Copyright 1997 Alan T. Hagan (athagan@sprintmail.com). All rights reserved.
Republished in part by express permission. Please note Disclaimer below.
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All oils are fats, but not all fats are oils. They are very similar to each other in their chemical makeup, but what makes one an oil and another a fat is the percentage of hydrogen saturation in the fatty acids of which they are composed. The fats and oils which are available to us for culinary purposes are actually mixtures of differing fatty acids so for practical purposes we'll say saturated fats are solid at room temperature (70 F) and unsaturated fats we call oils are liquid at room temperature. For dietary and nutrition purposes fats are generally classified as saturated, monosaturated and polyunsaturated, but this is just a further refinement of the amount of saturation of the particular compositions of fatty acids in the fats.
There is a problem with storing oils and fats for the long term and that is the fact that they go rancid rather quickly. There are some general rules you can follow to get the most life out of your stored cooking oil.
- Although darker colored oils have more flavor than paler ones, they don't last as long in storage. Therefore, for longer shelf life, buy paler colored oils.
- Heat, light and exposure to oxygen are the greatest factors in rancidity of cooking oils. If you can, refrigerate your stored oils. If possible, buy your oils in dark, opaque, airtight containers. Cooking oils should be stored in a cool, dark area.
- Unless they have been specially treated or packaged, cooking oils have a shelf life of about one year, with a few specialized oils having a shorter life. If you don't use a great deal of it, try not to buy your fats in large containers. This way you won't be exposing a large quantity of oil to the air after you've opened the container.
It seems to me that buying oil in large containers and then repackaging it into smaller, opaque, perhaps more airtight containers would be a good thing to do. I haven't found any data on this yet so I do not know if it would actually accomplish any useful extension of storage life or not. If anyone reading this should happen to have any good data on this, I'd surely like to see it.
Additionally, I'm also looking for information about the usefulness of possibly adding anti-oxidants to slow down the oxidative rate, such as butylated hydroxyansiole (BHA), butylated hydroxytoleune (BHT), propyl gallate or vitamin E.
DISCLAIMER: Safe and effective food storage requires attention to detail and proper equipment and ingredients. The author makes no warranties and assumes no responsibility for errors or omissions in the text, or damages resulting from the use or misuse of information contained herein. Placement of or access to this work on this or any other site does not mean the author espouses or adopts any political, philosophical or meta-physical concepts that may also be expressed wherever this work appears.