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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 (

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%).

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.