What is Rancidity: Definitions, Examples, Types, Factors Responsible, Prevention, Causes and Rancidification

What is Rancidity Overview

When fats and oils undergo incomplete oxidation or hydrolysis, the resultant spoiled food is known as rancidity. Food becomes rancid when it is exposed to air, light, moisture, or any bacterial activity. When exposed to air, unsaturated fats change into hydroperoxide. This produces volatile aldehydes, hydrocarbons, esters, alcohol, and other substances that have a bad taste and smell. Unsaturated fat in meals and other items undergoes aerial oxidation, which results in rancidity or rancidification, which gives off disagreeable smells or aromas. There are three different forms of rancidity: microbiological, oxidative, and hydrolytic rancidity.

What is Rancidity?

In chemistry, a state known as rancidity, also known as rancidification, is brought on by the aerial oxidation of unsaturated fat found in foods and other items that have off-putting smells or aromas. Unsaturated parts of a fatty substance can become hydroperoxides when exposed to sunlight, which then decompose into esters, volatile aldehydes, ketones, alcohols, and hydrocarbons, some of which have foul smells. Using some preventative measures, rancidity can also be avoided.

Examples of Rancidity

When milk is not heated in a humid environment, it occasionally turns rancid due to the degradation of the fats it contains in the oil. When butter is left out in the open for an extended period of time, its flavor and aroma change.

Types of Rancidity

There are three different forms of rancidity that fall into the following categories-

Hydrolytic Rancidity

There are some fats where short-chain fatty acids predominate. The glycerol and fatty acid connection can be severed by the LIPASE enzyme. Some fatty acids have flavors that, when present in large concentrations (as in butter), are unpleasant (when they are not attached to the glycerol). Butter infection with bacteria that produce lipases, untimely refrigeration, and other factors can all hasten the hydrolytic rancidity process.

Microbial Rancidity

When bacteria or molds, for example, use their lipases to break down the chemical structures of fat in oil, microbial rancidity results, generating an unpleasant odor and taste. Microorganisms can be killed or inhibited in order to slow down this process. Pasteurization and the inclusion of antioxidant substances like vitamin E can help minimize it.

Oxidative Rancidity

Large unsaturated fatty acids are subject to oxidation more easily. Aldehydes, ketones, and similar compounds are the byproducts of oxidation, and they can impart an off flavour at high temperatures (exposure to air, cooking, and other chemical pollutants can speed up oxidation). Oils are given antioxidants to lessen oxidative rancidity.

Factors responsible for Rancidity

The following are some of the several key elements that might cause food to go rancid-

1. Microbes: Many microbes secrete the lipase enzyme, which causes the breakdown of lipids. They use the food material to produce their enzymes, which causes the optimum food composition to be destroyed and results in the loss of the desired feature. 
2. Oxygen: Food that has been exposed to the outside air, which contains a lot of oxygen, is the main reason why it becomes rancid. The oxygen causes an oxidation process that generates free radicals, which in turn cause food damage. 
3. Physical Factors: Rancidification is significantly influenced by heat, light, and air. Free radicals are generally produced by the oxidation process, which is mostly triggered by heat, light, and air. Unsaturated fatty acids are prone to breakdown when exposed to light.
4. Trace Elements: The rate of rancidity is also accelerated by trace elements like Fe and Zn. 

Prevention of Rancidity

There are several potential defenses against rancidity, which are as follows-

1. By keeping food in dimly lit areas.
2. By replacing the oxygen in the bag with inert gas, such as nitrogen.
3. Food can be kept in sealed containers to inhibit the rancidification process.
4. It is possible to hoover the pack to keep oxygen out.
5. The majority of processes that contribute to rancidity will be slowed down.
6. The refrigerator can be used to store food. 
7. To prevent oxidative degradation, antioxidants can be added to diets that include oils and fats.

What causes a substance to become Rancid?

Food products with oil and fatty acids in them can go rancid. The primary building blocks of fatty acids are cholesterol, steroids, and fats. These have a lengthy aliphatic chain and might be saturated or unsaturated carboxylic acids. Any material can become rotten in three simple steps- 

Initiation Reaction

Radicals are produced on dietary items as a result of the initiation reaction, which is sparked by environmental elements including heat and air. An atom, molecule, or ion with an unpaired electron is referred to as a radical. Chemical radicals are particularly reactive due to their unpaired electrons. 

Propagation Reaction

At this point, the peroxides are created as a result of the atmospheric oxygen. These peroxides then continue to interact with the unsaturated fatty acids, producing additional radicals in the process.   

Termination Reaction

The two radicals join at this point to create a brand-new single bond. At the conclusion of the rancidification process, the fats, lipids, and other components are broken down, creating highly reactive molecules. This is the cause of the food's foul odor and terrible taste once it becomes rotten. Due to the rancidity process, there might occasionally be a loss of vitamins.

At the conclusion of the rancidification process, fats, lipids, and other substances are broken down. Highly reactive compounds are created as a result of the procedure. As a result, food begins to taste awful and emit an unpleasant odor. 

Rancidification

When exposed to air, light, moisture, or bacterial activity, fats and oils undergo full or incomplete autoxidation or hydrolysis, which results in the production of short-chain aldehydes, ketones, and free fatty acids. These processes in food can produce unpleasant flavors and odors. These flavors are collectively referred to as warmed-over flavors in processed meats. However, in other circumstances (such as with matured cheeses), the flavors could be appealing. The nutritional value of food can also be diminished by rancidification since several vitamins are vulnerable to oxidation.Other hydrocarbons, such as lubricating oils, fuels, and mechanical cutting fluids, also experience oxidative deterioration, which is similar to rancidification.

Points to Remember

1. Fats and oils oxidize during the process of rancidity, which is immediately identifiable by a change in flavor and odor.
2. Food may be kept from going rancid by using antioxidants, storing it in the refrigerator, using airtight containers, and avoiding exposure to light.
3. Microorganisms, such as bacteria or mold, use their enzymes, such as lipases, to break down fat in a process known as microbial rancidity.
4. The aerial oxidation of unsaturated fat found in food and other items is what causes rancidity.
5. There are three different sorts of rancidity: oxidative rancidity, microbial rancidity, and hydrolytic rancidity.