Influence of roasting on the thermal degradation pathway in the glucosinolates of fragrant rapeseed oil: Implications to flavour profiles

Purified desulphated glucosinolates (GSLs) were subjected to thermal treatment in model systems without interference to investigate the formation of volatile components derived from GSLs only. Desulphated progoitrin (PRO), desulphated gluconapin (GNA), and desulphated glucobrassicanapin (GBN) were isolated from rapeseed (Brassica napus L.). Their structures were identified via spectroscopic data. According to the final thermal degradation compounds of the desulphated GSLs, the thermal degradation pathways of the GSLs identified herein in rapeseed during roasting were speculated. PRO degradation formed 2,4-pentadienenitrile by eliminating the hydroxyl group of the R group to generate the double bond at C-2. GNA degradation produced 4-isothiocyanato-1-butene. Two degradation pathways were possibly involved in the degradation of GNA and GBN. The main precursors that produce the pungent flavour of rapeseed oil were obtained by exploring the relationship between the degradation of the GSLs and the volatile flavour of this vegetable oil during roasting.