SPECIAL REPORT: Mixing It Up

You might not always pay much attention to the floor mixer sitting in a corner of your facility, but it’s one of the stars of your equipment team. If you bake, make sauces or dressings, prep vegetables or create from-scratch pizza, you’re probably using some sort of mixer. With the right mixer, you may be able to do even more.

There are a couple of different types of mixers, and multiple sizes within those groups. Types most commonly found in foodservice include spiral mixers and planetary mixers. Spiral mixers have a stationary agitator, usually a dough hook, and the bowl rotates on a motorized base. These are typically used in operations making a high volume of bread or pizza dough.

Planetary mixers have a stationary bowl, but the agitator (and there are many options) spins while the shaft oscillates around the circumference of the bowl, much like the movement of a planet around the sun.

Mixer sizes range from small, 5-qt. tabletop models to enormous 500-gal. or larger industrial mixers. Commercial foodservice mixers typically range from the 5-qt. size up to about 140 qts., and anything up to about 20 qts. is usually a countertop model. Anything larger sits on the floor. Most common, and for our purposes, are floor mixers ranging in sizes from 30 qts. to 80 qts.

Size Does Matter

Matching a machine to the jobs at hand is important. Size matters, not only in terms of a machine’s capacity—meaning, the volume of product it can process—but also its capability or performance.

The capacity you need depends in part on the products or ingredients you intend to work with, as well as how much product you need to make for your operation at any given time. Even if you’re simply mixing dressings or sauces, you obviously wouldn’t fill a mixer to the brim. Doing so means you’d risk contents slopping over the sides when you start up the machine. And lots of batters, doughs and other ingredients expand when mixed, so you can’t assume that you can put 40 qts. of product into a 40-qt. bowl.

If you’re beating egg whites for a cake batter, for example, you can put about 1½ qts. in a 40-qt. bowl. If you’re making a batch of whipped cream, a 40-qt. mixer will hold about 6 qts. of heavy cream. Mashed potatoes? A 40-qt. mixer typically can handle anywhere from 25 lbs. to 30 lbs., depending on the make.

A Primer On Dough

If you plan to use your mixer for batters and dough to make baked goods or pizza, sizing a machine becomes even trickier. A machine’s ability to mix these depends on a number of factors that affect the consistency and viscosity of the product. Four variables have an effect on mixability of a dough or batter: moisture content, fat content, gluten and temperature.

Most dough consists primarily of water and flour. The more water a recipe calls for, the easier it is to mix the dough. Less water makes dough thicker and harder to mix. The relative amount of water and flour in a recipe is called the absorption ratio. To find the AR of any recipe, you simply divide the amount of water by the amount of flour, and then multiply by 100 to get percentage points. If a recipe calls for 50 lbs. of flour and 30 lbs. of water, for example, the AR is 60%.

If you make thick pizza dough in your operation with a 60% AR, you can mix about 40 lbs. at a time in a typical 40-qt. mixer. But if you make a stiff dough for a thin-crust pizza with a 40% AR, the same machine will only be able to mix about 14 lbs. at a time.

Dough or batter with a high-fat content is softer and easier to mix, so you may be able to mix more per batch than a mixer is rated for based on the AR alone. 

Temperature also has an effect on how malleable or mixable dough will be. Most mixer capacity charts assume an ingredient mixing temp of about 70ºF. Many recipes, however, call for cold water, or even ice, and the lower the temperature, the smaller the batch must be. If you use 60ºF water, for example, you should reduce the batch size by about 10%.

Finally, gluten—the protein in flour that gives some doughs their unique properties—also affects mixability. The higher the gluten content, the stronger the bonds in the dough and the harder the dough is to mix. Most manufacturers recommend reducing the amount of dough you mix by at least 10% if you’re using a high-gluten flour.

Power And Performance

Size isn’t the only determination in choosing the right mixer, though. Again, depending on your application, one manufacturer’s 40-qt. mixer might be perfect, and another’s inadequate to get your job done.

First, horsepower varies from one manufacturer to another on the same size machine. Some makers put 1½-hp motors in their 40-qt. machines, for example; others use 2-hp motors. More horsepower is likely to give the mixer more torque to handle heavier loads or dough with a low AR.

Some manufacturers make more powerful models specifically to handle pizza dough. These typically use a 2- or 3-hp motor, depending on the size of the machine. One maker has an enormous 140-qt. mixer designed primarily for volume feeders like hospitals, hotels or correctional centers with a 5-hp motor, but its pizza dough mixer (a bit smaller in capacity) has a 2.7-hp motor. And one maker has a line of heavy-duty machines that uses a 3-hp motor in its 60-qt. machine and a 5-hp motor in its 80-qt. unit.

Next, take a look at mixing speed. Almost all models offer at least three speeds, though a few have only two, and some offer four. One even has five speeds. The faster the agitator spins, the smaller the amount of product the mixer will be able to deal with. Some manufacturers, for example, suggest reducing mixer loads by as much as a third once the mixer rpm goes above 100.

Check manufacturer specs carefully. Some tout higher rpm as a benefit, and it may be, but what you’re looking for is the right range of rpm at each speed that will best suit your needs. That can vary a fair amount. One maker has models that operate between 74 rpm and 272 rpm; another’s range from 96 rpm to 319 rpm; and a third maker’s units range from 50 rpm to 250 rpm. Yet a fourth’s models range from 65 rpm to 310 rpm.

All will probably do an adequate job for you, and their speeds will be varied enough to give you flexibility with a wide range of products. But you may want to test your products in some mixers to see if their mixing speeds are well suited to your recipes.

The majority of mixers on the market are gear-driven with hardened alloy gears and heavy-duty clutches and ball bearings. Gear drives offer durability and reliability, but they can be expensive to repair. At least one manufacturer uses a V-belt drive, which it says is reliable and less expensive to repair if the belt ever fails.

Speeds are typically selected with a gearshift lever on the side of the machine. On many models, employees can’t change mixer speeds unless they first stop the machine. Several new models, however, offer a feature that allows you to switch speeds while the machine is mixing. In most cases, the transmission will gradually increase the agitator speed from one “gear” to the next so the contents don’t splash out, usually in about 5 secs.

Finally, several models offer a slow “stir” speed in addition to their three or four set speeds, giving you even more flexibility.

A few manufacturers now use variable-speed motors to switch mixing speeds rather than changing gears. One uses the motor on two of its models; they have a fixed gear set, and the motor changes the mixing speed. As noted above, a couple of suppliers offer machines with what might be called hybrid drives with three or four fixed speeds, but a variable-speed motor that either lets you shift while the motor’s running or select any speed in between.

Another maker’s entire line of mixers offers variable speed, letting you set the speed wherever you want between the machine’s minimum and maximum rpm. Instead of a variable-speed motor, moveable, variable-speed pulleys in the transmission are spring loaded to maintain tension on the belt drive as it changes speed.

Attachments And Accessories

Most models come with a number of agitators as standard equipment. Typical are a batter beater or paddle used for mixing cakes, batters and icings or for mashing potatoes; a dough hook for mixing bread and pizza dough; a wire whip for making meringue or whipped cream; and a sweet dough beater for mixing dough at slow speed without overworking it.

Also available, but sometimes optional and not standard, are a pastry knife for mixing pie dough; a four-wing whip for products too heavy for a standard whip, such as mayonnaise or whipped potatoes; and an automatic bowl scraper. Some specialty beaters or beater shapes also may be available if you have special needs.

Check to see which agitators come with the model you want. Also look at construction. Some of these utensils may be made with stainless, others with galvanized aluminum. Stainless, though more expensive, is more durable and less likely to pit or stain. (These attachments, especially aluminum ones, shouldn’t be run through the dish machine for that reason.)

What makes mixers so versatile is not just the variety of agitators for mixing, beating and whipping, but also the attachments that you can operate on the mixer. Most, if not all, floor mixers have a power take-off (PTO), or standard #12 attachment hub, that can drive attachments such as choppers, shredders and grinders. While these are typically sold as optional equipment, you may find them indispensible.

A slicer attachment typically comes with several rotating blades that allow you to slice or chop vegetables for steaming or for salads, and to shred or grate cabbage, carrots, cheese or other ingredients. Another attachment lets you grind your own meat for burgers or sausage.

Speeds of the PTO hub are typically a bit slower in each gear than the mixer, so a model with maximum speed of 300 or so rpm in high gear may have a PTO speed of around 185 rpm in the same gear. Gearing down in this way provides more power (torque) for tasks like chopping vegetables or grinding meat.

Features And Options

Most mixers come with a variety of features, especially safety features, as standard equipment, but in some cases certain features are optional. Check to see what is included in your purchase.

Bowls. A manufacturer’s standard bowls may be galvanized aluminum or stainless. The former may be more prone to dents and pitting, particularly if you mix a lot of acidic foods like dressings and sauces. The finish may also wear thin after heavy use and could rust at the bottom if not properly dried after washing. They can be refinished, but stainless bowls will save you the hassle.

Safety interlocks. All floor mixers have a safety interlock switch that disables the motor if the bowl isn’t locked in either the up or down position. And all have thermal overload switches that shut down the motor if they get too hot because of a too-heavy load.

Safety guards. Floor mixers have stainless safety guards that look like a cage over the top of the bowl to prevent employees from getting their hands near the agitator while the machine’s running. Typically, these are hinged so you can open the front of the guard to load ingredients in the bowl. A safety interlock shuts off the motor if the guard isn’t in place or properly closed.

Splash guards. To reduce splatter, several makers offer a cover that fits around the rim of the bowl. Look for a tight fit, and as always, stainless construction offers easier maintenance.

Ingredient chutes. To let you add ingredients to a mixer while it’s running, several manufacturers offer an ingredient chute that fits onto the safety guard, some as standard equipment.

Bowl lifts. Smaller floor mixers—30-, 40- and 60-qt. units—usually have manual bowl lifts. A lever or hand crank on the side of the machine lifts the bowl in place. The arms that hold the bowl in place may swing out to release the bowl and swing in to grasp and lift it, or they may be stationary with pins that fit into tabs on the side of the bowl. Manual bowl lifts should be ergonomic and operate smoothly to allow even smaller employees to easily lift bowls into place.

Larger mixers offer power bowl lifts, some as standard equipment, others as an option. Typically, once a bowl is in place, employees simply push a button to raise or lower the bowl, and the lift automatically locks in place. Even some smaller 40- and 60-qt. mixers offer a power lift as an option.

Bowl trucks. Bowls on larger mixers will likely be too heavy for employees to lift when full of product, so manufacturers offer ring-shaped dollies on which bowls can be easily moved.

Small batch kits. There may be times when chefs want to make smaller batches of product and find it difficult to mix in a large bowl. Several manufacturers offer small bowls and special attachments that allow employees to mix small batches on large mixers. At least one manufacturer’s models let you mix in a smaller bowl without the special attachments.

Timers. Most models offer a timer to help you optimize mixing results and prevent over-mixing. In most cases, the timer will shut the machine off after a set time. If this feature is important to you, check closely because some models offer electro-mechanical timers while others now have digital timers, and maximum set times can range from 15 mins. to 30 mins. depending on model. Also, digital timers typically offer a “last batch” memory so employees don’t have to reset the timer if they’re making another batch of the same product.

Care And Maintenance

Floor mixers are built to withstand the rigors of foodservice kitchens, but like any piece of equipment, they’ll perform better and have a longer life if you take care of them properly.

Be sure you specify the right electrical specs to match the electric service your utility provides. Most manufacturers give you a choice of voltage and amperage for each model so you can match a model with your service.

Position mixers where they’re easily accessible for both cleaning and moving product. Allow at least 8″ between the mixer and walls or prep tables, and situate them near where product will be used—bakery prep if you’re using them to mix dough, or vegetable prep if you’re using them to mix sauces and dressings and slice or shred vegetables.

Clean the mixer after each use. Hand-wash aluminum utensils and bowls with mild detergent and brush or soft cloth. Don’t use abrasive cleaners or materials like steel wool or nylon scrub pads. Stainless bowls and utensils can be run through dish machines. Wipe down the outside of the mixer with soapy water and a cloth or a pot brush to remove food, and pay special attention to the beater shaft and the area around it as well as the bowl arms or saddle.

Lubricate the mixer regularly per the manufacturer’s recommendations, and service it as required or suggested.

Warranties vary, typically ranging from 1 yr. to 2 yrs. on parts and labor. That may influence your purchase decision along with the extent and expertise of the manufacturer’s service network.

With lots of choices out there, you’re bound to find a mixer that suits your needs as well as your budget.