Theory and Practice
February 01, 2009
by Laurie Gorton
Laminating is all about creating texture. Repeated stretching and folding of dough builds up a layered structure. When baked, such doughs yield flaky, not crumbly, finished products. Lamination systems are most often employed to make pastry items comprised of multiple layers of dough and fat, but this method is also used to prepare hard biscuits and crackers in which the physical layering of the dough alone creates the desired textural effects.
When moving from manual methods for sheeting and folding to more automated technologies, or when adding capacity to a lamination system, several factors enter the decision. Ingredient and product characteristics — in particular, taste and appearance — are the primary considerations, but also important are the choice of component machines and environmental conditions. Getting it right requires balancing product and process.
RHEOLOGICAL THEORY. Referring specifically to hard biscuits and crackers, Michel van Zittern, sales director, DFE Meincke-Vuurslag, Etten-Leur, The Netherlands, observed, "When stretching the dough in the sheeting and laminating process, the texture of the dough and, thus, the quality of the cracker improves." The same is true for Danish, croissants, sweet goods, pastries and many other baked foods. The sheeting and laminating process puts the science of rheology into practical effect.
Rheology studies matter as stress is applied to non-Newtonian fluids and soft solids such as dough. These materials flow rather than deform — behavior that cannot be described simply by viscosity. Molecular size and distribution affect such actions, and in bakery doughs, gluten’s long protein chains come into play. The initial stretching and lapping creates layers of high energy (stretched sections) and low energy (lapped breaks), and the layers remain when the dough relaxes. Roll-in fats added during lamination also separate dough layers.
The layered structure is responsible for the finished product’s texture, so care must be taken to keep layers intact, especially during sheeting. The less energy added to the dough/fat layers during lamination, the smaller the risk of disrupting the fat layers.
A single large-diameter sheeting roll can make a 2:1 or 4:1 reduction, but any tighter setting will disrupt the dough’s structure. The development of rolling stations, sometimes referred to as satellite heads, consisting of many small-diameter rolls, each impacting the dough for a very short time, can accomplish a 10:1 reduction without disturbing the layering. The larger the exterior diameter of the satellite head, the smaller the attack angle to the dough band and the smaller the added force.
When fat-layered doughs are baked, the oven’s heat raises the temperature of the fat, prompting water in the dough to flash off as steam, thus leavening the item. Additionally, the fat helps flavor the finished product.
GOING AUTOMATED. When making laminated doughs by hand, the baker repeatedly rolls out and folds a block of dough. The resulting "book" is set aside to rest under refrigerated conditions. Each book may go through three or more rolling-and-folding sequences to build up the number of layers and strengthen the gluten. Reversible sheeters turn this labor-intensive activity into a semi-automated process, and full automation is the only alternative to reach the high output volumes demanded by many food service customers.
It is now possible for bakers to produce their goods in an "efficient, flexible and economical (fashion with) fully automated and motorized functions that are monitored and stored as a ‘recipe’ for easy reproduction," Mr. van Zittern said. "The impact of changing to a new DFE Meincke-Vuurslag line is that weight differences, product coloring and efficiency are improved a lot." The result is a flexible line that operates in a positive and simple way, he added.
Switching from manual and semi-automated traditional dough ball equipment to fully automatic sheeting lines entails changes. "The transition will require some formula adjustments and tweaking," said Jerry Murphy, president, Rondo Doge, Inc., Moonachie, NJ, "and our advice to customers is to be patient."
FEEDING THE LINE. For crackers and cookies, dough is fed directly into the sheeter heading up the makeup line, but items such as Danish pastry and croissants require the addition of roll-in fats (butter, margarine or various vegetable shortenings) as separate layers. Here the baker has a choice of technologies: co-extrude the dough and fat together or extrude or sheet the dough separately and then add a layer of fat.
A recent development in depositing the first layer of dough employs low-stress sheeting methods, which depend on gravity with a roller assist. Conventional dough extruders tend to use large-diameter rolls to pull dough through the system. "In past years, Rademaker started its lines with an extruder," explained Dennis Everaers, process bakery technologist, Rademaker bv, Culemborg, The Netherlands, "but now we have changed most lines to use our low-stress sheeter (LSS) because it is less damaging to the dough." Also, low-stress sheeting can handle high-absorption and pre-proofed doughs that won’t run through extruders.
The dough sheet coming out of a low-stress system can be more irregular in depth than that sheeted by a conventional extruder, so Rademaker added a cross-roller to bring dough into proper dimensions. Dough sheets produced this way have an additional advantage; they are already 15 mm thick, while the sheets made on conventional extruders are usually 40 to 50 mm thick, according to Mr. Everaers. The lower the stress during sheeting, the greater the dough’s tolerance to use of very cold fats, whose hard structure might rip through less resilient layers.
The Rondo Doge 3-roll dough band former was designed to adapt to different dough needs by independently regulating roller speeds and gap settings. "The rollers can be linked to drive the top two rollers together, with the bottom independent, or to run one top roller and the bottom roller together and the second top roller independently," Mr. Murphy explained. Also, the rollers can be made with differrent levels of corrugation to manage dough movement and the energy imparted to it.
Satellite rollers have been further refined, and Rondo Doge has patented the use of two offset rollers below the multiple roller head. "The two rolls can run two reduction curves back-to-back without adding excess energy," Mr. Murphy said. By combining these two steps in one unit, overall line length can be decreased by 6 to 8 ft. "Customers want to run more pounds per hour, more tonnage, but in the same space," he observed.
FAT SPECTRUM. In recent years, the fats used in bakery formulas have undergone tremendous change as bakers move away from the partially hydrogenated styles containing trans fatty acids. Some are going back to all-butter formulations. Choices among roll-in fats have also blossomed, necessitating engineering changes in equipment.
Rademaker, for example, introduced a new design for its fat pump. It uses both horizontal and vertical feeding screws and is capable of taking a whole 25-kg (55-lb) block of fat, rather than being manually fed with chunked fats. "While the machine is actually smaller than earlier fat pumps, it functions better," Mr. Everaers observed. It readily handles real butter, margarines and even more uncommon fats such as lard, the choice of bakers in Spain.
"Our emphasis has always been on sheeting in the margarines and shortenings on laminated lines," said John McIsaac, vice-president, strategic business development, Robert Reiser & Co., Inc., Canton, MA. "We have developed machinery to put down very accurate sheets of fats at precise rates. This has become important as companies develop more nutritious versions of laminated dough products. We have also improved the applicators to minimize operator adjustment and ensure an even flow across the width of the sheet required."
He noted that Reiser equipment is designed to handle multiple fats. The recipe-based programming of the system allows adjustment for different flow rates and automatic control of speed to match line requirements.
LAMINATING STYLES. Automated lines offer bakers a choice of laminating methods. As Mr. Everaers explained, retracting belts, lapping systems and cut-and-stack methods may all be used. "Different customers have different needs, so all three methods can be incorporated into lines as needed. For example, with retracting belts and lappers, you always work with an even number of layers, but with the cut-and-stack system, you can do odd or even layers of dough." He noted that cut-and-stack is best used in the second laminating section because there will not be enough layers at the first section.
The value of cut-and-stack methods was emphasized also by James Cummings, president, Tromp Bakery Systems, Lawrenceville, GA. "Our company’s stack-and-cut method provides much straighter dough sheet edges while taking the tension off the folded edges of traditional laminators," he said. "Tromp’s latest laminators offer complete flour and debris removal systems to provide a better work environment as well as a cleaner bakery during production."
How a line handles scrap dough affects its efficiencies, as Mr. McIsaac observed. "We also have numerous applications where we take the side cut scrap, feed it in to the hopper of a Vemag unit and meter it back into the mixing process," he said. "This allows the dough to be recovered and reused at a controlled rate."
Consistent, uniform doughs are essential to success with laminated products. Mr. Murphy explained that when bakers use rework, the process must be rigorous and well-controlled. "The more consistent the control over mixing, temperature and rework, the better the finished product," he said.
RESTING STAGE. Laminated doughs are like other doughs in that they require resting time to recover from handling during sheeting and makeup operations. "Giving floor time after mixing helps establish end-product characteristics," Mr. Murphy said.
Using the croissant as an example, Mr. Everaers observed, "Resting is taste." By this, he emphasized the importance of resting, or retarding, to flavor formation.
"In France, for example, bakers rest croissant doughs for many hours, allowing the yeast to activate and give more flavor to the finished croissants," Mr. Everaers said. "When making croissants manually, you can put the dough book into the retarder, laminate it again and then retard once more. But in an automatic system, the dough needs resting tunnels above the line. It’s a big investment to put in a resting conveyor, but that also allows high capacity and results in high-quality products."
He described a recent installation in France of a croissant line that uses two resting tunnels. The first resting stage takes place before the fat is added. The dough is then laminated twice and rested for 1 to 2 hours before croissants are formed.
SKILLED APPROACH. Automation cannot account for every variable in producing good laminated doughs; the operator is a key factor. "It is important that the line operator also be a good baker," Mr. Everaers observed. The manual method should be the "standard" for judging operator skills, even for automated systems, he stated.
"With automated machinery, there is a lot more dough coming off the line, and even though the process is more controllable than manual systems, the operator still makes a difference," Mr. Everaers concluded.
This article can also be found in the digital edition of Baking & Snack, Feb. 1, 2009, starting on Page 101. Click here to search that archive.