Swollen cans of Morning Moo's honey wheat pancake Mix?

We have 6 - 10lb cans of honey wheat pancake mix we bought a couple years ago that I just noticed were swollen to capacity (all 6 of them). I couldn't see an expiration date on the can. I called the company and they said it should be find so long as it is sealed. I opened one can, it hissed for several seconds as pressurized are escaped, and it doesn't smell like normal pancake mix - almost has a fruity smell to it. Is it still safe to eat?