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September 2007
The New World Of Combis
By: Mike Sherer

More options and easier-to-use models make it simpler to navigate your menu with a combination oven steamer.

About 30 years ago, some European engineers had the brilliant idea of putting together a steamer and a convection oven. The idea was simple: Create one piece of equipment that can be used as a steamer, convection oven or combination of the two. The power of the idea is in the versatility of the unit when used in its "combi" function.

Water turns to steam at 212º F. Injecting that steam into a convection oven turns it into super-heated steam. Moist, convected air cooks food faster with greater yield than convection alone. And controlling both heat and humidity inside an oven gives you a wider range of cooking options in the same appli-ance, from proofing and poaching to steaming and baking.

While the idea is simple, operating early combina-tion oven steamers was not. For a long time, finding the delicate balance of steam and heat required to cook different types of products seemed to be the provenance of white tablecloth chefs with time to experiment. Combi ovens took off fairly quickly in Europe due to the need to get as much productivity out of as small a footprint as possible.

A number of industry segments in this country have picked up on the benefits of combis in recent years. Schools, hard-pressed to rid the menu of fried foods, have discovered they can cook crispy chicken nuggets and French fries in a combi with no added oil. Large institutions and major hotels have found that combi ovens can cook or retherm mass quantities of banquet food in a fraction of the time it normally takes. Casinos use combis to proof and bake bread in the morning and steam batch after batch of crab legs for a buffet at dinner.

Even better, advances in technology have not only made combis simpler to operate, but nearly fool-proof for anyone once they are programmed. You don't have to rely on the chef being around to get one to work properly.

Boiler Or No Boiler?
Another thing that's changed is that these days you can purchase both a traditional combi equipped with a boiler or a new style that's boilerless. Boilerless models may not be traditional, but if they operate in steam-only, convection-only and combination mode, they fit the definition of a combi cooker.

While traditional and boilerless combi ovens ac-complish essentially the same tasks, there are dif-ferences between the two.

The built-in steam generator in traditional combis means a virtually limitless supply of steam. In steam-only mode, the unit will be able to cook batch after batch of product with no recovery time needed. And in combi mode, you can vary the tem-perature of the oven cavity while injecting humid-ity, giving you broader cooking range to handle items such as delicate seafood or dessert, as well as sous vide meals.

Meanwhile, new technology in traditional combis helps maintain energy and water efficiency. Newer models can operate using either treated or untreated water, and most have an indicator light that warns you when it's time to de-scale the steam generator. Many also feature a semi- or fully automatic de-liming cycle.

Boilerless combi ovens produce "flash" steam by blowing or spraying water onto the oven's heating elements or heat exchanger. The advantage of not having a separate steam generator is potential en-ergy savings, and water savings can be up there, too, since there's no reservoir to keep filled and then flushed at the end of a cooking cycle or shift. To produce steam, a boilerless combi's heating ele-ments must be on, meaning it's easier to control humidity levels in the oven at higher temperatures.

The other difference between the two types of combi ovens is price. Boilerless models tend to cost less than their traditional counterparts because there's no separate steam generator. Fortunately, most manufacturers offer both, so you should have no trouble finding a model—with or without boiler—that works well in your operation.

Taking Control
Because it' s multi-functional, a combi oven can save you energy, labor and food costs in a smaller footprint than comparable pieces of equipment. But no one's going to use it if they can't figure out how. Newer electronics have made it much easier to con-trol the cooking process in a combi. And programmability has enabled chefs to make the process re-peatable for any given menu item.

Control panels range from analog knobs and switches to touchpads with digital displays depend-ing on make and model. Some manufacturers offer a single set of controls, others a choice of basic or deluxe packages. Be sure the control package you select has the capability of controlling the features and processes you want and need.

Controls should be easy to use, and in most cases the icons on function keys and the displays are clear and intuitive. Pre-set keys allow you to program cooking instructions for a particular item, so any time you roast chicken, for example, all an em-ployee need do is push a button and the oven will do the rest. At least one model has just nine buttons with icons—you pick the type of food and cooking process (e.g., chicken, roasted), the level of browning you want and the desired degree of doneness, and the oven will self-program a cook cycle.

A key to newer models is their ability to monitor and control humidity in the oven cavity. Humidity is a function not only of how much steam is released into the oven, but how much moisture is pro-duced by the product being cooked. Controlling heat and humidity gives you much greater flexibility over how to cook. Adding moisture sen-sors to combi ovens makes low-heat roasting possible, for example. Some models give you manual (or programmable) control over humidity. One maker has a patented system that controls humidity based on the food being cooked.

Control panels on many models also provide diag-nostics, letting you know when the unit needs ser-vice, or pinpointing problems when the unit's not working properly.

As an option, several models also record data for HACCP reporting.
Some can be connected to a PC via USB or RS-232 cable; others offer a
Wi-Fi connection.

Keeping all those electronics cool is imperative, and every combi maker recommends a certain amount of clearance (up to 14 in.) between its units and other cooking equipment in the kitchen. Manufacturers also use a variety of ways to keep control boards cool. One line of ovens has five fans cooling the control board. Another maker routes the incom-ing water line right behind the control board, letting the ambient water temp cool the electronics in addition to a fan. And the electronics are split among five boards rather than putting them all on one motherboard, so if something goes wrong you can replace less-expensive modules.

Features To Look For
Like convection ovens, the better the airflow through the oven cavity, the more evenly product cooks—and usually the more efficient the oven. Combi ovens, of course, add steam to the equation, making them faster, and more efficient, than regular convection ovens. Fan design and control affect both even cooking and efficiency.

Most combi ovens will provide you with at least two-speed fans, so you can cook delicate products or crank up the heat and fan speed to quick-cook other types of products. Some models offer multi-speed fans, and a few have variable-speed fans.

Another fan feature that improves performance is an auto-reversing function that changes the direction of the airflow through the oven at regular intervals for more even cooking. If you're interested in a model with an auto-reversing fan, make sure it has an elec-tronic brake to reduce strain on the motor when it reverses direction.

Oven doors get a workout, so they have to be durable and well designed. These days, most models feature doors with double-paned glass for insulation and to help prevent burns. One line even has a curved outer panel, keeping it cooler to the touch than others, according to the maker. Most have hinged inner panes so you can clean both sides of each pane.

Most doors are also designed with a "slam" feature that automatically latches the door when it's slammed shut. Slamming is hard on door seals, so most models now have press-fit seals for easy re-placement.

Another common feature is a two-step door latch that vents steam from the oven when turned one way and opens the door when turned the other. (Typically, combi ovens also have an "auto-vent" feature that clears steam from the chamber at the end of a cooking cycle.)

Check to see if the door has a well-designed drip rail on the inside to prevent grease or juices from dripping on the floor when the door is open. And doors should open up to 180º so you can easily load and unload pans. Doors on one line lock in position at 120º and 180º. Another line features a door that opens 90º and then slides out of the way alongside the oven so it's out of the way entirely.

Temperature probes make it possible for the oven to monitor the internal temp of whatever you're cooking. Some models feature a permanent probe. Others feature removable probes that are easy to insert in product, easy to clean, and can help prevent cross contamination.

You might not think a thing like lighting would make much difference, but it does to your kitchen staff. The amount of light in different mod-els varies, as does placement. Most makers use halogen lights, but the number of fixtures in a typi-cal seven-pan oven may be as few as one or as many as four. They're typically mounted inside the oven cavity and protected by Ceran glass or other high-impact material. One maker mounts them in-side the door to keep them a little further from the heat source.

Many models also feature end-of-cycle alarms. When oven contents have been cooked, a buzzer sounds. On some units, the buzzer sounds repeatedly for a length of time, then shuts off. On others, the buzzer continues to sound until you shut it off. Yet another line sounds an audible alarm, then flashes the oven lights until you open the oven door or shut it off.

Three Cheers For Cleaning
Since combi ovens are already hooked up to a water line, most come standard with a rinse hose attached. You can easily soften baked-on food inside the oven cavity using the steam-only mode, then scrub it out and rinse it with the attached hose.

Hoses have spray heads with variable jet strength, and they usually hang on the side of the unit. One manufacturer has cleverly tucked the hose and spray head out of the way inside the door. The hose is re-tractable, making it easy to stow when you've fin-ished using it. Another maker has a similarly de-signed built-in retractable spray hose.

Several makers, however, now offer a self-cleaning mode either standard or as an option that does most of the work for you. In most cases, these units have a built-in spray arm inside the oven cavity. Starting the cleaning cycle activates the steam-only function to loosen baked-on food. Then the unit automatically sprays detergent inside the oven for cleaning and then rinses and sanitizes.

On some models you have to start the self-cleaning cycle manually. On others, you can use the program keys to set the cleaning cycle to turn on whenever you want.

And cycle times vary. A four-stage cycle on one model line, for example, is about 20 mins. per stage, or about 80 mins. total. Another manufacturer boasts a cleaning cycle of about 35 mins. If you plan to clean the oven between loads, you ll want a faster cleaning cycle than if you plan to clean it at the end of the day. Either way, the self-cleaning function typically will save you about $15 in labor every time the oven is cleaned.

Note, too, that different manufacturers use different cleaning solution methods. Most use a liquid cleaner. You fill a reservoir in the unit, and it dis-penses automatically. At least one manufacturer recommends a detergent tablet for its self-cleaning mode. Just toss one in the oven and start the clean-ing cycle.

A second key advancement on several lines is the addition of de-liming cycles. As men-tioned earlier, some offer warning lights that indi-cate when a steam generator needs de-liming. Others let you manually start a de-scale cycle that automatically meters the proper amount of solution, and flushes and rinses the generator. A couple of manufacturers automate the process entirely, letting you program in de-liming cycles as needed.

Manufacturers recommend you treat incoming wa-ter if you purchase a traditional combi with steam generator unless your water meets minimum quality standards of about 30 to 40 parts per million of total dissolved solids and a pH of between 7.0 and 9.0. That said, most combi makers now give you a choice of two water inlet connections, one with so-lenoids designed for treated water and one for un-treated water.

Here's To Different Sizes...
Since combi ovens come in such a wide range of sizes, you're bound to find one that suits your space and production needs. A new countertop model on the market is touted as a "mini" that holds about six half-size pans. Larger combi ovens can even ac-commodate roll-in racks. However, many manufac-turers make a variety of rolling racks and stationary stands to match intermediate size ovens.

Combi ovens also make modified cook-chill sys-tems more attractive because of their ability to keep food moist when retherming. Several manufacturers are making it easier by matching combi and blast chiller capacities to different production systems.

Manufacturers also offer stacking kits so you can stack a couple of units on top of each other without taking up more floor space. And some even have ventless hoods paired with their models, giving you the option of placing a combi anywhere in the kitchen, not just under the hood.

Combo Combis
As if combi ovens aren't already versatile enough, a couple of manufacturers are adding even more ca-pabilities. One of these new "combo" combis adds a smoker to its line of ovens. The units let you hot- or cold-smoke products in one batch and cook some-thing entirely different the next without any residual smoke flavor.

Yet another company has incorporated a microwave into its combi oven. The patent-pending technology lets you use standard metal hotel pans. The com-pany says the combination of microwave and steam convection heat can cut cooking time of some products by 50%.

The best way to determine if a combi is right for you is to see a demo with our menu items. Most combi makers have demo kitchens, some where you can see competitive units cook side by side. When you see how versatile and easy to use they are, you may end up trading in some of your old equipment.

Remember The Extras
While it's true that combi ovens will cook most foods as well or better than other pieces of equip-ment, manufacturers have designed special accesso-ries for their ovens that improve cooking perform-ance for certain items. If you have a specialty item and are considering a combi, you might want to look for a model that offers accessories designed for products or menu items like yours. Some of these accessories include:

Grill Grate
This specially designed grate puts grill marks on chicken breasts or steaks while the combi cooks them to the perfect degree of done-ness and browning.

Chicken Roasting Rack
Designed to hold whole birds, roasting racks turn a combi oven into a rotisserie-style oven.

Griddle Grids
Using these flat-top griddle surfaces in a combi oven lets you "pan fry" foods like fish fillets, home fries and so forth.

Fryer Baskets
Some folks swear that cooking off blanched fries in a combi using these specially designed baskets results in a crispy fry without additional oil.

Roasting spits are available with large combi ovens and can hold a whole lamb or pig.

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