When it comes to cooking oils, the choice between refined and unrefined can make a world of difference to your health. The key difference lies in the process. Let’s break down exactly what happens to refined oils and compare it with the gentle, nutrient-preserving process of unrefined (wood cold-pressed) oils.
1. What Makes Refined Oil… Refined?
Refined oils go through multiple industrial steps to increase shelf life, remove odour, and make the oil clear. But this heavy processing also strips away the natural nutrients, aroma, and flavour. The high temperatures and chemicals used can even produce harmful compounds like trans fats.
Here’s the typical journey of refined oil:
Step-by-Step Process of Refined Oil Production
Step 1 – Seed Preparation
Seeds (soybean, sunflower, groundnut, etc.) are cleaned, dehulled, and crushed.
Effect: This step doesn’t directly harm the oil quality, but the seeds are often stored for long periods before processing, which can lead to oxidation of fats even before extraction begins.
Step 2 – Extraction Using Solvent (Hexane)
Seeds are treated with hexane, a petroleum-based solvent, to extract maximum oil.
Effect: While efficient for yield, hexane is a chemical solvent. Even though most of it is removed later, traces may remain in the oil. This step also exposes oil to high temperatures, degrading heat-sensitive nutrients like vitamin E and polyphenols.
Step 3 – Miscella Separation
The oil-hexane mixture (called miscella) is heated to separate hexane from crude oil.
Effect: More heat = more nutrient breakdown. Essential fatty acids and antioxidants degrade further.
Step 4 – Degumming
Water or acid is added to remove gums (phospholipids).
Effect: Phospholipids, which support cell health and brain function, are lost here.
Step 5 – Neutralization
Oil is treated with an alkali (like sodium hydroxide) to remove free fatty acids.
Effect: Natural pigments, antioxidants, and vitamins are lost along with the free fatty acids.
Step 6 – Washing
Oil is washed with hot water to remove soap residues from neutralization.
Effect: More heat exposure accelerates oxidative damage, leading to rancidity over time.
Step 7 – Bleaching
Oil is filtered through bleaching clay or activated carbon to remove colour.
Effect: Along with colour pigments (like beta-carotene), many natural antioxidants are stripped away.
Step 8 – Filtration
The oil is filtered to remove bleaching agents.
Effect: Minimal nutrient loss here, but the oil is now almost stripped of its original bioactive compounds.
Step 9 – Deodorization
Steam is passed through the oil at 180–270°C to remove odour.
Effect: This is where trans fats are formed due to extreme heat. Almost all delicate compounds (polyphenols, plant sterols) are destroyed.
Step 10 – Winterization
Oil is chilled to remove waxes and keep it clear in refrigeration.
Effect: While purely cosmetic, it removes certain beneficial long-chain waxes that have health benefits.
Step 11 – The Final Refined Oil
By now, the oil is clear, odourless, long-lasting—and nutritionally hollow. What remains is mostly processed fat with little to no natural antioxidants or flavour.
Cold-Pressed (Unrefined) Oils – A Simpler, Healthier Path
Process:
Seeds → Mechanical Press (Wood/Cold Press) → Filtration → Oil
No chemical solvents like hexane.
No extreme heat—temperatures stay below 45°C.
Nutrients like vitamin E, antioxidants, and plant sterols remain intact.
Retains natural aroma, colour, and flavour of the seeds.
Effect on Health:
Supports heart health and brain function.
Provides natural antioxidants to fight free radicals.
Retains healthy fatty acids (like omega-3 and omega-6) in their natural form.
| Aspect | Refined Oil | Cold-Pressed (Unrefined) Oil |
|---|---|---|
| Processing Steps | 11+ steps: Seed Preparation → Solvent Extraction (Hexane) → Miscella Separation → Degumming → Neutralization → Washing → Bleaching → Filtration → Deodorization → Winterization | 3–4 steps: Seed Cleaning → Mechanical Press (Wood/Cold) → Filtration |
| Temperature Exposure | Very High (up to 270°C) during deodorization | Low (< 45°C) throughout process |
| Chemicals Used | Yes – Hexane (solvent), Sodium Hydroxide, Bleaching Clay | No chemicals |
| Nutrient Loss | Severe – Vitamin E, polyphenols, plant sterols destroyed | Minimal – Nutrients preserved |
| Trans Fat Formation | Yes – formed during high heat deodorization | No trans fats |
| Natural Aroma & Flavour | Removed intentionally | Retained naturally |
| Colour | Clear, pale (artificially lightened) | Natural golden/yellow/brown hues |
| Shelf Life | Long (6–12 months) due to preservatives & removal of natural compounds | Moderate (3–6 months) – best stored in cool, dark place |
| Health Impact | May contribute to inflammation, heart disease risk | Supports heart health, antioxidant protection |
| Purpose in Cooking | Preferred for deep frying & industrial food products | Best for everyday cooking, salad dressings, light sautéing |
Key Takeaway
Refined oil may look appealing on the shelf—clear, odourless, and long-lasting—but it comes at the cost of your health. Cold-pressed, unrefined oils, though less “perfect-looking,” keep nature’s goodness intact.
When you choose oil for your kitchen, remember:
The less the processing, the more the nutrition.