From the chemical definition, the saponification number is the weight in mg of potassium hydroxide needed for saponification of 1 grams of oil.

The saponification number of the fats in this way is inversely proportional to the chain lengths of the fatty acids, ie the molecular weights. The saponification numbers of fats which are esters of long chain fatty acids are lower than the saponification numbers of fats which are esters of short chain fatty acids. For example, the number of saponification in butter is high (between 210 and 235). The saponification number in coconut oil is 255 and palm oil is 245. In addition, the saponification number of vegetable oils is generally below 200.

The molecular weight of an oil whose chemically saponification number is known can be calculated approximately. Regardless of molecular weight, 1 molecular potassium hydroxide is required to saponify 3 molecular oil.

The saponification number is commonly used to determine the purity of fats and fatty acids. In addition, the saponification number must be known to remove free acidity in oil processing technology.

In 2012, the Turkish Food Codex Communiqué on Plant Oils Called by the Ministry of Food, Agriculture and Livestock (Communiqué no: 2012 / 29) was published. This Communiqué regulates the principles that will ensure the production, processing, storage, transportation and marketing of the oils mentioned under the scope of the plant with appropriate techniques and hygienic conditions.

In the annex of the mentioned Communiqué titled Physical and Chemical Properties of Vegetable Oils (Annex 3), the saponification number according to the oil types is given. Accordingly, the saponification number of several oil types is as follows:

• Sunflower oil 188-194
• Corn oil 187-195
• Cottonseed oil 189-198
• Soybean oil 189-195
• Sesame oil 186-195
• Hazelnut oil 188-198

In the authorized laboratories, saponification number is determined within the scope of chemical tests. In these studies, the standards published in our country and in foreign countries are complied with.