You first have to consider the plant source of the oil - seed oils, rice bran oil, olive oil, avocado oil, coconut oil or blended oils simply labelled vegetable oils (a misnomer as not from vegetables at all!). Then you need to make a decision over the types within one category.
Within olive oils the principle difference is whether the oil is ‘extra virgin’. This means it is quite simply the cold pressed juice of the olive fruit. If it doesn’t state ‘extra virgin’ then the oil has been refined.
What about other oils?
Other oils are extracted in a far different way to extra virgin olive oil. Just think of getting oil out of a hard seed, or a grain like brown rice that doesn’t contain much oil. These foods cannot simply be pressed. These food stuffs are highly processed to obtain the oil and the resultant oil must then be refined – often using chemicals – to make them fit for human consumption.
Is olive oil the same?
Refined olive oils are not the same as extra virgin olive oil and do not confer the same health benefits, nor the same fabulous taste. So why are they on offer in the supermarket?
"Refined olive oils are not the same as extra virgin olive oil and do not confer the same health benefits"
Well it all comes down to the efficiency of the olive oil producer. The key to a really good quality oil is the time it takes from harvesting the olives from the trees to pressing and producing the oil. On the Cobram Estate olive groves this is generally completed in less than 4 hours! That’s pretty impressive and is the principle reason almost all of the oil they produce is extra virgin.
In fact, this is true across the Australian olive oil industry. We are superbly lucky to have such good quality extra virgin olive oil available to us.
When olives are left for a longer period of time the fruit starts to ferment and turn rancid. The oil produced from such fruit is not edible - even just a few rotten olives can spoil an entire batch of oil! The resultant oil must undergo refining and is then sold as ‘olive oil’ or sometimes the misleading name ‘pure olive oil’.
Why is this important?
The distinction between extra virgin and refined is important as it dramatically affects the nutrition of the oil. Many phytonutrients are destroyed or removed during the extraction and refining process, there may be residual levels (albeit judged to be safe) of chemicals used in refining, and certain substances are produced in the oil such as stigmastadienes.
"Many phytonutrients are destroyed or removed during the extraction and refining process, there may be residual levels of chemicals used in refining, and certain substances are produced in the oil such as stigmastadienes"
Although we don’t yet fully know what the health effects of stigmastadienes are, we do know they are produced artificially, are not present in extra virgin olive oil and there are concerns that they have potential cancer activity. They are measured in oils for quality assurance and as a means of detecting if an extra virgin oil has been adulterated with refined oils. (You can rest assured that all Australian extra virgin olive oils pass this test).
"Stigmastadienes are measured in oils for quality assurance and as a means of detecting if an extra virgin oil has been adulterated with refined oils"
One final, but crucially important point. You do NOT need to buy a refined olive oil to cook with. Quite the opposite. Extra virgin olive oil is not only safe to cook with, but is beneficial to cook with. The antioxidants present help to protect the oil, the fats are very stable and the smoke point is well above almost all cooking purposes. The only decision you have to make is which flavour to use!
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