The problem with vacuum sealing is that you end up with a hard brick which takes up quite a bit more room, especially a problem if you're using a bear canister.

The straw, though, is a good idea--reduces bulk without creating a brick. I also remove as much air as possible, store unused amount in plastic bags in the freezer.

Be sure to let anything stored in the freezer come to room temperature before you open it up, or you'll have lots of condensation on the cold food! Having your stove burners or an electric heater going when you open up the food, to dry the air, helps, too. Or pick a hot, dry day.

The little packets of absorbent/dessicant designed for food storage also help. Just be sure to remove them before preparing your meal!

I bought my most recent bulk freeze-dried food from Packit Gourmet, which packages its stuff in mylar bags. You can fold the bag tightly, reseal it with tape and then put it in a large freezer bag (again removing as much air as possible) before storing the unused portion in the freezer.