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AACC Approved Methods of Analysis, 11th Edition -AACC Method 58-20.02. Refractive Index

AACC Approved Methods of Analysis, 11th Edition

Special Properties of Fats, Oils, and Shortenings

AACC Method 58-20.02
Refractive Index


The refractive index of a substance is the ratio of speed of light in a vacuum to speed of light in the substance. For practical measurements, including this method, scales of standard instruments indicate refractive indexes with respect to air rather than vacuum. Index of refraction of oils is characteristic within certain limits for each kind of oil. It is related to degree of saturation but is affected by other factors such as free fatty acid content, oxidation, and heat treatment. The method determines the origin and quality of normal oils and liquid fats. This method is equivalent to Official Method Cc7-25 of the American Oil Chemists' Society (AOCS).