Food | Refractive Index of Fats, Oils and Essential Oils
The analysis of the purity and quality of animal and 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 are among the basic building blocks of human nutrition. There are two groups of oils and fats: vegetable oils, which are extracted from plants or nuts, and animal oils, which are found in dairy products and meat. Oils are made up of triglycerides. They may be saturated or unsaturated. Oils that are solid at room temperature are called fats.
The refractive index of oils and fats depends on the content of the different glycerides. Fatty acids have a lower refractive index than glycerides, followed by triglycerides, diglycerides and monoglycerides, which have the highest refractive index. In addition, the refractive index depends on the age of the oil or fat and on the temperature, since the refractive index changes after heating (Löwe, 1949).
Essential oils are also called volatile oils. They are a concentrated hydrophobic liquid containing the essential aroma compounds of plants. They are often obtained through distillation.
Since fats and oils as well as essential oils consist of many different compounds, their refractive index also varies. For this reason, there is a predefined refractive index measurement range within which the sample must be designated as pure oil or fat.
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