Freshly picked tea leaves are brought straight to the factory and stored in containers. The raw tea leaves change until the sassei (steaming) process is complete. If the fresh leaves are left as they are, they immediately begin to ferment and generate heat. In order to preserve the freshness and ensure the quality of the leaves, the containers control humidity and temperature, and maintain moisture while preventing respiration heat from falling.
Freshly picked tea leaves have lots of moisture, and left as they are, enzymes in the leaf (polyphenol oxidase etc.) will cause the green color to be lost. Thoroughly steaming the leaves at about 100 degrees Celsius for about 30 to 90 seconds deactivates the enzymes, and by immediately air-cooling them the green color is preserved.
Steamed leaves are next sent through the limping machine in order to extract their moisture. Inside the limping machine are many hoe blade-like hands (rubbing hands) and fork-shaped hands (raking hands), which handle the tea while it is dried with hot air of nearly 90 degrees Celsius. The tea is processed for up to 15 minutes while its condition is monitored.
The tea is sent into the primary drying tea roller for crumpling under hot air. This process removes remaining moisture from the tea leaves by rolling it while being blown with hot air. The crumpling is a critical distinguishing aspect from the limping machine. The leaves are dried until they have about 40% of their moisture left. This process takes about 30 minutes, and the tea is monitored throughout.
In the roller, pressure is applied to the tea leaves which had been left unevenly dried by the primary drying tea roller, which ensures uniform moisture. Metal rods are embedded into the roller rack in a whirlpool shape, and a bucket-like "kneading tub" [momi-oke] rotates around above it. The tea leaves are placed inside the momi-oke, and a cone-shaped lid is pressed on top of it. By being "kneaded" in this way, the moisture in the tea leaves is squeezed out and made uniform. This takes up to 20 minutes.
More moisture is drawn out by placing the leaves in a drum-shaped rotator that blows hot air. This apparatus, too, has "rubbing hands," and further moisture is extracted by gently applying pressure to the tea leaves (about 20 minutes). At this point, the tea leaves have about 25% of their original water content.
The kneader is a device that presses the tea into shape. A flat lid-like disc is moved back and forth over an arched disc with a series of notched grooves (called the kneading disc), and the tea between these surfaces is rubbed into a needle-like shape.The kneading disc is heated like a kettle to a degree of 90 degrees Celsius. The process takes about 30 minutes.
The dryer dries the tea to about 5% of original water content. Here, moisture is removed to a point that long-term storage becomes possible. This takes about 60 minutes.
9. Crude Tea
Everything is thoroughly mixed together to ensure a uniform product. The tea resulting from the processes so far is called aracha, or crude tea. What follows is sorting and finishing, which will result in a variety of tea types. The manufacturing process up to this point has a yield of 23 kilograms for every initial 100 kilograms.
The finishing process begins with heating by a far infrared microwave machine. The microwaves pull out moisture from within, and the heat from the far infrared waves draw out a high-quality aroma and a mellow flavor.
11. Shape Sorting
As crude tea has a variety of shapes and sizes, shapes are arranged by sorting and cutting.
This is the color sorting machine. The colors of the tea leaves are identified via a color sensor and sorted.
The tea is mixed in drum-style tea blenders. Depending on the type of tea, the flavor, color, and aroma characteristics differ. In order to draw out those characteristics, the tea is blended to be of a uniform consistency. The blenders handle 250 kilograms at a time.
14. Foreign Object Removal
A machine and human check ensure that there are no foreign objects in the tea. (Metal detector)
The finished tea is weighed and packed in bags or tins. At our store, tea is placed in highly airtight aluminum bags, vacuum-sealed and nitrogen-filled in order to preserve the quality of the tea and prevent oxidation.