Proofers: Controlling critical conditions
March 27, 2017
by Laurie Gorton
Careful design of the ducting will ensure proper heat and humidity conditions within the proofer.
That warm, moist cabinet sitting in the middle of the bakery — the final proofer — is going high-tech to match the growing automation of bakery lines. Specs for final proofers now eclipse the basics of 95 to 120°F and 90% relative humidity.
Of course, a final proofer needs to maintain proper heat and humidity conditions throughout, but it should be conservative in its energy requirements. Airflow needs to be optimized and pan transfers smooth. Oh, and make it more readily cleanable and intuitive to control. And it might even boast a smaller footprint than earlier styles.
In many ways, proofers are unique to the bakeries where they operate. “With each system being custom designed, each proofer offers unique opportunities for innovation,” said Brian Doan, project engineer, The Fred D. Pfening Co.
Among other things, capacity requirements and production flexibility have steadily increased. “Customers would like to be able to run different products on the same production system,” observed Eric Riggle, vice-president, Rademaker USA. “Operation friendliness — the ease of controlling a proofing system and the reduction of errors — is becoming more and more important.”
Bakers give increasing focus to controls, according to Aaron Burke, territory manager, GTA/Western Canada, ABI Ltd. Air flow, temperature and relative humidity rank first, with size, capacity and treatment of dough being more specific to client and product. “Aside from size, capacity, controls and fuel options, we have also found that many clients these days are looking for closed-loop systems and/or systems that can accept whole racks so that product doesn’t have to be transferred as often,” he explained.
Keeping heat, humidity consistent
There’s a big difference between intermediate and final proofing. Intermediate proofers give yeast-raised dough pieces a period of rest to help recover from the rigors of dividing and rounding, but the final proofer is what enables leavening to bring bread and rolls to their optimum volume before baking. Intermediate proofers usually operate at the plant’s ambient temperature and humidity, with care taken to avoid drafts that could dry dough surfaces, while final proofers apply controlled heat and moisture in a controlled environment.
“One of the main issues with proofers is always control over heat and humidity,” said Frank Achterberg, president, CBF Bakery Systems. The company designed its step-style proofers with cooling, as well as heating, capacity to guarantee better humidity control. “We did that right off the bat,” he observed.
Gaining and staying in control over humidity and temperature can be quite complex, according to Mr. Burke. To achieve this, ABI combines precisely placed and tuned sensors, advanced ventilation and accurate temperature controls.
Pfening recently started to use temperature/humidity sensors with heated sensor tips. “This reduces the buildup of condensation inside the sensor, giving better accuracy at higher humidity,” Mr. Doan said. Engineers solved another problem involving false readings at high humidity levels by switching to on/off control valves. The result, he said, is similar to modulating valves but at lower cost.
Energy use is a significant factor in operating proofers. One way to cut energy costs for proofers is through a stack heat recovery system that moves excess oven heat into a hot glycol system to supply the proofer or steam heated coils or electric rods. More than a dozen such systems are in operation today, according to Dennis Kauffman, executive product manager, AMF Bakery Systems.
Steam makeup within the proof box also cuts energy costs, said Jim Cummings, president, Tromp Group Americas. This proprietary system generates steam only when needed. “You don’t have to keep a massive boiler running all the time,” he added.
Generating a homogenous climate within the proofer is essential, according to Richard Breeswine, president and CEO, Koenig Bakery Systems. “The humidity can be regulated with steam,” he added, “or a new system altogether. Koenig just developed a system of adiabatic humidification, which needs less cooling power.”
Engineers at the Middleby Bakery Group (Auto-Bake, Baker Thermal Systems, Spooner Vicars and Stewart Systems) turned their attention to humidification and specifically to steam. “There is no argument that the highest quality humidification system is low-pressure saturated steam,” said Scott McCally, vice-president of engineering. “Then why are we and the rest of the world moving away from steam in many applications? Steam systems unfortunately come with many negatives, including high maintenance costs and intense safety regulations.”
Such drawbacks prompted development of Middleby’s high-pressure humidification system (HPHS). Precisely machined nozzles disperse water in 2-micro-diameter droplets for near complete evaporation. “This characteristic minimizes excess water in the proof box, which can lead to significant sanitary issues,” Mr. McCally noted. He said that energy consumption by the HPHS is 50 times less than an equivalent steam system.
To complement this approach, Middleby developed a utility management system (UMS). It projects trends and totals power, water and fuel usage to monitor cost inputs by product and production run. “Operator behavior, production scheduling and seasonal variability can all have a significant impact on cost inputs,” Mr. McCally said. “The proofer UMS is the daily feedback system that quickly identifies issues for swift action.”
At Rademaker, engineers adopted a different concept: installing the HVAC systems inside the proof box. “Housing it inside the enclosure reduces the energy cost and condensation build-up in the system,” Mr. Riggle noted. It also went to a new air treatment method for its cooling and resting systems that cuts energy consumption by 28 to 35%, according to the company.
Read on to learn about managing air movement.