Internal quality control

Kyosun QC Laboratory

We test every batch of matcha in our in-house laboratory using four independent methods. The results determine the product's quality grade and decide its approval for sale.

Testing methodology

Four complementary measurement methods for objective quality assessment

Colorimeter

PCE-CSM 4

Colour measurement in L*a*b* space. The a* value determines quality — the lower (more negative), the greener and higher-quality the matcha.

Turbidimeter

Apera TN400

Suspension stability measurement. The turbidity drop over 5 min shows grind fineness — the smaller the drop, the finer the grind.

Moisture analyser

KERN DBS 60-3

Water content measurement. Optimal moisture is 3–5 %; above 6 % there is a risk of degradation and mould.

Sensory evaluation

5 parameters, 1–10 points

Colour, aroma, umami, bitterness and foam — each parameter 1–10 points. Maximum 50 points in total.

Colorimeter values (a*) by quality grade

The a* value determines the greenness of matcha — the lower (more negative), the deeper the green and the higher the quality. Measured with the PCE-CSM 4 in L*a*b* space.

Culinary

a* ≤ −10

Yellow-green

High Culinary

a* ≤ −12

Olive green

Ceremonial

a* ≤ −15

Green

High Ceremonial

a* ≤ −20

Deep green

Premium Ceremonial

a* ≤ −24

Rich chlorophyll

How it works: a* is the green–red axis in the CIE L*a*b* colour space. Negative values mean green — the smaller (further into the minus), the deeper the shade. The colour circles above are illustrative visual approximations, not exact colorimetric conversions.

Quality grades

Based on the measurement results, each batch is assigned to one of five quality grades

Grade	Colour (a*)	Turbidity	Sensory	Moisture
Culinary	≤ -10	—	≥ 21/50	—
High Culinary	≤ -12	—	≥ 21/50	—
Ceremonial	≤ -15	—	≥ 30/50	not critical
High Ceremonial	≤ -20	< 15 %	≥ 38/50	acceptable
Premium Ceremonial	≤ -24	< 12 %	≥ 43/50	3–5 %

Detailed grading rules

Each method has its own 0–5 point scale, which combines into the final quality grade.

Colorimeter (a* value)

PCE-CSM 4 · CIE L*a*b* space

The main matcha quality indicator. The a* value measures position on the green↔red axis — negative values mean green. The lower (more negative), the richer the chlorophyll and the higher the quality.

a* ≤ −24

Score 5

a* ≤ −20

Score 4

a* ≤ −15

Score 3

a* ≤ −12

Score 2

a* ≤ −10

Score 1

a* > −10

Out of limit (0)

Moisture

KERN DBS 60-3 · halogen analyser

The optimal water content in matcha powder is 3–4.5 %. Too low (dry) loses aroma and flavour profile. Too high causes chlorophyll degradation, oxidation and mould risk.

3–4.5 %

Optimum (4)

4.5–5 %

Score 3

2.5–3 %

Score 2

5–6 %

Score 1

> 6 %

Out of limit (0)

Turbidimeter

Apera TN400 · ISO 7027 nephelometry

Measures the stability of dissolved matcha suspension in distilled water. It tracks the turbidity drop (NTU) over 5 minutes — the smaller the drop, the finer the grind and the more stable the suspension (particles do not settle). Sample prep: 0.5 g matcha + 300 ml distilled water (20 °C).

< 12 %

Excellent (4)

< 15 %

Score 3

< 25 %

Score 2

< 40 %

Score 1

≥ 40 %

Score 0

Sensory evaluation

5 parameters · max 50 points

Evaluates 5 parameters on a 1–10 scale. For bitterness the value is inverted: the less bitter, the higher the contribution (1 = not bitter → 10 points, 10 = strongly bitter → 1 point). The maximum sum is 50 points.

Colour — visual assessment of the green shade in the bowl
Aroma — intensity and character (fresh, marine, grassy)
Umami — the fifth taste, depth and savouriness
Bitterness — less bitter = better quality
Foam — stability and texture of the foam after whisking with a chasen

≥ 43/50

Score 4

≥ 38/50

Score 3

≥ 30/50

Score 2

≥ 21/50

Score 1

< 21/50

Out of limit (0)

How the final quality grade is determined

The final grade is determined by combining the scores of all four measured methods. Each grade has its minimum requirements — the test must meet them all at once. If any parameter fails, the test drops to a lower grade.

Premium Ceremonial — colour ≥ 5, turbidity ≥ 4, sensory ≥ 4, moisture ≥ 3

High Ceremonial — colour ≥ 4, turbidity ≥ 3, sensory ≥ 3, moisture ≥ 2

Ceremonial — colour ≥ 3, sensory ≥ 2, moisture ≥ 1

High Culinary — colour ≥ 2, sensory ≥ 1

Culinary — colour ≥ 1

Note: If a method is not measured, it does not take part in grading (a missing parameter does not block a higher grade). The lowest grade is Culinary.

QC test overview

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