What is True Total Hydration in sourdough baking?

True Total Hydration measures the total water in the entire dough matrix (including the water contributed by your starter) divided by the total flour weight. Conventional calculators ignore starter water, resulting in dough that is 2.7% to 3.0% wetter than intended.

Why does adding 20% starter increase hydration by ~3%?

A standard 100% hydration levain consists of 50% flour and 50% water. When you add 100g of levain to a recipe with 450g flour and 315g water (70% apparent hydration), the total flour becomes 500g and total water becomes 365g. 365 / 500 equals 73.0%—a full 3 percentage points higher.

What is Desired Dough Temperature (DDT) and why does it matter?

DDT is the target dough temperature right after mixing (typically 76°F / 24.4°C). Temperature governs yeast metabolism and enzymatic activity. Controlling water temperature ensures bulk fermentation finishes at the predicted time without under- or over-proofing.

How does ice substitution work when DDT calculates a temperature lower than tap water?

In hot kitchens, the required water temperature may fall below what your cold tap can deliver. By replacing a portion of water with crushed ice, the phase change absorbs 80 calories per gram of latent heat of fusion, cooling the dough without adding excess liquid.

Why does whole wheat flour absorb more water than bread flour?

Whole wheat flour retains the fibrous outer pericarp (bran) and germ. The insoluble fibers and pentosans in wheat bran act like micro-sponges, absorbing up to 200% of their own weight in water.

The DDT Masterclass: How to Control Fermentation Speed Using Ice Water Calculations

Why Temperature Dictates Fermentation Physics

Wild yeast (*Saccharomyces exiguus*) and lactic acid bacteria (*Lactobacillus sanfranciscensis*) do not operate on a clock; they operate on a thermal metabolic curve.

At 70°F (21°C), commercial sourdough starter microbes double roughly every 90 minutes. At 82°F (28°C), that doubling time drops to approximately 45 minutes. More critically, high temperatures favor heterofermentative bacteria that churn out acetic acid, degrading gluten elasticity and yielding a gummy crumb.

The benchmark target for artisan open crumb is **76°F (24.4°C) Desired Dough Temperature (DDT)** at the completion of mixing.

---

The 4-Factor DDT Calculation

To achieve your target DDT, water temperature is the only dynamic variable you can adjust. All other inputs (room temp, flour temp, levain temp) are predetermined:

\text{Target Water Temp} = (4 \times \text{DDT}) - (T_{\text{room}} + T_{\text{flour}} + T_{\text{levain}} + \text{Friction Factor})

*Where Friction Factor (FF) is:* - **Hand mixing / Stretch-and-fold:** $2^\circ\text{F} \sim 4^\circ\text{F}$ ($1^\circ\text{C} \sim 2^\circ\text{C}$) - **Stand mixer (Low Speed):** $8^\circ\text{F} \sim 12^\circ\text{F}$ ($4^\circ\text{C} \sim 6^\circ\text{C}$) - **Spiral mixer (Commercial):** $15^\circ\text{F} \sim 20^\circ\text{F}$ ($8^\circ\text{C} \sim 11^\circ\text{C}$)

---

The Summer Crisis: When Target Water Temperature Drops Below Tap Water

During hot summer months, the formula frequently yields an impossible result: - Room Temp: $82^\circ\text{F}$ - Flour Temp: $80^\circ\text{F}$ - Levain Temp: $80^\circ\text{F}$ - Friction Factor: $10^\circ\text{F}$ - Target DDT: $76^\circ\text{F}$

\text{Target Water Temp} = (4 \times 76) - (82 + 80 + 80 + 10) = 304 - 252 = \mathbf{52^\circ\text{F}}

If your kitchen tap only dispenses $75^\circ\text{F}$ water, simply turning on the cold tap will cause your final dough to clock in at $82^\circ\text{F}$, cutting your bulk fermentation window in half and causing unexpected overproofing.

---

Thermodynamics: Ice Melting Latent Heat of Fusion

To drop the water temperature, professional bakers substitute a portion of the recipe water with crushed ice. Because phase change from solid ice to liquid water absorbs **80 calories per gram** ($144\text{ BTU/lb}$), ice provides vastly superior cooling power compared to chilled water.

The Baker's Thermodynamic Ice Formula: $$\text{Weight of Crushed Ice (g)} = W_{\text{water, total}} \times \frac{T_{\text{tap}} - T_{\text{target}}}{T_{\text{tap}} + 80} \quad (\text{in Celsius})$$

\text{Weight of Crushed Ice (g)} = W_{\text{water, total}} \times \frac{T_{\text{tap}} - T_{\text{target}}}{T_{\text{tap}} + 112} \quad (\text{in Fahrenheit})

*In the example above ($350\text{g}$ water, $T_{\text{tap}} = 75^\circ\text{F}$, $T_{\text{target}} = 52^\circ\text{F}$):*

W_{\text{ice}} = 350 \times \frac{75 - 52}{75 + 112} = 350 \times \frac{23}{187} = \mathbf{43\text{g Crushed Ice}}

You weigh out **43g of crushed ice** and **307g of tap water** ($350\text{g}$ total liquid). Stir until the ice melts completely before autolysing. Your dough will hit $76^\circ\text{F}$ on the dot every single time.

Why Temperature Dictates Fermentation Physics

The 4-Factor DDT Calculation

The Summer Crisis: When Target Water Temperature Drops Below Tap Water

Thermodynamics: Ice Melting Latent Heat of Fusion

The Baker's Thermodynamic Ice Formula: $$\text{Weight of Crushed Ice (g)} = W_{\text{water, total}} \times \frac{T_{\text{tap}} - T_{\text{target}}}{T_{\text{tap}} + 80} \quad (\text{in Celsius})$$

Ready to test this formula with your flour blend?