-friendly aqueous 14 solvents (water, citric acid-water or ethanol-water) were used under a controlled 600 W microwave power at 80 15 o C for only 4 minutes treatment in a close microwave system. MAE and conventional method gave similar extract 16 yields for both waste materials but MAE was more successful and economical completing the extraction in shorter 17 time. Using citric acid-water solvent in MAE significantly increased the extraction of individual catechins such as 18 epicatechin (EC) and epigallocatechin gallate (EGCG). This study showed that tea waste could be utilized for 19 production of valuable chemicals using nontoxic solvents at extremely short extraction periods. 20