Susceptors Enable New Generation of Microwave Foods

At the intersection of manufacturing, packaging and formulation, they make thorough cooking and browning possible.

By Mike Pehanich, Plant Operations Editor, and Dave Fusaro, Editor in Chief

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"Microwave baking" no longer seems an oxymoron. But credible technology to make it possible seemed a long time in coming.

Few modern conveniences have been treated with such a combination of welcome embrace and cynical sense of limitation as the microwave oven. Perhaps the biggest reason is that it is not an oven at all. Generating no actual heat of its own, the microwave agitates molecules in the food product in such a way they generate internal heat.

Even in the earliest, very costly iterations, microwave cookers had almost universal appeal in their ability to reheat leftovers and thaw freezer foods. Still they failed miserably in "real" cooking attempts and even disappointed in the reconstitution of prepared frozen entrees and dinners.

Complaints ranged from "too soggy" to "too many cold spots" to just plain "disappointing." Products that were supposed to remain moist dried out. Foods valued for their crisp, tasty exteriors and moist flavorful interiors often disappointed on both fronts.

But "irresistible convenience" endeared the microwave to the public, and processors learned to formulate foods for better microwave effect. The potential market for microwave foods that delivered homemade, oven-prepared taste and texture was clearly huge. Engineers and equipment and packaging materials manufacturers have created new packages and heating devices. A generation ago, few would have believed the quality of today's microwave foods possible.

Credit the susceptor

You can credit a number of innovations for the turnaround, but none, perhaps, has been more important than susceptor technology.

Susceptors are metal, most often aluminum, bonded onto a paperboard substrate. Sometimes a layer of polyester is involved, as well. They alter the usual microwave bombardment of food by focusing microwave energy. They redistribute the power of the microwave for more even heating, also enabling the "real cooking" qualities of browning and crisping to come through in microwave-prepared foods.

"When a susceptor is exposed to microwave energy, it gets very hot. The heat it creates reacts with the surface of food near it or in direct contact. The resulting is crisping or browning of the food," explains Andy Johnson, senior marketing manager of Graphic Packaging International, Marietta, Ga., one of the pioneers of susceptor technology. "In essence, it creates a conventional oven effect in a microwave oven."

The current generation of susceptors is the product of evolution. Development in incremental stages has disguised the technology's remarkable progress.

Hot Pockets, the handheld sandwich-snack, was the first microwaveable food to break the crisping barrier. Chef America launched the Hot Pockets brand in 1980. Three years later, Hot Pockets introduced the crisping sleeve to the retail market. Graphic Packaging created that susceptor. It was the first of its Active Microwave Packaging innovations to hit the market. GPI's objectives were to eliminate cold spots and to even-out the heating.

As in a certain fable, for some customers this technology was too hot, for others it was too cold. "For some customers, we removed some of the aluminum to lessen the heat," Johnson says. "We can customize the amount of aluminum for every application."

Other customers needed if not more heat then heat focused elsewhere in the product. GPI began shaping the metal into patterns that acted as antennas, directing the microwave heat into specified areas, sometimes deep within a product. "For a 40-oz. lasagna, microwaving would have overcooked the outside and left the inside cold," Johnson continues. "By having an antenna focus the heat deep inside the lasagna, it can cook evenly." Another application of this antenna technology, GPI's MicroRite line, cooks fruit pies thoroughly on the inside while browning the crust slightly and keeping it flaky.

The technology's latest version, QuiltWave, uses two polyester layers. Moisture naturally trapped between the layers creates pockets or bubbles in the substrate. As they expand, they contact the food at different points to effect browning. The pockets-effect enables this susceptor to make contact with uneven-shaped food products.

Arise and bake!

While Hot Pockets products, now part of the Nestle line-up, may be better and more popular than ever with their crispy baked crust and evenly heated interiors, Kraft Foods has leveraged the current generation of susceptors to produce the once unthinkable- a microwave rising crust pizza in its DiGiorno line. "There hasn't been a rise-and-bake microwave pizza before this," says a Kraft spokesperson.

Duplicating that distinctive bakery crust quality required a pair of susceptors: a cooking tray to ensure even heating of the bottom layer of crust and a crisping ring "to make the exterior crust crispy but keep the inside tender."

The product, which reached nationwide last fall, was a bold move for the DiGiorno line, which hangs its reputation on producing a take-out quality pizza.

Loblaw International, the Toronto-based marketer of the President's Choice product line, also incorporates susceptors into a number of popular frozen products. Sold in its Loblaw retail outlets in Canada as well as in select grocery chains in the U.S., the President's Choice lasagna pies, Scotch meat pies and four-minute microwaveable fruit pies are recent additions to a line that relies on susceptors for its success.

"The technology has been refined recently to make it seem that the products resemble a fresh, oven-baked product," says Geoff Wilson, a Loblaw vice president and spokesman. "They have a genuine baked texture. People love them."

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