A reader named Elaine asked a question about long-term storage of granulated sugar, and I figure I'd share it on the blog since it's an excellent question.
She wrote: How does one store sugar without it forming one solid block? I recall using a mallet to break the sugar into smaller lumps and filling the sugar bucket during WWII. Will storing sugar in the metallized bags prevent the clumping?
Right now sugar is cheap and readily available. Like so many other things, of course, it would become priceless if it were unavailable.
We have a lot of sugar stored away, so much so that I thought about devoting a 50-gallon food-grade barrel to it. We decided against this for two reasons, and kept our sugar in either 3.5 or 5-gallon buckets as always.
Reason One, sugar can harden. While there are steps to take to reduce this possibility, if hardening occurs I'd rather it happen in five gallon amounts instead of 50 gallon amounts.
Reason Two, sugar absorbs odors very readily. Our food-grade barrels used to hold strong-smelling stuff (anchovies and olives) and no amount of scrubbing will remove the odor. Though we have thick plastic bag liners in the barrels, the odor might still affect the taste of sugar.
Anyway, sugar in its crystalline form can store almost indefinitely (at least 30+ years). The key components for successful storage is keeping it dry, cool, and dark.
The biggest enemy of sugar is moisture. Even humidity can make it go hard. Thankfully, as Elaine pointed out, this can be remedied by breaking it up with mallets or running it through a grain grinder. Nonetheless, that's a pain in the patookus, so just keep it dry and you shouldn't have a problem.
I've read that sugar should not be stored with oxygen absorbers. Why, I don't know; but that's what I've read.
All this storage advice applies only to white refined crystalline sugar. "Raw" sugar is less refined and has a shorter shelf life. While I like raw sugar very much and often use it, we only put away refined sugar for long-term storage.
The paper packaging in which sugar is sold is not suitable for long-term storage. It will absorb moisture. Whether your buy your sugar in 10-lb. bags (expensive!) or 50-lb. bags from a wholesale grocer (cheaper!), re-package it by pouring it into a clean, DRY bakery bucket. Use a Mylar bag if you wish (Mylar bags will provide another barrier to moisture). Make sure the gasketed lid is on securely, then store in a cool dark place. Resist the urge to open your long-term stored sugar very often, as that may introduce moisture. I keep our long-term stored sugar in out-of-the-way places, whereas the frequent-use sugar is stored in an easy-to-reach place (my canning closet).
Sugar is an essential part of home food-storage. In addition to the "comfort" factor, it provides calories and carbohydrates. Honey is a superb sweetener and will store for literally thousands of years (Egyptian tombs!), but it's far beyond our price range, so we'll stick to crystallized refined sugar.