Phenolic compounds represent a unique and functional part of the polar fraction of virgin olive oils. Many different approaches for the analysis of these compounds have been published, which has led to ambiguous results that are difficult to compare. In order to explain the controversial data reported in the literature, extraction techniques (solid-phase extraction, SPE, and liquid-liquid extraction, LLE), methods of analysis (HPLC and colorimetric assay) and quantification methods have been re-investigated with genuine olive oil phenols. The optimized LLE system led to high recovery of the nine major olive oil phenolics (93%) and, in addition, was at least as good as the SPE technique in view of costs, solvent and sample consumption, and analysis time. SPE was shown to be problematic because of the selectivity towards the individual phenolics, particularly the aglycone-type ones. The proposed LLE/HPLC method was compared with the traditional colorimetric assay (Folin-Ciocalteu method) by analyzing 23 samples of virgin olive oils. A strong correlation between both methods has been found, suggesting that the colorimetric assay is reasonably valid for a rough prediction of the total phenolic content. In the literature, the level of phenolics is expressed in several different units (reference compound equivalents in case of colorimetric measurements and ppm in HPLC measurements). As these units can differ in orders of magnitude, it is necessary to convert the data to a common base before comparing or combining them.

Oil refining is essential for ensuring quality and safety of oils and fats. However, during the deodorization step of the refining process, the oil is exposed to high temperatures and changes in the lipid matrix may occur leading to the formation of 3-chloropropane-1,2-diol (3-MCPD) esters and possibly other processing by-products. This study was initiated to address the limited understanding on the formation of 3-MCPD ester in oil refining. The impact of refining conditions, both at pilot-plant and industrial scale, were investigated by subjecting palm and rapeseed oils to different refining treatments. The experiments showed that 3-MCPD esters and glycidyl esters were formed during the deodorization of palm oil, but not rapeseed oil. The level of 3-MCPD esters in the refined palm oils (3.5-4.9 mg/kg) was independent of the deodorization conditions. No correlation was found between the level of 3-MCPD esters formed and the content of the potential precursors, partial acylglycerols and chlorides. In contrast, the formation of glycidyl esters was affected by the deodorization conditions (both temperature and residence time). Higher levels of glycidyl esters (up to 3.8 mg/kg) were found in palm oil deodorized at temperatures above 2308C.

Esters of 2 - and 3-monochloropropane-1,2-diol (MCPD) and glycidol esters are important contaminants of processed edible oils used as foods or food ingredients. This review describes the occurrence and analysis of MCPD esters and glycidol esters in vegetable oils and some other foods. The focus is on the analytical methods based on both direct and indirect methods. Methods of analysis applied to oils and lipid extracts of foods have been based on transesterification to free MCPD and determination by gas chromatography-mass spectrometry (indirect methods) and by high-performance liquid chromatography-mass spectrometry (direct methods). The evolution and performance of the different methods is described and their advantages and disadvantages are discussed. The application of direct and indirect methods to the analysis of foods and to research studies is described. The metabolism and fate of MCPD esters and glycidol esters in biological systems and the methods used to study these in body tissues studies are described. A clear understanding of the chemistry of the methods is important when choosing those suitable for the desired application, and will contribute to the mitigation of these contaminants.

Three monovarietal extra virgin olive oils (EVOOs) were subjected to accelerated storage conditions (60 degrees C, dark) representative of the autoxidation process during shelf life. Oxidation markers, i.e., the peroxide value, conjugated dienes, the oil stability index, and minor components, were monitored. The changes in minor components, related to the stage of ongoing oxidation and expressed as a percentage of the induction period (IP), followed a similar pattern in all oils: o-diphenols diminished by the highest rate (halved within 15% of the IP), followed by alpha-tocopherol (halved within 35% of the IP). Carotenoids and chlorophylls were also affected by autoxidation, whereas squalene showed high stability (<20% loss within 100% of the IP). Polar phenols (especially o-diphenols) and alpha-tocopherol were deduced to be the most potent antioxidants of EVOO. They efficiently inhibited oxidative lipid deterioration and subsequent development of sensory defects (rancidity, discoloration), which occurred only after substantial depletion of these antioxidants. Therefore, they could also be used as markers for the oxidative status of EVOO particularly in the early stage of oxidation.

The availability of a reliable methodology for the quantification of fatty acid esters of monochloropropropanediol (MCPD) and glycidol is essential for understanding the mechanism of formation of these process contaminants and for developing effective mitigation strategies. While several analytical methods for the determination of MCPD esters have already been developed and evaluated, only very few procedures are currently available for the analysis of glycidyl esters. This work presents a new indirect method for the simultaneous quantification of fatty acid esters of 2‐MCPD, 3‐MCPD and glycidol. The method is based on the acid‐catalyzed conversion of glycidyl esters into 3‐monobromopropanediol (3‐MBPD) monoesters which, owing to the structural similarity to MCPD esters, are quantified by using the procedure we previously optimized for the analysis of MCPD esters. The critical step of the method, which is the conversion of glycidyl esters, was optimized by testing different reagent concentrations and varying other condition settings. The novel method showed good repeatability (RSD <2.5 %) and between‐day reproducibility (RSD ≤5 %). The limit of detection was 0.04 mg/kg for bound 2‐MCPD and 3‐MCPD and 0.06 mg/kg for bound glycidol. The trueness of the method was evaluated by the analysis of spiked samples and by interlaboratory comparison.