Enzyme inactivation analysis for industrial blanching applications: Comparison of microwave, conventional, and combination heat treatments on mushroom polyphenoloxidase activity

Browning reactions in fruits and vegetables are a serious problem for the f ood industry. In mushrooms, the principal enzyme responsible for the browni ng reaction is polyphenoloxidase (PPO). Microwaves have recently been intro duced as an alternative for the industrial blanching of mushrooms. However, the direct application of microwave energy to entire mushrooms is limited by the important temperature gradients generated within the samples during heating, which can produce internal water vaporization and associated damag e to the mushrooms texture. A microwave applicator has been developed, wher eby irradiation conditions can be regulated and the heating process monitor ed, Whole edible mushrooms (Agaricus bisporus) were blanched by conventiona l, microwave, and combined heating methods to optimize the rate of PPO inac tivation. A combined microwave and hot-water bath treatment has achieved co mplete PPO inactivation ina short time. Both the loss of antioxidant conten t and the increase of browning were minor in the samples treated with this combined method when compared to the control. This reduction iii processing time also decreased mushroom weight loss and shrinkage.