Acid value

Determination of acid value:

Deffinition:

The acid value is defined as the number of milligrams of Potassium hydroxide required to neutralize the free fatty acids present in one gram of fat. It is relative measure of rancidity as free fatty acids are normally formed during decomposition of triglycerides. The value is also expressed as percent of free fatty acids calculated as oleic, lauric, ricinolic and palmitic acids.

Table of Content

• Principle
• Analytical Importance
• Procedure
• Significance of Acid Vaulue

Principle:

The acid value is determined by directly titration the oil or fat in an alcoholic medium against potassium hydroxide solution.

Analytical importance:

The value is measure of the amount of fatty acids, which have been liberated by hydrolysis from the glycerides due to the action of moisture, temperature and/ or lipolytic enzyme lipase.

Procedure:

Mix the oil by heating.

• Take 10 gm sample in 250 mg clinical flask.
• Add 50 mL of freshly neutralized hot ethanol and about one ml of phenolphthalein indicator.
• Titrate with .1 N potassium hydroxide solution. End color is pink.
• Calculation:
acid value = 56.1x Burrete reading×Normality of Potassium hydroxide/ sample weight.

The significance of acid value:

The significance of acid value lies in the fact that it provides valuable information about the degree of hydrolysis, rancidity, or deterioration of the oil or fat. High acid values indicate the presence of excess free fatty acids, which can result from poor storage conditions, exposure to high temperatures, or microbial activity. This can negatively impact the sensory and nutritional quality of the oil or fat and also lead to the formation of harmful compounds such as acrylamide or trans-fatty acids.

The acid value is also used to monitor the progress of chemical reactions, such as esterification or transesterification, during the production of biodiesel. In this application, the acid value is used to determine the amount of catalyst needed to achieve a desired degree of conversion.

In summary

The acid value is an important analytical parameter that provides information about the quality and stability of oils and fats. Its measurement is critical in ensuring the safety and efficacy of many products that rely on these substances.