July 14 issue of The Sydney Morning Herald Digital
Edition.
Peter Barrett
All oils aren’t equal. With so many on the shelves to
choose from, which should you use for which kind of cooking?
This topic can lead you down a rabbit hole of scientific
claims and counterclaims. So, with that in mind, I put together a list of
common culinary oils, how best to use them in the kitchen and some tips from
nutritionists, including author Catherine Saxelby (see her foodwatch.com.au
website) and Associate Professor of Dietetics and Human Nutrition at Latrobe
University, Catherine Itsiopoulos. Finally, some scientific help came from Rod
Mailer, a research fellow with Charles Sturt University and Chakra Wijesundera,
a research fellow with the CSIRO. Thanks also for help from Beth Scholes at the
Heart Foundation.
BUT FIRST . . . Some general principles
Refined oils are more stable and better suited to
high-temperature cooking such as deep-frying than unrefined (mechanically
pressed such as extra virgin) oils. These oils tend to have higher smoke
points, the temperature zone at which the oil starts to break down and give off
acrid and sometimes toxic fumes.
Smoke points vary in any given oil due to the quality of
the oil, its specific terroir and any impurities that might be present. This,
coupled with the fact that the longer you heat an oil the lower the smoke point
becomes, means re-using oil for cooking is generally a bad idea. The smoke
point temperatures in this story are best understood in comparison with each
other and serve only as a rough guide.
All oils break down over time and become rancid,
characterised by an unpleasant odour or flavour . Although eating rancid oil
won’t kill you straight away, long-term consumption has been linked to obesity,
early ageing and cancer.
Store all oils in a cool, dark place away from heat (such
as your stove) to prolong their life and guard against rancidity.
With Australian olive oil growers all but squeezing the
last juice out of this year’s crop, now is an excellent time to consume it,
since it should be eaten as fresh as possible.
I love dipping bread into a good quality extra virgin
olive oil but I’m using it for shallow-frying , too. I even used it for
deepfrying recently but the price (and reduced health benefits – antioxidants
start to disappear when you raise the temperature) are prohibitive when you
look at all the other oils available.
My interest in oils started with a radical new way of
frying chips, gleaned from Nigella Lawson’s Nigellissima series. She cuts fat
potato chips, dries them with a tea towel and places them in a pan with cold
sunflower oil. She then heats to a rolling boil, stirring occasionally to
prevent burning and sticking, adding garlic and other herbs for flavour when
they’re nearly done.
It was a revelation. My chips were great: crisp and
golden on the outside with a fluffy interior. But even though she claims the
cooking method results in very little oil being absorbed by the potatoes –
apparently due to the temperature, rather than the cooking time – I didn’t
quite believe it. Plus, the sheer volume of oil I was going through spooked me
(there are places you can dispose of your oil, by the way – check with your
local council – and never pour it down the sink). But the health question mark
continued to niggle. Should I really be feeding this stuff to my kids? What are
the health issues with oils and how do they differ?
Even a cursory internet search on this
1 Extra virgin olive oil
The highest quality olive oil, it is made by mechanically
pressing olives and applying centrifugal force to separate the oil from water.
Extra virgin olive oil (EVOO) must contain no more than 0.8 per cent free fatty
acids (virgin olive oil must have less than two per cent). While most
Australian EVOO producers adhere to these standards, questions remain about the
integrity of some imported brands. EVOO is best consumed within 12 months of
harvest and up to six weeks after opening the bottle. Best for? With its vivid
colours and rich flavours it’s ideal for salad dressings, eating with bread and
drizzling over dishes. But according to research carried out by Cobram,
Australia’s largest olive oil supplier, high quality EVOO can reach smoke
points at temperatures of between 200-215 degrees, making it a healthy option
for most types of cooking, including oven baking. Nutritionist’s tip? Natural
antioxidants and vitamins A, D, E and K make this one of the healthiest oils to
eat. Research has shown good quality EVOO reduces the risk of heart disease,
type 2 diabetes and some cancers.
2 Olive oil
A blend of virgin or extra virgin oil with lampante olive
oil (obtained from used olive pulp, which in that state is unfit for human
consumption). The blend is then refined , usually by a chemical process that
involves bleaching and deodorising. While this makes the oil more stable and
neutral in flavour , the process strips most, if not all, of its natural
colour, vitamins, minerals and antioxidants. Often marketed as ‘‘ pure’ ’ or ‘‘
light’ ’ olive oil. Best for? An all-rounder cooking oil, especially for
Mediterranean food, suitable for shallow and deep-frying due to its relatively
high smoke point. Also good for use in cakes as flavour is relatively neutral.
Nutritionist’s tip? High levels of monounsaturated fatty acids make it a
generally healthy dietary fat but refinement cancels out many of its stellar
health benefits .
3 Avocado oil
Buttery-tasting , vivid-green avocado oil has a similar
fatty profile to olive oil, so it’s high in monounsaturated fats with some
saturated and polyunsaturated fats mixed in. Unrefined extra virgin avocado oil
is obtained by pressing the pulp and separating the natural oil in a
centrifuge. Due to its unusually high smoke point (up to 250 degrees) , it’s
ideal for high-temperature grilling or pan-roasting but costly at about four
times the price of extra virgin olive oil. Best for? Frying vegetables such as
brussels sprouts and drizzling over home-made pizzas. Nutritionist’s tip?
Antioxidants present can help with eye health and, like EVOO, by drizzling it
on your food you can help your body absorb fat-soluble antioxidants present in
vegetables, such as beta-carotene .
4 Macadamia oil
Known for its mildly nutty to gloriously buttery flavour
, this specialty oil grown extensively in northern NSW is an excellent addition
to sweet or savoury dishes. It’s often advertised as ‘‘ cold-pressed’’ , which
just means it’s been mechanically extracted in a technique similar to extra
virgin olive oil. High in monounsaturates (about 80 per cent), it’s more stable
than many other polyunsaturated fats and has a high smoke point of between
210-230 degrees. Best for? Pan-frying fish , veal and flavouring cakes and
slices, and in salad dressings. Nutritionist’s tip? A good oil for heart health
because it’s so high in monounsaturated fats, which are known to lower blood
cholesterol or LDL (‘‘ bad’ ’ cholesterol).
5 Sunflower oil
Extracted from the seeds of sunflowers , it is usually
refined , a process that involves the use of chemical solvents such as hexane.
While this process makes it more stable and therefore suitable for
high-temperature cooking, it does strip out some naturally occurring nutrients.
Best use? With a smoke point around 225 degrees, sunflower oil is good for
deep-frying dishes such as tempura and chips. Nutritionist’s tip? It’s high in
polyunsaturated fats, which have been shown to lower cholesterol, particularly
the ‘‘ bad’ ’ LDL cholesterol. The Heart Foundation recommends it as a suitable
replacement for butter.
6 Sesame oil
Made from one of the oldest oilseed crops around, most
sesame oils you’ll find are solvent extracted and refined , although it is
possible to buy mechanically extracted Australian sesame oil. Typically, it’s
equally high in monounsaturated and polyunsaturated fats (the Heart Foundation
recommends you use it to replace saturated fats, such as butter). Best use?
Given its strong flavour , it’s best used as an additive, particularly to Asian
dishes such as stir-fries . It’s also an excellent addition to marinades and
sauces. Nutritionist’s tip? Sesame oil is high in vitamin K, which is great for
blood coagulation and bone strength.
7 Peanut oil
Similar to macadamia oil with predominantly
monounsaturated fats, this fragrant oil, sometimes known as groundnut oil, has
a relatively high smoke point at about 230 degrees. Made by pressing peanut
kernels, the crude oil has a deep yellow colour, nutty aroma and sweet taste;
refined peanut oil is light yellow in colour and neutral in flavour . Best for?
Asian cooking, especially stir-fries . Nutritionist’s tip? While refined peanut
oil is allergen-free , cold-pressed or crude peanut is not and should be
avoided by people susceptible to anaphylaxis.
8 Coconut oil
Also known as copra oil, this oil is extracted from the
meat of matured coconuts. The jury is still out on just how healthy it is (it’s
very high in saturated fats at more than 90 per cent) but one thing is clear –
stay away from hydrogenated coconut oil, which undergoes a process of extreme
heat and pressure and the introduction of hydrogen in the presence of a
catalyst (usually a metal) to make the oil more stable and last longer. The
process makes the oil more viscous, as it will your blood, making your heart
work harder. Virgin or extra virgin coconut oil, on the other hand, is a
popular vegan replacement for butter in cooking. Best use? Its natural
sweetness makes it ideal for baking and certain sauteed dishes. A low smoke
point (about 175 degrees) makes it not great for high-temperature cooking, such
as deep-frying . Nutritionist’s tip? It’s a good source of lauric acid, which
has been shown to increase HDL or ‘‘ good’ ’ cholesterol levels but there are
plenty of kilojoules, so adjust your intake accordingly.
9 Rice bran oil
Extracted from the bran and the germ, this
neutral-tasting oil has a low viscosity and a relatively high smoke point
(around 260 degrees) making it ideal for roasting and cooking subtle
ingredients, such as seafood. It has an unusual mix of fatty acids – roughly
half-and-half monounsaturated and polyunsaturated – and some good plant sterols
but it’s industrially processed, not mechanically extracted (or ‘‘
cold-pressed’’ , as some people refer to the process where extra virgin olive
oil is produced). Best use? High-heat stir-frying or wokfrying . Nutritionist’s
tip? Don’t be confused by packaging that talks about being ‘‘ extra
coldfiltered’ ’ – it’s got nothing to do with the positive health benefits
associated with extra virgin olive oil.
10 Canola oil
A variant of rapeseed oil, it’s the largest oil crop
grown in Australia and is extracted from the canola plant, specially bred in
Canada in the 1970s (the name is derived from ‘‘ Canada oil low acid’’ ).
Canola oil is light and clear with a neutral flavour ; it’s high in monounsaturates,
low in saturated fat and has plenty of omega-3 s. It’s more stable at high
temperatures because it’s refined but then again, the refining process itself
raises questions about the healthiness of the oil. In short, a good oil for
quick frying but not for drizzling over finished dishes. Best use? You’ll find
it already added to foods such as oven-baked chips and frozen fish fillets but
with a high smoke point of around 205 degrees, canola is a good allpurpose
cooking oil. It does become unstable after heating, so never reuse.
Nutritionist’s tip? There’s a strong anti-canola movement at the moment but pay
no attention. The confusion may stem from the dangerous erucic acid that was
present in the old rapeseed plants – modern canola is fine .
11 Flaxseed oil
Also known as linseed oil, it’s a clear to
yellow-coloured oil made by pressing the dried, ripe seeds of the flax plant.
With a fatty acid profile higher in polyunsaturated fats it’s packed with the
highest amount of plant-based omega-3 s of all these oils but can develop ‘‘
off’ ’ flavours , so buy in small quantities and store in a cool, dark place,
such as the fridge. Tends to be a dietary supplement oil. Best for? Adding to
smoothies, yoghurt or bland foods such as quark to enhance flavour . This is
not a cooking oil. Nutritionist’s tip? Research says that it’s better to obtain
your omega-3 s from oily fish and grass-fed meats so, while it’s an interesting
oil, it’s not essential.
12 Cottonseed oil
Light and neutral-flavoured , cottonseed oil is a major
oil in Australia and a byproduct of the cotton-growing industry. It’s
relatively inexpensive and high in vitamin E. This highly stable (refined ) oil
was often used in chip shops for deep frying (you can use it multiple times
before the smoke point is compromised). A mix of predominantly saturated and
polyunsaturated fats. Best use? Occasionally for deep-frying . Nutritionist’s
tip? With a saturated fat level of about 27 per cent, cottonseed will never get
the Heart Foundation tick (20 per cent is the cut-off ).
13 Vegetable oil
This is a stable, refined , plant-based oil but the
difficulty is you never really know what it’s made of. In Australia, where a
lot of canola oil is produced, your vegetable oil could well be 99 per cent
canola – it could also be blended with soybean or sunflower . Check the
nutrition label on the back to determine specific levels of saturated,
monounsaturated and polyunsaturated fats. Best use? Deep-frying and
hightemperature cooking. Nutritionist’s tip? If the saturated fat content is
above 20 grams per 100 grams, consider something else.
Sources used for the story other than people mentioned:
Smoke points of cooking oils:
seriouseats.com/2014/05/cooking-fats-101-whats-a-smoke-point-and-whydoes-it-matter
.html Comparison of saturated and unsaturated fats in oils: uccs.edu/
~Documents/danderso/fats_oils.pdf
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