Part 6 - Grinding Matcha: From Tencha to Fine Powder

There are two main methods for turning tencha into powdered matcha: stone grinding and machine grinding.

Generally, matcha used for tea ceremony or high-end purposes is finished using stone grinding, while matcha intended for food processing uses machine grinding.

Stone-ground matcha has a rich aroma and deep flavor, resulting in a high-quality finish. MATCHA DIRECT also primarily uses stone grinding for its matcha (though some products are machine-ground). On the other hand, machine grinding features the ability to mass-produce in a short time using specialized grinders, making it widely used in the growing field of matcha-based food products such as matcha lattes, sweets, and ice cream.

Differences Between Stone Grinding and Machine Grinding

Aroma and Flavor

• Stone Grinding

  Matcha made by stone grinding offers a layered aroma and complex flavor when held in the mouth. The elements of umami, bitterness, sourness, and sweetness linger on the palate, leaving a deep impression. In stone grinding, tencha is slowly ground in one direction between an upper and lower millstone. The resulting particles vary in size, typically ranging from 2 to 15 microns. These uneven, angular particles contribute to the matcha’s rich aroma and complex taste.

• Machine Grinding

  Matcha made by machine grinding is characterized by a light mouthfeel and easy drinkability. However, compared to stone-ground matcha, the flavor may feel somewhat flat. This is because high-speed rotation pulverizes tencha evenly, resulting in more rounded particles and reducing the complexity of flavor and aroma typically found in stone-ground matcha.

Heat Generation

• Stone Grinding

  With stone grinding, the heat generated by friction is moderate—close to human body temperature—allowing natural fragrance and flavor of the matcha without damaging it. Furthermore, the millstones have excellent heat dissipation, preventing heat buildup and maintaining a stable grinding environment.

• Machine Grinding

  In contrast, machine grinding involves high-speed rotation, which tends to raise the internal temperature. In older grinders, prolonged use could expose the tea leaves to high heat, causing the matcha to turn yellow. However, modern grinders are typically equipped with cooling systems that appropriately reduce the internal temperature. Accumulated experience and technological advancements now allow matcha to be ground under conditions close to those of traditional stone grinding.

Processing Capacity and Average Particle Size

• Processing Capacity

  While machine grinding capacities vary depending on the type of grinder, they generally have overwhelmingly higher processing power compared to stone mills. In our facilities, a single machine grinder can perform the work equivalent to 250 to 300 stone mills.

• Average Particle Size and Variation

  Stone-ground matcha has a smaller average particle size compared to machine-ground matcha. However, it also has a greater variation in particle size, and this irregularity contributes to matcha’s distinctive depth of flavor, vibrant green color, and rich foamability. Machine-ground particles are generally larger than stone-ground ones but can be freely adjusted in size prior to grinding and are finished with uniform consistency. This uniformity allows for consistent quality suited to various applications. Some machine grinders can replicate the average particle size of stone grinding, but this drastically reduces processing efficiency, so it's generally not used.

Advantages and Disadvantages of Stone Grinding and Machine Grinding

Stone Grinding

Advantages

• Produces aromatic, rich-tasting matcha.
• Suitable for small-lot, multi-variety production.
• Excellent heat dissipation minimizes alterations to the tea resulting from friction heat.
• Gentle friction heat enhances matcha’s unique flavor.

Disadvantages

• Uneven particle size may be unsuitable for mixing with powders or liquids.
• Low production efficiency; limited hourly output.
• Requires manual management to maintain high quality.

Machine Grinding

Advantages

• Uniform particle size makes mixing with powders or liquids easy.
• Enables mass production in a short time.
• Can perform special processing like sterilization grinding, allowing for a wide range of applications.
• Automation allows for labor savings.

Disadvantages

• High initial equipment investment.
• Requires large installation space.
• Not suitable for small-lot production; minimum output starts from several tens of kilograms.
• Requires auxiliary equipment like raw material tanks and feeders.
• Regular maintenance and management are essential.

The Optimal Stone Mill Size Determined by Tea Manufacturer

The stone mill size most commonly used by tea (whole salers) manufacturer today is diameter of 1 shaku 1 sun (approx. 33.3 cm). The size of the millstone directly affects the particle size of the finished matcha powder.

In the past, both larger and smaller millstones were used, but years of experience have shown that 1 shaku 1 sun offers the best balance and is now the standard.

If the millstone is too large

The upper stone becomes heavy, making the powder excessively fine. Extremely fine particles cause strong light diffusion, making matcha appear whitish rather than green. It also becomes more prone to static electricity, leading to clumping in the tea bowl.

If the millstone is too small

The powder becomes coarse, resulting in a less smooth texture and diminished color.

After much trial and error, it was confirmed that the 1 shaku 1 sun size provides the best balance of flavor, color, and ease of whisking, and has become the current standard.

Types of Machine Grinding

There are various types of machine grinders, and production capacity and features vary depending on the grinding method and machine scale. Representative types are:

Bead Mill

A cylindrical grinding chamber filled with metal or ceramic beads, which collide with the tencha at high speed to pulverize it. Recent models are equipped with chiller water-cooling systems to suppress temperature rise and prevent quality degradation due to friction heat.

Ball Mill

Similar to the bead mill, but uses larger metal or ceramic balls. The equipment is large and typically noisy.

Hammer Mill

Uses flat-plate hammers attached to a rotating shaft inside a chamber with textured inner walls. Tencha is fed with air and pulverized by impact between the chamber wall and hammers. The powder is collected via bag filters.

Jet Mill

Creates high-speed airflow inside the machine and pulverizes tencha by making it collide with itself. Compact and efficient, suitable for large-scale production.

Importance of Sifting

Regardless of whether stone grinding or machine grinding is used, sifting (furuitoshi) is always performed as a final step. This removes leaf veins and large particles, ensuring uniform quality.

Neglecting the sifting step can result in difficulty creating creamy foam when whisking, or a gritty mouthfeel when consumed. Therefore, sifting is an essential final step to guarantee product quality and safety.

The finished matcha is carefully stored to avoid high temperatures and humidity, preserving its quality.

https://matchadirect.kyoto/blogs/matcha-insight/cultivation-method

https://matchadirect.kyoto/blogs/matcha-insight/part-2-harvesting-matcha-selecting-the-finest-leaves

https://matchadirect.kyoto/blogs/matcha-insight/part-3-processing-matcha-from-fresh-leaves-to-tencha

https://matchadirect.kyoto/blogs/matcha-insight/part-4-refining-matcha-the-finishing-of-tencha

https://matchadirect.kyoto/blogs/matcha-insight/part-5-distributing-matcha-tetcha-and-stone-milled-matcha