Regarded as one new technology,microwave is widely used for tea fixation(kill green),tea drying,tea sterilization .
In the fixation process, fresh leaves contains high moisture , and strong water absorbing microwave quality, can be polarized in microwave field , and change polarity orientation and make high speed movement as the frequency of electromagnetic field, produce friction heat,make whole tea heating in microwave , eventually make lots of water molecules overflow from fresh leaves and taken away by evaporation. Microwave heating can make tea rise temperature rapidly, reach passivation enzymecritical point temperature,it quickly passivation enzyme activity of tea.
And the electromagnetic field generated by the microwave heating and temperature field incombination will strengthen the deformation effect of the enzyme in tea, so as to achieve the purpose of fixation(kill-green).
Microwave advantages in tea dryer ,fixation:
1. Stable quality. Different seasons,different tea ,different time ,the fresh picked tea leaves have differences in intinal water content,fresh degree etc,microwave can flexibly adjust fixation,drying
data according to these characteristics,then can make every kind tea reach the ideal fixation effect.
2. Improve tea quality. Repeated experiments and practice show that after treatment with microwave heating technology, has excellent characteristics of high-grade tea, dried tea appearance even, colour and lustre is green, fresh and pure taste, aroma rich, tender leaves evenly bright.
3.Improve tea health . Microwave fixation, microwave drying don’t need coal or wood, no smoke and dust pollution, at the same time realize automate the tea continuousprocessing,, avoiding the conventional process to produce secondary pollution.
Microwave application in tea fixation:
The production of green tea, oolong tea, all need to heat fixation treatment, passivate the activity of polyphenol oxidase, evaporate moisture content, volatile grass smells, soften the organization. Now commonly used pan-fired method to deal with fixation, a few places using steam fixation method..
The test results show that the microwave and the traditional processing way .the tea quality is good, no obvious difference, but the short microwave fixation time(1/8 time of pan-fired)and canbe continuous processing. And steam fixation,because of high steam moisture content, the outer of raw material affected by high temperature, therefore almost no weight loss of tea after fixation treatment, partial chlorophyll was destoryed,the raw material contains nutrients loss along with the condensation water,quality is not ideal.
The application of microwave fixation for the tea is the main source of heat effect. When magnetron produce microwave ,effect on tea leaves, polar molecules inside tea affected by microwave cyclical change, cyclical activities accordance with microwave.Because high microwave frequency, make tea internal molecular collision at a high speed and generate a lot of friction heat,rapidly increase the temperature of the material,
Make tea molecules inside a lot of friction heat resulting from the high speed collision rapidly raise the temperature of the material, so as to achieve rapid heating effect.
Microwave application in tea drying:
General hot air drying process, material external heated, surface drying, heat transfer inwards, the direction and water diffusion direction in the opposite direction, affect the moisture to evaporate.But microwaveis an internal heating, The part of high water content heat up faster.So in the microwave drying process,water migration speed from the inner to the outer is high, drying speed is significantly faster than hot air drying.
Application of microwave drying in the drying tea has the following advantages:
1.fast drying speed ;
2.high products quality,because tea surface temperature is not too high, less chlorophyll changes, colour and lustre is green emerald green, less aroma loss;
3.Uniform drying;
Due to the fast evaporation speed, easy to form porous, good water complex content easy to dissolution when making tea.
Microwave application in tea pesticide and mildew:
Tea breeds insects easily in the shipping and storage process,also occur insects pollution phenomenon. Before commonly use fumigation insecticidal method,but have the problem of drug residues. Adopts microwave sterilization treatment can obtain good insecticidal effect,insects insecticidal effect in tea is closely related to the dielectric properties of insect body, while tea moisture content is less than 12%, can strengthen insecticidal effect.
Tea is easily affected with damp mildew in the storage process and debase its quality.
Through the trials show that microwave technology has excellent effectof killing tea mold.
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