Detection and Quantification of Free Glycerol in Virgin Olive Oil by 31P‐NMR Spectroscopy

Abstract

Abstract31P‐Nuclear magnetic resonance (NMR) spectroscopy was employed to detect and quantify free glycerol in virgin olive oils originating from various regions of Greece. This analytical method was based on the derivatization of the hydroxyl groups of glycerol with the tagging reagent 2‐chloro‐4,4,5,5‐tetramethyldioxaphospholane, and identification of the phosphitylated compound on the basis of 31P chemical shifts. Quantification of glycerol in olive oils was accomplished by integration of the appropriate signals in the 31P NMR spectrum and the use of the phosphitylated cyclohexanol as internal standard. A linear correlation was observed between the glycerol content and 1,3‐diacylglycerols and free acidity indicating that glycerol is the final product of the partial hydrolysis of triacylglycerols.