So Mrs. kdeus just bought 25 lbs of flour [Kirk]“COSTCOOO!!!”[/Kirk]. This is a few months supply. The flour will be stored in a (theoretically) airtight box. My neighbor and I had the following Brilliant Idea, and I would like to know what, if any, flaws exist in our plan.
The plan: Throw a (little) block of dry ice in the bottom of the container before you add the flour. The CO2 sublimates, permeating the flour with gaseous CO2, killing anything currently in it and discouraging infestation. Since the box has the lid on top and is theoretically air-tight, the gaseous CO2 should stay there for a long time. And since dry ice is cheap (right?) it is actually worth it to preserve about US$5 worth of flour.
And yes, I’d wait until the block sublimated before sealing. Although it might be worth seeing the floury “pop” in your kitchen.
So, Dopers: (1) Brilliant (2) Daft or (3) Other. Thanks!
Couldn’t you use a container that is bugtight, but not airtight? Something with a porous membrane or a tiny duct to let gas (such as sublimated CO2) escape, but that won’t permit bugs to enter the container? The CO2 would lay waste to any currently living thing in the flour, and then after that it’s OK for it to diffuse out, since the container itself would prevent trespass by new bugs.
Don’t throw it in on a humid day. Dry ice is colder than regular ice, after all, so it’ll collect a coating of water that will freeze into water ice. Anything that gets cold from contact with the dry ice (flour) can collect water and ice as well.
Eventually the dry ice completely sublimes and everything warms up. Any real ice melts into water. mixes with the flour, and creates paste. Have fun getting that off.
You could just fill the box with carbon dioxide gas. Or dry nitrogen, for that matter. But I admit it doesn’t sound like as much fun.
Since that, the CO[sub]2[/sub] will build up pressure until it either pops the lid off, or causes the box to explode.
Put the lid on loosely, and wait for the dry ice to sublimate before closing things up tight.
Ah! A subject on which I have a had a lot of practice. A “bug-tight” container doesn’t really work because the flour will possibly contain some eggs already.
But regardless of that issue, the problem here is that the oxygen in the air is going to cause that flour to slowly oxidize or go stale. So keeping it in an airtight container is a good idea, because once all of the oxygen that was in the container chemically bonds to the starches in the flour, you are left with nothing to further the process. The process is slow (and sometimes desireable in small amounts for bread making and exposure of proteins / gluten in the flour). But they make five gallon buckets with sealing lids for exactly this purpose.
So your dry ice / CO2 idea is a good one. Since CO2 is heavier than air, you also benefit from that fact, although sublimating the dry ice and then pouring in the flour is counter-productive because the majority of the CO2 is going to get pushed out of the container.
So here is what you want to do: Fill your bucket / container half full of flour. Place a chunk of CO2 in the flour, cover with the rest of your flour, and put the lid on LOOSELY. Give it some time to sublimate. Seal the lid using a rubber mallet. You should now be good to go for several years. I recently opened a bucket I sealed in this manner in 2005, and the flour was still nice and fresh (and made some lovely sourdough).
You can also use oxygen-absorbing packets or flush with nitrogen (welding shop will have this), but these methods can get pricey to get started.
On a side note, I am surprised that 25 pounds will last you a long time. I go through that much in a couple or three weeks for my personal home consumption, but then I make all of my own bread and have four teenagers to help consume it. The neighbors also appreciate a fresh loaf now and again. You may be surprised at the flavor advantages and cost savings when you make your own bread, especially just out of the oven with fresh butter and new honey. A couple hours in a weekend makes for a happy family!
Not necessarily “a bunch”, but you’d be surprised how many insects you consume everyday in your average food. Not to squick you out, but here is the USDA defect level handbook. Scroll down and look for wheat and wheat flour to see what fun things are allowed in your loaf of bread!
Then again, you way want to remain blissfully ignorant (but then you’ll have to turn in your Straight Dope Fan Club card).
I don’t do a lot of baking, so I don’t have that much experience with flour. But I did take a food safety course, and they claimed that flour was so dry when kept in airtight containers that bugs were unlikely to survive. Fine dry flours were supposed to be as effective as dessicants. The problem would be that flour readily absorbs moisture from the air. My only experience in this topic is a 5 gallon plastic bucket that I have kept a variety of flour and meal in for years without visible bug problems.
Practically any prepared food made from things grown naturally has insect parts, insect and rodent feces, and a variety of other goodies. Unless you eat magic food, you consume these things all day long in a normal omnivorous, vegan or vegetarian diet .
Do you think that when the reaper comes they send a guy out to shout “Run away little creatures, run away!” Bugs, spiders, field mice, toads, snakes, bunny rabbits, all kinds of organisms are caught up and many of them or their components make it through to you, the consumer. It’s the circle of life. Well, not for them so much, for them it’s more the thresher of death, but you get the idea.
Would doing this actually displace the oxygen in the container or just increase the partial pressure of CO2? I wouldn’t think that CO2 would necessarily prove fatal to an insect if there was oxygen present.
Putting the ice at the bottom of the flour might prove problematic – you’d probably build up a high pressure bubble that would eventually shoot flour everywhere – something like heating spaghetti sauce in a microwave.