JPH0570410B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing powdered tea. Steamed sencha, which is a typical example of traditional green tea, is made by plucking young tea leaves and steaming them for several seconds with saturated steam at around 100°C to release enzymes such as peroxidase and oxidase in the tea leaves. The tea is then inactivated, and then roughly rolled using a rough rolling machine to evaporate 65% of the water content, followed by six steps: rolling, medium rolling, fine rolling, and drying. Each of these steps is extremely important in determining the quality of the product, and there are many factors such as the condition of the picked tea leaves, processing time for each step, processing temperature, amount of hot air, force applied during rolling, air temperature and humidity, etc. A combination of factors influence product quality. Therefore, the current situation is that we rely on the intuition of craftsmen cultivated over many years. Therefore, the quality depends on the person doing the construction, and variations in quality cannot be avoided depending on the weather conditions that day. Regarding powdered tea, many methods have been proposed and some have been put into practice. A typical example is matcha, which has been known for a long time. This involves heat-treating the picked tea leaves using a steamer to inactivate the enzymes in the tea leaves, and then using a cooling tea sprinkling machine to remove the steamed dew that has adhered to the leaves and the surface and interior of the tea leaves. After equalizing the moisture content, the tea is processed with hot air at 170 to 190 degrees Celsius using a tencha machine, impurities are removed, and the stems are separated, followed by pulverization using a stone mill. This grinding process cannot be operated continuously due to the temperature rise due to the frictional heat of the stone mill, and as a result, the processing efficiency is extremely low and the processing efficiency is extremely low.
It's less than an hour. In addition, recently tea leaves are subjected to steaming treatment and once cooled,
A method of freezing tea leaves with liquid nitrogen, etc. to make them brittle at extremely low temperatures, and pulverizing them in the frozen state to prevent heat generation during pulverization, chemical changes such as oxidation of active ingredients, and post-drying. . Furthermore, a method is known in which powdered tea is produced by extracting soluble components from tea produced by conventional tea production methods with hot water and subjecting the resulting concentrate to freeze-drying, spray drying, or the like. However, these conventional techniques have complicated processes, consume a lot of energy because heating and cooling are repeated, and each process is dependent on the intuition of the person performing the construction. There were a number of drawbacks, including the fact that human factors affected the quality of the product, and that useful substances such as vitamins originally contained in the tea leaves were destroyed or deteriorated in the resulting product. The present invention provides novel means for solving these problems. The picked tea leaves are subjected to heat treatment under high temperature and high pressure for a very short period of time while applying pressure to inactivate the enzymes in the tea leaves. At the same time, the stems are crushed by pressure, and then the pressure is released to crush them all at once. The water in the tea leaves is vaporized and rapidly cooled by the heat of vaporization and the adiabatic expansion of the generated water vapor.The generated water vapor surrounds the tea leaves, blocking air, and the pressure of the generated water vapor causes the tissue of the tea leaves to cool down. , causing destruction and damage to cell membranes, and at the same time evaporating 90% of the water content and drying. In the present invention, these actions are completed in one step, and then the material is ground into fine powder using a known grinder. To explain an example of the present implementation, as shown in Fig. 1, the picked tea leaves 1 are continuously fed in an appropriate amount from an appropriate hopper 2 of a conventional leaf feeder, etc., and are supported by an arbitrary bearing and installed inside the hopper. They are heated by a known heating means such as a cartridge heater or heating steam, and have a surface temperature of 150 to 250℃, a diameter of about 200mm, and a hard chrome plated surface. rollers 3, 4, 3',
4' is supplied between the engagements. In order to control the gripping pressure applied to the tea leaves supplied to the roller at this time, it is preferable to provide a pressure device 5, 5' using a spring, an air cylinder, or the like. 6, 6', 6'', 6 are doctor knives for scraping off tea leaves that adhere to the surfaces of the rollers 3, 4, 3', 4' during operation of the device and keeping the roller surfaces clean. Note that in this production method, one pair of rollers is sufficient, but it is possible to install several pairs in series as necessary. It is gripped on the mating surface, and pressure is applied by the gripping pressure, and at the same time it is heated by heat conduction.This pressing crushes the tissues such as stems and petioles in the tea leaves, and at the same time maintains the tea leaves under high pressure. Along with high-temperature heating, it inactivates enzymes such as oxidase and peroxidase in tea leaves in an extremely short time, eliminates the grassy smell of tea leaves, and generates a unique sweet and cool aroma.This heating time is correlated with the roller surface temperature. From the viewpoint of deterioration of the useful components contained in the tea leaves, it is desirable that the time be as short as possible, and as a result of experiments, a period of several seconds or less is appropriate.The applied pressure depends on the age of the tea leaves, that is, the degree of hardening. , is determined by the temperature that the tea leaves should reach, and usually a few dozen to several hundred kg/ ^cm2 is appropriate, and the roller surface temperature affects the processing speed.As a result of experiments, a temperature of 150 to 250℃ is suitable for production. Next, by releasing the gripping pressure to atmospheric pressure, the water in the tea leaves evaporates at once, and the vapor pressure causes destruction and damage to the cell membranes and tissues of the tea leaves, and at the same time The heat of vaporization of the water and the adiabatic expansion of the vaporized water vapor cause a rapid temperature drop and the tea leaves are rapidly cooled.The generated water vapor has a pressure higher than atmospheric pressure, so the tea leaves are kept isolated from the air.
Coupled with the fact that the heating time is extremely short, this has an important effect on the quality of powdered tea, which will be described later. This phenomenon is a phenomenon in which more than 90% of the water in tea leaves is removed, and it coexists with the drying effect. As described above, the basic technical idea of the present invention is to produce the above-mentioned effects by processing tea leaves at high temperature and high pressure for an extremely short period of time, and at the same time rapidly cooling and drying them. The surface temperature of the roller is determined by its diameter, material (thermal conductivity),
The characteristics are determined by the relationship with machining efficiency such as surface speed, etc., and the limitations do not have an extremely strict meaning. Next, the dried tea leaves are pulverized with a pulverizer 7 such as a known impact mill or disc mill to obtain fine powder tea 8. This pulverization process is extremely efficient, and even a normal pulperizer has a limited throughput.
It reaches 100Kg/hour. This is because more than 90% of the water contained in the tea leaves is removed during the pre-processes, namely heat treatment and drying, and the tissue of the tea leaves is being destroyed, so less energy is consumed. Furthermore, the particle size and particle size distribution of the obtained powdered tea can be freely selected, and the apparent color tone can be arbitrarily selected from bright green to dark green by adjusting the particle size distribution. Practically speaking, a particle size of about 3 to 400 microns is appropriate. In the present invention, the content of useful ingredients in the obtained powdered tea is also high, and the content of amino acids such as theanine, glutamine, and aspartic acid, caffein, catechins, free reducing sugars, and aroma components is also lower than that of conventional tea. It is larger than other types of vitamins, and there is less destruction and deterioration of vitamin groups.An example is as follows. The table compares the powdered tea of the present invention with tea leaves made from tea leaves (first and second tea) of the same variety cultivated under the same conditions using a conventional standard sencha manufacturing method.

[Table] The high content of useful ingredients means that compared to conventional methods, the heat treatment time is extremely short, drying occurs almost simultaneously with heating, and the oxidation effect of the air is prevented as much as possible. This is due to the simple processing steps. The powdered tea produced in this way can be consumed directly (in this case, it leaches well even in low-temperature water), but if it is mixed into food, drinking water, or confectionery, it may be contaminated with tea leaves. water-insoluble vitamins,
Fibers such as cellulose and various minerals have health effects. As mentioned above, traditional methods require several complicated steps, each step depends on the so-called "intuition" of the person performing the process, consumes a large amount of energy, and has drawbacks such as the loss of useful components that affect the quality of tea. The process can be completed in one or two steps, consumes 1/3 to 1/4 of the energy, and can be operated unmanned. The quality of the obtained product is also as described above. In addition, the leaves and stems of plants such as persimmon leaves, sweet tea vines, and bittern can also be treated in the same way, and the tea products used in the present invention can be treated in exactly the same way, including those that have been artificially cultured using methods such as sterile culture. The same applies to plant tissues, callus, etc. Even in these cases, the residual rate of useful ingredients is high, similar to tea leaves, and processing costs are also reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the invention. 1... Tea leaves, 2... Hopper, 3, 4... Roller, 5, 5'... Pressurizing device, 3', 4'... Roller, 7... Grinder, 6, 6... Doctor knife, 8...Powdered tea.

Claims (1)

[Claims] 1. The picked tea leaves are heated using an appropriate heating method.
The tea leaves are heated to a surface temperature of 150 to 250°C, are pressed against each other at the same surface speed, and are gripped between the engagement surfaces of two rollers rotating in opposite directions, and the gripping pressure applies pressure to the tea leaves. By applying heat treatment for a very short time of several seconds or less under high temperature and high pressure, and releasing the gripping pressure, the water in the tea leaves is vaporized and the resulting adiabatic expansion of the water vapor causes rapid cooling and drying. A method for producing powdered tea, which is characterized in that it is made into a fine powder of about 3 to 400 microns using a grinder.