February 01, 2009
by Jim Romeo
Dividing dough into manageable portions is a fundamental step in the breadmaking process. Although pocket dividers traditionally have been used for this process, dough extrusion is gaining popularity as a useful alternative technology. Extrusion provides control and subsequent efficiencies to a production line.
Extrusion’s main benefits center on flexibility, increased sanitation and safety, energy conservation, greater reliability and less maintenance and overall enhanced performance to produce a better quality product.
Jörg Sonnabend, marketing services manager at Rondo Doge, Burgdorf, Switzerland, noted that the merits of extrusion technology stem from three key areas: greater automation, higher levels of sanitation and a broadened range of application, leading to overall improved product quality.
“Improved automation leads to greater accuracy of the equipment and eliminates human errors, resulting in a positive effect on the quality of the baked products,” Mr. Sonnabend said. “A higher level of sanitation improves productivity, minimizing downtime for cleaning. A wide range of application offers the possibility to automatically process more types of dough such as very soft or sticky dough and ultimately provides additional business opportunities.”
Extruders require less maintenance and are faster than other types of dividers, according to John McIsaac, vicepresident of strategic business development at Robert Reiser & Co., Canton, MA. In addition, recipe-driven extruders can be easily adjusted to maintain weight control. Yet, flexibility is extrusion’s key benefit. “This flexibility offers performance characteristics that subsequently aid production,” he said.
Like Mr. McIsaac, Dulcinea Brendlen, marketing manager at Reading Bakery Systems, Robesonia, PA, said the specifications of extrusion equipment can enhance the flexibility of the process, making it nimble and quick, as well as improving the overall performance and quality of the dough. “We see several trends developing with respect to extrusion technology,” she said.“As production needs increase, wider machines with faster cutting speeds are needed. Extruders have expanded to 2 m in width and have cutting speeds as high as 265 cuts per minute.”
Increased speeds and widths have created more demand for dough-feed automation with metal detection. “Reading offers complete dough-feed automation from the discharge of either a batch or continuous mixer, which delivers chunks of dough on-demand to the various units of the extruder, whether it’s a 3- or 6-unit machine,” she said. “This offers labor savings, fewer worker complaints and improved piece-weight accuracy.”
Automation also means dough is easier to work with and helps achieve the desired output. For example, Reading relies on the rotary cutting of pieces and the work imparted to the dough, which makes for a denser product without an open texture. Generally with extrusion technology, the dough is not worked as much, and intermediate proofing is inserted in the production line to allow development of the dough after the rigors of extrusion, adding a more open texture to the final product.
A low-pressure (LP) extruder can offer even greater flexibility and additional advantages compared with high-pressure extruding. Reading’s LP extruders output both sticks and die-cut shapes and don’t impart much work energy to the dough because it does not exit the machine under enough pressure to alter the dough as it might with high-pressure extruders. “LP extruders can be supplied with gauges on the compression head to indicate the dough pressure just prior to extrusion,” Ms. Brendlen said. “For wheat-based dough such as pretzels, we would expect them to run in the 40 to 120 psi range. For potato-based snacks such as fried rings, we expect to see them in the 100 to 200 psi range.” Shapes can be changed by simply replacing the die assembly, and easily-dissembled components and sanitary construction materials facilitate sanitation. Reading uses only plastic, stainless steel and other non-painted surfaces in the dough zone to improve sanitation. Because Reading’s extruder is a series of 380-mm wide units, it is possible to individually control these units and use different dies on the same production run.
EXTRUSION OR DIVIDING?
Dough extrusion and dough dividing are often used interchangeably; however, some distinctions exist. With extrusion, dough is subject to a specified pressure that enables it to divide flow and form. Dividing commonly uses the pocket method, which is purely volumetric. Once a certain amount of dough fills a pocket, the pocket closes, and the dough is deposited.
Extrusion technology offers key advantages over dividing technology, according to Mr. Sonnabend. For one, dough extrusion allows dough to be processed without destroying its structure. “This leads to higher quality baked products and enables dough extrusion equipment to produce preproofed dough,” he said. “In addition, you are running a continuous process, which is much easier to control than a discontinuous one.”
Extrusion and pocket dividers each have their own advantages and disadvantages. “From an extrusion perspective, there is speed, weight control and reliability, but the product is different because there is more mechanical work on the product,” Mr. McIsaac said. “Pocket dividers have been gentler, but maintenance, reliability and mineral oil requirements are drawbacks.”
Combining dough technologies also can be advantageous and is gaining in popularity, according to Larry Gore, director of product marketing for AMF Automation, Richmond, VA. Unifying extrusion and dividing technology for bread and bun production offers greater scaling accuracy, according to Mr. Gore. By combining these technologies, bakers should expect accuracies of approximately 1%, vs. 3 to 5% for conventional dough dividing.
THE RIGHT DEGREE OF TECHNOLOGY.
The design of extrusion technology yields significant benefits: flexibility, reduced energy consumption , improved sanitation, increased safety, increased reliability and maintenance, and enhanced performance. But how much technology do you need?
The right degree of technology is always a challenge in designing the best equipment to meet market needs, and this may be the reason that extrusion technology has become valuable. The driver behind technological advances is linked intrinsically with customer needs, according to Mr. McIsaac. “If we cannot produce an item that meets a customer’s quality specification, our divider will not stay in the plant,” he said. Reiser has honed in on scaling accuracy and provides equipment where the downtime is minimized. Well-designed equipment and parts, as well as excellent technical support, means this equipment will run longer without need of maintenance, according to Mr. McIsaac.
Finding the right technological features stems from understanding the needs of both bakers and technicians. In fact, extrusion technology has been enhanced by equipment manufacturers who combine the intellect of technicians with the pragmatic needs of bakers. “The right mix of technology for dough extrusion will drive its expansion forward,” Mr. Gore said. “Over the next few years, this technology will continue to expand. Part of this expansion will be in the pan bread and bun-and-roll business sectors. However, another part of this growth will be in new baking business sectors that traditionally have only used conventional volumetric dividing, including flour tortilla, pita and specialty and hard rolls.”
Dough extrusion continues to grow in popularity among industrial bakers. This expansion is made possible by technology advances in extrusion dividing in the areas of advanced dough feed and metering control technology and in advanced dough-flow control technology. Dough extrusion offers significant product quality and performance advantages over conventional volumetric dividing.
Jim Romeo is a freelance contributor with a background in engineering and writes on a broad range of topics relating to technology.