How to carry Out RANCIDITY Test

 RANCIDITY 

This is the natural process of decomposition of lipids by either oxidation or hydrolysis or both. The ingestion of rancid lipids can cause the development of many diseases including atherosclerosis, cataract, diarrhea, kidney and heart diseases, cell membrane damage, neurodegeneration and carcinogenesis. 

Vegetable fats are less stable and turn rancid more quickly. Unsaturated fats are more susceptible to oxidation meaning the more polyunsaturated a fat is the faster it will go rancid because the more unstable double bond, the more oxygen react at those points 

TYPE OF RANCIDITY 

OXIDATIVE RANCIDITY: It is also known as Autoxidation, occurs when oxygen is absorbed from the environment. Oxygen is 8 times stable in fat than in water and increase the saturation of the fat. 

HDROLYTIC RANCIDITY: This is also known as Hydrolysis or Enzymatic oxidation occurs in the presence of moisture and absence of air. This is an enzymatic peroxidation, where enzymes found in plants (Lipoxigenase, Cyclooxygenase) and animal (Lipase) can catalyse reaction between water and oil. 

AIM: To determine if a fat or oil will undergo Rancidity 

APPARATUS: Calibrated tube, beaker. 

REAGENT: 0.1% Phloroglucinol, concentrated HCl. 

PROCEDURE: 

Measure 10ml of the sample (heat to liquid if solid and then take 10ml) into a calibrated tube

Add 10ml of concentrated HCl and 10ml of 0.1% Phloroglucinol and shake

The appearance of pink colouration indicates Rancidity.