Q: At the Lawrence Home Show this past weekend, I saw an induction cooktop for the first time. How does it work?
A: First introduced as a home appliance concept in the mid-1970s, induction cooking or "cool cooking" is starting to become more popular, especially in commercial kitchens. I discovered induction cooking a few years ago when I presented several nutrition programs at KU Dining Services. Each of the residence hall dining centers feature "made while you wait" entrees using ingredients that students individually select. The entrees are then stir-fried at the "induction cooking" station. Wow, what a great way to encourage healthy options - fresh, fast and tasty!
The power behind induction cooking is an induction coil that sits beneath a ceramic cooktop and, when supplied with electric current, creates a magnetic field. When the pan sits flat on the burner, it activates the magnetic field, exciting iron molecules in the pan and creating heat. The transfer of energy is virtually instantaneous and direct. Heating (or the intensity of the magnetic field) can easily be regulated by output control buttons.
Essential to the mechanism is the cookware, which must contain some magnetic element. From a practical standpoint, they must be a "ferrous," some form of iron, or have a ferrous core. The acceptable ones are magnetic stainless steel or cast iron. Copper, aluminum, ceramic and heat-resistant glass cookware cannot be used. A simple test: Take a household magnet, and if it sticks to the bottom of the cookware, the cookware will work fine. Pans also must be in good condition, not warped or dented.
There is no transfer of heat from the surface to the pan, making it an efficient cooking technology. You can even place your hand on the induction-cooking surface and no heat will be felt. If however, you place a magnetic pan on the surface, the pan will heat up, and the heat the pan generates will be the only thing that heats up the surface of the cooktop. Since the cooktop surface is flat and stays cool to the touch, cleanup is easy - there's no crevices to collect spills, splatters do not burn on, and cleanup can take place immediately with a sponge or paper towel. With no flame or hot metal element, the risk of an accidental fire is greatly reduced.
As an added safety precaution, the unit has a pan-sensing electronic circuit, which shuts the power down to a standby level if the cooking utensil is removed. The standby level eliminates a warm-up period and enables the unit to resume cooking at the selected power level as soon as the pan is returned to the unit. This means that cutlery, spatulas and other cooking tools will not accidentally heat up if left on the unit, but also means that cooking utensils must exceed some minimum size.
According to the American Council for an Energy-Efficient Economy, although energy consumption can be cut using an induction cooktop rather than an electric coil or radiant element, unless you do a lot of cooking, it is probably hard to justify on energy savings alone. At this time, these cooktops are still not price competitive. However, portable countertop units (like KU Dining Services have) are much more affordable if you already own the right cooking pans and are interested in experimenting with "high-tech" appliances.