What does rancid mean?

The word "rancid" is from a latin term dating back to 1646 meaning a rank smell or taste. Rancid oil and food has a nasty, pugnant, acrid taste that lingers in your mouth.

Essentially, the food or fatty acid is damaged by a free radical process which is both oxygen and temperature driven (oxidation). As a result, the fatty acid is broken down into smaller, lighter and more volatile fatty acids.

The oxydation process yields aldehydes, ketones and alcohols that give the fat its rancid taste and smell.

Unsaturated fats high in omega-3 fatty acids, like canola oil, are prone to rancidity especially at temperatures above 120 F triggers. The rancidity of oils are lethal to rats and can cause several degenerative diseases in people.

Unfortunately, many oils in natural food stores and supermarkets are rancid because of poor processing and storage. Most are bleached, de-flavored and deodorized at temperatures above 500 degrees. when rancid oil is stripped of flavor and aroma we no longer taste its rancidity, but it is still there.

Different oils stay fresh for different peroids of time. Always keep oil tightly covered and stored in the dark and away from heat. Unopened peanut oil, corn oil and other vegetable oils are good for up to one year. Once opened, they're good for about four to six months.

Olive oil will keep for 6 months in the pantry, but up to one year in the refregerator. Walnut and sesame oil are inclined toward turning rancid. Kept in the refregerator they are good for two to four months.

When you cook at high temperature (over 240) use solid, saturated fats, like butter, coconut oil and lard. Frying at moderate temperatures (up to 240 degrees) you can use unsaturated, omega-6 fatty acid oils like sesame and safflower.

Omega-3 fatty acids, like canola, flax and hemp oil, should never be used to cook with. If they were manufactured with high temperature, they're rancid and don't use them at all. If processed at low temperatures and taste fresh they use them as a supplement or in sald dressings.