The next-generation kitchen ovens promise perfect cooking using solid-state RF transmitters and sensors
Every year, we hear about new models of ovens and microwaves with new functions and features that are meant to make our lives easier in the kitchen. But the truth is, the microwave oven’s fundamental technology has improved very little since its mid-20th-century introduction. That might all change this year, when the first ovens based on technology developed by startup company Goji hit the market.
Goji is promising nothing less than perfection: the ability to perfectly cook, in minutes, entire meals, on one tray, that involve different components with different heating requirements—and doing so without depriving the food of its moisture or nutrients.
Both microwave ovens and conventional ovens have fundamental drawbacks. A microwave is fast, but it often heats unevenly, doesn’t work well when heating food with low water content, and has a questionable ability to preserve nutrients. A conventional oven can heat, cook, and brown food, and make it crisp, but it is typically slow to do so. As Nathan Myhrvold wrote in IEEE Spectrum: “Oven walls radiate heat unevenly because they vary in thickness and in their proximity to the heating elements. So the temperature can fluctuate by tens of degrees from one spot to another. And many oven doors contain a window, which radiates a lot less heat into the oven cavity than the walls do.”
Goji aims to solve all of these problems and add some new capabilities that we’ve never seen in any commercial oven—conventional or microwave.
Goji’s core technology came from an unexpected source—organ transplant research. During the middle of the last decade, researchers at Hobart Group (one of Goji’s funders) were looking for ways to preserve transplant organs when they discovered a way to evenly and precisely defrost frozen tissue using radio-frequency energy. Although the medical aspects of that technology did not move past the laboratory stage, the company quickly realized that there are many more people who need a way to heat a turkey and mashed potatoes than there are doctors who need to defrost a liver. So in 2006, Goji was formed.
Last year, I was invited to the offices of Goji’s R&D subsidiary in Israel, where I became the first international reporter to see (and taste) food prepared using the company’s technology. Goji has been operating mostly under the radar for 10 years, but now, with the approach of its first product launches, it was willing to open its doors to the press.
Fishy: As a stunt Goji used its RF tech to cook a fish inside a block of ice. Photo: Goji
We’ll get to the tech shortly. But first, the food:
Goji employs two professional chefs who have been working with prototypes of the company’s ovens for several years. They prepared me a dinner that included various types of food of different shapes and sizes with very different cooking needs and times. Into the oven, the size of a conventional built-in unit, went several large chunks of raw beef, a few servings of salmon, leavened dough balls, zucchini, and mushrooms. All of these were placed together on one oven tray.
Ten minutes later, to my amazement, all of the food on the tray was cooked or baked to perfection. The fish was fully cooked but still very moist. The meat was browned on the outside, but pink and tender on the inside. And the bread was brown and crisp on the outside and soft and easy to chew on the inside. Finally, the zucchini and mushrooms were warm but not too hot, and more important, were not drowning in their own juices as you might expect if they were heated in a microwave.
So how did Goji do it? Some of the magic is kept as a trade secret, and the rest is protected by no fewer than 250 different patents and patent applications. The core of the technology, however, uses advanced solid-state heating hardware based on RF, but unlike with microwave technology, there is no magnetron here.
The magnetron, which has its origins well before World War II, was widely used during the war in a new generation of radars developed by the allies. (For more, see “When Nuking Food Was Novel,” IEEE Spectrum, October 2016.) The magnetron is a device that generates high-power RF signals using magnets and resonant chambers. After the war, the magnetron was used to create the first microwave ovens, and improved versions are still in use today. However, the magnetron has some inherent limitations: It has only on-off control; its frequency is only approximate and tends to shift; and there is no accurate control of amplitude or phase. For these reasons, large parts of the magnetron’s communication and radar applications moved to solid-state RF technology, which allowed for much better flexibility and accuracy.
The solid-state heating unit Goji developed includes both transmitters and sensors. Unlike a magnetron in a standard microwave oven, which typically emits energy in the 2,440- to 2,460-megahertz range, Goji’s RF cooking uses a broader range of frequencies, from 2,400 to 2,500 MHz. The inclusion of both a transmitter and a receiver turn the oven from a passive unit, which simply dumps a set amount of heat into an oven, into an interactive system that collects RF reflections from within the oven and uses a proprietary real-time algorithm to optimize power-delivery parameters such as frequency, phase, and amplitude. Every 2 seconds, the algorithm recalculates the output according to what the sensors are telling it and optimizes the transmission parameters as the food changes its properties due to the heating process itself.
Goji’s oven. Photo: Iddo Genuth
It is worth mentioning that although you can use Goji’s solid-state RF technology to heat and cook food on a standalone basis, in order to get the familiar appetizing look of a brown loaf of bread, for example, Goji, with its industry partners, did include a more conventional heating technology in its oven design. However, this component is used for a very short time and only to heat the outer part of the food, not to cook the inside. Also noteworthy is the fact that unlike a microwave, Goji-based ovens will have no major restrictions in terms of the materials—such as most metal skewers—that are placed in them.
As with other RF systems, Goji’s technology utilizes a signal generator and a high-power transistor, which amplifies the emitted signals. However, in common telecom uses, the target is a nonreflective load that absorbs all the power that’s directed toward it. In the Goji oven, the power is transmitted into a closed space, which acts as a reflective load.
Dozens and even hundreds of components in an oven can influence the final cooking results. Goji relies on simulation software developed in-house to accelerate the development process. This software combines electromagnetic wave propagation—with millions of points representing an entire oven and food—transmission and measurement hardware models, software algorithms, and estimations on known reactions of food to different RF frequencies, into a single tool. The tool, called SARA, enables quick design cycles performed without the need for costly and lengthy lab experiments. The simulation is so complex that sometimes computers run an entire weekend to generate a result.
Feedback loop: Goji uses sensors to control the energy input to the food. Illustration: Goji
I asked Goji’s president, Yuval Ben-Haim, about the power level and efficiency of Goji’s technology. He explained that the company’s technology is scalable. A single RF module could use 125 watts, 250 W, or 500 W of power, and a single oven may use one or multiple RF modules, depending on the application. A home oven would require less power than a commercial-grade oven. Goji has been working on both products with industry partners.
As for the efficiency, Ben-Haim said that the wall-socket-to-food power efficiency is comparable to that of a microwave oven. Goji’s technology is about 50 to 60 percent efficient, while a typical microwave oven is anywhere from 40 to 70 percent efficient (depending on the type of dish and weight of the food).
However, energy efficiency, according to Ben-Haim, is not the most important performance factor. The ability of Goji’s system to tune and select frequencies according to the specific type and size of the food is what really sets it apart from a microwave.
Goji’s technology will first reach homes in premium built-in ovens manufactured by a leading appliance maker, according to Ben-Haim. Some of these ovens have been hooked up to computers in the Goji headquarters’ kitchen, where they were used to heat my dinner. These first products will be expensive. Pricing and release date is still to be determined, but Goji was willing to say that the first generation of ovens based on its technology will cost at least as much as existing top-of-the-line conventional ovens, around US $5,000 or more.
Although Goji’s initial consumer product is likely to appeal to a small target audience, the company already has plans to release a much more affordable countertop unit. This will take a few years, according to Ben-Haim, but it could be a real game changer. The company is eyeing the huge “TV dinner” market: During my tasting portion of the interview, Goji’s chefs served me a very simple TV dinner–style dish with fish, rice, and some vegetables. Although this wasn’t as tasty as the main dish I tasted, it was far better than any other frozen dish I’ve tried.
The company plans to improve the accuracy of heating these meals by working with food manufacturers. It hopes to get these companies to include a Goji-specific bar code on the packaging. A user could scan the code with a smartphone, which would transmit the information to the Goji oven. The oven would then heat the dish to exactly the right specifications with the touch of a button.
Goji isn’t alone in the race to bring solid-state RF ovens to market. The RF Energy Alliance, which is dedicated to promoting this emerging market, lists multiple companies that have joined forces, including Whirlpool and Panasonic. New and unconventional players are also entering the market. For example, Wayv, a Texas-based startup, promises to launch in 2017 the Adventurer—a portable, battery-powered, solid-state RF food-heating unit the size of a thermos—for hard-core outdoor enthusiasts.
Regardless of who makes it to market first, a revolution in food-heating technology is coming.