Oxidative rancidity is often responsible for the off-odors and off-flavors that can develop in many foods. Rancid foods are characterized by sharp offensive odors and tastes and may be actually unfit for consumption. The condition of rancidity develops in foods that contain fats or oils and occurs when atmospheric (molecular) oxygen reacts with the unsaturated part of fatty acid esters to form peroxides, hydro peroxides, and finally carbonyl compounds. Reaction products such as aldehydes, acids, ketones, and alcohols impart the harsh flavors and odors that render foods useless.
There are some important facts about oxidative degradation of foods that need to be remembered.
Oxidation can be catalyzed by light, heat, or the presence of metal ions.
Once the oxidative reaction is initiated and left unchecked, it will progress at an ever increasing rate.
Most important, once a food item becomes rancid, nothing can reverse the oxidative process or restore the food to its original quality.
For many years, antioxidants have been used safely and effectively to retard oxidative deterioration of foods.
Antioxidants are compounds or substances that will inhibit or interfere with the formation of free radicals in food fats, thus terminating the oxidative reaction in its initiating step. From a practical standpoint, this simply means that an antioxidant system properly selected to meet the needs of a particular food item and correctly applied will help to maintain the product's original freshness, flavor, and odor for a longer period of time which would not be possible otherwise.