hi Cindy,
Yes, "milling" is the same as grinding, so what you had was flax "meal" or ground flax seeds. This product is typically sold in a foil or other heavy opaque package, vacuum-sealed to keep out air. And it should be kept in the refrigerated section of the store, and in your fridge or freezer at home. The reason is that the precious omega-3 flax oils are very delicate, and are unstable in the presence of warmth, air and light. Flax oil goes rancid very quickly.
Whole, unground flax seeds on the other hand have a very long shelf life, and no need to refrigerate (although I do keep mine in the fridge). The outer coating of the whole seed is hard, tough and protects the oils inside. In fact, whole seeds will resist even the strong acid in our stomachs and alkaline digestive juices in the intestines .. and will come out intact
So grinding is the only practical way for humans to benefit from both the soluble fiber and the omega-rich oil.
Once ground, the flax meal has a short shelf life, just like bottles of fresh flax oil ... 4 to 6 weeks after opening, tops .. and keep tightly sealed and in the fridge or freezer.
IMO, it's more efficient to buy whole seeds and grind them yourself at home. Way less expensive, even for organic seeds; and you only need to grind up a few days' worth at a time. Yes, a coffee grinder or spice mill is preferable ... the seeds are so small and hard, they'll just dance around and make a mess in a blender or food processor. I've found it works best to "pulse" the grinder in short bursts, rather than let it run steadily. The reason is the blade will generate a lot of HEAT as it spins, which causes the seeds to release oil as they're ground. This can damage the oil, and also makes cleanup difficult as it will gum up the blades. That's one reason why I store the whole seeds in the fridge .. keeps them cold for grinding
I use a small pastry brush to sweep out the grinder after each use, and occasionally wipe with a piece of paper towel or other absorbent material if there's any residue.
hth,
Doreen