Anonymous Coward wrote,
Of course there are microwaves made with competent stirrers and well-placed feeds. ... The main problem is that the cheapest microwave ovens are just good enough to follow recipes that call for some number of seconds on the high setting while being unreliable at other settings, and the food industry targets its instructions accordingly. This is a global problem, not unique to the USA.
I think your comment is misleading, for it incorrectly implies that the main problem is cheap microwave ovens and directions to "the masses" about how to use them on food packages. In my opinion, this is wrong for the following reasons.
Firstly, the stirrer technology is you refer to is just a some rotating metal near the magnetron. It is more than 20 years old. By and large, it sucks. That's why it has been replaced by the rotating carousel, which is far superior and why you cannot, actually, buy it easily today in a new microwave-capable oven unless rotation is ruled out for a different reason. However, field unevenness in no way is the main cause of the problems discussed in the article, which is not one-sided heating, as can be the case in non-rotating ovens, but that heating is concentrated in already defrosted areas and food edges/corners.
In other words, even with a perfect EM radiative bath the edges and corners of a hotpocket will still burn or be overcooked if heated rapidly enough while the center is still frozen. That's why even if you buy the most expensive microwave oven on the planet, it will still have this same problem of producing food that is overcooked on the edges and the corners, which experience the highest EM radiation. The cause is not any unevenness of EM modes in an unloaded oven cavity. Rather, it is the shielding effect of food and the relatively small field skin depths to food size ratios.
Your comment about pyrolytic surfaces is interesting, but also misleading, for it implies that convection microwave ovens solve the problems discussed in the blog post. The problem is that microwave ovens use steam cooling of the corners, which boil and splatter food all over the oven as the steam turns things like beans into tiny bombs. Even with simultaneously convective and microwave ovens, of which I own one, one still has a frozen center burnt corner issue, since convective heating is even worse at edge heating. The reason is of course that the convective oven relies upon thermal conduction, which is entirely skin heating, although in truth one gets some infrared radiation which can penetrate a little bit.
You asked,
why not cook with microwaves and brown with the grill simultaneously?
Great question. Ceramic would work for that, but it is expensive. Traditional stainless steel grills are conductive, so they would reflect the EM radiation back into the magnetron, which will shorten it's life. So here is where your comment is spot on; it is indeed a cost and consumer ignorance issue, although grills have other issue I won't go into here. Regardless, dual mode ovens do not fully fix the underlying issue anyway, which, again, is over the overheating of food portion edges and corners.
The primary reason one probably sees less burning in dual-mode ovens may come as a surprise. This just my hunch, but, in my opinion, it is primarily because dual-mode microwave/convection ovens tend to have a larger cavity. The FCC regulates how much leakage can occur in a microwave oven, and there is more cavity area. So larger ovens have to have less maximum magnetron power, due to the FCC. Therefore, dual mode ovens tend to use less magnetron power, which gives more time for conductive heating to defrost the food centers. Another alternative reason has to due with the amperage limitations of most nema (or other) sockets. If there is power going to a heating coil, that's less power for the magnetron. Same effect, however; longer time to cook = more time to thaw center. Regardless, in no way is the real problem fixed, IMO, which is to cook fast and efficiently. To do that, IMO, you need new approaches, such as the AdaptiveWave technologies.
Disclaimer: I have a conflict of interest, so do not trust anything I say about microwave ovens.
