November 09, 2003
Pumpkin seed oil, avocado oil, borage and camellia oil; it used to be that a choice of oil for cooking was simple. You used a liquid canola or corn oil for frying or sautéing and a hardened oil such as Crisco for baking.
We now live in the age of boutique oils. All seeds have oil in them as the energy source for the growing seedling. Man's ingenuity and desire to create a niche market has led to the extraction of many unusual oils.
The marketing angles on these oils are manifold. Some claim to have health benefits, others to have flavor. Buyers of argan and shea butter oils may be supporting women's cooperatives in developing nations. Hemp seed oil diehards are "sticking it to the man". Grapeseed oil has the romance of the vine. JoJoba oil is a earth friendly alternative oil. While it is hard to compare or argue some of these points there is one point which should be easy for comparison: the smoke point.
A high smoke point is desirable for a cooking oil. When frying, best results occur when the oil is very hot. The food is placed into the hot oil and the natural sugars caramelize and proteins denature into a thin shell which protects the food from soaking up the oil. The outside is crisp and the interior is just cooked. One of the bibles of cooking, Irma Rombauer's "The Joy of Cooking" recommends frying at 365 degrees F for best results.
When heated oil smokes, it is not just a nuisance. Besides coating your home interior with a varnish like substance, where there's smoke there's fire. An oil at its smoke point is closer to its flash point - the point where it will burst into flame.
So a high smoke point is one yardstick for a "good oil". If you go the internet or the market to look for smoke points you will see something interesting. Every oil claims to have the highest smoke point. One website for macadamia nut oil puts their oil at the top of the list with a smoke point of 410 degrees F. On their chart olive oil comes in at a measly 190 degrees F. Avocado oil sites say their oil has the highest smoke point and claim nut oils are terrible for frying.
The smoke point for a vegetable oil will vary according to the variety and growing conditions, and how the oil was produced. The smoke you see may be impurities in the oil which are burning. Unfiltered olive oil has small bits of olive in it. When the oil is heated these bits will burn and smoke before the oil itself. A well filtered or clarified oil will have a higher smoke point generally.
Oil which has oxidized because of exposure to air, heat and light will have a lower smoke point. Using oil repeatedly will also make it smoke sooner. When looking for the smoke point of an oil you should expect a range of values.
The Olive Oil Source claims that extra virgin olive oil smokes from 400 to 365 degrees F according to it's free fatty acid content. But the macadamia nut folk say that olive oil smokes at the temperature of hot water out of the tap; 190 degrees. When I suggested to the macadamia people that it seemed unlikely that olive oil smokes at a temperature lower than boiling water and that maybe they were confusing centigrade with Fahrenheit they insisted they were right.
So who do you trust for the real smoke point? The industry group which is advertising and promoting the oil, a random website or a food chemistry text? Here is what some research yielded:
The International Olive Oil Council: 410˚
Institute of Shortening and Edible Oils: 420˚
Or why not get some olive oil off the shelf and heat it up in a saucepan with a frying thermometer. This is properly done in a lab with special lighting which shows the first hint of smoke. My stovetop experiment yielded 350 degrees for a jug of discount store oil which had been sitting open in the garage for a few years and 380 for a premium fresh extra virgin oil. Olive oil is fine for frying.
It is annoying to counter these conflicting claims when most people would not fry with olive oil anyway. A cheap, flavorless oil with a high smoke point is usually recommended - something like canola, soy or peanut oil. Avocado, macadamia and premium olive oils can cost up to a dollar per ounce. It is unlikely that you are going to deep fry that Thanksgiving turkey in 5 gallons of oil at that price.
Besides, if we are so worried about our health, why fry at all? Better to talk up the flavor qualities of olive oil, an area where it shines compared to bland seed oils.