Comparison of Analytical Methodologies Based on ¹H and ³¹P NMR Spectroscopy with Conventional Methods of Analysis for the Determination of Some Olive Oil Constituents

Abstract

The present study was designed to assess the agreement between analytical methodologies based on 1H and 31P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.

Tannin Structural Elucidation and Quantitative 31P NMR Analysis. 1. Model Compounds

“…The reactions of various phospholane chlorides with labile centers present in coal and lignin samples were investigated by Verkade's 33 and Argyropoulos's 39−41 research groups, respectively. Recently, we reported the use of 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (Cl-TMDP) for the structural characterization and quantitative evaluation of tannin model compounds.…”

Impact of High Pressure Homogenization (HPH) Treatment on the Nutritional Quality of Egg/Yogurt, Vegetable and Fruit Based Creams

“…Determination of free acidity, considered an indicator of triacylglycerol hydrolysis, was performed by titration using NaOH as the titrant for the free acids [12]. Free acids contained in 1 g of sample were dissolved in a neutralized diethyl ether/ethanol (2:1, v/v) solution, and titrated while stirring with 0.01 N NaOH using 1% (w/w) phenolphthalein solution for the detection of the endpoint.…”

High resolution NMR characterization of olive oils in terms of quality, authenticity and geographical origin

“…Comparison NMR-conventional analyses [69] Free acidity, fatty acids, iodine number, diacylglycerols 31 P, 1 H, 500 Adulteration with seed oils [27] Free acidity, diacylglycerols (sn-1,2; sn-1,3; total) total free sterols 31 P, 500 Adulteration with lampante olive oil and refined olive oil [64] Fatty acids 1 H, 500 Adulteration with hazelnut oil and sunflower oil [65] Fatty acids, triacylglycerols 13 C, 300 Adulteration with hazelnut oil and other seed oils [66] Polar fraction (diacylglycerides, monoacylglycerides, sterols, free fatty acids) 13 C, 300 Classification of edible oils [79] Fatty acids, triacylglycerols 13 C, 500 Geographical origin (PDO scale) [51] Fatty acids, iodine number 1 H, 300 and 400 Acyl chain composition of edible oils [71] b-sitosterol, squalene, cycloartenol, terpenes, aldehydes 1 H, 600 Geographical origin (national scale), harvesting year [52] b-sitosterol, aldehydes, squalene, cycloartenol, linolenic acid, triacylglycerols 1 H, 13 C, 600 Variety, geographical origin (international scale) [53] b-sitosterol, aldehydes, terpenes, squalene 1 H, 600 Geographical origin (regional scale) [54] b-sitosterol, aldehydes, terpenes, squalene, sn-1,3 diacylglycerol, sn-1,2 diacylglycerol, unsaturated fatty chains, saturated fatty chains 1 H, 600 Geographical origin (PDO scale) [55] Triacylglycerols 13 C, 600 Variety [60] b-sitosterol, wax, terpenes, aldehydes, squalene, sn-1,3 diacylglycerol, sn-1,2 diacylglycerol, unsaturated fatty chains, saturated fatty chains, triacylglycerols more techniques. For instance, the group of Spiros and Dais [46] has reported a 1 H and 31 P NMR approach based on the determination of fatty acids, iodine number, phenolic compounds, diacylglycerols, sterols and free fatty acids, useful for olive oil authentication and fraud detection.…”

“…In this way, the content of free fatty acids has been determined showing a good correlation with official titration method. [69] Besides, using the same derivatization method, sn-1,2, sn-1,3-diacylglycerides and monoacylglycerides have been quantified [70] and have showed a characteristic trend during olive oil storage. [61] Fatty acids composition and positional distribution on the glycerol moiety…”