Mixer type: Horizontal
Applications: Breads, rolls, buns, donuts, flour tortillas,
sweetgoods, cookies, crackers
and English muffins.
Processes: Horizontal mixers are the workhorse of U.S. bakeries. They are big and sturdy, and handle multiple types of dough with either roller bars or single- and double-sigma arms. Roller bars typically process yeast-raised bakery foods, and sigma-style arms mix items such as cookies and crackers.
What’s new: Evolving bakery food product lines have caused mixer manufacturers to change horizontal mixer designs and capabilities. Increased demand for stiffer doughs, such as whole grain and multigrain breads, has necessitated increased horsepower usage to maintain batch size. One manufacturer of horizontal mixers estimates that bakers will have to reduce batch size by as much as 30% if they use standard, 100 horsepower horizontal mixers to mix whole grain products.
| Many bakeries use vertical mixers for their flexibility in handling different types of dough. |
If this reduced capacity is unacceptable, bakers must increase horsepower. Unfortunately, bakers simply cannot add horsepower by upgrading existing horizontal mixers. “Bakers have to look at buying a new mixer or be content with smaller batch sizes,” one mixer manufacturer says. “You have to buy new equipment because you have to design around an increased horsepower motor.”
The amount of horsepower needed depends on absorption rates. One equipment manufacturer has built 200 horsepower mixers to handle stiff doughs. When constructing a mixer with increased horsepower, equipment manufacturers design from the ground up, engineering new agitators, drives and bowl construction to accommodate the increased horsepower.
“It’s not like dropping a Corvette motor into a Chevy Cavalier,” one mixer manufacturer says.”
Besides increased horsepower, mixer manufacturers also are seeing increased demand for variable frequency drives. In the past, horizontal mixers mainly used two-speed starters, but falling prices for variable frequency drives have spurred bakers to ask for this added flexibility.
Variable frequency drives allow bakers to change agitator rpm. This benefits bakers that mix many types of doughs in one mixer. Variable frequency drives also minimize shock load and energy spikes because the agitator bars ramp up and down.
Equipment manufacturers also are improving maintenance features on horizontal mixers. One manufacturer’s unit features an open frame design that eliminates cabinets and enclosed parts, allowing bakers to take care of minor sanitation problems before they become major issues.
Mixer type: Continuous
Applications: Specialty bread, sweet dough, cracker dough and cake batter.
Processes: Continuous mixers allow bakers to process dough without interruptions, thus reducing labor, eliminating manual dough handling and improving raw ingredient control.
The crux of a continuous mixing system is proportionate feeding. Instead of adding large quantities of ingredients into a mixing bowl at one time, before mixing, continuous mixers take small amounts of proportionate ingredients and continually feed them to the mixer.
“Instead of trying to mix 200 lbs. of flour with 200 lbs. of water, continuous mixers are mixing 5 lbs. of flour with 2 lbs. of water,” one continuous mix manufacturer says. “When you add the ingredients at these ratios, it takes very little energy to mix.”
Continuous mix systems use ingredient metering systems that feed streams of dry and liquid ingredients to the mixer. These ingredients are preblended, then fed to a large cylinder that continually works dough as it moves down the length of the cylinder. After mixing, dough is either discharged in a continuous log or cut into desired weights.
What’s new: One equipment manufacturer offers a tri-level continuous mix system that simplifies bulk delivery and metering. Existing bulk ingredient handling systems deliver ingredients to the metering system, which continually feeds ingredients to the mixer.
Mixer type: Vertical/spiral
Applications: Artisan breads, rolls, buns, donuts, flour tortillas, sweetgoods, cookies, crackers and English muffins.
Processes: Vertical mixers are known for their ability to stretch dough’s gluten structure without ripping and damaging the dough’s integrity. In the United States, vertical mixers commonly are found in small to intermediate-size bakeries. These mixers accommodate a variety of doughs, and provide bakers with the flexibility to run small batches for easy changeovers. More recently, vertical mixers have expanded their uses in large wholesale bakeries. For example, many large artisan bread bakeries use multiple vertical mixers to process water-laden doughs that contain hydration levels as high as 85%. For these applications, vertical mixers provide one of the only solutions for mixing highly hydrated doughs in a gentle manner.
|High-speed mixers use two types of mixing implements: bars for muffins and cookies with particulates, and blades for most other products.|
What’s new: Equipment manufacturers continually seek the ideal mixing tool for dough mixing. And surprisingly, most mixer manufacturers disagree about the ideal shapes, sizes and number of mixing tools. Standard spiral mixers contain a single spiral arm that mixes dough.
Another manufacturer uses twin semi-spiral mixing tools and a moving bowl to cut mix times in half. The twin mixer arms move in opposing circles to “stretch the gluten structure as opposed to ripping it,” the manufacturer says.
Casting aside traditional spiral mixer designs, one equipment manufacturer offers a vertical mixer that uses two vertical bars as mixing implements. “These mixing tools have a combination of compression and stretching that builds the gluten structure in a way where it can accept and hold on to more water,” the mixer manufacturer says. The mixer accommodates batches as large as 1,000 lbs., and processes doughs with hydration levels as high as 85%.
Mixer type: High-speed mixer
Applications: Batters, pies, cookies, bagels, flat breads, buns and pizza dough.
Processes: High-speed mixers use mixing tools that spin as fast as 1,200 rpm, which greatly reduces mixing times for a variety of doughs and batters. Mix times range from 90 seconds for muffin batter to 180 seconds for bun dough. Mixed dough is discharged from the bottom of the mixer in chunks of dough. Batch sizes range from 550 lbs. to 2,000 lbs.
What’s new: Similar to horizontal mixers, high-speed mixers are gravitating toward variable speed operation. This is especially beneficial to products such as muffin batters, which often incorporate particulates. Variable speeds allow bakers to use high speeds for mixing the batter, and then slower mix speeds to add fruit pieces, nuts or other particulates.
“The mixer slows down to the speed of a typical mixer and we’re able to fold or blend in the fruit particulates without turning the product into a smoothie,” one high-speed mixer manufacturer says.
In addition to variable speeds, some high-speed mixers also allow bakers to mix under vacuum conditions, which increases the amount of water that is used in a batter without making it more runny.
Mixer type: Planetary
Applications: Mainly batters, such as cake, muffin and brownie batters; and cookies.
Processes: Planetary mixers are built for versatility in sweetgood applications. These mixers possess more than 20 different mixing tools, allowing sweetgood producers to mix muffins, brownies and cheesecakes in one shift. Most planetary mixers contain two mixing implements and a bowl scraper. Dual mixing tools allow bakers to tailor the mixing process to specific applications.
In the U.S. baking industry, planetary mixers mainly are used to to mix cake, muffin and brownie batters. Cookie manufacturers also use this style of mixer to gently incorporate inclusions in cookie dough. “When you’re blending chocolate chips, planetary mixers work very well and do not pulverize inclusions,” one planetary mixer manufacturer says.
Planetary mixers are “infinitely variable,” the manufacturer says, allowing bakers to change speeds on the fly and customize the mixing process by starting, stopping and raising and lowering the bowl at any time.
What’s new: One manufacturer designed a planetary mixer with a jacketed bowl that applies heating and/or cooling during the mixing cycle. The feature mainly is used to eliminate bacteria buildup in products that are not baked, such as creams. “Bakers should always be concerned with food safety,” the mixer’s manufacturer says. “By mixing with heat and then cooling the temperature back down, we’re preventing contamination.”
The mixer operates by building up the temperature in the mixer, then rapidly cooling the temperature with a vacuum and jacketed bowl. The mixer also has control features that allow bakers to customize mixing profiles.