Microbiologist Investigates After Her Beef Soup Turned Blue in the Fridge | Hacker News Reader

Microbiologist Investigates After Her Beef Soup Turned Blue in the Fridge

iflscience.com

104 pointsnotamy45 comments

The Hibiscus tea I use turns blue when I steep it at my mom's place, but not at mine. I have a very good water filter, she does not. First time it happened, I was quite startled. She had a filter at her place she never used, so we tried it. Yep, filtered water resulted in pinkish tea.

What's in the water is unclear, but there was a lingering unease related to it.

The water in your mom's place is probably a bit acidic if I had to guess, and the filter removes the ions

Shouldn't it turn red if it's acidic and blue if it's basic?

Yes.

Also, it is my understanding that calcium in water (which is a normal part due to the water taking up minerals in the ground) is making it slightly basic. I don't know enough about chemistry in this area, but I think the calcium in the water is mostly calcium carbonate, which definitely is basic[1]. So it's no surprise that water taken directly from the tap is making the tea blue, but after removing the calcium carbonate (maybe as part of a removal of any salts) that the tea remains red. I think this hints that an ion exchanger[2] is being used in the "very good water filter" e40 is using.

But removing calcium from water (along with other potentially beneficial minerals) is a bad idea, because we need it for building our bones etc. Hopefully those using ion exchanger are still getting enough calcium from other sources. But it's long been said that ion exchangers should not be used to "filter" water.

[1] https://en.wikipedia.org/wiki/Calcium_carbonate [2] https://en.wikipedia.org/wiki/Ion_exchanger

PS. you can put some drops of lemon juice into your tea and it will shine red :) (and have a nicer taste)

That might be iron actually, somehow. I once cut a banana with a carbon steel machette and it turned blue.

If you pardon my intrusion, may I inquire why were you using a machete to cut a banana?

It's been a couple years (or more), I think I was just fucking around with a newly sharpened machette. Also I never managed to replicate it, though perhaps for lack of trying.

I remember a grade school science experiment where something about moisture or humidity caused a color change from blue to pink (or vice versa?).

I think the important bit was cobalt chloride. Doesn't sound like an ingredient in hibiscus tea though!

silica dessicant. chemists use it in their dessicators to keep things dry - pink is dry, blue is 'full' (i think, it's been 25 years...). i think it's a low level cobalt doping and as the silica matrix swells with water absorption it changes the UV absorption and the colour changes. or something like that.

There are lots of people that love to mock those that prefer bottled water. https://xkcd.com/1599/

I’ve lived in lots of areas were the water burned going down. One place were water was just brown. Filtered leaves it weirdly bland. But acceptable for coffee / tea.

Hibiscus is a litmus indicator. Blue means your water is basic. That specific thing is how I make blue hibiscus pancakes.

Many flower petals can be made into a pH indicator.

Wikihow: How to Make an Indicator for Acids and Bases Using Hibiscus Petals

https://www.wikihow.com/Make-an-Indicator-Using-Hibiscus-Pet...

You can also use red cabbage water

Litmus itself comes from plants. (Lichens)

There could be something in the filter. A good test would be to make one tea with distilled water, and another with distilled+filtered water. Compare the colour.

Since nobody has linked to that yet: anthocyanins are sensitive to pH and can be found in a lot of things: https://en.wikipedia.org/wiki/Anthocyanin

This. Should have called a botanist not a microbiologist. That just looks like red cabbage was in there, shame there is no talk of other ingredients.

> If it turns out that the pigment is caused by P. aeruginosa, they would have to stop working on the blue soup due to its infectious nature.

microbiologists work with much more dangerous organisms than pseudomonas all the time. speaking as an ex microbiologist.

Not a migrobiologist, but I understand that labs are equipped with progressively more stringent procedures depending on the type of material they can handle.

They may work in a very regular, run of the mill lab that is not equipped to deal with anything that is even remotely dangerous.

And seeing they have only nitrile gloves for protection and everything lays on the table it looks like this is likely the case. (Not that I ever worked in a lab. My ideas of how lab safety works are based on The Andromeda Strain).

pseudomonas is a very common urinary tract infection, along with e.coli and proteus, none of which commonly cause deaths. it is not particularly dangerous. using common sense and basic aseptic technique will keep you safe.

back when (early to late 70s) we did not use gloves at all, because they were uncomfortable - just washed our hands a lot. nobody ever died or got infected. before i joined, someone did die from the hepatitis virus. we were not a virology lab, but we did do immunology, which is where the blood that caused the death came from - we did use gloves when dealing with that.

for the more dangerous organisms, such as mycobacterium tuberculosis, we used air extraction hoods.

i think pseudomonas still qualifies as bsl2 nowadays

this is why we can't have nice things

ok, i looked that up. i really don't believe ppe does anything useful, i have never seen any double-blind tests that suggests it does. pseudomonas clings to the petri dish agar medium and will not get on your body unless you do something very silly.

one way of diagnosing bacterial infections is by smell. for example, if you put your nose next to an agar plate where haemophilus influenzae is growing, you get a very characteristic smell. there are other smells. i have never heard of any microbiologist contracting an infection doing this.

too much snowflake stuff here. the most scary thing that happened to me was not dealing with the bacteria, but the reagents and stains we used. i was making up some gram stain (basically iodine and NaOH in solution) when i added the water to the two solids - result steam explosion (because NaOH + H2O is exothermic) in my face. my thought was "shit, you have blinded yourself" but luckily there was an eye-wash bottle and a sink next to me, so my eyes survived. why i did this i have no idea, as i had been taught from the age of 15 to always add solids to water.

anyway, so bugger bacteria - chemicals (and steam, electricity etc.) much more dangerous.

there's a reason progress is so much slower now than it was 50 years ago, and it's not that we don't have enough scientists or enough papers

Do you believe parachutes do anything useful when jumping out of a plane? Do you have a double blind study that proves it?

yes, i do belive that - there is clear and obvious evidence. there is no clear and obvious evidence that ppe (plastic aprons, masks) does anything. which is why we need a double blind trial.

i spent all my time as a microbiologist using only a white cotton lab coat (mostly for writing nurses/docs phone numbers on) , and often not that. nobody i have ever known that worked as a microbiologist has ever caught an infection. as i said elsewhere, reasonable common sense and aseptic technique does the job.

A reply this comment asked: "Do you believe parachutes do anything useful when jumping out of a plane? Do you have a double blind study that proves it?"

A randomised controlled trial:

https://www.bmj.com/content/363/bmj.k5094

Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention. However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps.

the biologist from the blog post literally got the bacteria all over her arm when collecting the sample

We're all human. "unless you do something very silly" is literally what the safety rules are for

> unless you do something very silly.

DO NOT LICK THE SCIENCE! For the sake of the world, please do not!

https://ivanteh-runningman.blogspot.com/2021/03/can-you-lick...

Pseudomonas is a dangerous UTI actually

the only sensitivity spectrum looks like this: (1) fluoroquinolones (severe neurological and connective tissue side effects) (2) IV tazobactam + piperacillin (3) IV ceftazidime

If you're not in life threatening danger they will default to (1) which is a serious detriment to society and not adequately risk assessed. At least, this is how it was in 2014 when I was rendered disabled due to fluoroquinolone toxicity. It is possible because of public outrage over fluoroquinolones that the order has since changed but yeah. Nasty.

Yes, but they won't have done a risk assessment for it. As you will know, microbiologists are supposed to have risk assessments for precisely what they're doing; as you will also know, they are often pretty approximate about it; but in the case of work documented in a virally popular Twitter thread, it would probably be sensible to be seen following the rules.

Was there garlic in the soup? Garlic can turn green or blue when cooking depending on the ingredients involved. I assume the bright blue photo in the article isn’t an actual picture of the soup in question.

There’s an actual picture in an embedded tweet further along the article.

https://mobile.twitter.com/bielleogy/status/1630811835527213...

There was no garlic in the soup. There are links to the twitter thread although most of the interesting tweets are shown in the article as well.

It really peeves me how often articles use unrelated stock photos for their hero image, often without even noting it.

Once in 1991 I left some cooked rice in a pot in the kitchen. The next day, it was covered with a bright violet slime. I don't know what it was, but I still remember it vividly (as the colour was).

Possibly b. cereus

There's no reason to assume he's not being serious.

It's probably due to climate change.

Instead of Beef Soup, she should be eating Insect Soup. Most likely, it wouldn't have turned blue.

Few years ago there was a case in my country where store bought ham/sausage glowed in the dark:

https://youtu.be/WgsBF9jzDEw

"Don't it make my brown eyes^H^H^H^Hsoup blue."

My stomach turned at "meat soup." What is that?

     Oh, you don't want to hear about that. They lined us up in front of a hundred yards of prime rib. All of us, you know, lined up lookin' at it. Magnificent meat, really! Beautifully marbled. Magnific. Next thing, they're throwin' the meat into these big cauldrons. All of it! Boiling it! I looked inside, man, it was turning grey.

Soup with beef in it is relatively common in the two places I've lived - UK and Czech Republic. Couple of very common examples of "beef soup" from each:

https://www.bbcgoodfood.com/recipes/oxtail-soup

https://www.daringgourmet.com/traditional-scotch-broth/

https://www.angusfarm.cz/recepty/hovezi-vyvar-698/

http://www.pradobroty.cz/2019/03/gulasova-polevka.html

I think what the saucier in your quote[0] was upset about was cooking good quality meat very badly, not the idea that meat generally could be used in soup :)

[0] - for those who don't know, it's this scene: https://www.youtube.com/watch?v=YbFvAaO9j8M

It's definitely an odd phrase.

"Beef stew" is the normal way to say it. Is "beef soup" a common expression somewhere for the same thing, or is it something different?

I don't know what your quote has to do with anything though. Beef stew is the perfect use for tough cuts, simmered for hours.

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