HOW IS DECAF TEA PRODUCED?
It is helpful to understand how decaf teas are produced. Decaffeination is the process of extracting caffeine from tea (or coffee).
Common methods of large-scale decaffeination include:
- Use of supercritical carbon dioxide. The supercritical carbon dioxide method of extraction is considered a superior method because it removes caffeine without removing other flavor components. The extraction technology used is also generally considered the safest method of decaffeination. The extraction process uses carbon dioxide (CO2) in its supercritical state, causing the liquid and gas phases to become indistinguishable from each other. This is advantageous because CO2 can reach into small spaces like a gas but can also dissolve and act like a liquid solvent. The physical properties of supercritical CO2 are easily manipulated. Specifically, when applied to tea leaves, the supercritical carbon dioxide bonds to the caffeine molecules, extracting them from the tea leaves. Because carbon dioxide is non-toxic, inert and easy to separate, it does not remain on the leaves after the extraction process. Carbon dioxide is relatively cheap, easy to obtain, and the extraction process is relatively simple. CO2 use ensures that the original flavor of tea is intact. Compared to traditional chemical solvent extractions, supercritical carbon dioxide extraction has many advantages, and is growing in popularity worldwide.
- Use of traditional chemical extraction, including ethyl acetate and dichloromethane. Ethyl acetate is a manufactured solvent, but is also a naturally occurring ester in wines and some fruits. Use of ethyl acetate is an inexpensive solvent that has been determined to carry no toxicity hazards, but is considered inferior to the carbon dioxide method because it also causes extraction of more flavor compounds from the tea. Some studies on dichloromethane have raised concerns about health and environmental hazards when used on an industrial scale.
ADVANTAGES OF SUPERCRITICAL CO2 VS SOLVENTS
- Residues: Supercritical CO2 extraction leaves no residues, while residues (usually small amounts) of solvents used may remain
- Heat & decomposition: Supercritical CO2 can be performed at lower temperatures, thereby lowering the occurrence of decomposition of volatile flavor/aroma molecules
- Solubility: By adjusting temperature and pressure, the supercritical CO2 process allows for more precise solubility
HOW DOES SUPERCRITICAL CO2 DECAFFEINATION WORK?
The basic steps of CO2 decaffeination involve:
- Tea leaves are placed in high pressure vessels.
- CO2 is pressurized to a supercritical state that gives it both liquid and gaseous properties.
- This supercritical CO2 is circulated into the vessels that contain the tea leaves, where the caffeine molecules in the tea leaves bond to the CO2.
- The caffeine-bonded CO2 is then pumped out of the vessel into a separation tank where the caffeine and CO2 are separated. The caffeine can be discharged from the tank, and the CO2 can be reused.
The CO2 process results in removal of 95-97% of total caffeine, which means caffeine levels of 0.2-0.4% caffeine by dry leaf weight.
DOES DECAFFEINATION REMOVE ALL CAFFEINE?
No– not all caffeine is removed during decaffeination. The US tea industry voluntarily accepts a standard of no more than 0.4% caffeine by dry leaf weight. These teas are labeled as decaffeinated teas, and not as caffeine-free.
Caffeine-free is reserved for tea products that naturally contain no caffeine. Many herbal teas are caffeine-free.
DECAF TEAS PRODUCED
Firsd Tea decaf teas are produced in Zhejiang province, and manufactured at the Zhejiang Longyou Mingda facility. This first-generation technology has an annual output of 150 tons of decaf tea leaves, and began in 2008. Second-generation CO2 technology has been developed and is used in production at Jiuyu Tea Company, a subsidiary of Zhejiang Tea. Together, these facilities produce decaffeinated black tea, green tea, white tea, and steamed green tea.
Zhejiang Province tea field – leaf used for decaf black and green teas
See also these links related to decaffeination: