Determination of Soap Number in Liquid Oils: Reliable Analysis Methods

Why Soap Number Analysis in Oils?

When oils are treated with strong acids or heated with water under pressure, fatty acids are converted into soap. The soap number determination determines the sodium soap content and other basic substances that react with hydrochloric acid. The result of the analysis is calculated as the percentage of sodium soap or the percentage of sodium hydroxide.

What is the Soap Count?

Soap number refers to the amount of mg KOH (potassium hydroxide) required to completely saponify 1 gram of fat or fatty acid. The soap number depends on the chain length of the triglycerides in the oil and the amount of free fatty acids:

• High Soap Count: Contains short chain fatty acids.
• Low Soap Count: Contains long chain fatty acids or high molecular weight esters.

Soap number determination is based on the determination of the amount of soap dissolved in oils as oleate. Oleate is a fatty acid ester with low viscosity and high flash point.

Importance of Soap Number Determination

1. Determination of Oil Quality: Provides information on the molecular structure of the oil. In processed oils, it checks whether the saponification process is complete.
2. Use in Fraud Detection: Helps in the detection of blended or counterfeit oils.
3. Legal Compliance and Standards: It is performed to assess the conformity of food and industrial oils to standards.

Legal Regulations and Standards

Soap count determination is carried out in accordance with certain standards. Important standards are as follows:

• TS EN ISO 3657: Determines the soap number determination methods of oils and fatty acids.
• Codex Alimentarius: Sets the quality standards for food oils.
• Turkish Food Codex: Contains soap number limits for the properties of vegetable oils.

According to the Turkish Food Codex Communiqué on Oils with Plant Names (Communiqué no: 2012/29), it should not be present in cold and pressed natural oils. In refined oils, the limit is 0.005 (m/m).

If the oils are not washed well, the amount of soap is high. However, if bleaching is done, the amount of soap will be low. Therefore, it is important to determine the amount of soap to have an idea about the processes performed on the oils.

Nano-lab Laboratories Group continues to provide services within the scope of Soap Number Determination in Liquid Oils. We also provide services in Olive Oil Analysis.

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