Food | Refractive Index of Vegetable Fats, Oils and Essential Oils

The analysis of the purity and quality of vegetable fats and oils as well as essential oils can easily be done with refractive index measurement. Anton Paar refractometers are following international regulations such as ISO, AOAC and international pharmacopoeias and offer a refractive index scale and a butyro scale reading.

Along with carbohydrates and proteins, fats and oils belong to the basic building blocks of human nutrition. Vegetable oils are extracted from plants or nuts. Oils consist of triglyceride. They can be saturated or unsaturated. Oils which are solid at room temperature are referred to as fats.
The refractive index of oils and fats is dependent on the content of the different glycerides. Fatty acids have a smaller refractive index than the glycerides, followed by the triglycerides, diglycerides and monoglycerides which have the highest refractive index. Moreover, the refractive index is dependent on the age of the oil or fat and from the temperature as the refractive index changes after heating (Löwe, 1949).
Essential oils are also referred to as volatile oils. They are a concentrated hydrophobic liquid with the essential aroma compounds from plants. They are often obtained by distillation.
As fats and oils as well as essential oils consist of lots of different compounds, their refractive index varies as well. For this reason, there is a predefined refractive index measurement range in which the sample has to be referred to as pure oil or fat.

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