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the good oil

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I was delighted to learn recently that my nine-year-old step grand-daughter is a fan of Mythbusters. This is important as the family I’m almost attached to isn’t hugely sciencey – there are few geeky types to set standards or to inspire a love of questioning and wonder [though I’m sure some family members will be offended at this, so I’d better shut up now]. I loved her enthusiasm in talking about it and her accurate reporting of the results of experiments. So I thought I might engage in some occasional mild-mannered and explosion-free mythbusting research of my own – armchair research, or perhaps computer chair research, or google research. Anyway, this one’s for Courtney – one day.

As part of my job overseeing a cooking class, ostensibly for the development of foundation skills [the student skill-base in this class is all wrong for the funding, but that’s another headache], I heard the chef, an affable Dutchman, tell the students that extra-virgin olive oil shouldn’t be used for general cooking. Vegetable oil was much better. The reason – the olive oil burns at too low a temperature. It should only be used for cooking at low temperatures and for ‘finishing’ a dish. One of the students spoke, I think for almost the entire middle-class baby boomer population of the country in saying ‘oh really? I never use anything but extra virgin olive oil’.

So here’s the myth: Extra virgin olive oil is the best oil for general cooking purposes [based on taste and also on good health and dietary requirements]. Confirmed or busted?

In exploring this we’ll also look at the different grades of olive oil, and also of course different types of cooking, and the best oil for each type.

Well, I may as well say at the outset that the myth is busted. Go to any reputable cooking site and they’ll all say much the same – that extra virgin olive oil is reserved for dipping, salads and finishing [on soups for example], though usually they won’t tell you why.

Extra-virgin olive oil is less acidic than the next grade, virgin olive oil. The difference between these two is judged on acidity levels, but also on taste. The term ‘virgin’ essentially means untouched by any chemical processes or heat treatment. Often virgin olive oil is labelled as ‘cold pressed’. This is because olive oil can become degraded and lose nutrients if it’s pressed at a temperature above 25 degrees celsius. For example, in the northern regions of Italy the olives are harvested and processed during winter, but the icy temperatures make for processing problems, so the olives are heated artificially. This presumably means they can’t be described as ‘cold pressed’, even if they’re only warmed a teeny bit. It’s not a problem in the warmer climate of southern Italy. The point here is that the ‘cold-pressed’ designation isn’t necessarily a sign of better quality or greater ‘authenticity’. It just might mean that  they were harvested and pressed in a warmer climate.

The problem for extra-virgin in general cooking is that it burns at a temperature of about 175° celsius. Or more accurately, its unrefined particles start to burn, which affects flavour. This is called the smoke point. Generally speaking, the more refined an oil is, the higher the smoke point [though the best quality, low-acidity extra-vrgin actually has a higher smoke point than other extra-virgins], though some oils have a ‘naturally’ high smoke point. The highest I’ve found is in avocado oil – not a well-known oil but apparently very healthy and stable for cooking.

What happens at the smoke point is that the oil breaks down into glycerol and free fatty acids. The glycerol further breaks down into acrolein, an eye-irritating component of the smoke. Olive oil, and other oils, that have reached this point have been permanently degraded, and should be discarded.

Now to the health benefits of olive oil and the question of whether, for general cooking and deep frying, other oils should be substituted, or whether we should just switch to ‘pure’ or ‘light’ olive oil – and what’s the difference between these various categories of olive oil?

This opens up a real minefield, for not only do all these oils differ in flavour, making the choice quite subjective, but their chemical structures differ, and there’s an endlessly raging debate about the health benefits or otherwise of mono-unsaturated versus polyunsaturated oils and fats. And of course, with olive oil, there are different varieties of olive, different climatic conditions, different soil qualities, different harvesting times and different extraction processes, all of which affect flavour and structure. No two ‘extra-virgin’ olive oils are necessarily alike, and reading labels is no substitute for a discerning palate. Freshness is also a factor – extra-virgin olive oils generally have a shorter shelf life than refined ones.

The first thing to say is that extra virgin olive oil is really good for you, and olive oil generally is something of a wonder food, with the added cachet of a vibrant history. For example, in ye old Olympics of a few millenia ago, the [all-male] athletes would run, jump and wrestle in front of an all-male audience, naked and thoroughly basted with olive oil [the athletes, that is, not the audience – but who knows?]. They must’ve looked quite quite edible. It was used for ritual, cosmetic and general lubricant, as well as culinary, purposes. Homer described it as ‘liquid gold’. Even today, the per capita consumption of olive oil in Greece [which has by far the largest per capita consumption in the world] is around 50 times that in the USA – and some 80% of the oil produced there is extra-virgin.

Virgin olive oils contain a higher proportion of polyphenols [tannins] which have antioxidant properties, and olive oil generally contains many antioxidants not found in other oils, including hydroxytyrosol, the major antioxidant compound found in olives. Epidemiological studies indicate that these compounds act as preventives for various cancers. Olive oil is also rich in mono-unsaturated fats, particularly oleic acid, which tend to reduce the risk of heart disease.

There are many other benefits claimed for olive oil, and there’s been a lot of research to back up those claims, but that’s not to say that other types of oil don’t have benefits. It would just take too long to go into all the claims here, but it seems to me that you could do worse than to use olive oil for all your cooking purposes, as the Greeks appear to do. Of course variety is the spice of life and other oils such as peanut oil and sesame oil impart distinctive flavours to particular dishes. Vegetable oils are also generally cheaper than olive oils. So suit your taste, and your budget.

In summary, though the myth is busted for extra-virgin olive oil, it isn’t for olive oil in general. Extra-virgin is best for salads and for light sautéing, but deep frying with it rather defeats the purpose. Also, extra-virgin has a strong flavour, not to everyone’s taste. For general cooking suit yourself, but olive oil is a guaranteed winner.

 

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Written by stewart henderson

October 2, 2011 at 10:49 am

Posted in Uncategorized

2 Responses

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  1. the good oil on oil! very informative, i salivate at the thought of a well basted young Greek, preferably sprinkled lavishly with dukkah!

    Sarah

    October 3, 2011 at 4:31 pm

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