Hot Pans - Does Pan Temperature Matterr?

 

HOT PANS

Does Pan Temperature Matter?

Sourced from ‘The BRI Bakers Technical Bulletin No. 95/02

In most bakeries, pans are filled more than once on any shift.  A perennial question asked by bakers is, “are these pans too hot or too cold?”  For an answer to this question and others, read on.

Plant bakeries commonly cool empty bread pans before they are re-used.  The cooling operation takes equipment, space and lots of energy.  Furthermore the heat removed from the pans not only heats the bakehouse, but must be replaced after the pans are refilled and enter the prover.

Other factors which may affect pan temperature include changes in bakehouse temperature from the start to the finish of a shift and the removal or addition of pans from/to the line during production.

Some observations in a plant bakery indicated that pan bottom temperatures were running at 40 – 45°C before dropping to 30 – 32°C in the coolers.  The heavy straps around the top of the pans were about 20°C warmer.  The pan bottoms continued to lose heat and were 23 – 28°C at panning time.  When the cooler fans were turned off for a short test, the pan temperatures at panning time reached 30 – 36°C still below prover temperature (ie. The coolers reduced the temperature by 7 – 8°C).

  • Does it matter what the pan temperature is at the time of panning?
  • Does variability in pan temperature affect bread quality?
  • Are there energy savings to be made?

A Pan Temperature Experiment

Breads were baked in pans which had been pre-heated to different temperatures.  The temperatures were chosen to cover the daily range expected for pans returning to the dough panning operation, with or without cooling.

Straight-moulded high-top and square 680 g white breads were baked in the BRI pilot bakery.  A commercial type formulation was used with a typical NSW baker’s flour, mixed in a 5 kg capacity spiral mixer.  The dough temperature was 29°C and we used 3% compressed yeast (equivalent to 4.5% liquid yeast).  After the doughs were scaled at 780 g and moulded, they were placed into 3-strap pans which weighed 3.20 kg empty, and proofed at 40°C and 85% Relative Humidity (R.H.).

At panning time, the pans were at 6 different temperatures as follows:

  • Room temperature(25°C)
  • Pre-heated to 45°C
  • Pre-heated to 240°C.Then cooled on a steel bench top until the pan bottoms reached
  • 30°C
  • 50°C
  • 60°C
  • 70°C

The times required to proof the doughs to a fixed height of 16 mm above the pan rims were noted before they were baked in a rotary oven at 240°C for 30 minutes.

What happened to Proof time?

There was a small reduction in the time required to proof the doughs to a constant height for both the square & high-top loaves (Fig. 1).  Proving time for the room temperature pans was 55 minutes for the high-top and 39 minutes for the squares.  When the pans had been pre-heated at 240°C in the oven, then the bottoms cooled to 50°C, the times were 55 and 37 minutes, respectively – see Figure 1 (below).  At the hottest temperature tested 70°C, the times were 52 and 29 minutes, respectively.  There appeared to be some time savings possible, but they were probably not significant at the pan temperatures expected in a commercial bakery.  It must be remembered that when the pan bottoms had been cooled from oven-hot pans, the heavy side strapping was still quite hot, and retained heat which it carried into the proving cabinets, slowly releasing it to the pan bottoms and the air in the prover.

Figure 1 Pan temperature effect on high top proof time and loaf volume

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Did Anything Happen to Bread Quality?

Average loaf volumes for the high-top loaves did show a response to pan temperature (Figure 1). Bread baked in pans at room temperature, achieved the highest volume and pans cooled only to 70°C the lowest.  There was little difference between the pans at 30°C and 50°C which covers the range of typical bakery conditions.  Volumes were not measured on the square loaves.

The high-top total loaf scores ranged from 76 for the room temperature pans, to 75 for the pans at 50°C, and 73 for the 70°C.  Scores for the square loaves were all 73 except for the 70°C pans where the score was 72, (Figure 2).

IMAGE

Figure 2 Pan temperature effects on loaf quality scores

Conclusion

Pan temperature did not make a significant difference to proof time or bread quality.  However, at the highest temperatures there were some scorch marks on the bread.

If the bottoms of your bread pans are no warmer than 50 – 60°C when the pan coolers are tuned off, you may be able to save the capital and operating costs of the coolers, reduce the amount of heat released into the bakery, and minimise the amount of heat that must be added in the provers.  The bread quality is unlikely to change, and you may even be able to shorten proofing time by a few minutes.

If you would like to check the opportunities to reduce pan cooling in your plant, if you wish to audit for other possible energy saving measures, or you need to balance the heat flows in your ovens, please contact the BRI engineers for further advice.

Good Advice

"If the pan is too hot to pickup, don't put a dough in it".  Pans become too hot to hold at about 55 - 60°C.