LAUSR

The inactivation kinetics of the enzymes polyphenoloxidase, peroxidase, and myrosinase, the degradation of anthocyanins and antioxidant activity of the red cabbage were studied during steam blanching at 100°C and in water at 80 and 90°C, in times of 1, 2, 4, 6, 8, and 10 min. Losses of anthocyanins and antioxidant activity during blanching in water were caused by heat and diffusion. The results indicated that the best blanching condition was obtained by steam for 4 min, with reduction of 98.0 and 47.6% in the enzymatic activity of peroxidase and polyphenoloxidase, respectively, and in this condition the losses of anthocyanins and antioxidant and myrosinase activities were of 37.9, 6.7 and 64.2%, respectively. The rate constants of reaction increased for all the enzymes with the rise of blanching temperature, and for the anthocyanins and antioxidant activity the rate constants of reaction were lower for steam. Practical applications Blanching is an important unit operation used for inactivating enzymes that produce deleterious changes, such as the browning and loss of texture in vegetables. However, as a consequence of overheating, losses in sensorial, nutritional and bioactive properties may occur in foods. Red cabbage has important quantities of anthocyanins, which have antioxidant properties. In addition, red cabbage contains glucosinolates, which when hydrolyzed by the enzyme myrosinase produce bioactive compounds and products involved in cancer chemoprotection. However, blanching might inactivate this enzyme and this way reduces the production of these beneficial compounds. The results obtained in this work might be used in the preservation of beneficial enzyme (myrosinase) and inactivation of peroxidase and polyphenoloxidase.