Effect of cooking on the contents of glucosinolates and their degradation products in selected Brassica vegetables

• Glucosinolates contents of raw and cooked Brassica vegetables were compared.
• In the cooked vegetables significant losses in total GLS content were detected.
• Not all species reduced the sum of indoles and isothiocyanates due to cooking.

Changes in the levels of glucosinolates and their degradation products in selected Brassica vegetables due to the cooking process were investigated. The purple cauliflower was found to be the best source of aliphatic and indole glucosinolates, and it was also abundant in compounds such as sinigrin, glucoraphanin and glucobrassicin. As a result of cooking rutabaga, green cauliflower and purple cauliflower, a significant decrease was noted in total glucosinolates (6.6, 68.9 and 69.2%, respectively) compared to raw vegetables. The hydrothermal processing applied led to a decline in the sum of indoles and isothiocyanates of 48.5 and 11.0%, respectively, in green cauliflower; and of 75.8 and 42.4%, respectively, in purple cauliflower; whereas, in rutabaga it led to an increase of 142.9 and 329.4%, respectively, compared with raw vegetables.