Proofer design provides a specific temperature and relative humidity conditions to boost yeast activity of the fermenting dough pieces.

Proofer Design

What is Proofer Design?

A proofer is a piece of equipment designed to provide a specific temperature and relative humidity conditions to boost yeast activity of the fermenting dough pieces.

Proofing equipment provides convective surface heating and conduction of heat from the dough surface to its interior. Typical proofing conditions essential for optimum quality yeast-leavened bakery products include:

  • Temperature: 95–110°F (35–43°C)
  • Relative humidity: 80–85%
  • Cycle time: 40–70 minutes

How does it work?

Compared to ovens and other thermal processing equipment used in bakeries, design of high-speed proofers is less complex and can be operated at much milder conditions.

They range from manual to completely automated. Heat and humidity conditions are controlled by air conditioning systems that operate either by steam injection or water spraying (atomized), or a combination of the two.

Steam injection proofers

Saturated steam at low pressure, from a remote or built-in boiler, is released into the air to bring the internal proofer atmosphere to the humidity set point (%RH) for proofing. Temperature of the moist air is controlled by heat exchangers, usually radiators.

How does steam injection effect bread?

Water spraying proofers

Instead of using steam to increase the air moisture content, atomized water is sprayed from nozzles to maintain the dough’s moist external surface. The humid air is also heated by heat exchangers to set the required temperature.

Conditions provided by the proofer help ensure moist dough external surface moist. Formation of a dry skin is an indication of improperly functioning/designed proofer.

Aspects of proofer design

Designing bread proofers follows standard approach to equipment design, including:1,2

  • Mass and energy balances
  • Process modeling
  • Process simulation
  • Equipment sizing
  • Equipment rating
  • Equipment costing


Proper proofer design, especially flow rates and capacity should be matched very closely to those of the baking oven. This helps in preventing issues with scheduling and minimizing idle times. Proofers considerably with larger capacity than baking ovens risk wasting capital and floor space.

Considerations for oven design:

  • Product and pan dimensions (width and length)
  • Pan capacity (dough pieces per pan)
  • Shelf surface area required to proof a given number of pans (per shelf) at a given production rate (units/batch or units/min)
  • Spacing between pans
  • Capacity/throughput required plus long-term business growth (units/batch or units/min)
  • ...

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