February 2008

Specifying For Soft-Serve
By: Mike Sherer

Soft-serve treats deliver tremendous profit if you choose a machine that suits your operations.

Soft-serve machines make it a snap to add profitable ice cream and yogurt treats—cones, sundaes, shakes and novelties—to your menu. Newer technology also makes cleaning and maintenance easier then ever. But knowing which machines might be right for you requires some understanding of soft-serve product itself.

Back in the late 1930s, a father-son team looked for a way to dispense the ice cream mix produced in their ice cream plant while it was still soft. They found a noisy machine that worked as a prototype and had some improvements made. In '41, an ice cream shop that exclusively served the pair's product opened in Joliet, Ill., eventually growing into the Dairy Queen chain. Then in the early '50s a team of British chemists, including a young Margaret Thatcher, invented a means of incorporating more air into ice cream to make it creamier and easier to dispense.

These days, to make traditional hard-pack ice cream a mixture of milk, cream, sugar and flavorings is churned at below-freezing temperatures. When frozen, but still soft, other ingredients—nuts, candies, cookie pieces, etc.—are "shot" through it if desired, and it's packed in containers. Ice cream makers then hard-freeze it at sub-zero temps.

Soft-serve ice cream is basically ice cream that hasn't been hard-frozen, but soft-serve ice cream machines do something else. They add air to the ice cream mix, increasing its volume by up to 45%. The combination of higher temperature—around 18º F—and more air gives the ice cream a creamier consistency and makes it easy to dispense.

The amount of air in soft-serve ice cream is called overrun. A soft-serve product with a 35% overrun has 35% air mixed into the liquid mixture as it freezes, so one 1 gal. of ice cream mix will yield 1.35 gals. of soft-serve ice cream. The greater the overrun, the greater your profit.

Soft-serve ice cream performs another neat trick, including fooling consumer palates. Because butterfat melts at around 90ºF to 95º F, the warmer the ice cream, the more pronounced its flavor because it melts faster on the tongue. Because it's so cold, hard-pack ice cream generally has butterfat content of about 16% or more. In contrast, soft-serve ice cream gives you the same mouth-feel in the range of 5% to 6% butterfat because it's served at a higher temperature. That means less costly ingredients.

Machine Size, Capacity And More
Soft-serve machines are remarkable self-contained factories capable of storing mix, churning and freezing it into ice cream, and dispensing it. As with many other equipment categories, the model you choose depends on a range of factors, not least of which is size.

Physical size is one consideration. Footprints of even larger machines are relatively compact. A typical high-volume twin-barrel machine runs about 26" wide and 34" to 36" deep. Most suppliers give you a choice of floor or countertop models at each capacity level. Floor models are usually mounted on casters, making it easy to clean around them.

Capacity is another size consideration. Machine capacity is typically measured in volume, broken down into gallons per hour or servings per minute. Capacity ranges from two or three servings per minute to about 38 servings per minute. When you consider sizing, you have to consider peak volume in addition to how many customers you expect to serve per day.

In the summertime, for example, if you expect to serve 500 customers per day, but half of them come in from noon to 2 p.m., you'll need a machine that can dispense at least two servings per minute, or faster if you don't want customers standing in line getting impatient. If you serve shakes, too, you'll need to multiply that capacity several-fold. And if you want to serve multiple flavors or "twist" cones that combine two flavors in a single cone, you'll need a double-barrel, or two-cylinder, machine.

Recovery time is key, too. A machine may be able to dispense 10 servings per minute, but it also has to continue to freeze additional product to replenish what you're drawing out of it. Machines with larger freezing cylinders, or "barrels," with appropriately sized compressors will give you faster recovery time.

Your anticipated volume and peak demand will help you make your first choice—gravity-fed or pressurized machine. As the name implies, gravity-fed machines use gravity to supply mix to the barrel and dispense the frozen product. Employees manually load liquid ice cream mix into a hopper located on top of the machine, and gravity does the rest.

Pressurized machines, on the other hand, use pumps to supply the freezing cylinder. They offer a few advantages, depending on your operations' needs. The product hopper can be located anywhere, usually in a refrigerated cabinet below the dispensing head. And pressurized machines often provide greater capacity, so employees don't have to load product as often.

Pressurized machines also allow you greater control over the amount of overrun. Gravity-fed machines allow a certain amount of air into the mix every time you draw off finished product. A pressurized machine lets you pump as much air into the mix as you wish, up to the 45% maximum. That way, you control both the consistency and creaminess of the product as well as your profit margin.

Pressurized machines may be designed with either a traditional piston-driven pump or a peristaltic pump. The former allows ice cream mix to come into contact with some of the pump parts, meaning more parts to clean. Peristaltic pumps force product into the barrel by squeezing it between two rollers, like a tube of toothpaste.

Controlling Your Soft-Serve Product
Because soft-serve machines are little ice cream factories, controls are important. With advancements in electronics, they've become more sophisticated, but some machines still rely on electro-mechanical operation, which can keep both purchase and repair costs down.

Here again, you can choose between two types of machines representing different philosophies. One type uses temperature to control finished product, while the other controls product density.

A temperature-controlled machine essentially says the ice cream is ready to dispense when it reaches a certain temperature, usually 18º F to 19º F. For the most part, it's a perfectly sound approach to determining when soft-serve ice cream is ready to dispense. An advantage is that temperature-controlled machines can use less sophisticated and less expensive electro-mechanical controls.

One thing to monitor with a temperature-controlled machine is the brix of your ice cream mixtures, which can affect how they freeze. Brix is a measure of sugar content, and the higher the brix of a product, the lower the temperature at which it freezes. Butterfat content and even flavor can also affect the temperature at which a mix will freeze. If the mix you purchase varies from batch to batch, or if you change suppliers, consistency of final product in a temperature-controlled machine can vary, too.

Machines that control density electronically measure amp resistance as the dasher bar scrapes the barrel and churns the ice cream. The resistance indicates how hard the dasher is working, which tells the machine how thick the product is becoming as it freezes. When it reaches a certain density or consistency, the machine says it's ready to dispense.

Electronics make all of these variables pretty easy to control. Many models now have touchpad LED displays that let you set either the temperature or consistency of the final product you want. Once set, the machines automatically adjust for whatever mix you place in the machine.

Other controls typically include a low-mix light that indicates when it's time to replenish the mix hopper. Some models also have an audible signal to let employees know when to add mix. If the barrel isn't full, the mix can freeze solid, preventing the dasher bar from turning. A frozen cylinder can break the blades, bend the dasher bar, or burn out the compressor.

Several models have a safety mechanism to prevent compressor burnout. On some, the compressor automatically shuts down if you don't respond to the low-mix alarm within three minutes. The compressor will cycle every 10 minutes to keep the product cold until more mix is added. Other models shoot hot refrigerant gas from the condenser to the barrel to keep it from freezing solidly when the mix level is too low.

Many models also now have a "night" or "sleep" switch that lets you conserve energy overnight, where permitted by local health codes. In this mode, the ice cream is allowed to thaw and be held at 38º F. until you're ready to restart the machine. Some machines automatically go into this idle or standby mode if the machine hasn't dispensed any ice cream for an hour. This conserves energy and helps maintain the quality and consistency of the product. Though soft-serve ice cream has lower butterfat content than hard-pack product, it will harden and eventually break down if you churn it too much.

Blades, Compressors And Cooling Options
The heart of any soft-serve machine is the barrel where the ice cream is produced. Each manufacturer uses its own design, many of which are patented, for both the freezing cylinder itself and the beater or dasher bar that mixes and pushes the ice cream to the dispensing head. A couple of things to remember when you're developing specs:

Ask your supplier how it designs and constructs the dasher bar and attached blades. There are two types of dasher bar designs: low- and high-displacement. High-displacement beaters are typically designed for batch, hard-pack ice cream production. Some manufacturers use them in soft-serve machines, saying that it may improve the machine's efficiency.

Dasher bar motor speed is something to consider depending on the type of product you want to serve. You might not want a higher rpm motor if you plan to use a product with higher butterfat. Even with sophisticated controls, mix that's held for a while in the barrel before dispensing may be churned too much by a high-rpm motor.

Blades attached to the dasher bar scrape mix off the walls of the cylinder as it freezes. Most are made with some sort of plastic these days. They have to stay sharp to keep the barrel walls clean. They do wear, however, and if worn blades leave frozen mix on the walls of the barrel, the machine will operate less and less efficiently.

Some manufacturers claim to have "self-sharpening" blades. Others attach blades to the dasher with a calibrated spring. That puts constant pressure on the blade as it wears to press it tightly against the cylinder wall. Eventually, all blades must be replaced. Some have wear lines to show employees when to change them. And some manufacturers design blades in such a way that prevents employees from installing them improperly when they're cleaned or changed. Blades typically need replacing every six months or so depending on volume.

Look for heavy-duty guts—compressor, dasher motor, and other components—when you spec soft-serve machines. The power of any machine you choose should match the kind of production you need for your operation. Dasher bar motors, for example, range from ½ hp and higher. Compressor motors start a 1 hp on small machines, and typical machines have 2-hp compressors, about the same as a walk-in. You need that power to pull product from 38º F down to 18º F quickly, and dispense cone after cone. Many newer models now use Scroll compressors, which are more energy-efficient traditional compressor motors.

When you put all that power in a small box, it's going to throw off a lot of heat. Since most soft-serve machines are right behind the counter or out in serving areas, that heat will affect both employees and customers in addition to how hard the machine itself works. You have a few options on how to handle that heat.

Most machines are available in both air- and water-cooled models. The advantage of air-cooled units, like ice machines, is that you can put them anywhere. They don't require a water hook-up, only an electrical outlet (figure on 208v/230v single-phase or three-phase service). But you do need about three inches of clearance around an air-cooled machine, and you can figure that each barrel will use a lot of air conditioning to dissipate the heat from the compressor, dasher motor and condenser.

Water-cooled machines are a good option if 1) you buy a model that has a self-contained recirculating system so you're not paying for water going down the drain; or 2) you can use the waste heat from the water that cools the soft-serve machine to heat water in the rest of your operation.

A third option: models with a remote condenser, usually roof-mounted, that dissipates some of the heat outside. That only works, of course, if your layout accommodates a relatively short run to the roof for the refrigerant lines.

In the end, it's always a good idea to see soft-serve machines demo'd in conditions similar to those in your operation before you make a buying decision.

Keeping Inspectors Happy
A sticking point for a lot of operators is the cleaning soft-serve machines require. Since dairy products are a potentially hazardous food, health departments are very particular about how thoroughly and frequently these machines are cleaned. Dairy products are susceptible to coliform bacteria, which can rapidly multiply to dangerous levels.

Many health departments want you to break down, clean and sanitize soft-serve machines daily, but others have relaxed the rules, with conditions. Always check with your local inspector or health department to find out what rules apply in your area.

Several methods have been developed to ease the cleaning process, including washout kits, which are essentially faucet hookups for the top of the machine that let you turn on the water right into the hopper. Most suppliers also offer parts trays that give employees molded spaces in which to store parts as they disassemble and clean them. This helps employees track parts and know exactly which they should have to properly reassemble the machine.

Still other models have an auto-cleaning mode that flushes and cleans the machine innards at the push of a button. Even these models require disassembly periodically to clean and sanitize parts that may not get a thorough cleaning otherwise. But auto-cleaning can save employees a lot of time—and you, labor cost—if it cuts the number of times they have to strip the machine for cleaning.

Machines that have sleep or night holding modes can be used in some districts as long as they're NSF approved and hold the product at 40º F or below. Manufacturers generally recommend that you don't use "holdover" mix to start the machine the next day. Instead, they suggest draining the machine, starting with fresh mix, and adding the holdover to the hopper. Again, your local health department may have specific rules regarding holdover.

And at least one manufacturer makes machines that have a pasteurizing mode. Periodically, the machine will raise the temperature of the ice cream mix to 165º F or above and hold it there for a short period to kill any bacteria that may have multiplied. The machine then cycles back into cold-holding mode until you're ready to start it up in the freezing and dispensing cycle. That way you may be able to go several days between cleanings if your health department says it's okay.