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Idle Science

The Physics of Hot Pockets 222

Posted by samzenpus from the when-you-absolutely-have-to-eat dept.
StartsWithABang (3485481) writes "You've all had the experience: you're all excited to microwave your favorite snack. So you pull it out of the freezer, you throw it in, and you let it rip. A minute or two later, you pull it out, and there it is: boiling on the outside, frozen in the middle. Finally, a physicist answers the eternal question: why do microwaved foods remain frozen on the inside when they reach scalding temperatures on the outskirts? Starts With A Bang explains the whole phenomenon. Bonus for the crisping sleeve explanation!"
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The Physics of Hot Pockets More

The Physics of Hot Pockets

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  • Microwave trays (Score:5, Informative)

    by Travis Mansbridge ( 830557 ) on Friday May 16, 2014 @12:19AM (#47015275)
    Also those with rotating microwave trays (because microwaves tend to heat unevenly) ought to be aware that anything at the center of the tray will not get the benefit of rotation and heat at the same rate the entire time. To roll around in a (relatively) even distribution, none of your food should sit in the center of the tray.

    • Re:Microwave trays (Score:5, Interesting)

      by Anonymous Coward on Friday May 16, 2014 @05:07AM (#47015937)

      Of course there are microwaves made with competent stirrers and well-placed feeds. Panasonic makes microwave ovens that feature both (the feed is at the bottom of the cavity), so no rotation is necessary. They also use variable fast pulse width modulation to drive the magnetron, resulting in a smooth output power, thus avoiding another common contribution made by on-off duty cycles to burnt skin / frozen middle problems especially at lower power settings. (Triac controlled magnetrons can only go on and off; most PWM microwave ovens not driven by an inverter supply do a cycle on the order of 30 seconds.) There is work on continuous phase shifting, which will avoid heating the same islands in food even in pessimal cases (like poorly conducting food put in the centre of a rotating tray). Finally, there is still substantial research going into probes inserted into food so as to provide feedback to the driver logic (dynamically or for capture into programs which take food type mass as variables) and whether non-invasive probes can provide useful dynamic feedback every time the oven is in use.

      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. However, as large-cavity combination microwave/grill/convection ovens become more popular in densely populated areas (why waste space having two or three ovens? why not coat your microwave with pyrolytic surfaces that you clean by simply baking or roasting something? why not cook with microwaves and brown with the grill simultaneously?) this is likely to change faster than patents expire, especially as several key manufacturers (Panasonic, GE) will not be cannibalizing conventional oven products. The critical path and most visible extra cost to the first time buyer is mainly in the design of trays and dishes which work well under arbitrary conditions in a combo oven, and avoiding damage when someone uses the wrong tray, dish or tool for a given programme.

      • Why not do both at the same time? Power draw. A microwave can take over half the available load on a standard household circuit. Most are wired for 15 amps before the breaker starts tripping. Heating elements are just as power-hungry, which is why you typically see electric stoves on a dedicated 240V, 20A circuit. I would guess most houses do not have the wiring to support this.

        • Anyone who can support a microwave and an oven now, can support a ovenmicrowave in the future, although it might need a two-plug dongle.

        • Re: (Score:2)

          by tlhIngan ( 30335 )

          Why not do both at the same time? Power draw. A microwave can take over half the available load on a standard household circuit. Most are wired for 15 amps before the breaker starts tripping. Heating elements are just as power-hungry, which is why you typically see electric stoves on a dedicated 240V, 20A circuit. I would guess most houses do not have the wiring to support this.

          Modern houses to modern code actually specify 20A per circuit to the kitchen, with each plug being on their own circuit.

          Why? Becaus

          • Modern, yes, but most places I go "modern" is the exception, not the rule. I'd give my current house aa 50-50 chance of being built in the 20th century (vs the 19th...)

      • You may be the foremost microwave geek (I mean that in a good way)!

        Since you seem to have given it substantial thought, what would you say are the best standalone and best over-the-range microwaves on the market?

        I'll be interested to see if your theory about the combo devices come to pass--I have a hard time seeing it working out, probably because of the trays and dishes. Popular cooking trays for conventional ovens are metallic (e.g. cookie sheets), which would be a catastrophic to have in your combo oven

      • Re: (Score:3)

        by dissy ( 172727 )

        Finally, there is still substantial research going into probes inserted into food so as to provide feedback to the driver logic (dynamically or for capture into programs which take food type mass as variables) and whether non-invasive probes can provide useful dynamic feedback every time the oven is in use.

        I myself just recently discovered the existence of non-invasive probing (a feature included in a microwave just purchased by a friend last month), and while very impressed with the concept, was less so with the outcome.

        I'm not sure if there are different non-invasive methods on the market, but this particular model somehow ended up using the water vapor released during microwaving to obtain its feedback.
        In cases where it couldn't read anything (seemingly for foods that don't release much vapor) it wouldn't

      • Re: (Score:3, Interesting)

        by jasonataylor ( 787485 )
        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 can

    • Re: (Score:2)

      by antdude ( 79039 )

      Som what's the best way to heat everything?

  • Somebody needs to buy... (Score:5, Interesting)

    by Bin_jammin ( 684517 ) <Binjammin@gmail.com> on Friday May 16, 2014 @12:20AM (#47015279)
    a microwave with more than 300 watts of power. I've never had the issue of hot outside/cold inside, my problems have always been of the hot outside/nuclear inferno/solar coronal mass ejection on the inside variety, regardless of where I've microwaved them. I don't even follow the instructions on the package very closely, just pull it out of the wrapper, put it in the sleeve, toss it in, slap the door shut, 3 or so minutes, and out comes an external breading hot to the touch with napalm in the center. Maybe there are just a lot of broken microwaves, or even more likely, people that don't know how to use them properly?

    • Re: (Score:2)

      by aevan ( 903814 )
      My place reeked for a week as I went through a few dozen backs of microwave popcorn, trying to find the balance of power and time that didn't leave either a bag of charcoal, or a bag of kernals. We don't even pretend that popcorn button on it is anything more than a cruel joke. [Ended up being 60% for 1m50].

      Oven instruction? Sure. Stove-top instructions? Maybe. Microwave instructions? Put in the same category as "may have been in the same building as a peanut" disclaimers: there on the off chance that

      • Re:Somebody needs to buy... (Score:5, Informative)

        by war4peace ( 1628283 ) on Friday May 16, 2014 @03:08AM (#47015655)

        How to microwave popcorn:
        Put the bag in, turn microwave on. When number of pops/second goes down to 1, stop, pull bag out, enjoy results.

        • Re: (Score:2)

          by AK Marc ( 707885 )
          I've had a microwave where that would get you 3-4 tbsp (about 1/4 to 1/2 the bag) unpopped, and the popped parts black, charred and inedible. For my current microwave, that works.

        • Better method that doesn't taste like shit:

          Heat a few T of coconut oil in pot (narrowish but tall works best; think along the lines of a pasta pot, not a dutch oven or saute pan) with ~3 kernels of popcorn in it. When the probe kernels start popping, add a few T of popcorn. Agitate pot gently until kernels are popped. Pour into bowl and add some salt.

          Oops, I forgot to use the microwave. Shit. I dunno, I guess you could store the popcorn in it as long as it doesn't interfere with the things a microwave is go

          • Oh, yeah, I should add a few caveats for the geniuses at slashdot.

            You'll want to either use a vented cover (vented so that the steam doesn't build up and make the popcorn soggy) or, better, hold the cover above but not flush with the pot, so that the kernels and oil stay put, but steam can escape. The latter requires a modicum of muscle tone and dexterity, so you might want to consider it an Advanced Technique.

            Also don't shake the pot so hard that you splash hot oil on yourself, and remember to hold the pot

          • Re: (Score:2)

            by cusco ( 717999 )

            An older thick-walled pot works better than the newer thin-walled ones too. Cast iron is best, cast aluminum next.

            A word from the *Voice Of Experience* - Do not make popcorn when you're on acid unless there is a fire alarm nearby.

            • yes, adequate heat retention/dispersion helps a lot. my favorite is thick-walled anodized aluminum; once you get the oil ratio correct, the popcorn absorbs almost all of the oil (without getting greasy), and cleaning off the anodized aluminum is very fast.

              Do not make popcorn when you're on acid unless there is a fire alarm nearby.

              lol, or, maybe just "do not make popcorn when you're on acid." :)

        • Put the bag in, turn microwave on. Wait 3 minutes.

          Add/subtract ~10 seconds depending on the season and microwave's power rating.
          750-800 W in the summer - ~3 minutes.
          750-800 W in the winter - ~3 minutes 10 seconds.

          Also... Not every single kernel is supposed to pop. That's why you get a bag of them instead of an EXACT number of kernels.

          If you're refilling your bags with popcorn bought by a pound...
          Pour the corn in a glass or cup first, pour a little oil over it (teaspoon or so will do for ~100 grams of corn),

        • popcorn:

          [SNIP] pull bag out, enjoy results.

          "Popcorn" and "enjoy" in the same sentence?

          Bowfing shite. Fit for horses and ... well I'd even hesitate to feed it to an American. Unless the waterboard was broken.

      • Just underpop it every time. Not only will it not be burnt, but if you stop it early enough you also get less-dry popcorn. Cooking to the last pop takes out every bit of moisture (and you can taste the difference). If that's not enough, pop 2 bags.

      • My old microwave used to burn the popcorn, then it died.. I purchased a new one that does it right given you can figure out how many ounces are in the bag.

        I don't have any problem with hot pockets mostly because if I'm going to have a hotpocket at lunch I pull it out of the freezer in the morning before work and stick it in the refrigerator. It's mostly thawed out by lunch when I pop it in the microwave.

    • Re:Somebody needs to buy... (Score:4, Interesting)

      by TapeCutter ( 624760 ) on Friday May 16, 2014 @04:01AM (#47015787) Journal
      Hmmm, my MW is 1100 watts. For frozen meat pies (Australia's national dish), heat for 1min, stand for 5min, heat for 1min, stand for 2min, it comes out like a warm pie from the bakery. However if I heat for 2min straight, the outside is hot, the centre is frozen, and the pastry has turned into something that would be suitable for re-treading tyres. Thermal inertia explains the frozen centre, but I'm neither a cook or chemist so I have no idea why the pastry turns to rubber?
      • Ever seen a microwave oven with the words "CHAOS defrost" written on it?

        Your microwave outputs at a standard rate; A percentage of the full 1.1KW output for the time you have specified. Microwaves work by exciting water to boiling point extremely quickly, and in that absorbing the microwave energy. You put your pie in for two minutes straight and the outside of the food will be utterly ruined, having absorbed the entire X/1100 you threw at it. Leaving the pie to cool in between allows the food around the b

      • You can get a similar effect by adjusting the "power level" on the microwave. Usually this doesn't actually lower the power level, it just cuts it on and off a percentage of the time. For example, on my microwave power level "10" is full force (High). Power level 5 (50%) will cook on high for a 30 seconds, then switch off entirely for the next 30 seconds, then back on again for 30 seconds, etc.

        • Not just "usually". I think it's in every case but Panasonic. I don't know of anyone else using an actual inverter to adjust the output voltage.

      • Thermal inertia explains the frozen centre, but I'm neither a cook or chemist so I have no idea why the pastry turns to rubber?

        I don't know what the ingredients in your specific pastry are, but generally toughness and rubber-like texture are caused by excess development of the protein (gluten and/or eggs). If the outer layer gets very hot, it drives out the water, leaving this "protein skin" to get tough. If you do this in stages, the pastry will only get mildly warm, then cool back down a little bit during the rest, and then get warmed again. If you do it like that, the moisture inside the various layers can come back to equili

    • I've found that with microwave cooking, the implied (but all-too-often unwritten) instruction is to let the food sit for a while before you actually try to eat it. With two Hot Pockets, you cook them for 3 min 30 sec. Then (not mentioned in the instructions), you need to let them sit for about 10-15 minutes. If you were foolish enough to try to eat them right out of the oven, your mouth and throat would probably be incinerated into a fine ashy substance.

      I'm not sure why so few microwave instructions don't m

      • you cook them for 3 min 30 sec

        You cook them for 3 min, 30 seconds? Try 3 minutes 33 seconds. Your finger is already on the 3 key. Why waste the seek time needed to bring it to the 0 key? Or try a 3:21 swipe. 3 min, 30 seconds - Who's got that kind of time?

        Also, do not be afraid to explore the posibilities of 77, 88, or 99 second cook times.

        • Re: (Score:2)

          by Richy_T ( 111409 )

          But the 0 button may be on the way to the "Start" button, requiring only a passing swipe to register.

        • My method: minute-plus, minute-plus, minute-plus
          Your method: 3, 3, 3, start

          3 entries vs 4

        • Re: (Score:2)

          by chihowa ( 366380 ) *

          Speaking of saving time, I find that most everything will cook well enough in some multiple of even minutes. The "minute plus" key is the only key I ever actually use on my microwave.

          Also, for anything under 99 seconds, you can save a button press by entering seconds instead of minutes:seconds. It's obvious, but it annoys me enough to type this to see people hit 1-3-0, when 9-0 works just as well.

          • but it annoys me enough to type this to see people hit 1-3-0, when 9-0 works just as well.

            Of course, 8-8 would be close enough to 9-0 to work and be quicker to enter also.

        • Maybe his microwave has a "30 seconds" button, and a rotating +/- dial instead of buttons 1 to 9?

    • Re: (Score:3)

      by Greyfox ( 87712 )
      You gotta let those fuckers cool off for a couple of minutes, until the gooey center of liquid hot magma cools down. Third degree tongue burns are no fun!

  • learn the tools you use (Score:4, Funny)

    by HybridST ( 894157 ) on Friday May 16, 2014 @12:26AM (#47015295) Homepage

    Most microwaves have a power control. 90 seconds at power 2 or 3, wait 1 minute. Flip, 1 minute at full power. Wait 3 minutes. Serve.

    There exist websites and books devoted to this appliance and how to use it correctly. This is a non-story.

    Caveat: there are some nice physics going on in the explanation but only for the layman. Look elsewhere for the gritty detail we /.ers are used to seeing.

    • Comment removed (Score:4, Interesting)

      by account_deleted ( 4530225 ) on Friday May 16, 2014 @01:14AM (#47015423)
      Comment removed based on user account deletion

  • Seriously. (Score:5, Funny)

    by adolf ( 21054 ) <flodadolf@gmail.com> on Friday May 16, 2014 @12:31AM (#47015303) Journal

    I've never had a problem with Hot Pockets: Follow directions, learn how it works in a given microwave oven, and...done: Ridiculously-hot cheap, bubbly, unhealthy goodness.

    Meanwhile, I don't need to read TFA to learn how the powdered aluminum wrapper turns RF energy into thermal energy. And I don't need TFA to know that any thing has a certain reluctance toward changing temperatures, as nothing is a perfect thermal conductor.

    In fact: Dude, I've been cooking with a microwave since I was a little kid: It was the first kitchen appliance I was certified on other than -- maybe -- an electric can opener.

    Up next on /.: How shoelaces work to keep our shoes on our feet, followed by a lesson in using a light switch to illuminate a dark room. Or "Toast: Why bread is caramelized only on the outside when using the every-day toaster."

    *head in hands*

    • Re: (Score:2)

      by darkonc ( 47285 )
      If you don't have a problem with Hot Pockets, then you probably have a freezer section that borderline doesn't work. If a hot-pocket is nearly thawed when you throw it into the microwave, it will have pockets of semi-liquid that quickly heat up and help to thaw the internals which then heat up nicely. It doesn't have a whole lot to do with the power of your microwave.

      The other solution is to run the thing on 'defrost' for a couple of minutes -- (a short blast of microwaves every 10 seconds or so, wit

      • If there were no fat in a hot pocket, then maybe I'd agree with you. As long as I put the pocket to the edge of the turntable instead of the middle, it comes out fine. I only cook at 60% power, but that's not enough change to fully defrost the water alone.

    • How shoelaces work to keep our shoes on our feet,

      Here is a Ted Talk [google.com] on how you are probably tying your shoelaces wrong. Did you know there are two versions of that knot. One is the strong version and the other is the weak version. Most people learn to tie the weak version. The weak version also causes the bows to align along the long axis of the shoe instead of lying across the shoe as it should.

  • It's on purpose (Score:5, Funny)

    by Rosco P. Coltrane ( 209368 ) on Friday May 16, 2014 @01:10AM (#47015419)

    Scalding on the outside and frozen inside is a feature: it's the Hot Pocket's way of telling you it really isn't proper nutrition.

  • I always assumed it was something to do with losing energy as the microwaves penetrated the substance, and I don't see how this explanation really changes that. After all, when the pocket comes out of the freezer it is ALL frozen. OK, so frozen stuff doesn't microwave easily, but then why does the outside heat first? My intuitive thought that the microwaves don't penetrate as well seems unrefuted.

    • OK, so frozen stuff doesn't microwave easily, but then why does the outside heat first?

      When a wave penetrates a conducting medium, it transfers energy into the medium, and as a result it gets weaker exponentially. The intensity vs. depth is given by

      E=Ei*exp[-C(depth/wavelength)]

      where Ei is the intensity at the surface, and C is a constant that depends on the characteristics of the medium. C is small in ice, so the wave doesn't transfer much energy initially, and most of the energy just trucks on through and out the other side. Still, there is some attenuation, so the intensity is greatest at

  • Hey, if idiots wrote it then RTFM is a bad idea, OK?

    Simply keep the Hot Pockets in your fridge. Then place them in your toaster oven to cook them.

    • Re: (Score:2)

      by cusco ( 717999 )

      Better idea. Keep the Hot Pockets in your freezer, then when you sell the freezer make sure they go with it. Bleah, nasty things . . .

  • Jim Gaffigan sums up my feelings on Hot Pockets.
    https://www.youtube.com/watch?... [youtube.com]

    • I think Daniel Tosh did a better job of summing up my feelings on hot pockets, but it seems like Jim Gaffigan helped.

    • Dr. Evil has a different opinion: "Have you tried the Hot Pockets? They're breathtaking!"

  • I "airwave" frozen food lately. (Score:3)

    by Maxo-Texas ( 864189 ) on Friday May 16, 2014 @03:04AM (#47015641)

    I know I'm going to eat a frozen dinner so I sit it on the counter for 10 minutes before i heat it. They heat up evenly and faster.

    I also nuke for a 15% longer but at 80% power.

    Of course, I also gussy frozen food up too. Adding just a teeny bit of herbs, or sour cream, more vegetables or some fresh cheese can make them quite tasty.

    • I never bought a microwave. Parents had one, but I bought a toaster oven when I moved out. I've never needed a microwave.
  • "We offer a Hot Pocket; the outside is boiling lava-hot and the inside is frozen solid."
    "Will it burn the roof of my mouth?"
    "Oh, it will destroy it. Everything will take like plastic for a week."
    "I'll have the Hot Pocket."

  • 1100 watt oven 3 minutes 10 seconds, without the crisping sleeve, on a paper plate, on the outside of the turntable. Let cool for a minute, or two, Eat. Better tasting fillng that way too.

  • Comment removed based on user account deletion

  • I used to eat 3-4 Lean Pockets a week, so I've got a pretty good idea what I'm talking about: I've never had the problem he describes with the outer portions being lava-hot but the center being frozen. This has been so across 3 different microwave ovens, one of which was an ancient late-'80s unit made when turntables were a premium feature and you set the time with a dial.

    My secret? Following the goddamn directions on the box and adjusting for the microwave's rated power. The directions are usually for a

  • ...is that people try to eat microwaved food right out of the microwave. The food hasn't finished cooking at that time. Leave it another minute for the internal temperatures to equalize.

    I thought every college student knew that.

    Mind you, Hot Pockets are nasty. Lean pockets are slightly less nasty.

  • I've never ever experienced a Hot Pocket that was anything less than flesh-searing hot on the inside.

    That said, TLDR: Energy is supplied to the outside faster than it can be conducted to the inside of the food.

    I'm too lazy to count, but I'm pretty sure that would fit in a tweet, and hopefully it was a "no shit" situation for 99% of people with brains. Essentially it's the same reason a steak can be burnt on the outside and raw on the inside.

  • Perhaps you missed the direction about cooking the hotpocket inside the crisper it comes with in a 1100 watt microwave oven; preferably in a microwave with a rotating carousel. Or possibly the direction to let it sit for 5 minutes after cooking.

    A minute or two later, you pull it out, and there it is: boiling on the outside, frozen in the middle. Finally, a physicist answers the eternal question: why do microwaved foods remain frozen on the inside

    Because the microwaves are high energy, they are absorbe

  • Would microwaving frozen food in a vacuum (or conversely under high pressure) make any useful difference in how evenly the food cooked? A lower pressure would lower the boiling point and a higher pressure would raise it. What about subtly modifying the wavelengths or amplitude? I'm not a physicist so I have no idea. Just throwing that out there to see if someone smarter than me can make it stick.

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