Heat, humidity and time are the essential elements of final proofing. Maintaining these conditions in the proof box, which is also known as a steam box, is the key to helping yeast doughs rise to three to four times the moulded piece size before baking. Some final proofers also can serve as retarders, which are cool environments that slow or stop the fermentation of the dough, before subjecting the product to higher heat and humidity.

The old school of thought was that proofing should be at 95°F and a relative humidity of 85% for 60 to 65 minutes; however, today bakers are using a wider range of times, temperatures and relative humidity (RH) during final proofing. The RH in a proofer is typically between 90 and 98%, according to Peter White, president of I.J. White Systems, Farmingdale, NY. However, it is also reported that for lower proofing temperature, relative humidity as low as 75 to 80% is used in proof boxes. Temperatures range from 80 to 115°F, depending on the dough.


Bakers want advanced conditioning systems that offer a consistent environment for good repeatable yeast activity and proofed product, and they require adjustability for hot days and pans or ambient conditions in the facility, according to Austin Kozman, PhD, PE, product manager, thermal systems, Stewart Systems, Plano, TX “To this end, we have the most extensive conditioning system offered in the industry,” he claimed. “We offer variable frequency drive adjustable main blowers so the volumetric airflow rate can be changed as required for the sensitivity of the product, proofing speed and accuracy desired. Our full-length, damper-adjustable, supply-andreturn ductwork provides even air distribution to all tiers on both loops of the proofer without any stagnation zones.”

Stewart Systems’ conveyorized proofers feature direct steam injection, electric duct heaters, or steam- or fluidbased water wash conditioning systems depending on customer desires or application needs. It cools the unit with dual PID controllers using atomized water spray for small levels of cooling or complete closed loop-cooling coils for extensive cooling, according to Mr. Kozman. “Some customers even prefer our direct expansion refrigerant cooling,” he said. “In some proofers, we are able to control humidity and temperature to within ±1% relative humidity and 1°F.”

Accu-Proof Systems proofers from I.J. White, Farmingdale, NY, are continuous spiral systems that offer maximum environmental control to maintain uniform temperatures and humidity from floor to ceiling, according to Mr. White. The proofers’ Accu-Proof technology allows processors to independently control temperature and humidity. “Traditionally, these were linked, so if the temperature was raised you increased the humidity and vice versa,” he said. “Today we can control the environmental conditions independent of one another to produce a better quality product.”

In some situations, the proofer may require refrigeration to keep the proofing system’s temperature from rising beyond the needed level. Because of environmental issues and the fact active yeast releases heat, Accu-Proof can include an integrated refrigeration package.

Bakers want ‘tighter’ control over the temperature/humidity of the proofer, according to Brian Doan, PE, project engineer in The Fred D. Pfening Co.’s air conditioning department. “The biggest challenge for us as a company is to balance benefits of tighter control with the cost of more equipment and elaborate systems required for the tighter control,” he said.

Companies are also looking for greater throughputs, Mr. Doan added. “They are using proofers for many different types of specialty products that require more heat capacity,” he observed. “Therefore, we have seen an increase in orders of larger conditioning systems to meet these requirements.”


I.J. White also offers Dual-Zone Systems, which is not possible with traditional continuous belt systems. The system is divided into two separate conditioned zones. In some cases, the first zone can be used as a retarder, or in other processes,, it may require a very low humidity. Then product will enter the second zone, where the higher heat and humidity give lift to the dough structure. Also, some companies may want to have the product travel through different temperature and humidity settings to get the best development for its products, and Accu-Proof is able to accommodate this process. I.J. White employs its Automatic Pressurization Systems, also known as APS, to restrict the airflow between the two conditioning rooms to ensure they maintain their separate heat and humidity levels.

“One of the great advantages of Accu-Proof is that it can accommodate all sorts of carriers such as trays, boards and pans and products on paper or cardboard,” Mr. White said. “Our system can handle 4-, 5- or 6-strap bread pans up to 30 lb pans. We even proof product such as pretzels, pita and bagels directly on the belt. Others proofers are designed around the carrier; ours is designed around the process.”

I.J. White also offers an Ultra-Series version of the Accu-Proof for USDA-inspected processing plants that includes many unique features and is focused on meeting the stringent cleaning requirements. The evolution of the Accu-Proof design has been focused on delivering superior hygiene and to improve sanitary conditions, according to Mr. White. The proofer’s open design also improves access and makes cleaning and maintenance easier. The floors are slopped to internal drains and air distribution ductwork is stood off from the walls so that the insulated panel rooms can be thoroughly washed down.

There are also integral clean-out ports , and everything is designed to slope and drain.

Advanced sanitation packages for Accu-Proof include portable high-pressure cleaning, clean-in-place systems with strategically placed spray balls and the Typhoon Belt Washing station with 3-stage wash and sanitize.

Stewart Systems most recently built proofers that can be expanded. “The proofer is designed for 400 to 600 pieces per minute (ppm) now, but track supports, enclosure, conditioner, etc. are sized for future expansion to a larger system of 800 to 1,000 ppm, when the bakery is ready in a few years for that capacity,” Dr. Kozman said. “This requires more engineering time and some upfront cost, but future expansion is extremely simplified compared with retrofitting an existing system without expandability built-in.”

Stewart’s standard design allows for low chain tension that prolongs bearing and chain life. “Our system can run with a drive down for a period of time, if necessary, so motor or other failure does not halt production,” Dr. Kozman added.

The company also offers an in situ airblow-off station to minimize debris buildup on the chain prior to relubrication and an improved grid brush design with higher speeds to dual-driven brushes for top and bottom cleaning.


Gemini Bakery Equipment Co., Philadelphia, PA, offers automated tray proofers for high-speed operations. To minimize space requirements these units can be designed in an inline overhead configuration. Its tray proofers are used for hearth/ peel board products as well as pan breads and rolls, and dwell times normally range from 45 to 120 minutes, depending on the product and client preference, according to Mark Rosenberg, president of Gemini.

“Very low maintenance costs and minimal long-term repairs and parts replacement make this proofer ideal for variety bakers,” he said. “A recent installation was designed to produce high-end specialty rolls at a rate of up to 500 per minute, feeding a new Gemini 13 ft wide by 118 ft long indirect fired tunnel oven.”

Capway Systems, York, PA, offers racetrack and Capstep final proofers. “The racetrack-style proofer is a continuous running chain that conveys the pans upward on the inner track and back down on the outer track,” said Frank Achterberg, president of Capway. “This type of proofer requires floor space and height.”

Capstep proofer uses angles mounted on lifting chains that lift the pans on the outer edges. Pans are fed into the proofer in a slug, and as soon as the slug is in place, the upward section of the proofer raises, and the next slug enters the proofer. This process continues until the first layer of pans reaches the top of the upward proofing section. The slug of pans is than transferred from the upward section to the downward section. This process continues until the pans reach the bottom of the downward proofing section, and the pans are discharged. The Capstep systems can be used for proofing, retarding and freezing. “Capstep is very space saving as it uses the height of the building and does not require any curves,” Mr. Achterberg said.

Available with different angle pitches, Capstep can be adapted to many pan and product types. “The system can be configured in many ways to accommodate building and system requirements, and it is totally selfcontained and requires minimal maintenance ,” he noted.

Another unique proofer is the fully continuous Serpentine proofer from Auto-Bake Pty. Ltd., Hornsby, Australia. The Auto-Bake system uses the proven technology of the traveling tray system, exposing each tray to the various atmospheres of the proofer for consistent and even proofed product, according to Jim Diver, vice-president of operations, Dunbar Systems, Inc., which is the exclusive North American Representative for Auto-Bake. The proofer conditioning system is designed to control the temperature at ±3°F and ±3% RH from the operator setpoint, he added.

The Auto-Bake’s temperature and humidity are maintained using injections of steam and mist, which are circulated throughout the system, according to Amanda Hicks, director of marketing, Auto-Bake Australia. “To achieve flexible proofing times and proof-to-bake ratios, the Serpentine proofer can be designed with up to three individual Serpentine-configured transport zones, with optional bypass, within the one module,” she said. “Depending on the required proofing schedule for any given product, the unit can operate using one, two or three of these zones, running at different speeds if necessary, to adjust the overall proofing dwell time.”

Serpentine proofers are customconfigured to meet the throughput and space requirements of individual bakeries. “Whether a proof-to-bake ratio of 1:1 or 6:1 is required, the Serpentine system is ideal for all kinds of products, including loaves, baguettes, artisan bread, and proofed pastries such as croissants and Danishes,” Ms. Hicks said. “This system also ensures consistent orientation of the proofed goods throughout the entire process.”

The proofer can use thermal oil as both its heat and steam source, which can lead to substantial savings, according to Mr. Diver. “By using this technology, the need of a steam boiler is eliminated,” he added. RACK-N-ROLL. For bakeries needing very long retention times of 3 hours or more, Gemini also provides a fully automated racking system for either boards or pans. Gemini is installing the largest automated auto-rack-style retarder for bagels ever built, he said. The new system will handle up to 20 boards per minute and can accommodate up to 12 hours of retarding capability. “The system is equipped with a new design that minimizes maintenance and also allows for easy access for sanitation ,” Mr. Rosenberg added. “This new system is ideal for any type of product that benefits from extended retention times, which includes bagels and artisantype bread products.”

Belshaw Adamatic Bakery Group, Auburn, WA, offers BAP roll-in proofers and BARP retarder/proofers. Its proofers can hold up to 20 racks at a time, and pass-through models are also available. The proofers feature system-matched conditioners as standard, and digital controls for rapid response heat and humidity. The proofers offer a non-immersion humidity system with no possibility of boil-out, and oversized, corrosion-resistant evaporators are used to maintain high humidity.

Revent, Inc., Piscataway, NJ, recently introduced a new innovation in proofing, moving the proofer’s humidification unit to the front, so that maintenance staff only need to drop two axes to get the filter out, according to Kristie Peckham, national sales manager for the company. Revent offers proofers and retarder/ proofers in a variety of sizes and can also do push-through systems. Operators can set the controls on the retarder/proofers so that the dough will be retarded overnight and then switch over to proofing so dough is ready to bake when the bakery begins operations the next day, she said.

Pfening rack proofers feature the equi-temp conditioning system, which uses a venturi effectto create more airflow within the proofer, and its automatic proofer conditioning systems have been updated with more supply duct to give better coverage of the proofing area, according to Mr. Doan.

He said the biggest change to its proofers in the past few years has been to the controls. “We now offer a customizable PLC-based control, which is capable of storing trending data, operate several different types of control valves and flexibility to change,” Mr. Doan explained.

A wide variety of proofers are available to bakers, and all of them from racetrack to rack and tray to spirals are focused on offering a consistent environment for which bakery products can be exposed to heat and humidity.