Enzymatic and non-enzymatic degradative reactions during the thermal treatment of glucosinolates and their reaction products

• Applicant: Dr. Franziska Hanschen
• Subject Area: Food Chemistry
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279035656

The main objective of the study during the second phase is to elucidate and quantify non-enzymatic products of isothiocyanates (ITC), such as thioureas and amines, which are formed during the thermal treatment of Brassica vegetables. ITC are the sharp tasting compounds which are enzymatically released from glucosinolates (GLS) in cruciferous vegetables, such as mustard and broccoli. These isothiocyanates are thought to be cancer preventing compounds. However, many of these vegetables are not consumed raw but rather after thermal treatment. Therefore, these compounds can be non-enzymatically degraded. The reactivity of ITC is strongly dependent on their structure, which could be already shown during the first phase of this project. Already some N,N‘-di[alk(en)yl]thioureas were identified using NMR-spectroscopy, while most so far are only tentatively identified (using high resolution mass spectrometry). These thioureas, being products from ITC, were observed in models as well as in heated Brassica matrices. Further, there are hints, that a multitude of other products is formed from the ITC, such as amines. Therefore, the question occurs how much of these compounds are formed in Brassica-food. In consequence, during the second phase of the project these thioureas will be synthesized in order to identify their still not comprehensively elucidated structure. Further, methods will be developed to quantify the formation of these thioureas and amines in the models as well as in Brassica matrices. Only based on such data conclusions concerning the uptake of these potentially bioactive compounds can be drawn.To achieve the goals the following approach is planed:- The thioureas will be synthesized and their structure elucidated. - A method for quantification of thioureas will be developed and their formation in Brassica vegetables will be traced and compared to the models.- For the quantification of amines a method will be developed as well and their formation will be monitored in the models as well as in Brassica matrices.- Finally, Brassica foods will be prepared and the changes in GLS, their enzymatically released hydrolysis products and the formation of ITC-breakdown products will be followed with the treatment time.The results will multiply the knowledge about GLS-based reactions during thermal processing of Brassica-vegetables. Due to newly identified degradation products further questions will occur, concerning their biological relevance (e.g. toxicity) or their importance in food chemistry (e.g. interaction of amines with other food constituents). The gained knowledge will enable to optimize thermal treatment during food processing in order to optimize the content of health-preventive breakdown products.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Sascha Rohn