Personally I rarely cook anything in the microwave (I stick to reheating foods in it), so I don't use it for blanching either. I have a couple of large kettles for the hot water bath canning method that I also use for blanching. Much of what I freeze is better when it is blanched - otherwise it dries in the freezer and isn't a good consistency. (Freezing without blanching resulted in unused food that was thrown away because it didn't look tempting.) Maeve's answer about stopping the enzyme action is succinct as any answer.

If a food isn't eaten fresh you have to give it the best preparation for long-term storage. I go by the Ball Blue Book: The Guide to Home Canning and Freezing. What you want is food that comes out next best to fresh, and that can take a little planning.

Good luck!

SRS