Friday, March 17, 2023

Carbon dioxide process of decaffeination

The most selective process for removing just caffeine and not the other flavor precursors from coffee is carbon dioxide.

The coffee beans are sprayed with steam and hot water to raise their water content to 35%. Following the hydration of the coffee beans, they are pneumatically blown to the top of a 280-foot tower. The walls of the chambers in the tower are 6 inches thick and clad on the inside with stainless steel.

After being shot up into the tower the beans then begin to fall down. As the beans are falling supercritical carbon dioxide is pumped up through the beans. Supercritical fluid extraction allows for waste separation and minimization, as well as solvent recycling. Other advantages of supercritical extraction include high efficiency, high extraction rates and more selectivity.

Due to the supercritical nature of the CO2, it behaves more like a liquid than a gas. In this sate it has other liquid-like properties, such as the ability to dissolve other material when it is in a heavy glass or steel container under pressure. Extraction processes that use supercritical CO2 leave no such residue. Also, supercritical CO2 is selective exclusively for the caffeine.

Liquid CO2 is forced at a pressure of 1,000 pounds per square inch into the extraction chamber and when the CO2 comes into contact with the coffee beans, it passes through them and captures the caffeine, leaving the coffee beans with the caffeine in tow, the flavor compounds within the coffee bean intact.

CO2 does not affect the carbohydrates (sugar, starch) and peptides that during roasting are converted into the various compounds responsible for the flavor and aroma of brewed coffee. The caffeine-laden carbon dioxide is then blended into a column of water.

After being blended into water it flows into a chamber where the pressure drops from supercritical pressure to normal atmospheric pressure.

When the pressure comes back to normal atmospheric pressure, the caffeine is attracted to the water as the CO2 evaporates. This carbon dioxide is then captured to be recycled back into the process.
Carbon dioxide process of decaffeination

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