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Supercritical CO2 fluid extraction of caffeine

Caffeine a methylxanthine alkaloid. Chemical Formula C8H10N4O2, soluble in water.White crystalline powder, odorless, bitter and weakly alkaline. On October 27, 2017, the WHO Agency for International Cancer Research (IARC) released a preliminary list of carcinogens, with caffeine in the list of Category 3 carcinogens.

300L supercritical CO2 extraction equipment
Supercritical CO2 fluid extraction of caffeine

Caffeine is a central nervous system stimulant which can refresh and relieve fatigue and keep the body in good condition. However, high-dose intake can lead to caffeine poisoning, the body produces a series of adverse reactions.

Supercritical CO2 fluid extraction of caffeine
Supercritical CO2 fluid extraction of caffeine

First, coffee beans are pre-treated, mechanically washed coffee beans to remove dust and impurities; followed by steam and water pre-soaking, to increase its moisture content of 30% -50%; then extracted with a supercritical extraction equipment will be Pre-soaked coffee beans into the extraction tank, continue to the tank into the CO2, caffeine gradually extracted;

The second, the caffeine-containing CO2 was sent to the cleaning tank of the supercritical extraction equipment, caffeine into the water phase last, and then caffeine in the aqueous phase to be recovered by distillation, C02 is recycled; 10 hours, SFE The content of caffeine in the treated coffee beans decreased from 0.7-3% to 0.02%.

There are currently three ways to remove caffeine from coffee beans

  • The first, called water treatment, removes 94 to 96 percent of the caffeine.
  • The second method is the chemical extraction method. In the early days, chloroform (Chloroform) and Benzene (Benzene) were used as solvents to extract caffeine. Later, it was learned that these chemicals cause cancer, and they were gradually replaced by other less harmful chemicals, but they are chemicals after all. Not natural enough, this method can extract 96-97% of caffeine.
  • The third method is supercritical carbon dioxide treatment, and its extraction rate can reach 96-98%. The most efficient of the three methods for decaffeinating.

Carbon dioxide treatment uses two natural elements

Carbon dioxide treatment uses two natural elements, pure water and carbon dioxide (the mixture of which we usually call him soda water) to extract the caffeine in green coffee beans. The founder of this method is Kurt Zosel.
In chemistry, we are also called supercritical CO2 extraction technology. The density of supercritical carbon dioxide (hereinafter referred to as SC-CO2) is hundreds of times that of gas, and is close to the density of liquid, but its viscosity is slightly the same as that of carbon dioxide in gaseous state. . Its diffusion coefficient is about one percent of that of gas and hundreds of times larger than that of liquid. Therefore, material movement (Mass transfer) or distribution, etc., are faster than in liquid solvents.

Features of supercritical carbon dioxide treatment method

This method was developed as a method for extracting caffeine from coffee beans because of the following characteristics:

  1. The critical temperature of carbon dioxide is 31.1°C, and the critical pressure is 73 atmospheres (Atm). Since the critical temperature is relatively close to normal temperature, it is suitable for the extraction of thermally unstable substances. It has a good effect on the retention of aroma substances in coffee.
  2. Carbon dioxide is an inert gas, non-flammable, chemically reactive, and non-residual, harmless to the human body, and does not cause environmental pollution
  3. It is easy to produce high-purity carbon dioxide for use and it is cheap.

supercritical carbon dioxide treatment method

The method of supercritical CO2 extraction of caffeine is to let the coffee beans absorb water, expand to twice the size, the caffeine molecules loosen in the beans, add carbon dioxide and give a pressure greater than 100 atmospheres (Atm) in the water, so that the water and carbon dioxide mix to create a Soda environment. The carbon dioxide acts like a magnet to attract the caffeine molecules, and once the caffeine is captured by the carbon dioxide, the caffeine begins to move. Carbon dioxide has high selectivity, and it will not capture carbohydrates and proteins in coffee beans, because carbohydrates and proteins are the main components of flavor and smell in coffee beans. When the extraction is finished and dried naturally, the caffeine-containing water can be easily separated from the caffeine and used for other commercial purposes.

Advantages of supercritical carbon dioxide treatment

  1. The efficiency of extracting caffeine is very high, without chemical pollution.
  2. It will not cause any chemical changes with the carbohydrates and proteins in coffee beans.
  3. Its by-product (caffeine) is natural and 100% recyclable!

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