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Comment by londons_explore | Hacker News Reader

I would like super sensitive cameras like this to be used inside fridges to see the very faint glow of food going off.

Chemical reactions by bacteria breaking down food produce light, enough for humans to see in only the darkest of places (if you live in a city, you won't ever encounter dark enough situations).

A camera simulating a 1 hour exposure time in a closed refrigerator ought to be able to see it pretty easily.

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Reading between the lines of [1], bioluminescence is used to detect bacteria/fungi/other organisms in food, but only by adding luciferase to a sample and measuring the light emitted when luciferase reacts with ATP. Because living organisms contain ATP, the ATP content can be used as a proxy for contamination by microorganisms.

But I didn't find anything on bioluminescence occurring naturally in the kinds of bacteria you'd want to be warned about. Did you ever personally see glowing food?

[1] http://cdn.intechopen.com/pdfs/27440/InTech-Use_of_atp_biolu...

Luciferase, easily the coolest (hottest?) name I've come across in a while. Here's the wiki:

https://en.wikipedia.org/wiki/Luciferase

"Luciferase is a generic term for the class of oxidative enzymes that produce bioluminescence"

and,

"Bioluminescence is the production and emission of light by a living organism"

Rotting meat definitely glows. I've personally seen decaying mammal carcasses glowing in the woods at night (always either green like foxfire or an odd almost monochromatic cyan that must really stimulate the eye's rod cells).

It's very faint and would be difficult to notice without trees to shield it from moonlight. A camera could pick it up with a long exposure.

Thanks, I hadn't known about this effect. Apparently it's been known for a long time. In the 1600's, Robert Boyle claimed to have been able to read an issue of The Philosophical Transactions by the light of a rotting Neck of Veal: https://blogs.royalsociety.org/publishing/boyle-and-biolumin...

Hmm, I can't find any research about spoiled food being bio luminescent, you say "bacteria breaking down food produce light", but experience seems to suggest lots of food spoilage is due to fungi (molds). Though it'd be fun to see lactobacteria in pickles or kimchi glowing...

On a similar note, it would be nice if some of the drawers of the fridge had red LED lights to keep leafy greens photosynthesizing, to keep them green.

Can you link to some research on that? I'd love to throw together a hack where you use LED light strips to do this. Isn't it possible that the light would increase bacteria though? https://biology.stackexchange.com/questions/66878/blue-light...

I'm sadly unable to find the original study where I found this. If memory serves me it was from around 2003.

Not sure how it would increase bacteria, as bacteria don't photosynthesis light, unless the lights gave off sufficient heat to increase their activity. If anything I would think the light might inhibit bacterial growth.

Cyanobacteria, purple sulfur bacteria, and I forget another type, those all undergo photosynthesis

I stand corrected! Are any of those likely to be found on vegetables, and break them down?

This is really interesting. I'm tempted to attach red LEDs to a battery and put it in the fridge. But it would be quite tricky to measure whether it works. (Almost impossible to do accurately, without different fridges.)

Put two cardboard boxes in a fridge. Put a leaf of lettuce in each, and a red LED in the top of each box.

Turn one LED on, while the other stays off.

Observe the leaves of lettuce after a week.

I never knew I wanted a "smart" fridge, but a fridge that can detect food going off sounds incredible. Sign me up if this is feasible.

A fridge that prevents food going off would be better, no? That wouldn't require smarts, just replacing the air with pure nitrogen, like modern grain silos do. Doing it at "consumer scale" would probably only require the same sort of compressor that your fridge already uses for its cooling.

There are some really low-tech things you can do to extend the life of things in the fridge. At least for vegetables, you can stick them in one of the fabric bags, add water, and they'll survive for weeks. And that costs just a few bucks.

For meat we've got freezers. Is ready food going spoiled a big issue?

Chemical reactions by bacteria breaking down food produce light, enough for humans to see in only the darkest of places (if you live in a city, you won't ever encounter dark enough situations).

Some city folk have doors and window shades. My old apartment kitchen was on the windowless side of the apartment with a door. If you close the door (and unplug the microwave), it was pitch black. Though I never saw any glowing food, not even the spoiling fruit on the counter.

I have the same kitchen setup. I develop film in there with the door closed. Nothing has ever looked fogged.

(I'm talking about developing sheet film in trays, btw... you don't need a darkroom to develop rolls or 4x5 sheets.)

It would be really interesting to then display this on the screen of smart refrigerators. Maybe you could even flag food that is above a certain brightness as spoiled.

Or rfid tag everything and add a scale so that your fridge can tell when you're out of items or low on milk! Would potentially make recycling easier too

I used to help teach a undergraduate senior design course, and the number of students who want to do exactly this is staggering.

I don't know if its really that bad of an idea, but we didn't allow projects that had been done before so they were all rejected.

Really, you can predict goods spoilage just given how old stuff is. You don't need a smart fridge; you just need an ETL pipeline from a ScanSnap (reading in your grocery-store receipts) to an inventory tracker app. You've got "smarts", but they're not in the fridge.

(And in the end, that's better: an inventory-tracker app that's on your phone is able to tell you to throw stuff out without you needing to own a "smart-home hub" or configure your fridge to connect to your wi-fi; and, unlike the fridge, its notifications will probably keep working even if its manufacturer goes out of business.)

I can't recall where I came across this idea but how about fridge shelves that (like mini moving sidewalks) slowly move food towards an edge to drop to a lower shelf and eventually to a composter or trash -- the idea being to put food items at a certain spot on a given shelf based on items' expiration date. Wildly impractical IRL, but clever enough to be memorable (for me anyway).

https://xkcd.com/1109/

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