Mixer Capacity and Bagel Batch Planning
A bakery has a 60-quart spiral mixer rated by the manufacturer for 25 kg of flour at 60% absorption for bread dough. To make 1,000 bagels at 110 g each, the baker loads 35 kg flour, 17.5 kg water, 0.7 kg sugar, 0.7 kg salt and 0.7 kg fresh yeast. The dough is stiff and climbs the spiral; the mixer’s overload trips during the first mix. The final dough temperature is 29°C instead of the target 24°C. The bakery has a 2-hour production window and one mixer. Bagel dough is normally 50% hydration; the formula also includes 2% sugar, 2% salt and 2% yeast. The baker wants to know the maximum safe batch size, how many batches are needed, and whether the mixer is suitable. Scrap dough and trimming losses are about 2%.
1. Calculate the dough yield from the formula and the number of batches needed for 1,000 bagels, allowing 2% loss.
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Formula total per 100 kg flour: 50 kg water + 2 kg sugar + 2 kg salt + 2 kg yeast = 156 kg dough, so yield is 156%. Need 1,000 × 0.110 = 110 kg dough; with 2% loss, 110 × 1.02 = 112.2 kg. The mixer is rated 25 kg flour at 60% absorption, but bagel dough at 50% is stiffer, so derate to about 20 kg flour. At 18 kg flour per batch, dough = 18 × 1.56 = 28.1 kg. 112.2 ÷ 28.1 = 3.99, so four batches. Four batches use 72 kg flour and make 112.3 kg dough. A nominal three batches at 25 kg would make 117 kg dough, but that is not a safe load for this stiff dough.
2. Why did the 35 kg batch overheat and trip the mixer even though the mixer is rated for 25 kg?
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The batch used 35 kg flour, which is 40% above the 25 kg rating. Total dough was 35 × 1.56 = 54.6 kg. Bagel dough at 50% hydration is stiffer than the 60% absorption bread dough used for the rating, so torque and friction are higher. The motor overloads, and the extra mechanical work raises dough temperature to 29°C. The trip is a capacity problem, not a yeast or flour problem. The stiff dough also climbs the spiral, reducing mixing efficiency and increasing uneven friction. The correct response is to reduce batch size, not to add more water or mix longer.
3. Recommend a production plan and controls for the 2-hour window.
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Plan four batches of 18 kg flour, 9 kg water, and 0.36 kg each of sugar, salt and yeast. Target dough temperature 24°C: water = (3 × 24) − flour 22 − room 24 − friction 8 = 18°C, so use ice. Mix each batch within the derated capacity, probe the dough, rest, shape, boil and bake. Stagger batches and hold later dough at 4°C so it does not overferment. Never exceed 20 kg flour in this mixer for bagel dough. Record batch weight, dough temperature and mix time. With four mixes in two hours the schedule is tight, so start the first batch immediately and assign one person to shaping and boiling while the mixer runs.