Study on the Extraction of Natural Essence from Green Tea Leaf by Supercritical CO2

A simple and clean way of extraction of natural essence from green tea leaf by supercritical CO₂ was developed. The optimum extraction conditions to produce the high-quailty natural essence were found: loading about 100g/L, operating at 5000 psi and 50 °C, and separation kettle temperature 75 °C, static extraction three times with 40 min every time, the yield of natural essence was 0.5%. The product was analyzed by gas chromatography-mass spectrometry (GC-MS) show that dimethylsulfide was the characteristic aroma components of the natural essence with more than 50 kinds of alcohols, ketones, aldehydes, ethers and esters etc.. There were only little other biochemical composition of raw material and 0.4% caffeine in the product detected by high-performance liquid chromatography (HPLC), and the biochemical composition in the raw material were almost no loss before and after extracted by supercritical CO₂, it indicated that the specificity of the method for extraction tea natural essence is very strong, and propitious to improve the secondary utilization of the tea raw materials.