Stock bomb

[Blether]

So what's this thing where you put a half-full pot of strained chicken stock over a high flame so you can reduce it, and after a couple of minutes, without warning it violently boils all at once and 3/4 of the stock throws itself all over your stove and kitchen ? Is this sort of behaviour USDA approved or what ? I am now officially pissed

[Mjx]

What?! What exactly did you do? I want to try this, now.

[annabelle]

I was hoping you were going to make fun of Marco Pierre White who is selling Knorr stock "blobs" on the teevee.

[Blether]

After life made such fun of me, I've barely the heart

Procedure:

- Buy usual-sized chunk of frozen chicken carcasses & necks - about 2kgs

- bring it home to discover the new pressure cooker is enough smaller than the stock pot that it'll have to be two batches

- make one batch last night, taste & find a little weak, refrigerate

- make second batch today, strain, wash pressure cooker

- return strained stock to PC, add refrigerated stock from yesterday. At this point, PC is 2/3 or 3/4 full. The lid is off now, of course

- put on high gas flame, walk away across room for like 20 seconds

- stock erupts violently, puts out flame, forms expanding puddle on floor, inundates under-stove cabinet

- clean floor, cabinet, stove, etc.. Pot now half full.... (wait for it)

- put pot on stove again while finishing washing up

- after about a minute it happens again

- clean etc.

- stock not concentrated in flavour, but reduced enough to fit not in the planned 2 containers, but only one. With room to spare.

- put thin stock in fridge and give up cooking forever tonight

10 o'clock on a Sunday night - you think you'll just cook that stock down before bed, then suddenly it's midnight, you're sweating like a pig in the unseasonal heat and you've gained as much as you would have by throwing your stock out of the window. Sweet.

[annabelle]

Hey, stuff happens. I have lovingly prepared stock and then strained it through a colander---directly down the drain instead of ito the container that was sitting on the countertop.

[Robert Jueneman]

ROTFLMAO! Sorry.

This sounds like what happens when I microwave a can of chile and it spatters everything. Some kind of localized boiling is taking place, obviously. But you said that the stock was too thin, so that doesn't make much sense.

Hmm. Had you degreased the stock after pressure cooking it? If not, perhaps there is a oil/water mixture, and somehow the water would begin to boil, but the oil would not. But the oil might keep the bubble from bursting for a while, until the steam pressure increases and goes supercritical. Then BOOM!

But this is purely speculation.

A watched (or at least stirred) pot never boils!

Assuming you haven't forsworn cooking entirely, the next time you try this, I would chill the pressure cooked stock, then skim off the congealed fat before reducing it.

But on a slightly different subject, what are the pros and cons of sous vide stock making vs. pressure cooking? I'm working with a professional chef for my forthcoming Modernist Cuisine class, and he suggested foie gras consumme, His recommended approach was to cook the legs and thighs sous vide at about 70C for 12 hours with about 2 oz of chicken stock per pound of chicken. I've done that, but haven't yet degreased or fined it, but it didn't make very much consumme -- I think i may have to add more stock before I add the foie gras, but I have't tasted it yet.

[pastrygirl]

Do you routinely boil in the pressure cooker without the lid? I wonder if the shape of the vessel has something to do with it, assuming the pressure cooker does not have straight sides like a regular stock pot.

[gfweb]

Here's what happened, I think. The cold stock has a lot more dissolved gasses in it since cold liquid holds more gas. ( PV+nRT for the chemists). When heated it gives up the excess gas fast and boils over.

The trick would be to heat it slowly.

[ermintrude]

Had the stock jelled due to the gelatine extracted. So heating from cold, the bottom portion melts, then turns to steam and the pressure launches the rest up and out all over the stove top etc?

[slkinsey]

I've had weird, violent boiling behavior when reducing osmazome. I wonder if it has to do with % of some dissolved substance.

[ChrisTaylor]

Had the stock jelled due to the gelatine extracted. So heating from cold, the bottom portion melts, then turns to steam and the pressure launches the rest up and out all over the stove top etc?

I'm going to put my money on this. Stir the stock as you heat it gently.

[Blether]

I guess I'll take away from this, that exploding chicken stock isn't all that common.

It's a very normal, straight-sided Aluminium-bottomed pot; the first batch of stock had gelled a bit but much, still being on the weak side, and the second time apart from being violently stirred once the combined stock had sat about for the best part of an hour; not much fat on the stock and not much in the fixings (no skin, this time). There isn't really a "routinely" here, though, since the PC's still quite new.

I have to say the way it went off - like a geyser - was more like some kind of super-saturated gas release than any ordinary boiling, though what/how I can't imagine.

I did have fun reading up on osmazome. Thanks for that, Sam.

[scubadoo97]

Hey, stuff happens. I have lovingly prepared stock and then strained it through a colander---directly down the drain instead of ito the container that was sitting on the countertop.

I've done that once. Hopefully only once

Never had the exploding stock scenario. Not sure why that would happen. It's not super heated like in a microwave

[scott123]

Superheating

[slkinsey]

I did have fun reading up on osmazome. Thanks for that, Sam.

Also known as meat juices from the sous vide bag. This stuff definitely exhibits strange boiling behavior similar to what you describe: very little activity, then violent localized bubbling, then back down to very little activity, etc. This is true across a range of starting temperatures, and generally speaking I am only using small volumes.

[Eastgate]

This phenomenon is familiar to all bench chemists, though you seldom see itin e kitchen. Chemists call is "knocking", and it's a real hazard. In this cad, it's a tribute to the clarity of your stock and the cleanness of your cooking vessel.

The underlying science is a little were. As you know, liquids boil -- changing from fluid to vapor. It turns out that, of you heat a solution, it can run past te boiling point like Wiley Coyote running over a cliff, and not notice where it is. The vapor bubbles don't form right away, and then when they DO form, whoosh!

Vapor bubbles like to form at scratches in your cookware, or at little suspended articles floating in the solution. Chemists -- who tend to like pristine Pyrex and dislike random particulates -- add a piece of ground glass called a "boiling chip" to avoid bumping. It's not common in the kitchen, but I've seen it once or twice on the stove, and more often in the microwave.

A contrary case happens when you're making caramel or brittle and --oops!-- suddenly your lovely liquid caramel turns into a pot of brown sugar! Here, you had a supersaturated solution that didn't know it as supposed to crystallize, and if things had gone according to plan, you wouldn't have told it until it was too cold to do anything about it. But sometimes the sugar gets ahead of you and you get a pot of hot rock candy

[alex james]

I've had the same problem with chicken stock. Not to the extent of it ending up all over the shop but violent bubbling which is mildly annoying.

It only seems to occur with me when reducing filtered, defatted and otherwise finished stock. What I do not understand is why I've never had the same problem with beef stock. Might it be a difference in particle size?