Cooking oil is one of the most used ingredients in modern kitchens. It is also one of the least understood.
Most people choose an oil based on habit, price, or a headline they read once. But oils differ significantly in how they are produced, how stable they are under heat, and what happens to them during processing.
If you are searching for answers about seed oils, refined oils, cold pressed oils, or which cooking oil is best in Australia, this guide will give you the fundamentals without the noise.
What Cooking Oil Actually Is
Cooking oils are composed primarily of triglycerides. These are molecules made up of glycerol attached to three fatty acids.
The structure of those fatty acids determines:
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how stable the oil is under heat
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how easily it oxidises
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how it behaves in the body
The three main categories of fatty acids are:
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Saturated fats
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Monounsaturated fats
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Polyunsaturated fats
Oils high in monounsaturated fats tend to be more stable than oils high in polyunsaturated fats, particularly when exposed to heat and oxygen.
Seed Oils vs Nut Oils: Structural Differences
Seed oils and nut oils are often grouped together in online debates. Structurally, they are not identical.
Common seed oils include:
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Canola oil
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Soybean oil
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Sunflower oil
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Vegetable oil blends
These oils are typically high in polyunsaturated fats, especially linoleic acid.
Nut oils such as macadamia oil, almond oil, and hazelnut oil generally contain a higher proportion of monounsaturated fats and lower levels of polyunsaturated fats.
Macadamia oil is particularly high in oleic acid, often ranging between 55 and 65 percent, and contains relatively low levels of linoleic acid compared to most common seed oils.
From a chemical stability perspective, monounsaturated dominant oils tend to resist oxidation better than polyunsaturated dominant oils when exposed to heat.
How Cooking Oils Are Made
This is where differences become significant.
Mechanical Pressing
Cold pressing or mechanical expelling extracts oil through pressure without chemical solvents. Temperatures are controlled to prevent significant degradation.
Cold pressed oils:
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Retain natural flavour compounds
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Preserve minor nutrients such as tocopherols and phytosterols
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Avoid solvent residues
Unrefined oils are typically filtered but not chemically altered after extraction.
Solvent Extraction
Many large scale seed oils are extracted using hexane, a petroleum derived solvent.
The process typically includes:
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Crushing and flaking
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Solvent washing
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Evaporation of hexane
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Further refining steps
While hexane is removed to regulated limits, the oil then undergoes additional processing.
Refining Steps Explained
Refined oils often go through:
Degumming
Removal of phospholipids using water or acid treatment
Neutralisation
Use of caustic soda to remove free fatty acids
Bleaching
Adsorbent clays remove colour pigments and oxidation products
Deodorisation
High temperature steam distillation, often above 200 degrees Celsius, removes volatile compounds
These steps extend shelf life and create neutral flavour. However, they also reduce naturally occurring minor compounds.
Refining is not inherently unsafe. It is a trade off between shelf stability and natural composition.
Refined vs Unrefined Oils
Refined oils:
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Higher smoke points
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Neutral taste
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Longer shelf life
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Highly standardised
Unrefined oils:
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More flavour
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Retain minor plant compounds
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Shorter shelf life
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Reflect the quality of the raw material more directly
The choice depends on how and how often you cook.
Smoke Point Is Only One Variable
Many people search for “best oil for frying” or “highest smoke point oil”.
Smoke point matters, but it is not the only factor.
Oxidative stability, fatty acid profile, and frequency of heating are equally important.
An oil with a very high smoke point but high polyunsaturated content may oxidise more readily during repeated heating compared to a monounsaturated dominant oil with a moderate smoke point.
This is why avocado oil and macadamia oil are often discussed as alternatives to heavily refined vegetable oils.
How to Choose the Right Cooking Oil
Ask yourself:
How hot am I cooking?
How often am I heating the same oil?
Do I want neutral flavour or natural character?
Is processing method important to me?
Do I value short supply chains and local sourcing?
If you frequently deep fry at very high temperatures, a refined high smoke point oil may suit that purpose.
If most of your cooking sits in the 160 to 200 degree range, which covers sautéing, roasting, baking, and air frying, a monounsaturated dominant oil that is cold pressed and unrefined can offer a balance of stability and minimal processing.
Where Macadamia Oil Fits
Macadamia oil sits structurally closer to olive oil in fatty acid profile, but with lower polyunsaturated content than many seed oils.
Cold pressed, unrefined Australian macadamia oil offers:
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High monounsaturated fat content
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Moderate smoke point appropriate for most home cooking
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Minimal industrial processing
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Short supply chain transparency
For people seeking less processed food choices without sacrificing everyday usability, this category deserves serious consideration.
The Bottom Line
There is no single perfect cooking oil.
There are different tools for different jobs.
Understanding how oils are made, how they are refined, and how their fatty acid structures behave under heat allows you to choose deliberately rather than reactively.
In a market crowded with labels and claims, clarity about processing and structure is more useful than slogans.