How Seed Oils Are Processed
By now, you must have seen our previous blog on why vegetable oils are the enemy within. They have been for long the trusted cooking partner, but new research shows that the same vegetable and seed oils we so love to use, might as well be our ultimate killers. This blog explains why:
Traditionally, seeds were hand-pressed under very low temperatures and delivered to homes like milk, in dark amber bottles due to the volatility of these oils. Today, as a result of such massive processing, most vegetable and seed oils are so refined that they can be sold in clear bottles.
Modern Method of Processing Seed Oils:
Step 1: Cleaning and Grinding
During this process, the seeds are washed, cleaned, de-hulled and de-skinned. The coarse material is then ground into a matter from which the oil will be pressed. The grinding process adds significant heat from the grinding friction, rendering volatile oils rancid.
Step 2: Cold Pressing
The material is then put in a screw press, where temperatures can reach anywhere between 54-93°C (130-200°F). Most oils go rancid when temperatures exceed 50°C (125°F).
Step 3: Solvent Extraction
Most seeds are not suitable for cold pressing, because it would leave many undesirable trace elements in the oil, causing it to be odoriferous, bitter tasting, or dark. With this, a solvent extraction technique is commonly used.
Hexane is typically used as a solvent to dissolve the oil out of the seed cake after pressing, and is then reabsorbed through evaporation and distillation.
Step 4: Refine, Bleach, and Deodorize
- The oil is then refined to remove color, odor, and bitterness, along with many minor but important constituents of the oil. Refining can heat the oil to between 41°C and 87°C (107°F and 188°F), and involves mixing chemicals, like sodium hydroxide or sodium carbonate, into the oil.
- Oils are also de-gummed at this time by treating them with water heated to dangerously high temperatures – between 87°C and 97°C (188°F and 206°F) – with steam, or a combination of water and acid. The natural gums, most of which are phosphatides, precipitate out.
- The oil is then bleached by filtering it through bleaching clay, which absorbs certain pigmented material from the oil, making the oil tolerant to light, and thus stable enough to be packaged in a clear bottle. Again, so many more vital nutrients, minerals, and other beneficial components are lost here.
- The oil is then deodorized, because processing incurs rancidity from significant free radical damage, giving the oil a terrible smell. The deodorizing process involves passing steam over hot oil in a vacuum at between 226°C and 251°C (440°F and 485°F).
- The oil is now dead! It is refined, odorless, tasteless, colorless, indigestible, and void of most any nutritional value.
What is Lost During Processing of These Seed Oils:
- Antioxidants – like naturally occurring vitamin E, carotene, and others, which protect the oils from oxidizing as bad cholesterol in the blood.
- Chlorophyll – which fertilizes the gut with pre-biotic support for the proliferation of good bacteria, and is a rich source of magnesium, which is essential for heart, nerve, muscle, and blood sugar function.
- Lecithin – which helps to emulsify fats, making sure they are easily digested.
- Naturally occurring flavor molecules, color molecules, and other oil-soluble beneficial molecules.
- Phytosterols – which support and protect immunity and cardiovascular function.
Point to note:
Oils can legally state that they contain no additives, preservatives, or special flavorings, because the majority of the chemicals added during processing are subsequently taken out. The question is: which chemical residues remain, and how many nutrients, vitamins, and minerals are lost?
Alternative Oils To Use:
Olive oil is the recommended alternative, but its low smoke point makes it not the best for cooking. Check for oils with higher smoke points. They do not oxidize at those high temperatures and remain stable. They are also not highly processed. They include: unrefined coconut oil and macadamia oil. The olive oil will be easily subjected to oxidation at higher temperatures.
Organic coconut and macadamia oils are the better options for multipurpose cooking oils, because they are healthful saturated fats that can withstand the heat of cooking without altering chemically.