Litchi is a whole fruit with shell drying. In hot air drying, the disadvantageous phenomenon affecting the quality of litchi drying is shell cracking, which is easy to occur within a few hours after the beginning of drying. Due to the heating characteristics of microwave drying equipment, under microwave irradiation, the internal moisture of litchi rapidly vaporizes to form steam pressure, which drives the water to be removed from the litchi.
In the early stage of drying, litchi has a high moisture content, which is a strong driving force and easy to burst the shell, which has been confirmed in the preliminary experiments. In addition, the whole litchi is heated by microwave to form a volume heat source. The temperature of litchi rises rapidly, which can easily cause the loss of sugar and excessive drying of the pulp of litchi.
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