Manufacturers of modern cold-pressed cooking oils state that they contain no additives, preservatives, or special flavorings - but that’s only because most of the chemicals added during their processing are subsequently removed, even though trace chemical residues are likely to remain.
Unfortunately, many nutrients, vitamins and minerals are also lost during cold-press processing.
You may think that oil seeds used to make cold-pressed oil were carefully pressed at a cool temperature to protect it from rancidity, trans-fats and other toxic processing chemicals - but this is simply not true.
Modern ‘cold pressing’ methods actually heat the oil - not just once, but many times - to temperatures that are likely to turn most of them rancid.
So what exactly happens to an oil seed on its journey to become your favorite cooking oil?
According to Udo Erasmus, author of the book ‘Fats That Heal, Fats That Kill’: “Cooking oils are highly processed using manufacturing methods that are destructive to oil molecules. These practices are utilized primarily to lengthen and stabilize the shelf life of oils.”
These are the steps involved in so-called cold-pressing:
- Step 1: Cleaning and grinding - seeds are washed, cleaned, de-hulled and de-skinned before being ground into a paste from which oil is pressed. Grinding usually heats the seed paste to temperatures which are likely to turn volatile oils rancid.
- Step 2: Cold pressing - the paste is placed in a screw press with temperatures between 130-200 degrees F. Remember, most oils turn rancid at greater than 125 degrees.
- Step 3: Solvent extraction - most seeds are not suitable for cold pressing, because remaining trace elements would leave the oil smelly, bitter tasting or dark. Typically a solvent extraction technique is used with hexane to dissolve the oil out of the seed cake.
- Step 4: Refine, bleach and deodorize - the oil is ‘refined’ to remove color, odor, and bitterness. Refining heats the oil to 107-188 degrees and involves mixing in chemicals such as sodium hydroxide or sodium carbonate.
The oil may also be degummed by treating it with water heated to 188-206 degrees F, steam, or a combination of water and acid. It is then bleached by filtering through bleaching clay which absorbs pigmented material, making the oil tolerant to light and stable enough to be packaged in a clear bottle. Many vital nutrients, minerals, and other beneficial components are lost in this step.
Finally the oil is deodorized by passing steam over hot oil in vacuum at 440-485 degrees F.
The oil is now refined, odorless, tasteless and colorless - not to mention indigestible and completely lacking in any nutritional value.
This process also removes valuable beneficial ingredients, including:
- Antioxidants, such as vitamin E, carotene etc. which would otherwise protect oils from oxidizing as bad cholesterol in the blood.
- Phytosterols, which support immunity and cardiovascular function.
- Chlorophyll, which fertilizes the gut with good prebiotic bacteria, and is a rich source of magnesium.
- Lecithin, which emulsifies fats, making sure they are easily digested.
- Naturally occurring flavor molecules, color molecules and other oil-soluble beneficial molecules.
So what are your best options for cooking? Coconut oil, palm kernel oil, palm oil, cacao oil, ghee and butter are the most heat stable.
Finally, non-cooking oils that have a short shelf life but are healthful in your diet include those:
- Pressed from organically grown seeds and nuts.
- Protected from light, air (oxygen), and heat during pressing, filtering, and filling.
- Sold in dark glass bottles that say “unrefined” on the label.
- Expeller pressed (screw press) at pressing temperatures below 122 degrees F.