Dry ice for rapid cooling of stocks and other food items

[paulkaye]

Has anyone tried using dry ice for rapid cooling of stock or other food items? I am looking at starting a food business where the customers are particularly vulnerable to disease and, as a scientist, I'm paranoid about bacteria.

The bottle-of-ice idea sounds great but I'd be worried about contamination (yes, it could be washed but...).  My current thought is to put the giant pot of stock (or small containers of finished product) in a water bath containing dry ice. This would prevent any contact between potentially contaminated items and the cooling food. A ladle in simmering stock will be virtually sterilised. But once the food starts to cool it's best to have nothing touch it. I'm waiting for price quotes and delivery options for the dry ice but, in the meantime, I wondered if anyone had any experience with this.

Thanks in advance,

Paul
 

 

[benway]

I'm not sure I understand.  Right after the stock is cooked you're worried about contamination?  Or are you looking to decontaminate it for storage?  A lot of kitchens store their weeks worth of stock a few gallons at a time in the freezer.  I don't see the merit of freezing a little quicker and a lot more expensively in dry ice.

As a scientist you must know that a dry ice/water bath won't be any colder than 0 C. 

 

[paulkaye]

Yes, at any point after the stock (or any food) comes off the heat, I'd be extra-careful about potential contamination. That means I'd prefer to touch the food directly as little as possible. Placing the stock-pot or closed final food containers in an ice bath should bring the temperature down quicker than in the air and safer than in the fridge but without having to purchase a blast-chiller (or whatever they're called). Dry ice is more convenient (less messy, lighter, colder) than regular ice - I just wondered if anyone had experience in doing something like this. If the costs are, indeed, too high then I wouldn't do it but I'm interested to hear, nonetheless.

 

[chefedb]

For all the money you are going to spend for ice , buy yourself a quick chiller machine.. Its better and cleaner, and as far as covering a hot item and chilling ? I don't think so. Dry ice here is about $ 1.60 a pound

 

[chefbillyb]

Never used dry ice to cool, we do a ice bath on large stock pots or large pots of Chili, clam chowder, whatever. The other way is to break it down into small containers to cool............Chef BillyB

 

[tamtam39]

I tried dry ice before and it works well, especially when chilling some seafood, meat, veggies in an ice box. Can last long. Works for picnics and outing stuff. Just be careful, cause dry ice can burn your skin. 

 

[paulkaye]

I guess a lot will depend on the price and I'm still waiting to hear about that (as well as reliable supply). If I go ahead I'll post the results here. Thanks for all your thoughts.

 

[mycroftt]

You can only chill water to 32 degrees whether it is being chilled by water ice or dry ice. Adding salt will allow the water to get somewhat colder. Placing dry ice in water causes the dry ice to become coated with a layer of water ice which will be 32 degrees (or somewhat colder if you salted the water).  I doubt using dry ice in salt water would cause a significant reduction in cooling rate. 

If you wanted to test it use identical amounts of water heated to the same temperature in identical pots and dunk each into its respective water bath. Use an instant-read thermometer to check the temperatures every couple of minutes.

 

[boar_d_laze]

As an economic proposition, the best method is probably to divide the stock into smaller "portions," and place their respective containers in an ice/water slurry. 

The thermal efficiency of the slurry combined with the surface area/volume ratios of smaller containers will outwork dry ice -- especially for the money.  Dry ice in water just won't last long enough, I'm afraid.  Partly because a lot will "boil" off as fog. 

Salt won't help you enough to make that much of a difference, as you're not really going to super-cool a slurry much.  It's not quite like making ice cream where you're trying to retard the phase shift on the ice.  On the other hand, it will super-cool by a few degrees and, as we say, "it couldn't hurt."

Don't forget that you can "can" into sterilized containers and avoid the necessity of chilling at all. 

I find it hard to believe that safe cooling rates for soups has not been extensively studied.  My educated guess is that despite the sensitivity of your chosen customer group, you're looking into serious and expensive overkill.  Don't reinvent the wheel. 

Good luck,

BDL

 

[pete]

Sorry, but this sounds like serious overkill.  I understand wanting to keep your stock as contaminant free as possible, but using standard methods will keep things safe.  Then, on top of that, you are probably reheating both stocks and soups well above 165, high enough to kill off most all microbes.

 

[paulkaye]

I'm starting to think you're right. The price isn't obscene but I need to plan delivery in advance, whereas ice is available more locally and immediately. The mess of melting ice is annoying but I think I'll have to deal with it.

Thanks to everyone for your comments.
Paul

 

[boar_d_laze]

Mess? 

Schelpp the stock pot to your sink.  Or, transfer the stock to smaller containers.  Because of the ratio of surface area to volume, smaller containers will cool much quicker.

Put a LOT of ice in the sink with ice.  Add cold water a few inches from the top of the sink to make an ice water slurry.  When the ice melts, add more ice so the liquid level rises to the top of the sink.  When done, drain the sink.

No mess!

BDL

 

[petemccracken]

...The bottle-of-ice idea sounds great but I'd be worried about contamination (yes, it could be washed but...). ...
Paul
 

If you are contemplating a "food production business", you are probably very familiar with the Food Code, or soon will be, and you will understand that "contamination" is one of the foremost concerns for "food production facilities". That is why a "triple sink" system is MANDATED for warewashing, Wash, Rinse, Sanitize. As long as you wash, rinse, and sanitize the "bottle of ice" container after each use, there should not be a contamination problem.

Keys to cooling soups, stocks, and other liquids in food production:

• Keep it shallow
• Cool within two (2) hours to under 70°F.
• Chill to under 41°F. within the next four (4) hours

Then again, you COULD purchase a "Blast Chiller", if you've got the $$$$ /img/vbsmilies/smilies/crazy.gif

 

[titomike]

Obviously everything posted above is correct so the issue is more about you feeling comfortable about the method you choose.

Perhaps you should try several methods, take samples and get them tested. If the differences are negligible as we would expect you are free to confidently choose the most practical and put the 'first-time mum' feelings to bed.

Otherwise specialised operations with particular concerns require specialised equipment......like a 'blast chiller'.

 

[foodpump]

Dry ice is expensive, needs airtight containers to be stored in, and can burn your skin if you're not carefull.  Other than that, it works very well.

You want to cool down your stock in a hurry.  I applaud you.

Go to a restaurant supply store and buy a special item for this.  It looks like a bottle with four pronounced "wings".  Comes in a few sizes.  Said bottle is washed in the dishwasher, filled with water, capped, and frozen solid prior to cooling the stock.  Fill up your sink or other container with cold water/ice, set in your hot pot of stock, drop in the frozen water bottle.  Every now and then give the bottle a swish.  Within half an hour your stock will be cold enough (around 10 Celcius) to put into the fridge safely.

Bonuses of this system:  You only buy the bottle once, it can be washed and sanitzed for many years to come, in combination with a cold water/ice bath it will cool down your stock very quickly, and  the system is recognized and endorsed by many health officials

O.t.o.h, if you're cheap, like me, save up your 1 gallon plastic milk jugs or 2 l Coke bottles, run them through the dishwasher, fillup with water, cap, and freeze.  Not as much surface area as the "winged" water bottles, but very effective and cheap.....