What is the shelf life of whey protein?

If it remains unopened, it should have a “use by date” or “sell by date”.

I got it from the bulk bin.

You could call the store and ask. Aother alternative is to put it in a Ziploc freezer bag, and stick it in a deep freeze. That way it will last indefinitely. Just be sure to thaw it out to room temperature before you open it.

Thanks, @snowberry. Well, I don’t know if it’s too late for that. I bought it some time ago and put in a Ziploc bag, but not in the freezer. I’m wondering if I should throw it out. That’s why I’m asking.

My rule of thumb would be to go ahead and try it. Unless it’s a few years old, if it tastes all right then it should be good.

Here’s the thing to remember about plastic bags. Most of them are air permeable. That means that they will exchange air (and odors) through the membrane. Freezer bags are not air permeable, so if you are storing it next to something smelly, such as next to your onions or garlic cloves, you will want to use freezer bags or glass.

Thanks, @snowberry, good to know!