Kenya Coffee School Cluster 1 Training

What Is TDS in Espresso — And Why It Changes Everything

If you cannot measure it, you cannot control it.

Total Dissolved Solids (TDS) is the percentage of soluble material extracted from coffee into water. In espresso, it is not an abstract number — it directly influences body, strength, and clarity.

Espresso typically ranges between 8%–12% TDS. That number represents the concentration of dissolved compounds in the final beverage.

But here is where misunderstanding begins.

High TDS does not automatically mean “better.”
Low TDS does not automatically mean “weak.”

TDS measures concentration — not balance.

How TDS Is Measured

A refractometer measures light refraction through liquid. The more dissolved solids present, the more light bends.

From TDS, we calculate Extraction Yield:

Extraction Yield = (Beverage Weight × TDS) / Dose

Example:

36g espresso
10% TDS
18g dose

Extraction Yield ≈ 20%

That sits inside the specialty target window (18–22%).

Why This Matters Practically

Without TDS measurement, baristas rely only on taste memory.

With TDS data:

You detect under-extraction early.
You identify over-extraction trends.
You compare brew consistency across shifts.
You isolate grinder inconsistency.

TDS transforms espresso from guesswork into repeatable engineering.

Cluster 2

Diagnosing Espresso Channeling: A Practical Troubleshooting Framework

Channeling is not random. It is structural failure inside the puck.

When water finds weak points, it rushes through them. The result is uneven extraction — part of the puck over-extracts while the rest remains underdeveloped.

Symptoms in the cup:

Sourness and bitterness together
Thin body
Fast shot time despite fine grind

Root Causes

Uneven distribution
Inconsistent tamp pressure
Clumping from grinder retention
Damaged basket or warped portafilter
Excessive pump pressure

Channeling is rarely solved by grind size alone.

Practical Correction Method

Instead of random adjustments, use sequence:

Check distribution technique.
Inspect basket for damage.
Confirm pump pressure calibration.
Observe shot flow visually.
Only then adjust grind.

Professionals isolate variables rather than adjusting everything at once.

Channeling is physics responding to imbalance.

Cluster 3

Brew Ratio vs Extraction Yield: Why They Are Not the Same

Many baristas confuse brew ratio with extraction yield.

Brew ratio: Coffee in → Beverage out

Extraction yield: Percentage of coffee mass dissolved.

A 1:2 ratio does not guarantee 20% extraction.

Two shots with identical ratios can taste radically different if grind size or water chemistry varies.

Scenario Comparison

Shot A:

18g in
36g out
10% TDS
20% yield

Shot B:

18g in
36g out
8% TDS
16% yield

Visually identical. Chemically different.

Ratio controls dilution. Yield measures solubility.

Confusing them leads to flawed calibration.

Cluster 4

Pressure Profiling Explained for Practical Baristas

Traditional espresso machines operate at fixed pressure. Modern systems allow pressure modulation during extraction.

Why does this matter?

During the first seconds of extraction, dry grounds resist water penetration. Gentle pre-infusion allows uniform saturation before full pressure engages.

A declining pressure curve later in the shot can: