Soy milk is often sold in aseptic packaging, which has an unrefrigerated shelf life of at least a year. Once opened it needs refrigeration, and, according to all the sources we can find, should be used within five days. Soy milk is also sold refrigerated in plastic containers. We have no reason to believe that the manufacturer’s use-by date is any more liberal for soy milk than for cow’s.
You can also buy powdered soy milk, which is said to lose in flavor what it makes up for in convenience. (One of our sources even suggests that the powder should be refrigerated, which takes away any possible benefit the powder might have.)
Eden Foods sells small aseptic packages of its Edensoy Organic Soymilk (just over a cup per package), and perhaps other brands are available in small size as well. Rather than carry the weight of that ice on your camping trips, why not just pack as many small containers of soy milk as you think you’ll need, and pour out whatever you don’t use each day? It’s organic, so the environment won’t mind.
[Since posting this article, at least one reader informed us that, indeed, the environment does mind. How can you practice the good stewardship of carry-in/carry-out camping, he implied, if you are strewing whole tablespoons of leftover soy milk in the 261 million acres of public land in this country? "All food should be burnt, buried, or packed out," he says. "This is all part of the leave-no-trace philosophy with camping. The scent of soymilk on the ground will lead bears and other critters towards the campsite."
We are not going to argue. We are grateful for this reader's comments, as he clearly knows more about camping and bears than we ever will. We suggest that henceforth you bury or burn your leftover soy milk.]