Rancidity

Rancidity is associated with characteristic of flavour and odour of fats and oils
A condition produced by aerial oxidation of unsaturated fat present in foods and other products, marked by unpleasant odour or flavour.

1. Rancidity Dr.Gayathri Devi.M Dept. Nutrition & Dietetics SRNM College,Sattur

2. Introduction Rancidity is associated with characteristic of flavour and odour of fats and oils A condition produced by aerial oxidation of unsaturated fat present in foods and other products, marked by unpleasant odour or flavour .

3. Cont. When a fatty substance is exposed to air, its unsaturated components are converted into hydroperoxides , which break down into volatile aldehydes, esters, alcohols, ketones, and hydrocarbons, some of which have disagreeable odours .

4. Butter becomes rancid by the foregoing process and by hydrolysis, which liberates volatile and malodorous acids, particularly butyric acid. Saturated fats such as beef tallow are resistant to oxidation and seldom become rancid at ordinary temperatures.

5. Rancidity Rancidity  is the process of complete or incomplete oxidation or hydrolysis of fats and oils when exposed to air, light, or moisture or by bacterial action, resulting in unpleasant taste and odor.

6. Causes Temperature – Rancidity rate increases with increase in temperature. Duration – For the more time you keep a thing unattended or without using it, it has more chances to turn rancid. Oxygen – Oxygen promotes the decomposition of food. Light - In the presence of oxygen, light promotes the decomposition of unsaturated fatty acids. Microorganisms and fungi (molds) – They are the most common reason for the food to become rancid . They use their enzymes on the food material and destroy its chemical composition. Moisture - Moist air helps the microbes in their activity upon the food material. Trace elements – Trace elements like Fe and Zn also increase the rate of rancidity.

7. Types Hydrolysis is the decomposition of fats into free fatty acid and glycerol by enzymes in the presence of moisture. These free fatty acids released are responsible for the unpleasant flavour and odour .

8. During oxidation, oxygen is added to the unsaturated linkage and this result in the formation of peroxides. These peroxides decompose to yield aldehyde and ketones which are responsible for the pronounced flavour . Rancidity may also be caused by the absorption of odour and action of micro organism and enzymes.

9. Preventive measures

10. Preventive measures Adding inert Gases  Inert gas can be added to the packet or the container like nitrogen, which does not react with oxygen Example Chips packets are flushed with nitrogen gas, so they don’t become rancid. Adding antioxidant:  are added to some foods to slow down or eliminate oxidative deterioration. Refrigeration  reduce the temperature and hence don’t allow the microbes to continue their processes.

11. Preventive measures Vacuum Packaging  is done to keep oxygen out. By using oxygen scavengers  or oxygen absorbers are added to enclosed packaging to help remove or decrease the level of oxygen in the package. They are used to help maintain product safety and extend shelf life. Keeping food in air tight containers  Less air too prevents rancidity. By storing food in dark place.