Experimental determination and modelling of size variation, heat transfer and quality indexes during mushroom blanching

Process time during mushrooms blanching is determined either by shrinking rate or by polyphenoloxidase (PPO) inactivation, depending on the value of heating bath temperature. Quality losses during blanching can be minimized through an adequate selection of the time–temperature schedule. In this work shrinkage and PPO enzymatic activity of mushroom during blanching were measured. A simple kinetics of mushroom shrinkage was developed and was coupled to a heat transfer model based on the finite element method with irregular domain. The effect of this process on the textural and colour quality was experimentally studied and compared with the cooking value predicted from temperature simulations. Shrinkage was found to be the limiting factor to estimate the processing time for bath temperature higher than 60 °C; while polyphenoloxidase activity reduction was the limiting factor at lower bath temperatures. Quality indexes diminished with thermal treatment. Texture measures were in good agreement with simulated cooking values. This last parameter can be optimized by selecting the most appropriate conditions for the blanching process.