Comparison of volatile components in raw and cooked green beans by GC-MS using dynamic headspace sampling and microwave desorption

The effects of four culinary treatments (steaming and boiling in a covered pot, a pressure cooker or a microwave oven) on the volatile component profi le of green beans were evaluated. Volatile compounds in raw and cooked bean s were analysed by means of dynamic headspace sampling onto an adsorbent, f ollowed by microwave desorption into a gas chromatograph equipped with a ma ss spectrometric detector. Twenty-seven compounds were identified, includin g alcohols, aldehydes, ketones, esters, terpenes, sulphur compounds and alk enes. All of the thermal treatments caused important changes in the volatil e compound profile in particular an increase in carbonyl compounds and a de crease in alcohol compounds, most notably in the case of the covered pot. I t is concluded that the change in aroma during the cooking of green beans d epends on compounds from lipid oxidation as well as compounds from other ty pes of reactions, for instance the Strecker degradation.