I go camping with my son’s scout troop and I want the boys to start making stews, either at home to take or while at the camp. I want to deep freeze the food so that it can be packed and stay out of the temperature danger zone until cooked. I do not have a deep freezer but I heard that a I could do the equivalent and transport it with dry ice. And yes, I know about dry ice and ventalation and that having dry ice in a closed environment like a car with the windows rolled up can result in a severe case of death.
How would the Dopers use a styrofoam ice chest and dry ice (along with anything else that might be necessary like a heat sink or filler or whatever) to make a campfood freezer. Oh and would freezing in liquid nitrogen then packing it be a better option since it is so quick? How quickly would something frozen in N2 defront in or out of the cooler?
I would just pack the food in the cooler with dry ice and not use any filler material.
But if I had access and wanted to spend some money I would place the food and dry ice in a styrofoam cooler and fill it with alcohol, acetone or some other liquid that won’t freeze at those temperatures. THe good thermal contact by the extremely cold liquid will freeze you food faster (but not colder). Then I would dump out the liquid because I wouldn’t want to carry it around.
Dry ice in alcohol or acetone is a common way scientific cold traps are set up.
You can use liquid nitrogen too, but I really think that would require a lot of liquid nitrogen to cool it down.
Actually, what I would do is just use 2 liter bottles stuck in the freezer. then stick those in the cooler. That coupled with choosing appropriate food that won’t require more than a week of freezing is the most logical thing to do. I can’t imagine a boy scout case where you would need more than just a few days of cooled food.
Changing water from liquid to ice requires removing a LOT of thermal energy. If you assume that your food item is mostly water (a safe assumption), then changing it from a liquid at 32 F to ice at 32 F requires removing X amount of thermal energy. If you then cool it down to -112F, you have removed an additional X amount of energy.
Liquid nitrogen boils at -320F, so you end up removing several X more energy. However, with the food item this cold, heat transfer from the environment will happen at a much more rapid rate: it won’t take very long for the item to come back up to 32F and begin thawing. A heat sink ((e.g. a big lump of cast iron) doesn’t help nearly as much as having an item that requires a phase change before it can heat up. Ice fits the bill nicely: it takes a lot of energy to melt a block of ice, and since its at 32F (instead of -320 F), the heat transfer doesn’t happen all that quickly.
Dry ice and a styrofoam cooler seems to work well for keeping food reliably frozen solid for extended periods. Some companies ship food this way. A few years ago we bought some stuff from Omaha Steaks, and it arrived in a styrofoam cocoon with a lump of dry ice. Everything was still frozen, despite a shipping time of a couple of days. In this situation, it’s important to keep the meat frozen, because freeze-thaw cycles are bad for quality.
That said, dry ice for a weekend at scout camp seems like a logistical hassle, and I wonder if it’s really worth the trouble. When I was a kid my family and I went on cross-country camping trips, and Mom routinely kept various raw food items in an ice chest for a couple of days before cooking them. Never a problem. I would suggest the same for your boy: freeze the stew meat in your home freezer, put it at the bottom of an ice chest with ice on top of it, and then put the other stew ingredients above the ice.
I have always been able to get several days out of a standard cooler with ice. Leave it out of the sun and don’t open it except when you really need to. Styrofoam coolers just don’t compare well to the double-walled plastic variety that someone else has already linked to.
I will often put drinks in a separate cooler from food. The drinks cooler will probably run out of ice first because we’re always going in and out of it. However, most drinks don’t spoil. We may have to put up with warm soda, but we won’t be dealing with spoiled mayo.
When my family would do week-long trips, we added another cooler with dry ice to supplement some regular ice. This was for food that we wouldn’t access until the contents of the regular-ice cooler were eaten up. Since it wasn’t for immediate access, much of the food (meats and such) in that extra cooler were already frozen when we put them in there.
Yeah… I do actually know that, but I keep saying mayo as a general substitute for things that spoil quickly. It’s a stereotype, but it’s also because of that semi-clear, gelatinous phase mayo can reach when it’s been left out for a while. Safe or not, just the sight of - or even the thought - of that makes me ill.