Using Agar agar beyond its use by date A friend of mine came over the other day to borrow some agar agar from us. We had two boxes in the cupboard, and handed him one that was within its use by date, not knowing the ramifications of using the one that was past its use by date.

However, we were thinking about it, and couldn't really find any reason not to use agar agar even well after its use by date. The box in question is a year over.

My question is this: is the use by date merely there because everything must have one, or does agar agar go "off" beyond some point in time?
If you store it properly (i.e., dry), it won't go bad in the unsafe sense. It has a pretty long shelf-life. Its possible that it'll lose some gelling strength eventually, particularly if stored in harsh conditions (elevated temperature, exposure to humid air, exposed to sunlight, etc.). Like anything else, it could conceivably pick up off-flavors if not stored in an air-tight container.

I'd make a small bit of agar-agar gel with it, to see if its still OK. I expect it is.