Three week out of date coleslaw juice

[MicroPunter]

I found a tub of coleslaw in the fridge, it was three weeks past its use by date. Instead of eating it I put some of the liquid in the tub under the microscope. Needless to say, I decided not to eat it. I’m not a bacteriologist but I think the movement seen here can’t be due to Brownian Motion or capillary action, it must be bacteria, it certainly didn’t smell very good.

This was my first time using oil immersion. Having watched a few YouTube videos on oil immersion, I was a little nervous but it was okay. No objectives were harmed in the making of this clip.

Microscope used: Swift SW380T
Objective: 100x using oil immersion
Camera: 5 megapixel SwiftCam

Kevin

[DonSchaeffer]

You are probably right to worry. lol

[thomasfrank]

I can see clearly those movements indeed appear indicative of bacterial activity,pokedoku making it a wise choice to avoid this juice.

[einman]

Having microscopy as a hobby makes you worry about a lot of things! LOL

Like swallowing water while swimming in a lake or river etc..

[MicroPunter]

Therefore, if anything is past its expiration date, it should not be used. Everything under the microscope makes us worry about our health gorilla tag

I’ve become a little paranoid about ‘best by’ dates and keeping everything in the fridge, even the things I’d previously just have kept in the cupboard, like tomato ketchup.

Having microscopy as a hobby makes you worry about a lot of things! LOL

Like swallowing water while swimming in a lake or river etc..

A friend of mine is a mad keen river/sea/cold water swimmer. She’s asked me not to share anything with her. It makes me glad I never learnt to swim!

[apochronaut]

Actually, coleslaw is the beginning stage of sauerkraut and kim chee. The idea with coleslaw though, is that it should not ferment or be only very slightly fermented. A bbd for coleslaw is not based on health concerns, it is based on it's quality as a coleslaw. If left to it's own devices , coleslaw will gracefully ferment into a version of sauerkraut.
Where this can go off the rails is that commercially prepared coleslaw is usually doctored with one or more preservatives to extend it's unfermented life as coleslaw. The preservatives, benzoate of soda, potassium sorbate and or a metabisulphite are selective, so some of the beneficial organisms that would normally take hold in fermenting coleslaw are inhibited whereas others not so much. This allows opportunistic yeasts or more undesirable bacteria that are more resistant to the preservatives to dominate the fermentation leadjng to off aromas and flavours.
The condition would be different, depending on whether the product was opened or not. Many of the undesirables are oxygen dependent, so will proliferate at the surface; bacteria, yeasta and molds. Down in the liquid, the population of species would be more akin to what one would find in old kim chee.

Traditionally, kim chee is made in the fall and kept in clay pots in the ground until into the following summer or later. It goes through stages of maturation until it's ultimate end as soup. Generations of Korean children will attest to their aversion to the summer holidays, when they would have to use up the last of the skimmed kim chee in soup. The solution to this is to stir the kim chee regularly, bringing CO2 rich brine to the surface and submerging any developing oxygen obligates.
Unopened, a commercial coleslaw would probably eventually swell with CO2, indicating that some sort of fermentation had begun..

There really isn't much to fear from this type of product, it is far from dangerous, unless left too long and in a state of putrefaction. Most bbd's are gustatory in nature. Note that it is best before, not it will kill you if you eat it after.
A yogourt bbd for instance has nothing to do with the yogourt. It has to do with the commercial milk supply being riddled with psychrotrophic bacteria amongst other forrigners, which are spore bearers and can survive pasteurization in the spore stage. They proliferate in both fresh and pasteurized milk and yogourt, eventually releasing chemicals that turn the product clabbered and bitter. That is one reason it is so hard to make really good raw milk cheese. The psychrotrophs take over even more quickly, turning the young cheese bitter. Only very special herds can supply raw milk cheese makers and the herds need to be kept isolated from commercial herds which are usually part of a contaminating milk pool. Tanks and trucks even need to be kept separate and sterilized between fillings.
All of these problems are not really caused by naturally occuring processes. They are the result of humans monkeying with the system in the aid of convenience and profit. There should be no psychrotrophs in cow's milk. It is just that they are survivors and can withstand extreme conditions such as deep refrigeration and industrial cleaning agents, both of which turned the environment of the dairy system into a hostile environment for a cow's naturally occuring flora. Psychrotrophs, which are putrefactive bacteria, without the aid of chemistry and anti-biotics would not survive as flora in a cow.
All that said, bitter dairy is not a death sentence : that's why regulators turned a blind eye to it's emergence, because up until the 1950's it didn't exist. If you left a pail of milk in the barn in mid-summer 2 things would happen.The cream would rise to the top at about 22% butter fat and in a couple of days, turn into wholesome kefir, or
" curds and whey".What little miss muffet was eating was delicious, not horrible. The 22% +- butter fat on top would be sour cream, also delicious and not horrible. If collected fast enough, i.e. the following morning, the 22% is the basis for ice cream. Churned you would get more, 35 or 40% for whipping cream and cut in half with separated milk you would get half and half or roughly 10% cream.That's why these all exist today but performed industrially and pasteurized , in order to stave off the psychrotrophs as long as possible. They are in probably 98% of the milk.
Anyway, psychrotroph or not, all of it makes for excellent microscopy, and with dairy, phase contrast is king.

[MichaelG.]

WARNING:

When coleslaw or any similar food product reaches its expiration date, it's a good idea to err on the side of caution and discard it. Signs of spoilage may include off smells, changes in color or texture, or the presence of mold.
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