Investigation Into The Formation Of Volatile Sulphur Compounds In Cooked Hens Eggs

This investigation was undertaken to examine the volatile sulphur compounds produced in cooked hens eggs and to determine the possible mechanisms by which such compounds are formed. The parameters for gas chromatographic analysis of mixtures of volatile sulphur compounds were determined for optimum separation. The response characteristics and operating conditions of a gas chromatographic flame photometric detector for the detection of sulphur were also investigated. Six methods for the isolation of volatile sulphur compounds from cooked hens eggs were evaluated, following which two were selected for further investigation. One of these methods incorporated extraction of the head space vapours of cooked hens eggs with diethyl ether, followed by liquid nitrogen cold-trapping of the mixed ethereal vapours. Eleven sulphur-containing volatiles were isolated in detectable quantities by this method. Despite the absence of artefact formation during the process, the method was found to isolate volatile sulphur compounds in a non-quantitative manner. The second method involved the adsorption of cooked egg volatiles on small columns containing Tenax GC, followed by direct desorption onto a gas chromatographic column. This porous polymer was found to effectively separate twenty-one sulphur-containing volatiles from cooked hens eggs in detectable quantities, and work with synthetic mixtures of sulphur compounds indicated that adsorption and desorption were quantitative. Artefacts did not appear to be formed at desorption temperatures. Five volatile sulphur compounds isolated by these techniques were tentatively identified by retention data and sensory evaluation of the eluted components. A modified inlet system was developed whereby a Tenax GC porous polymer pre-column could be linked directly to a Reoplex 400 capillary column. Some improvement in separation of volatile sulphur compounds was effected. This chromatographic system was interfaced with a mass spectrometer and as a result of gas chromatographic/mass spectrometric analyses six volatile sulphur compounds isolated from cooked hens eggs were identified. Volatile sulphur compounds produced in heated model systems of sulphur-containing amino acids and vitamins were separated and identified by gas chromatography/mass spectrometry. The proposed mechanisms by which the identified volatiles were formed are detailed. Information gained from these experiments has been used to elucidate the possible pathways of formation of the sulphur-containing volatiles identified in cooked hens eggs. " The differences between production of sulphur-containing volatiles in heated vitellin, albumen and specific albumen proteins have also been investigated.