Production of decaffeinated green tea leaves using liquefied dimethyl ether

We developed a new technique for green tea decaffeination involving ingredient extraction and drying of green tea leaves by using liquefied dimethyl ether (DME) as a safe extraction solvent. After hot water extraction with water content of 74.6–76.2%, green tea leaves were tested to verify the DME extraction in both laboratory- and bench-scale processes. The distributions of caffeine and catechins in the extracted residue, organic extracts, and removed water were tested by high-performance liquid chromatography. Caffeine was completely removed from the green tea leaves. Approximately 25.2–56.0% of catechins remained in the residue after DME extraction. In particular, 56.0% of epigallocatechin gallate, which has the greatest activity of all catechins remained in the residue.

► A single step method combined decaffeination, drying, and ingredients extraction for green tea leaves.
► Caffeine was completely removed from the green tea leaves using liquefied dimethyl ether.
► 25.2–56.0% of catechins remained in green tea leaves after DME extraction, especially, 56.0% of EGCG.
► This method is safely, economically and environmentally friendly.