Oil Extraction Techniques

There are different extraction processes for making an oil from a fruit, vegetable, nut or seed. You may have seen the words "expeller-pressed" or "cold-pressed" on a bottle before and wondered what that meant.

The cheapest and most common method for extracting oils involves heating the seed to an extremely high temperature and crushing it, thus causing exposure to even more heat through friction. Any oils not obtained through the pressure are treated with a hexane solvent, some of which remains on the oil even after it is washed away.

The high heat from this process creates free radicals and destroys the antioxidants that normally protect us from them. And although hexane levels are generally low in the oils, hexane poisoning can cause muscular and vision problems.

Another extraction process is called expeller-expression. In this technique the seeds are drilled and exposed to lower temperatures. Some expeller-pressed oils are still treated with hexane. This is why it is important to make sure your oils are organic.

Cold-pressed oils are those that have not been exposed to high temperatures, but there is little regulation in the United States as to what defines a high temperature. Some expeller-pressed oils are not considered cold-pressed.

Why does it matter how the oils are extracted?

As I mentioned before, organic expeller-pressed oils are not treated with chemicals, additives or preservatives. But these oils are also healthier because if stored correctly they are not rancid like oils made from other extraction processes. Most oils turn sour when they are exposed to too much heat, light or oxygen. So, the bottles of oil on the grocery store shelf are usually rancid before you even open them, making them full of free radicals and bad for your intestinal health. The oils generally don't smell sour because they go through a deodorizing process.

Tip: Always remember to store your expeller-pressed oils in a dark container in the fridge so you limit their exposure to light and heat.

To see a chart of oils from best to worst for you, click here.

-Jessica

Source:

Fallon, Sally. Nourishing traditions the cookbook that challenges politically correct nutrition and the diet dictocrats. Washington, DC: NewTrends Pub., 1999.