Dry Blending: Making Mixes
October 01, 2009
by Shane Whitaker
Scratch baking in many respects is a lost art; therefore, many consumers today rely on premixed cake, brownie, cookie and muffin mixes for home baking. Many in-store bakeries and donut shops use 25- and 50-lb bags of premixes to make a variety of products. Restaurants also may require packaged mixes for breadings and batters. Even wholesaler bakers often turn to bases or premixes in their operations to assist with efficiencies.
For complex products such as cake donuts and Danishes that have a dozen or more ingredients, premixes can be beneficial to efficiently manage ingredients. In addition, they can assist production schedules in bakeries especially for products requiring unique ingredients made in a relatively low volume.
For wholesale operations, weighing out a large number of ingredients can cause inefficiencies in operations, as can warehousing and ingredient handling for specific formulas. Therefore, bakeries will often use complete mixes or bases. A complete mix contains all the ingredients except water and yeast, while bases include all ingredients except those readily available in bulk to the baker such as flour, sugar, yeast and water.
Premixes are manufactured by regional operations as well as large national firms, and both generally offer a wide range of products. A variety of mixers are used for manufacturing dry mixes including ribbon blenders, plow and chopper mixers, vertical cone blenders, tumble blenders and paddle mixers.
Charles Ross and Son’s most popular mixers for the baking industry are ribbon blenders, according to Christine Banaszek, application engineer, at the Hauppauge, NY-based company. A ribbon blender consists of a U-shaped horizontal trough and an agitator made up of inner and outer helical ribbons that move material in opposite directions along the radius. “The differential speed between the inner and outer ribbons moves material laterally along the axis and also in opposite directions,” she said. “The ribbons rotate up to approximately 300 ft per minute, depending on the application.”
A ribbon blender works well with straight dry mixes. Ribbon blenders will break up most agglomerated materials, and one of the newest features on Ross’ blenders are high-speed choppers mounted on the top side or bottom of the blender to break apart agglomerates, according to Ms. Banaszek. “To eliminate any dead spots in the blender trough, metal end scrapers are added to the ribbon agitator and set as close as possible to the wall without touching,” she added.
Ribbon blenders are a common choice for the blending of cake, bread and muffi n mixes, flours, starches, spices, etc. “Liquid ingredients such as flavors, coloring, oils and other additives are uniformly added to the blend through nozzles installed in a spray bar,” Ms. Banaszek noted. “Compared with other mixing equipment such as vertical blenders and tumble blenders, the ribbon blender is typically more cost-effective.”
Ross recently began offering ribbon blenders with a discharge/extruder assembly, which features a discharge screw across the entire length of the trough. This screw is powered by a separate direct drive system for independent speed control. The assembly allows the processor to discharge continuously at variable rates to match downstream packaging operations, according to Ms. Banaszek.
Ross standardizes on a 1-piece motor setup with direct-drive gear reducer as opposed to belt or chaindriven designs that can be noisy and prone to slippage and breakage. Also, its ribbon blenders have no external moving parts to guard and no chains to oil.
Ross custom builds its equipment to meet manufacturer’s batching requirements, and typically it can build complete system in one to two weeks. “Our 2-week delivery is made possible by our extensive inventory; we stock all components that are most commonly added to a piece of equipment,” said Warren Ang, product manager for blenders. “We can stock a large inventory of parts because we manufacture 90% of the complete system.”
The food industry is Ross’ largest market for blending equipment, and it has observed that many startup or specialty food companies are moving blending operations from outside toll manufacturers to their own facilities. “It used to be that only large-scale bakeries had capital to purchase ribbon blenders, but now we are seeing an increasing number of orders from small- and mediumscale companies that usually cater to a specialized bakery trend,” Ms. Banaszek observed. “These companies are doing well in the market as people are consciously trying to eat healthier even if it means paying a little bit more.”
Although Littleford Day, Inc., Florence, KY, offers a variety of mixing equipment for various industries, if a bakery inquires about a machine for blending ingredients, the company always recommends a plow and chopper mixer, according to Bill Barker, the company’s market manager. “These mixers offer shorter cycle times and the greatest throughput for baking mixes,” he said.
The company’s Ploughshare mixer offers cycle times as low as 10 to 15 minutes, and Mr. Barker pointed out that bakery mixes can generally be completed in 15 to 50% of the time required by a ribbon blender and finisher. Plow mixers are configured as a horizontal cylinder with a horizontal-driven shaft, but the mixing elements are large plows or scoops that move the material vertically and horizontally. They frequently incorporate high-speed blades in the wall that quickly disperses plastic shortenings even when added in large chunks. This makes them excellent choices for making high-fat mixes such as cakes and cake donuts.
Plastic shortening is often difficult to mix because it does not disperse when a mixing blade contacts it, and it tends to remain in large lumps or adhere to the mixing blade. Mr. Barker noted the Ploughshare mixer can evenly disperse either liquid or plastic shortenings in mixes. “The unique action developed by the Littleford intermediate intensity mixer assures a rapid and complete dispersion of powders and shortenings in minimal cycle times,” he explained. “This action is developed by the turning of plow-shaped mixing tools at a speed suffi cient to cause the material to mix and become a pulsating, mechanically fluidized bed.”
The Ploughshare’s plow mix action is supplemented by high-speed, high-shear chopping devices that are mounted between the adjacent plows and act as a finisher does to agglomerated powers and disperse shortening. “Since the chopping devices can be operated independently of the plows, there is little chance of overworking, or greasing, the mix,” Mr. Barker said.
For biscuit and donut dry mixes that contain up to 20 to 22% fat, Littleford’s mixers use indirect cooling such as dry ice or liquid nitrogen in the batch to keep it cold to ensure the product does not fat out. Its plow and chopper mixers are available in a wide variety of sizes, producing batches from 100 up to 7,000 lb.
Littleford and Ross offer testing facilities, so that bakers can bring in raw materials and get a hands-on experience of using the companies’ technologies.
In addition to ribbon blenders, Ross also manufactures paddle, vertical and tumble blenders. A paddle mixer runs at approximately twothirds the speed of a comparable ribbon blender and provides a gentler blending with less heat development.
Vertical cone blenders feature a conical container and a screw-like mixing element that rotates to lift ingredients, while at the same time moving around the wall of the container. Ross’ vertical blenders use a slow-turning screw that is advantageous for heat-sensitive products. Discharge is fast, especially with a screw design that is unsupported at the lower end.
Double cone and V-shaped tumble blenders are available from Ross. Materials are missed as the vessels rotate, and intensifier bars help to disperse minor ingredients and to break up agglomerates.
One of the biggest trends in the blending of bakery mixes, according to Mr. Barker, is that most manufacturers want to make multiple products in a single mixer. The other trend he noted is that customers want an automated process. “We supply controls with our units, where you have different recipes,” he said. “An operator selects a recipe and everything is set including cycle times and discharge.”
Ross offers its Syscon PLCs and operator panels for handson control of its blenders. “These systems enable bakeries to store recipes, track blender cycles, vary agitator speeds, make quick flavor changes and discharge efficiently,” Ms. Banaszek said.
Processors need the mixer to quickly discharge bakery mixes. Littleford’s plows move during discharge and its mixers can empty within 20 seconds, according to Mr. Barker. Its newest Plowshare mixer, the “E” Design, is available with option dual discharges or oversized discharge doors.
However, the greatest improvement of the new “E” Design is that it is easier to clean. A large door allows complete access to the interior of the mixing vessel. Previous versions featured smaller doors, and with the way the mixer is set up, he said it was difficult for processors to properly clean the unit. However, that is no longer an issue as companies can easily access the entire unit and brush out, vacuum or sweep the unit using an air hose. The larger access door reduces downtime for cleaning and provides a better solution to address cross-contamination issues, according to Mr. Barker.
Cleanability of dry blending mixers is always an important issue for bakeries, according to Ms. Banaszek. And to that end, Ross’ ribbon blenders for many years have conformed to the general principles of design, construction and cleaning as set for forth by the Baking Industry Sanitation Standards Committee.
Its ribbon blenders feature stainless-steel interiors with at least 150-grit finish, and all welds are ground smooth, cleaned of spatter, slag and discoloration. In addition, its blenders, including the discharge valves, can be cleaned entirely with clean-inplace systems and wash ports for quick change in flavors.
Processors manufacturing bakery mixes must demand thorough and uniform blending of ingredients to ensure customers receive quality, consistent products. The latest mixers are capable of doing this quicker for greater throughput than ever before. And today’s equipment is more automated and cleanable.