Macrocosm of mixing options
Other manufacturers take a swath of strategies to maintain consistent dough temperatures.
“My philosophy since we began designing mixers is, ‘If you don’t make the dough hot, you don’t have to worry about excessive cooling,’ ” said Damian Morabito, president and chief executive officer of Topos Mondial Corp.
The company’s thesis involves one main postulation based on three guiding principles.
“We want to knead and not mix, and in order to do that, it gets down to optimizing bowl geometry, roller bar gap and the rpms or speed,” Mr. Morabito said. “A three-roller-bar mixer should stretch, sheet and fold the dough. When you go too fast, the dough tends to wrap around the bars, and you lose that kneading action. If it wraps around, the dough just rides around for 13 or so minutes, and it is not kneading or developing your dough as needed.”
AMF Bakery Systems offers mixers ranging from 250- to 3,300-lb capacities with effective cooling.
“AMF has recently developed the best material for heat exchange properties in mixer construction,” said Bobby Martin, executive product manager. “This material combined with optimized control technologies ensures the best results in consistency of dough temperature from one mix to another.”
Moreover, he noted, the AMF Dough Guardian helps bakers collect data to enhance their knowledge of what’s going on during the mixing process, resulting in a dedicated operating recipe for each item. This recipe management system also creates individual cooling system set-points to gauge final dough temperatures depending on each product’s recipe.
“Various temperature control modes — by timer versus by set-point — allow better controls independent of changing environmental conditions,” Mr. Martin pointed out. “This ensures better repeatability than former manual timer systems, thus compensating for summer versus winter bakery conditions or slight fluctuations in coolant temperatures, ingredient temperatures and flow rates.”
Tonelli Group combines software and computer controls with mechanical cooling options to maintain predetermined dough temperatures in high-volume bakeries.
“Double-walled jacketed bowls with a chilled water/glycol circulation loop are the most common and effective method,” said Kevin Wilkinson, North American sales, Tonelli Group. “Tonelli’s new horizontal high-speed dough mixers with direct-drive, variable-speed motors and recipe management software provide precise processing and product control.”
Fundamentally, bakers rely on three means of control to regulate temperature in a dough mixing operation. These are cooling the mixer itself by a glycol jacket, chilling ingredients and substituting ice for formula water, suggested Jim Warren, vice-president, Exact Mixing, Reading Bakery Systems.
“Each has advantages and disadvantages, and the ‘best’ method depends on the individual operation,” Mr. Warren said. “It is quite common to use combinations of these three methods or sometimes all three.”
Reading, for instance, continues to improve the chilling capability of its continuous mixers by reducing the temperature of all possible dough-contact surfaces. Its mixers also have increased the coolant’s flow rate within the jackets and the amount of cooled surface area that the dough is exposed to during the process.
Some manufacturers such as companies making frozen pizza and baked goods may opt for more advanced choices. Linde L.L.C. published a 12-page white paper, titled “Bottoms up: How better mixer chilling can improve your food process,” which describes cryogenic bottom-injection (BI) mixer chilling technology. The report also outlines the benefits of such systems and how they can be integrated into food processing operations.
Linde noted cryogenic BI chilling systems achieve high efficiency with a controlled injection of liquid nitrogen or carbon dioxide from the bottom of mixers, blenders, cookers or kettles. Advanced BI systems deliver accurate temperature control and can be tailored to the process. The company stated they can be retrofitted to existing equipment and can enhance production of a growing variety of products including dough and bakery mixes. Additionally, Linde’s cryogenic BI chilling systems can eliminate the time, labor and safety issues associated with storing and handling dry ice pellets.
And, oh yes, ice. Many bakers try to avoid using ice, but it may be the only option for some facilities located in warm climates or during the summer. The challenge? Ice needs time to melt, and when it does, the cooling effect is limited to the immediate area surrounding the cubes or shaved flakes.
“Your doughs run differently when you have to use ice rather than chilled water,” Mr. Bartsch said.
For specialty bread bakers, factors such as the type of mixer, temperature of ingredients, size of the dough and type of the mixing tools influence dough temperature. It also depends on the distance of the mixing tools to the bowl and the bottom of the bowl, suggested Rich Breeswine, president and c.e.o. for Koenig Bakery Systems.
The amount of moisture or slackness of the dough can also reduce friction and heat.
“With a hydration of 57 to 60%, one can say that the dough temperature rises by 1 (degree) C with each minute of mixing,” Mr. Breeswine said. “The higher the dough hydration, the lower the dough warming during mixing since there is less resistance.”
With its spiral and vertical mixers, WP Kemper analyzes the bowl, guide bar, spirals and scraper for each product.
“We do this with a highly sophisticated test rig,” noted Patricia Kennedy, president of WP Bakery USA. “It is equipped with many sensors that allow us to build the perfect mixer.”
Control, and not just chilling the dough, provides the key for a good mixing result.
“The process requires constant monitoring of the temperature of your ingredients starting with the silo and dosing systems,” Ms. Kennedy said.
WP Kemper has developed different analyses and system engineering methods to control dough development. Its PT100 sensor continuously measures dough temperature during the mixing and kneading process while a graphical user-interface shows the mixing temperature in real time, said Ms. Kennedy.
To configure the automated WP Kemper controls, the baker first manually sets the mixer’s rotational speed as well as the time for kneading and then continuously monitors the kneading process. During this process, the mixer’s computer system runs its algorithms and validates them with the collaboration of the professional baker.
“The overall goal of this work is to develop an intelligent kneading machine that autonomously decides how to set the speed and when to stop kneading,” Ms. Kennedy explained.
