title: Thermally induced degradation of aliphatic glucosinolates: identification of intermediary breakdown products and proposed degradation pathways.
abstract: In  Brassica  vegetables, heating processes lead to thermally induced degradation of glucosinolates (GSLs), resulting in the formation of nitriles and isothiocyanates (ITCs). To date, the mechanism is not yet satisfyingly elucidated. Thermally induced degradation of the model GSL sinigrin was studied in dry as well as aqueous medium at different pH values and temperatures. The influence of the presence of iron ions and plant matrix (broccoli sprouts powder) on the degradation was studied as well. Next to the degradation of the GSL, the formation of nitrile and ITC and the release of sugar derivatives were investigated. Because d-glucose and ITC are main thermal breakdown products under aqueous conditions, hydrolysis seems to be the initial step in the degradation pathway during cooking. In contrast, under dry conditions, the desulfo-sinigrin was identified as a main intermediary thermal breakdown product for the first time. Further, degradation of the desulfo-GSL results in the release of d-thioglucose and the corresponding nitrile. Iron(II) ions and plant matrix influence the thermal stability of the GSL and favor the formation of nitriles.
authors.affiliation: Department of Food Chemistry and Analysis, Institute of Food Technology and Food Chemistry,  Technische Universität Berlin , TIB 4/3-1, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany.
authors.forename: Franziska S
authors.initials: FS
authors.lastname: Hanschen
authors.forename: Anna
authors.initials: A
authors.lastname: Bauer
authors.forename: Inga
authors.initials: I
authors.lastname: Mewis
authors.forename: Claudia
authors.initials: C
authors.lastname: Keil
authors.forename: Monika
authors.initials: M
authors.lastname: Schreiner
authors.forename: Sascha
authors.initials: S
authors.lastname: Rohn
authors.forename: Lothar W
authors.initials: LW
authors.lastname: Kroh
mesh_terms: D001937:Brassica / Q000737:chemistry*; D003296:Cooking; D005961:Glucosinolates / Q000737:chemistry*; D006358:Hot Temperature; D017879:Isothiocyanates / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*
chemical_list: D005961:Glucosinolates; D017879:Isothiocyanates; D009570:Nitriles