How to keep good oils from going bad

October 06, 1998|By Lynn F. Little

We have long heard that it is better for your heart to choose liquid oils over hard/solid fats.

But what about oils that develop an "off" odor?

Are they still better for you than hard/solid fats, such as hydrogenated shortening and lard? Chances are they are not, assuming the hard/solid fat is fresh.

A putrid "off" odor indicates that the fat is rancid. All fats and oils become rancid given enough exposure to air, sunlight and heat.

Polyunsaturated fats, like vegetable oils, are very prone to such deterioration. While eating rancid foods won't make you sick, it may be unhealthy in the long run. Rancid fat contains chemicals called peroxides and aldehydes that can damage cells and cause cholesterol to clog arteries.


Oils are not the only product prone to rancidity. Anything that contains fat can go bad if kept too long or stored improperly. If you smell the same, bad odor from other foods, like margarine, butter, crackers, cookies, popcorn packaged with oil, nuts and peanut butter, it is best to discard the item.

Here are some safety tips for keeping foods rancid-free:

* Buy oils and fat-containing foods only in quantities that can be used within a few months. Unless you use it promptly or share it with a friend, don't buy the biggest bottle of oil just because it is on sale. If you do purchase a large bottle, divide it into two or more smaller bottles and freeze the extra portions to use within the year.

* Tightly cap oil, store in a cool place away from sunlight and use within six months. Although oils tend to cloud in the refrigerator, this may be the best place to keep them.

* Because olive oil is especially sensitive to light, keep in an opaque can or bottle rather than a clear one.

* Freeze extra butter or margarine. Butter and margarine will keep for up to two years in the freezer. Freeze microwaveable popcorn to keep it from turning rancid or going stale.

* Keep nuts in the refrigerator. Freeze extra quantities for use within a year.

* Wrap meats tightly in air-tight packaging before freezing. For best results, use ground beef, pork, poultry and fish within a few months. Whole cuts of beef keep well in the freezer for up to one year.

* Let smell and taste be your guide for rancid-free oils and fat-containing foods. If it tastes bad and has an "off" odor, chances are you want to discard that food rather than use it.

Maryland Cooperative Extension programs are open to all citizens without regard to race, color, sex, disability, age, religion or national origin.

Lynn F. Little is a family and consumer sciences extension educator for Maryland Cooperative Extension, Washington County.

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