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The establishment of effective strategies for the mitigation of 3-MCPD esters in refined vegetable oils is restricted by limited knowledge of their mechanisms of formation and decomposition. In order to gain better understanding on the thermal stability of these compounds, a model system for mimicking oil refining conditions was developed. Pure 3-MCPD esters (3-MCPD dipalmitate and 3-MCPD dilaurate) were subjected to thermal treatment (180-260°C) and the degradation products where monitored over time (0-24h). After 24h of treatment, both 3-MCPD esters showed a significant degradation (ranging from 30% to 70%), correlating with the temperature applied. The degradation pathway, similar for both compounds, was found to involve isomerisation (very rapid, equilibrium was reached within 2h at 260°C), dechlorination and deacylation reactions. The higher relative abundance of non-chlorinated compounds, namely acylglycerols, in the first stages of the treatment suggested that dechlorination is preferred over deacylation with the conditions applied in this study.

During cooking oils and fats are exposed to high temperatures that may affect the nutritional quality of foods that are prepared in this way. Concerns have been raised about the degradation of polyunsaturated fatty acids and the formation of potentially harmful compounds during deep frying, but relatively little is known about these changes in other cooking processes. In the present study sponge cakes and fried potatoes were prepared via standardised baking and shallow frying procedures by using different oils and fats (sunflower oil, rapeseed oil, various margarines or butter). The effect of cooking on the retention of two essential fatty acids (linoleic acid and α-linolenic acid) and the formation of trans fatty acids (TFA) and polymerised triacylglycerols (PTG) was evaluated by analyzing fat extracted from the cooked food. It was found that over 95 % of essential fatty acids were retained upon completion of both cooking techniques. The formation of TFA was not significant. Polymerisation was noticeable only in shallow frying, although the final levels of PTG were negligible (

Fat-based products like vegetable oils and margarines are commonly used for cooking, which may enhance oxidation of plant sterols (PS) present therein, leading to the formation of PS oxidation products (POP). The present study aims to assess the kinetics of POP formation in six different fat-based products. Vegetable oils and margarines without and with added PS (7.5-7.6% w/w) in esterified form were heated in a Petri-dish at temperatures of 150, 180 and 210°C for 8, 12 and 16min. PS and POP were analysed using GC-FID and GC-MS-SIM, respectively. Increasing PS content, temperature and heating time led to higher POP formation in all tested fat-based products. PS (either naturally occurring or added) in margarines were less susceptible to oxidation as compared to PS in vegetable oils. The susceptibility of sitosterol to oxidation was about 20% lower than that of campesterol under all the applied experimental conditions. During heating, the relative abundance of 7-keto-PS (expressed as% of total POP) decreased in all the fat-based products regardless of their PS contents, which was accompanied by an increase in the relative abundance of 7-OH-PS and 5,6-epoxy-PS, while PS-triols were fairly unchanged. In conclusion, heating time, temperature, initial PS content and the matrix of the fat-based products (vegetable oil vs. margarine) showed distinct effects on POP formation and composition of individual POP formed.

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

The quantification of 3-chloropropane-1,2-diol (3-MCPD) esters in fat-based matrices is currently carried out according to a number of methods that involve either the conversion of all the esters to the free form that is then quantified (indirect methods), or the separation and quantification of the individual esters (direct methods). Indirect methods of analysis show a better sensitivity, however, the series of chemical reactions that take place during sample preparation may affect the reliability of the results because of the potential ex-novo formation of 3-MCPD from precursors present in the sample. This study is focused on the evaluation of the selectivity and robustness of an indirect acid-catalysed method of 3-MCPD esters analysis. The interference of chloride ions and glycidyl esters was evaluated. 3-MCPD esters are overestimated only when high levels of chloride ions (>1.7 mmol/kg oil) were added to the samples. The interference by chloride ions can be easily eliminated by a single extraction step of the samples before analysis. In contrast, glycidyl esters did not interfere with the determination of 3-MCPD esters. Further investigation on the robustness of the method showed that the time allowed for the transesterification, a major drawback of the previous version of the method, can be reduced from 16 to 4 h without any significant reduction of the accuracy and repeatability (RSD = 0.7%).

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 230°C.

Several indirect methods have been developed for the determination of 3-chloropropane-1,2-diol (3-MCPD) esters in fat matrices, but the variation between these methods leads to an uncertainty about the comparison of the results. All the indirect methods are based on the conversion of 3-MCPD esters into free 3-MCPD upon transesterification (either in acid or alkaline solution), its purification, derivatisation and instrumental analysis. In this study, major critical factors of the methodology, particularly transesterification, salting out and the choice of internal standard, were evaluated. 3-MCPD showed low stability under the conditions of alkaline transesterification (only around 40% recovery) affecting the sensitivity of the method. Furthermore, the results obtained within the first 1-2 min were 10-20% higher than those obtained at longer (5-10 min) transesterification time. A comparison of results obtained by using two different internal standards (free or esterified form of deuterated 3-MCPD) revealed a slight overestimation (7-15%) when free deuterated 3-MCPD was used, which may be possibly explained by the different behaviour of the both forms during alkaline transesterification. The use of different salts and pH values of the reaction medium during salting out step had a major impact on the results due to the formation of additional 3-MCPD. Other compounds, like glycidyl esters, present in oil samples may be converted to 3-MCPD during this step, however, the conversion was not complete and varied substantially (12-93%) in dependence on the pH value of the medium. The method based on acid transesterification showed better selectivity and robustness.

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.

The formation of ascorbigen (ABG), one of the major indole-derived compound of Brassica vegetables, has been studied. An HPLC method developed previously in our laboratory was used to determine ABG precursors, glucobrassicin (GB) and L-ascorbic acid (AA), in intact plant tissues of four nutritionally important vegetable crops belonging to the genus Brassica – white cabbage, cauliflower, Chinese cabbage, and broccoli. The levels of GB varied within the range 25–142 mg kg–1 and AA contents varied within the range 110–840 mg kg–1. The amounts of ABG in homogenized Brassica vegetables was found to be between 7 mg kg–1 and 18 mg kg–1. The level of GB in the plant material was shown to be the limiting factor in the process of ABG formation. Calculated conversion values expressing the conversion of GB into ABG revealed that only 20–46% of GB present in intact plant tissues was employed in the process of ABG formation. The conversion values increased with decreasing pH values of the vegetable homogenates.

Fat-soluble vitamins and essential polyunsaturated fatty acids (PUFA) are nutrients that are sensitive to heat treatment and oxidation and therefore can be partly lost during cooking. It is well-documented that a long-term deep-frying process leads to a substantial degradation of PUFA and vitamins in a frying medium. In this study, the stability of vitamins and fatty acids was investigated in a series of liquid margarines (82% fat) varying in fat blend and the content of minor components. The tested samples were subjected to the standardised treatment that has been developed to mimic shallow-frying of food at 180°C and the recovery of individual nutrients is reported. The results show that fat-soluble vitamins possessed reasonable stability under the condition of the shallow-frying test. Essential PUFA of the frying medium were hardly affected by the treatment. Overall evaluation of the results suggests that oil-based cooking media rich in vitamins and PUFA have a positive impact on nutritional value of food prepared by appropriate means of cooking.

Bitterness and pungency, sensory quality attributes of virgin olive oil, are related to the presence of phenolic compounds. Fast and reliable alternatives for the evaluation of sensory attributes and phenolic content are desirable, as sensory and traditional analytical methods are time-consuming and expensive. In this study, two amperometric enzyme-based biosensors (employing tyrosinase or peroxidase) for rapid measurement of polar phenolics of olive oil were tested. The biosensor was constructed using disposable screen-printed carbon electrodes with the enzyme as biorecognition element. The sensor was coupled with a simple extraction procedure and optimized for use in flow injection analysis. The performance of the biosensor was assessed by measuring a set of virgin olive oils and comparing the results with data obtained by the reference HPLC method and sensory scores. The correlations between the tyrosinase- and peroxidase-based biosensors and phenolic content in the samples were high (r = 0.82 and 0.87, respectively), which, together with a good repeatability (rsd = 6%), suggests that these biosensors may represent a promising tool in the analysis of the total content of phenolics in virgin olive oils. The correlation with sensory quality attributes of virgin olive oil was lower, which illustrates the complexity of sensory perception. The two biosensors possessed different specificities toward different groups of phenolics, affecting bitterness and pungency prediction. The peroxidase-based biosensor showed a significant correlation (r = 0.66) with pungency.

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 (