Abstract

The invention relates to the tea industry. Green tea leaves are heat treated to inactivate the redox enzymes and then processed until they have a residual moisture content of 60-75%. The tea leaves are rolled, dried in two steps and then sorted. In the first drying step, a layer of tea leaves having a height of not more than 10 cm and a residual moisture content of 60-75% is heated in a drying chamber for 8-12 minutes using an electromagnetic microwave field under conditions of constant pressure in a range of 40-80 kPa and with the heating temperature being increased evenly at a rate of 3-4°С/s. The rate is selected based on the need to reach temperature vales in a range of 70-85°С by the end of the first step and taking into account the length of the first step. In the second drying step, pulsed heating is carried out in a range of 35-45°С using an electromagnetic microwave field, with the pressure in the drying chamber being lowered to a value of 15-4 kPa, until a residual moisture content of less than 10% is reached. After that, the vacuum pump is switched off and atmospheric pressure is restored in the chamber. The invention provides a simpler green tea drying technique, allows even heating of each batch of tea loaded into the drying chamber, prevents the caramelization of sugars in the initial stages of the drying regime, increases the extraction yield of the green tea when infused, and improves the organoleptic properties thereof.

IPC Classes  ?

• A23F 3/06 - Treating tea before extractionPreparations produced thereby
• A23F 3/12 - Rolling or shredding tea leaves
• F26B 20/00 - Combinations of machines or apparatus covered by two or more of groups

Abstract

A method for processing dry black tea includes withering tea leaves to a moisture content of 75-65% and rolling same, fermenting, drying to a residual moisture content of less than 10%, and drying a second time using the thermal action of a microwave electromagnetic field under a constant pressure of 50-60 kPa in a drying chamber until the dry black tea has been heated, over a period of 8-12 minutes, to a temperature selected according to the residual moisture content of the tea leaves after drying. The temperature is increased at a rate of 1.0°С/s – 3.0°С/s. Once the given temperature value has been reached and the thermal action time has elapsed, the thermal action is stopped and, at the same time, a pressure reduction regime is activated in the chamber to reduce the pressure to 14-4 kPa, the dry black tea being kept in the chamber under decreasing pressure until the temperature of the tea is less than the temperature in the production premises in which the drying chamber is situated.

IPC Classes  ?

• A23F 3/06 - Treating tea before extractionPreparations produced thereby
• A23F 3/12 - Rolling or shredding tea leaves
• F26B 23/08 - Heating arrangements using electric heating inductive heatingHeating arrangements using electric heating capacitative heatingHeating arrangements using electric heating microwave heating