An Investigation on Blast Precooling of Mushrooms

In order to get more profit, it is necessary to reduce weight loss of vegetables and fruits during precooling. In this paper, the heat and mass transfer in mushrooms during blast precooling is studied experimentally. Experimental result shows that the relative humidity of cooling air is the main factor which affects the weight loss, the higher the humidity the lesser the weight loss. The result also shows that the cooling rate of mushrooms is dependent on the velocity of cooling air, the faster the air velocity the quicker the cooling rate. To lower the temperature of mushrooms for 20 C by blast precooling, the weight loss is less than 2%, which is only about half of that caused by vacuum precooling. Using lumped parameters method, a heat transfer differential equation is developped, in which the latent heat of moisture evaporation from mushroom surface is considered. Numerical solution of this equation can be used to predict blast precooling of spherical and lump vegetables and fruits.