Microwaves: A Haven for Bacterial Diversity | Hacker News Reader

Microwaves: A Haven for Bacterial Diversity

tecscience.tec.mx

71 pointsrbanffy64 comments

Because microwaves don't heat matter. They heat* H2O molecules. This one weird fact is responsible for all of the weird differences between how they cook and how other more classic cooking methods work.

We're taught that heating has three styles: convection, conduction, radiation. But AFAIK, microwaving is a fourth and distinct style.

*: Even more specifically, they add rotational momentum to these molecules, which is not the same as heat, but gradually turns into heat (which is translational momentum) as they knock around. This, in addition to the fact that only the water is being heated, and that the microwave waves touch the food in an uneven pattern even if mitigated by a rotating platter, is why stirring or waiting or using "low power" (dithered) is an important part of microwave recipes, as well as why high moisture foods or intentional steaming works so much better in it

Microwaves also affect other polar molecules and ions in food, not just water.

This excitation leads to the generation of heat, which is then transferred through the food via conduction.

Microwaving is indeed considered a form of dielectric heating, which is a subtype of radiation. It’s distinct from conduction, convection, and traditional infrared radiation but still falls under the broader category of electromagnetic radiation-based heating.

> Microwaves also affect other polar molecules and ions in food, not just water.

So why does sugar seem to heat so preferentially?

I always found that microwaving any dish with a "syrup" made it the temperature of hot lava while the rest of the dish was still cold.

Microwaves seem to prefer syrupy foods because syrup typically has a high sugar and water content. Both sugar and water molecules are efficient at absorbing microwave energy, so they heat up quickly. This is why syrupy parts of a dish often get much hotter than other parts when microwaved.

Is that you GPT?

Huh?

Isn't that because sugar syrups don't boil and get temperature capped at 100C?

Microwave heating is not a fourth form of heat transfer as it name implies: microwave radiation. Yes, the heat is not being radiated by a thermal source of microwaves, but it is radiation being absorbed. Hence radiation is the mechanism.

Rotational momentum is also heat as it is kinect energy related to movement, linear or not.

I'm speaking from a practical cooking perspective, not a technical physics perspective. The radiation from flames or the sun affects food very differently than microwaves do.

For the same reason, I probably messed up other physics technicalities. It would have been nice if I added a caveat I guess, but so it goes. My mental model may be simpler than the truth, but it's a lot better for achieving practical results in the kitchen than nothing than "microwaves heat stuff up fast", which is what I had before and is a really shit model that fails to explain most of their odd behavior.

I suppose there's nothing stopping other forms of radiation like the visible spectrum. How about intense blue light? Could it penetrate better than microwaves?

Due to the higher frequency it wouldn't penetrate as well. But it is fun to think about the other EM sources used for cooking.

https://news.ycombinator.com/item?id=29042728

>According to the researchers, the findings underscore the importance of regularly cleaning microwaves to reduce potential health risks, particularly in environments where food is handled.

Does that follow? I'd expect that as organisms adapt to environments that diverge further from the inside of your body they also become less dangerous, all things being equal. But then again I'd never heard the idea that microwaves are sterile inside and given the standing waves inside I would have dismissed it.

I am also wondering how resilient these organisms are in the food matter we are heating up once it is heated up to certain temperatures. I guess that also means I am wondering how much of these organisms are airborne or are just living on the surfaces of the microwave without ever coming into contact with my food.

Having said that, one thing I regularly do is just place a bowl of water in the microwave with a bit of lemon juice (optional). Put it on for a very long time, so that is boiling for several minutes. Then wipe off the surfaces.

> I am also wondering how resilient these organisms are in the food matter we are heating up once it is heated up to certain temperatures.

I can't find the FDA food safety table right now but IIRC 12 minutes at 140F, 1 minute at 165F, or less than 10 seconds at 185F is enough to kill off everything except endospores.

Unless we have data that shows that people get sick from unclean microwaves I don't think you can conclude that they pose a health risk, no matter what bacteria you find inside.

Because so many people don't have the common sense to cover their food when they heat it up. A microwave is the worst thing to have in a college dorm. Guaranteed filth to be covering the inside.

It also doesn't help the default power is set to 100%, causing volcanic like explosion of anything with high amounts of moisture, like tomato sauce. God save your tongue on taking a bite out of a Hot Pocket that's been in there too long. You swear there's lava in the thing.

People just don't really know how to use microwaves.

I blame the UI. IMO should be two knobs and a button. (Maybe you just push one of the knobs instead of the button)

WDYM, but it is two knobs and a button?

My microwaves have no knobs

Every one I've used looks like a blown-up calculator watch from the 80s.

Two rotary knobs for selecting power and duration and two push buttons for start and stop.

Actually a third push button is also required, for storing a power+duration pair, when you want to have multiple segments where different powers are used.

When using a microwave oven for cooking, not just for reheating, it is very common to use a high power for a short time, then one or two decreasing power levels sufficient to just preserve the current temperature, in order to avoid making a mess in the oven, due to violent boiling or high pressure steam generation.

Knobs seem to be common on European microwaves. NA microwaves have all sorts of granular settings.

Yes, something like changing the power levels normally require pressing of multiple buttons. Many menus and options are also hidden that way. Unfortunately, the true potential of a microwave is locked away. Pretty much everyone I know just hits the 30 second button and is content with super hot or unevenly heated food.

Presumably Duration, Power and Start/Stop. My NEF microwave has a Duration dial, 6 different power buttons (presets for 900, 600, 300, etc) and separate Start and Stop buttons. Oh, and another small button for forcing the Duration dial into a clock setting mode (to set the time-of-day display which is the default when the thing isn't heating).

Works okay, quite intuitive, entirely used to it now.

Just don't get me started on the controls for my induction hob

yes! mine's like that, two knobs: one for how hot and the other is for how long. it's the dumbest one I could find and I'm never buying one with WiFi, thank you very much!

IMO, for prepackaged foods like frozen dinners, the UI should be that you put the food in the oven and close the door, and the microwave figures out the rest. (Of course there would also be manual controls available.)

The simplest way would be with a barcode on the plastic food tray. The barcode would contain the actual cooking instructions so that there's no internet dependency.

My Tovala oven does this (you scan before you put in), though it uses steam and broiler not microwaves.

But each food company would patent their own barcode retrieval system and put it behind a subscription, only $12.99 for the plan for foods with ads, $24.99 without!

Actually, all implementations would be nearly identical, non-novel, and not patentable. But each one would carry a trademark and microwave manufacturers would charge the TV dinner makers a license fee per meal to put it on the box

Juicero vibes here...

(Good idea, though)

Hmmm, only if the microwave worked with their own specially prepared frozen upscale meals.

This sounds like a next-gen microwave idea! Perfectly microwaved food every time!

Two knobs will do. The timer knob can be used to stop the microwave and it starts once the timer is set and the door is closed.

> People just don't really know how to use microwaves.

Usually don't care, not don't know.

The two factors mutually reinforce each other.

Most microwaves are terrible too, good microwaves are much more expensive so nobody buys them, but they can cook much more intelligently with higher quality parts.

I've been dreaming of buying an inverter microwave(the inverter allows it to put out lower intensity microwaves to achieve lower power levels instead of just turning them on and off entirely like most microwave ovens), but for some reason the market for them is tiny. The kind I need, over-the-range inverter microwaves with ventilation, isn't even sold in the US. Strangely enough it is sold in Canada, which has the same electrical outlets. I might do a road trip to buy a microwave...

We've had a Panasonic for a few years, and it's still weird (but good) hearing it running continuously on low power levels, versus the other microwaves that switch on and off for periods of time below 100%

I've had one for over a decade. It wasn't that expensive at the time. People always look at me weird when I suggest putting something in the microwave at 10% power for 20 minutes

Wut? That... does sound very weird but at the same time, why do most people treat microwave power levels like video game review scale (almost never go below 5/10). I don't think I've ever read anyone even contemplate using microwave below 50%. What do you cook at 10% power for 20m?

if I had a lasagna I wanted to heat up in the microwave, it's a great choice

I've never heard of this and it sounds great. Thanks for the heads up.

The only purpose a microwave serves in the first place is to heat as quickly as possible, and coffee and popcorn and hot pockets etc are not made any better by going slower. It is perfectly reasonable for the default to be 100%.

It doesn't matter that you can produce a nicer result by going slower. You can also produce a nicer result by using a regular oven and fresh ingredients.

The defined purpose of a microwave is to serve a different priority. A microwave with any other default is a dull saw blade.

I once had a baby spider living in the bottom corner of my microwave that I used about 5 or so times before it finally died. That's when I realized my understandings of microwaves was a bit cold in the edges.

Time for a combined microwave oven / UV sterilizer to enter the market?

Sound like million dollar idea buddy

Engineering or sales?

How about a UV oven?

Oven-shaped UV sterilizers exist, but I think bc UV really gets stopped at the surface, it would be really ineffective as an oven in the sense of cooking anything?

What harm is this causing? Are people getting sick?

IMHO the harm is more likely from lids that are reused to cover food. If these lids are not routinely dishwashed like other utensils are, then by extension, they are likely to harbor bacteria and maybe even risk passing some into food. These lids are a lot closer to the food than the walls of the microwave. Indeed this could make people sick even if the microwave itself doesn't. Dishwashing the lid is paramount.

That is a theory or hypothesis, but the question is, does this theoretical harm actually exist? Are there actually significant numbers of people harmed by this mechanism? It might be but they don't show that.

I don't know, but with an unclean lid, the potential is extreme. The lid accumulates water droplets that can easily drop back into the food with the bacteria included.

But we've all already been using microwaves this way for decades. If it's so harmful, then it should be easy to point to the evidense of the harm. It's not all that interesting in this case to just go by what seems obvious intuitively, because we aren't talking about a new thing and guessing if it will be a good idea or not.

Actually the use of dedicated microwave lids is not that old. It is somewhat new. These lids accumulate a lot of filth.

Everywhere is a haven for bacterial diversity. Bacteria outnumber human cells in your body 10:1.

Wow an article from my alma mater top to HN wow congrats folks!

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