Estimation of Saponification Value of Oils & Fats – Amrita University
Estimation of saponification value of oils and fats Saponification is the hydrolysis of fats or oils in the presence of a base like potassium hydroxide to afford glycerol and the salt of the corresponding fatty acid. The saponification value represents the number of milligrams of the base required to neutralize the fatty acids resulting from the complete hydrolysis of 1 gram fat. The saponification value gives an indication of the nature of fatty acids present in triacylglycerols. The longer the carbon chain of the fat hydrolysed, the lesser the amount of acid liberated per gram and hence lower its saponification value.
Principle: When fats and oils are refluxed in an alcoholic solution of KOH, glycerol and the potassium salt of the corresponding fatty acids are liberated.
The amount of KOH used up in this saponification process is then estimated by titrating the test sample as well as the control against 0.5 NHCl. Procedure: Weigh 1g of fat in a tared beaker Add 5ml of the fat solvent.
Mix well and transfer the contents into a conical flask.
Rinse the beaker with 5ml of fat solvent and transfer this to the conical flask. Mix well so that the fat dissolves completely in the solvent. Label it as “Test”. Now add 25 ml of 0.5N alcoholic KOH to the conical flask.
The blank is prepared by adding 10 ml of the fat solvent and 25 ml of 0.5N alcoholic KOH into a seperate conical flask. Label it as “Blank”. Reflux condensers are fitted on both the flasks and are heated in a boiling water bath for 30 min. The conical flasks are removed from the bath and are allowed to cool.
Add 1-2 drops of phenolphthalein indicator into both the flasks. The contents of the flasks are then titrated against 0.5N HCl taken in a burette The endpoint of the titration is indicated by the decolorisation of the pink soution in the conical flasks. The volume of KOH consumed by the fat is obtained from the titre values [(Blank- Test) ml].
The amount of KOH can be calculated using the equation Amount of KOH consumed = Normality of KOH x Volume of KOH consumed in ml x equivalent weight The saponification value can be calculated as the number of milligrams of KOH consumed divided by the amount of fat taken intially (1g).