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Name: Sarah
Status: student
Grade: 6-8
Location: VA
Date: November 2007

Question:
How do cooking oils (I guess all lubricating oils) work to prevent food sticking, and what are the key characteristics that makes one oil work better than others? Is spray-on oil better than poured liquid oil? Is it their density and purity (although I am just learning what those terms mean)? Is one oil best at one temperature, but a different one at another temperature -- is there a perfect oil (regarding 'stickiness') at each temperature range? I would like to test for these characteristics, but I do not yet understand how to observe or measure any differences -- I have not really had a chemstry class yet! I am just learning the basics.



Replies:
Sarah,

These are all good questions and I will try to answer them without referring to too much chemistry concept.

If you were able to see the surface of a cooking pan up close you would see two important features: (1) at the level of the size of molecules, the surface is very rough, and (2) it is made up of molecules that have a tendency to attract other molecules.

Cooking oil works on four levels, (1) it can insert into the rough areas so that, with those pits filled in with cooking oil, what is presented to the material being cooked is a smooth surface of the cooking oil, (2) because the cooking oil is not attracted to the pan, when the object being cooked is removed, while the oil may stick to that object, the oil will not stick to the pan and can be removed, (3) by providing a layer in between the object being cooked and the pan, the object is prevented from forming connections with the pan, and (4) by attaching itself to the pan, the natural attraction between the pan and the object being cooked is limited because now it is the oil that the object being cooked is attracted to.

From the above description, you can now think of the answers to the rest of your questions.

Greg (Roberto Gregorius)


In terms of cooking, the main things that make oils different are their flavor and their smoke point. More pure oils tend to have less flavor -- for instance an extra virgin olive oil would typically have a milder flavor than a regular virgin olive oil. Oils like sesame oil can have very strong flavor and aroma (although purified sesame oil is less flavorful), while canola oil is very neutral. The flavor you like in your oil is a culinary decision you have to make. The second factor is smoke point -- the temperature at which the oil begins to smoke. Different oils have different smoke points -- canola and peanut have higher smoke points, while butter has a notoriously low smoke point. Clarified butter has a higher smoke point. The more pure the oil, the higher its smoke point in general. Most oils will be equally effective for preventing sticking as long as you're below their smoke point. If you get too hot, the oil will smoke, and eventually catch fire (that is REALLY REALLY BAD). However, the oil will turn smoky and bad tasting long before it catches fire, so smoke point is more important in terms of flavor than safety (unless something really goes wrong).

Spray oils usually do not taste as good or work as well as poured oils because they contain anti-clumping agents and propellants in them. However, they do help use less oil, which is a good thing for many applications. I use an air-powered spray that I load my own oil into, which gives me the best of both worlds. Some people swear by the spray oils that contain flour (used in baking), but I have not used them.

Personally, I use canola oil on the grill or for high temperature sautéing (high smoke point), I use expensive olive oil when I'm going to be eating the oil (like dressings, dipping, and other non-cooking applications). And I use soybean (vegetable) oil for baking. For certain dishes I will use butter, sesame, grapeseed, or shortening as well.

As for an experiment to compare the oils, there is one easy thing you can do-- You can put a candy thermometer in the oil and measure its smoke point (be careful as the hot oil is VERY dangerous -- I recommend adult supervision and definitely wear protective equipment -- heat resistant gloves, a face shield, and a lab coat at least). Be sure to compare not only different oils, but different types of the same oil (especially olive oils).

To measure an oil's non-stick performance, that is a little tougher. I wonder if you could take potato slices of varying thicknesses (even a whole potato), cook them in a very thin sheet of oil, and turn your pan upside down and see which ones fall? That experiment would be very hard to control properly, but you would end up with a lot of French fries (which is a very good thing!).

I will keep thinking about the 'non-stickiness' experiment... I will email you again if I come up with anything that sounds good.

Hope this helps... and good luck!

Burr Zimmerman



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