Determination of dimethylsulfide and dimethyldisulfide in foods by thermal desorption GC/MS

Abstract

A thermal desorption-GC/MS was used for the determination of dimethylsulfide (DMS) and dimethyldisulfide (DMDS), characteristic odor components in various foods. These volatile components in food were vaporized by bubbling nitrogen gas, and were collected into a porous polymer beads-type tube, Tenax-TA, placed at the outlet of the flow. The tube was then transferred into a thermal-desorption apparatus and GC/MS analysis was performed. The bubbling time and the flow rate of nitrogen gas were examined to optimize the extracting condition. In the thermal desorption-GC/MS method, most of the vaporized compounds were collected in the adsorbent tube, and injected all at once, while only a part of the vaporized compounds was injected in by the headspace method, generally used for flavor analyses. The calibration curve showed good linearity in the range of 0.5-500 ng ml -1. The recovery of the compounds varried from 60 to 106%, depending on the type of samples. The detection limit of this method was 0.1 ng g -1 sample, and the reproducibility was 4.1-6.8% (R.S.D.). In this study, using the thermal desorption method, it was reconfirmed that the heating process affects the measurement value of the concentration of DMS and DMDS in several dairy products and vegetable extracts. This report also presents new findings concerning the quantities of DMS and DMDS in several fermented foods, seafood, and coffee products. © 2005 The Japan Society for Analytical Chemistry.