Can you explain Supercritical Fluid?
Not many of us know what is supercritical extraction, so let make it easy to understand.
Imagine you have something, like a plant, and you want to get certain valuable parts out of it, maybe the oils that give it a nice smell or have health benefits.
Normally, you might use a liquid, like water or alcohol, to soak the plant and pull out those valuable parts. This is like making tea – the hot water pulls the flavor and color out of the tea leaves.
Supercritical fluid extraction is a bit different, and in some ways, more powerful and cleaner.
First, what is a "supercritical fluid"?
Think about water. It can be ice (solid), liquid water, or steam (gas). If you heat water up and put it under a lot of pressure, you can reach a point where it's not really a liquid or a gas anymore. It becomes something in between, a "supercritical fluid."
This special fluid has qualities of both a liquid and a gas:
- Like a gas, it can spread out and get into tiny spaces.
- Like a liquid, it can dissolve things.
The most common substance used for this is carbon dioxide (the same stuff we breathe out and that's in fizzy drinks). When you heat and pressurize carbon dioxide past its "critical point," it becomes a supercritical fluid.
Now, how does the extraction work?
- Getting Ready: You put the stuff you want to extract from (like the plant material) into a strong container.
- Adding the Special Fluid (solvent) : You pump the supercritical fluid (like our special carbon dioxide) into the container with the plant material.
- Dissolving: Because the supercritical fluid can spread like a gas and dissolve things like a liquid, it gets into all the little nooks and crannies of the plant material and dissolves the valuable parts you want to extract.
- Separating: Once the valuable parts are dissolved in the supercritical fluid, the mixture is moved to another container. Here, the pressure is lowered.
- Releasing the Goodies: When the pressure drops, the supercritical fluid turns back into a regular gas (in the case of carbon dioxide). As it turns back into a gas, it can no longer hold onto the dissolved valuable parts, so they separate out.
- Collecting: You are left with the extracted valuable parts, and the carbon dioxide gas can be captured and used again until all the molecules you are looking for have been extracted
It's clean: Since the supercritical fluid turns back into a gas and separates easily, there's no leftover solvent in the final product. This is a big advantage compared to using some liquid solvents that might leave traces behind.
It can be controlled: By changing the temperature and pressure of the fluid, you can control which parts are dissolved and extracted. This means you can selectively pull out exactly what you want.
It's relatively gentle: It often works at lower temperatures than some other extraction methods (from 31.1 C), which is good for delicate substances that can be damaged by heat.
Examples of where it's used:
Making decaf coffee (removing caffeine from coffee beans).
Extracting oils from plants for food flavorings or health supplements (like extracting CBD from hemp or Triketones in Mānuka).
Removing unwanted substances from materials.
So, in simple terms, supercritical fluid extraction is a way to use a special type of fluid that acts like both a gas and a liquid to selectively dissolve and pull out desired substances from something, and then easily separate them by changing the pressure. It's a clean and controllable way to get valuable components out of materials.
