What is caffeine
Caffeine is a Methylxanthines alkaloid. Chemical formula C8H10N4O2, soluble in water. White crystalline powder, odorless, bitter, slightly alkaline.
Caffeine is a central nervous system stimulant that refreshes and relieves fatigue and keeps the body in a better condition. However, high-dose intake can cause caffeine poisoning, causing the body to produce a series of adverse reactions.
Coffee beans and caffeine
The most important source of caffeine is coffee beans.
The content of caffeine in commercial coffee beans is 0.7 to 3.0%.
Coffee beans are also the raw material of coffee. Coffee is one of the world’s three largest beverages, and it is popular all over the world.
Extract caffeine to make coffee healthier
The caffeine contained in the coffee is harmful to the human body because of the excessive drinking.
Therefore, the decaffeinated coffee is popular with consumers.
Moreover, caffeine removed from plants can be used medicinally, so caffeine extraction from coffee is a double benefit.
The extraction of coffee beans with supercritical CO2 not only resulted in caffeine, but also preserved the original flavor of the coffee.
How to remove caffeine from coffee beans?
There are three methods for industrial removal of caffeine in coffee beans:
Swiss washing method, dichloromethane extraction method, supercritical CO2 fluid extraction of caffeine.
Supercritical CO2 fluid extraction of caffeine
The specific process of supercritical CO2 fluid decaffeination is as follows: In the factory, green coffee beans are bathed in hot water. When the water content of the coffee beans reaches 50%, they will be poured into a giant pressure cooker.
Definition of supercritical fluid
• Pure substances present changes in the state of liquids, gases, solids, etc., depending on temperature and pressure.
• When the gas-liquid equilibrium substance continues to be heated and boosted, the thermal expansion causes a decrease in the density of the liquid, and the increase in pressure causes the gas phase density to increase. When the temperature and pressure reach a certain point, the gas-liquid two-phase The phase interface disappears and becomes a homogeneous system, which is called the critical point.
•The liquid with a temperature and pressure above the critical point is called supercritical fluid (SCF).
The main characteristics of supercritical fluids
• Density is similar to that of a liquid and therefore has a strong solvation power. Minor changes in pressure and temperature can cause significant changes in density;
• Has a similar gas diffusion coefficient and low viscosity;
• Pressure and temperature changes can change the phase change;
• Due to the above characteristics, the supercritical fluid can quickly penetrate into the interior of the object to dissolve the target substance and quickly reach the extraction equilibrium.
The principle of supercritical CO2 extraction
• In the supercritical state, the supercritical fluid has good fluidity and permeability, and the supercritical fluid is brought into contact with the material to be separated, so that the components having the polarity size, the boiling point and the molecular weight are selectively Extract it.
• The method of decompression and temperature increase is to convert the supercritical fluid into a common gas, and the extracted material is completely or substantially precipitated, thereby achieving the purpose of separation and purification.
Then, 250-300 atmospheres of pressure are applied to the coffee beans, and supercritical carbon dioxide is injected into the coffee beans to dissolve the caffeine.
The process of supercritical fluid extraction of caffeine: Supercritical carbon dioxide (bottom right) is injected into coffee beans (the two jars on the left). After the caffeine is dissolved, the carbon dioxide and caffeine are separated (the upper jar).
You may worry that other fragrance molecules will also be taken away? In fact, only caffeine was targeted.
This is because in the supercritical state, as long as the temperature and pressure are adjusted, carbon dioxide can imitate the polarity of different molecules, so that special extraction can be tailored for different molecules.
Then, the mixture of supercritical carbon dioxide and caffeine is filtered into another large tank, the pressure is reduced, and the carbon dioxide returns to the gaseous state to evaporate, and the caffeine is easily left behind. In the end, 96%-98% of caffeine can be removed in this way.
Extraction of caffeine
- First, the coffee beans are pretreated, and the coffee beans are cleaned mechanically to remove dust and impurities; then steam and water are pre-blistered to increase their moisture content by 30% to 50%;
- Then, extract, pre-soaked coffee beans into the extraction tank, continue to send CO2 into the tank, caffeine will be gradually extracted;
- Next, CO2 with caffeine is sent to the cleaning tank and the caffeine is transferred to the tank;
- Finally, caffeine in the tank is then recovered by distillation and CO2 is recycled;
- In 10 hours, the caffeine content in the SFE-treated coffee beans was reduced from 0.7 to 3% to 0.02%.
Advantages of supercritical CO2 fluid extraction of caffeine
Compared with the Swiss washing method and the methylene chloride extraction method, the supercritical carbon dioxide extraction technology is efficient and environmentally friendly, and does not affect the flavor of coffee beans.
Now it has become one of the mainstream methods of decaffeinating. At present, about 100,000 tons of decaffeinated coffee beans in the world are manufactured using supercritical flow technology. Not only coffee beans, tea, cocoa beans also use this method to remove caffeine.
However, the cost of equipment for this technology is high, and only those factories with an annual output of 3,000 tons can afford them. These factories are mainly distributed in the United States (such as Maxmos Maximus coffee), Germany (Kraft) and Italy (such as SKW). -Trostberg), the products are also mainly supplied to large supermarkets.
Therefore, if you want to try supercritical flow coffee, you can choose from those factories.