Induction Seduction


Walk into just about any relatively new hotel kitchen from Malaysia to Moscow and you’re likely to see nothing but a gleaming flat glass surface on the cookline. Induction cooking has been mainstream in Europe for years and has spread around the world. Here in the U.S., many if not most of us still prefer cheap natural gas. But both equipment makers and operators are catching up to European counterparts in their production and use of induction hobs.

Induction cooking has become so popular because of its many and varied benefits. Chefs who use it love it because it’s fast and precise. Since the pan itself is the heat source, not a gas flame or electric element, the cooking surface heats and recovers quickly. And as a result of the way induction works, control over the cooking temperature can be as precise as one or two degrees.

Safety is an additional benefit. With the pan as the heat source, the cooktop itself stays cool except the area directly beneath the pan, and even that cools quickly once the pan is removed.

No open flames and a cooler cooktop also means that the area in which you use induction, whether the kitchen or the front of the house, stays cooler, too. Employees are more comfortable, and there’s less need for make-up air, reducing the load on HVAC. In some cases, you don’t even need to place induction equipment under a ventilation hood (see “Necessity Is A Mother,” below).

Induction is not only an efficient way to heat food. It also saves energy another way. A piece of induction equipment is “on” only when a ferromagnetic pan is placed on its surface. And electronic controls can detect when something smaller than a pan—a utensil, say—is left on the cooktop, preventing the unit from operating.

Here’s what to consider when setting specs:

Hob Type: Ask yourself where and how you plan to use induction cooking. For front-of-house cooking—tableside service or cooking to-order omelets on a breakfast buffet, as examples—you’ll want a countertop unit using 115V/120V service. (That also likely will limit the power of the unit you buy to about 1,800W.) In the kitchen, select hobs based on the menu items you plan to cook. As with other cooktops, induction hobs are made for sautéing, griddling or grilling and cooking with woks or stockpots.

Essentially, your choices here are countertop, drop-in or built-in units. Countertop models, obviously, are self-contained and portable. Drop-in units are designed to plug into cut-outs in your kitchen or front-of-house counter so they can be easily traded out for another piece of equipment—a bain marie, for example, or a warming tray. Drop-in units can be single or dual hobs, and dual hobs are designed as front-back or side-to-side “burners.” Built-ins either are permanently installed in a kitchen cookline or already built into a range unit with an oven below. You also can order built-ins in cooking suites, arranged however you want. One maker has designed its built-in unit so the cooktop can be sealed to the counter, but the unit can be unclipped and removed from below for service or cleaning.

Higher wattage hobs for stockpots, woks or other high-temp cooking applications tend to be stand-alone units, but many makers offer these as drop-in or permanently installed models, too.

Coil Type and Size: The big key to efficiency of induction units is matching pans to hobs. Sauté hobs, for example, typically have 9-in. round induction coils to fit 9-in. sauté and sauce pans. Stockpot hobs have coils that are larger in diameter, as well as higher wattage, to heat contents of the larger pot faster.

Manufacturers also make induction hobs with edge-to-edge or full coils. The advantages of full coils are that you can place a pan anywhere on the cooktop and it will heat evenly, and you can put either a flat metal or grooved grill plate on top to create a griddle, grill or plancha to cook directly on the surface or a French top for multiple small pans.

Power: You’ll need from about 1,800W to 2,500W for light-duty cooking, and from 2,500W up for heavy-duty cooking. Lower wattage units are usually available in 115V/120V, but usually require a 30-amp circuit. You may need two circuits (or a higher amperage single circuit), for example, for a dual-hob drop-in unit. On a buffet line in the front-of-house, you may have to plug two 1,800W countertop units into two separate outlets on different circuits.

Higher wattage models will likely require 208V, 220V or 240V service. Be sure you have both the matching electrical service to the model you want to order and enough circuits with adequate amperage to handle the load.

Construction: You can buy a 1,500W induction hob at Walmart for less than $50. But you’ll get what you pay for. A few things to look for include rugged steel frame construction; a maximum ambient operating temperature of no less than 110°F (one maker says its units will perform in temps up to 124°F); adequate insulation to protect the electronics; a coated circuit board to protect electronics from grease and moisture (at least one maker also seals the unit with a membrane); a high-temp-resistant ceramic glass top (from a reputable supplier such as Schott or NEG); built-in heat sinks to dissipate heat away from electronics; and at least a G4 IGBT engine. (Insulated-gate bipolar transistors are switching devices that make precision temperature-control possible on induction hobs; a G4 engine has four IGBTs.)

Control: The precision of induction equipment does little good if you can’t control it. Manufacturers incorporate one or more of three methods of regulating warming and cooking temperatures—power, temperature and time. You may need a unit with one or all types of control depending on what you plan to cook and where. Some countertop units, for example, have only six power settings, which may be fine for light cooking or warming on a buffet station. Others have up to 27 power settings. One model series has 16 power settings, which maintain a steady wattage draw, but 31 temperature settings for the pan.

For typical back-of-house use, you’ll likely want units with more flexibility, and several manufacturers offer controls that you can adjust power from 0%-100%. Timers give chefs the added advantage of not overcooking food. And more models now can be programmed for a specific cooking recipe, adjusting power or temperature setting for specific periods of time to cook a dish—searing a piece of meat at high temp for a certain amount of time, for example, before lowering the heat to finish cooking it to the desired doneness. A couple of models have USB ports to make programming easier.

Digital displays—usually LCD or LED—let cooks quickly see cooking temperature, and show self-diagnostic messages. A few makers now offer high-resolution TFT LCD color displays.

Noise: Since electronics can get wonky when exposed to too much heat, induction hobs typically have internal fans to cool circuit boards. They can be noisy, which may not be a problem in the kitchen, but might not be desirable in display-cooking applications.

Some makers build countertop hobs with a high-speed fan and little insulation, which keeps innards cool and results in a cooktop that stays cooler, but these tend to be noisy. Others use a high-volume, low-speed fan and more insulation, which results in a quieter unit, but a cooktop that retains more heat from hot pans.

Whether you decide on countertop or drop-in/built-in hobs, make sure you leave plenty of clearance around the unit for adequate airflow—usually 1 in. on all sides, and several inches beneath the unit where it gets most of its ventilation. And be sure to clean fan filters regularly.

Features: Other than controls, standard features are pretty similar from unit to unit, and there are few options (typically color or finish choice and electric service and plug type). Standard features you should look for include: automatic overheating limit switch; automatic pan detection (the unit won’t operate without a pan on the cooktop); small object detection (the unit won’t operate if a small metal object is on the cooktop); empty pan detection (which shuts the unit off after a set amount of time if a pan has no food in it); and a pan optimizer that analyzes the size, shape and material of the cook pan and adjusts to provide the most efficient power. Pans, by the way, are important. The best pans are high-ferrous-content stainless. This last feature will get the most out of lower quality pans, but won’t turn on the unit if pans are inadequate or contain too much aluminum, for example.

Fast heating and cooking, precise control, programmability, safety, a cooler kitchen and lower energy costs—what more could you ask for in a piece of cooking equipment?

How’s It Work?
Discovered in 1831, induction is what happens when an electric current is applied to a loop or coil of wire. The change in magnetic flux induces an electromotive force. In simple terms, running electricity through a wire coil creates a high-frequency magnetic field. When you put a pan with magnetic properties on the induction coil the field generates an electric current that runs through the pan. The resistance of the metal in the pan then generates heat.

Instead of a gas flame or a radiant electric coil transferring heat to the pan and then transferring the pan’s heat to the food, induction cuts out a step, making it much more efficient than gas or traditional electric cooking. Cutting out that middle step also means induction cooking is fast.

“Induction requires more thoughtful cooking,” says Chef Justin Carlisle of Ardent in Milwaukee. “It takes some prep and organization. It’s also extremely precise. You can set it to a direct degree, and use it for everything from warming to slow roasting.”

With that combination of speed and control, induction hobs can help you produce even difficult and delicate items such as creme anglaise and sugar work.

What’s Watt?
If you cook with gas you may wonder how to choose the right power level. You can easily convert kWh to Btu/hr.—there are about 3,400 Btu/hr. in a kWh (3,413, to be exact)—but induction is about 85%-90% efficient, while gas is only 35%-60% efficient, so a direct comparison is a little difficult. Even comparing induction power to that of a heating element on an electric range burner with the same wattage isn’t apples to apples.

The Department of Energy established some standardized numbers several years back to make comparison shopping easier. According to the DOE, gas efficiency averages out to about 40%, and standardized induction efficiency is 84% (but that’s quickly rising on new units to between 85%-90%). Using DOE figures, you can get the equivalent Btu/hr. by multiplying the kWh by 7,185.

So, a 1,800W induction hob is the approximate equivalent of a 13,000-Btu gas burner. A 2,500W hob is similar to an 18,000-Btu burner. A 5kW wok hob is more or less the same as a 36,000-Btu burner. And an 8kW stockpot range will boil water about as fast as a 57,500-Btu burner.

The comparisons assume you’re working with a pan high in ferromagnetic content with a base about the same size as the induction coil. And, because the pan itself transforms energy generated by the induction coil into heat rather than conducting heat from an electric element or gas flame, induction cooking is fast. The high setting on many models can quickly burn food if cooks aren’t careful.

Necessity Is A Mother
When two-time James Beard Awards Finalist Chef Justin Carlisle wanted to open his own restaurant in Milwaukee in 2013, the space he found was a 900-sq.-ft. garden apartment in a seven-story building. The cost to vent kitchen exhaust up through the roof would have been prohibitive. So Carlisle turned to induction cooking that didn’t require him to install a ventilation hood.

Ardent, which features an eight-course tasting menu, opened with two countertop induction hobs and a toaster oven in the kitchen. Now, the restaurant has six induction hobs—four drop-in and two countertop units.

“Cooking over live fire is great,” Carlisle says, “but we can’t use it. Our induction units are wonderful pieces of equipment.”

Besides saving the cost of installing a ventilation system, induction offers great advantages, he says. The kitchen stays cooler, keeping staff members comfortable and saving on HVAC; cooks efficiently use space—countertops can be used for prep then cooking with a portable unit; menus are more flexible because cooks can use countertop units in the front-of-house as well as the back; and the kitchen is easier to clean—employees can pull out drop-in units so even the edges and space below get attention.

Carlisle says induction cooking requires more thought, planning and organization, but is easy to learn. Chefs who are used to adjusting temperature primarily by eyeballing gas flames need to learn to look at and listen to what’s happening in the pan. Carlisle’s key recommendations:
• Think about what you’ll use induction hobs for.
• Do your research before you buy.
• Evaluate how much power you’ll need.
• Pick the right pans.
• Give the units enough clearance to breathe and clean filters often.
• Have patience teaching staffers how to cook on induction.

As originally printed in FER Magazine

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