Please note the following,
Generally for oils which are natural products have complex composition (a combination of different fatty acids). Therefore, its assay / purity is not determined. Instead, following chemical parameters which are specific to the oils are estimated quantitatively, such as
- Saponification value
- Iodine value
- Peroxide value
- Ester value
- Unsaponifiable matter
- RMPK values (usually used for butter or ghee)- Reichert Meisel Polenske Kirschner values
- Acid value (index of Rancidity)
By determining above chemical values, one can estimate purity levels or grades of different oils or we can find out if those oils are adulterated with other cheaper oils.
For your information please refer following tables to understand composition of Linseed oils of different grades,
