Dough temperature drift during a heatwave
A craft bakery produces 180 kg of straight-dough white pan bread every night for wholesale. The dough temperature target (DDT) is 26 °C and the spiral mixer's friction factor is 12 °C. During this week's heatwave the mixing room sits at 28 °C, flour straight off the delivery pallet is at 26 °C, and the mains water runs at 24 °C. For six days the dough has been leaving the mixer at 29–30 °C. Bulk fermentation, planned at 90 minutes with 1.8 % fresh yeast, is finished in about 45 minutes. The bread now comes out with a pale crust, a coarse crumb with big irregular holes under the top crust, a sharp yeasty-sour smell, and it is stale by the next afternoon. Recipe, flour lot and mixer are unchanged. There is no water chiller and no air conditioning, and the owner wants tomorrow's schedule back on track.
1. Calculate the water temperature that would hit the 26 °C DDT, and explain how an over-warm dough produces each of the symptoms described.
Read the worked answer
Using the friction-factor form of the DDT formula:
Water temp = (DDT × 3) − (room + flour + friction) = (26 × 3) − (28 + 26 + 12) = 78 − 66 = 12 °C.
Check: (28 + 26 + 12 + 12) ÷ 3 = 26 °C. Correct.
Now test what is actually happening: (28 + 26 + 24 + 12) ÷ 3 = 30 °C - exactly the dough temperature observed. The water is the whole cause; the flour and yeast are not at fault.
At 30 °C versus 26 °C, yeast metabolism roughly doubles (Q10 ≈ 2 in the 20–35 °C range), which turns a 90-minute bulk into ~45 minutes and explains every symptom:
- Pale crust - fermentable sugars are consumed before the loaf reaches the oven, so there is little left for Maillard browning.
- Coarse irregular holes under the top crust - gas production outruns gluten extension and the dough degasses poorly at shaping.
- Yeasty-sour aroma - over-fermentation and partial yeast autolysis.
- Fast staling - an over-fermented, degraded starch–protein matrix holds water badly.
The fix is not 'mix for less time'; it is removing the heat before it enters the dough.
2. There is no chiller tonight. Set out a workable plan for tomorrow's 180 kg, with the arithmetic, and state the quality risk attached to each measure.
Read the worked answer
Target: get the effective temperature sum from 90 down to 78.
- Ice substitution (biggest lever). Replace roughly 30 % of the water with crushed ice, weighed 1:1 against water. Ice at 0 °C plus latent heat pulls the effective water temperature well below 12 °C. Risk: uneven hydration and ice pockets if the ice is not fully melted by the end of the mix - add ice at the start and verify dough temperature, not the clock.
- Chill the flour overnight. Flour at 10 °C instead of 26 °C removes 16 ÷ 3 ≈ 5.3 °C from the dough. Combined with 18 °C water: (28 + 10 + 18 + 12) ÷ 3 = 22.7 °C - too cold, so do not stack both measures at full strength. Risk: condensation on cold flour changes scale weight slightly; bag it.
- Shift the mix into the coolest window, e.g. 02:00–05:00, and draught the room. Risk: none to the dough, but it moves labour cost and needs a supervisor sign-off.
- Reduce fresh yeast from 1.8 % to ~1.2 % and hold bulk at 90 minutes only once the dough is back at 26 °C. Reducing yeast while the dough is still at 30 °C risks a half-proofed, collapsed loaf at the moulder.
Sequence matters: fix temperature first, then adjust yeast and time - never both at once.
3. Suppose the coldest water you can obtain tomorrow is 18 °C. What do you change, and what new risk does each change carry?
Read the worked answer
Water at 18 °C gives (28 + 26 + 18 + 12) ÷ 3 = 28 °C - still 2 °C over target, so about a 40 % speed-up in fermentation.
Levers, in order of preference:
- Pre-chill flour to 18 °C in the cold room: (28 + 18 + 18 + 12) ÷ 3 = 25.3 °C. This alone solves it. Risk: cold flour hydrates more slowly, so extend the mix by one minute and check gluten development by windowpane, not by timer.
- Cut fresh yeast to 1.3 % and hold bulk to 80 minutes. Risk: if the bakery cools overnight the dough may under-proof; you must judge by dough condition (dome, 70–80 % expansion, gas bubbles) rather than the clock.
- Move fermentation to the 20 °C cold room for the first 40 minutes, then finish warm. Risk: uneven temperature through the trough if the dough is deeper than about 15 cm; use shallower troughs.
- Add salt earlier or increase it slightly to slow fermentation. Risk: salt tightens gluten - do not exceed the recipe by more than about 0.1 % of flour weight, or the crumb becomes dense and the loaf loses volume.
What I would not do is shorten bulk to 40 minutes and call it solved: that trades over-fermentation for under-developed flavour and a tight, uneven crumb that the wholesale customer will notice within a week.