Is expired flour usable?

Thank you so much for all of the answers. She bought Bob Red Mill for all of these so they are all sealed in a bag so they may be that much fresher. We'll see! Thanks again!

The smell test is very reliable. Wheat flours in particular contain enough fats that they can go rancid over time, especially if they've been exposed to light and/or heat, which it doesn't sound as though yours have. Still, time doesn't affect any of us especially well sometimes, so give them a sniff. The smell of anything rancid is absolutely unmistakable. I agree that the arrowroot is probably the safest of the lot. As long as it hasn't been exposed to any moisture (in the form of atmospheric humidity), which would degrade its starch molecules, it should be just fine.

When in doubt, throw it out. Although I would think the arrowroot would last the longest. It's the dryest to begin with, by far. I've used very old arrowroot with no problem. Many dates on packages are not "use by," but rather "sell by." And those dates are almost always very conservative.

I would toss the Arrow Root Flour to be safe. Occasionally these other types of flours can expire due to trace amounts of oils that can be found in the flour.

All purpose flour should be fine. Make sure you give it the smell test. Most expiration dates reflect when the flour will perform the best, and not that it's un-usable after the date. I've used expired flour in the past and it's just fine.