Q. What do you mean by Acid Value and Free Fatty Acids?
Acid value is a measure of hydrolytic rancidity present in the sample of oil/fat. It reflects the state of freshness or deterioration of the material and also the quantity of glycerols to be released as a result of neutralization of fat/oil. It has a wide implication in the oil refining industry as it gives the fair idea of the state of oil/fat and also the total quantity of alkali required to neutralize a particular batch of oil or fat to make it suitable for the purpose of hydrogenation. Acidity also helps in predicting the quantity of oil or fat, which will pass into soap stock as a compulsive by-product of the refining process.
High acidity oils or fats produce excess smoke during heating. Moisture content, temperature of heating, duration of heating, type of metal container are parameters which act as catalysts to the process of hydrolysis in fats or oils.
Acidity is expressed as FFA% on oleic acid basis like in ghee. However, in certain oils and fats it is expressed on the basis of the fatty acids which are predominant. For example, castor oil which has 86-94% recinoleic acid, coconut oil having its fatty