In cooking, this term refers to a method of preparing vegetables. A large pot of
water is brought to a
rolling boil, and the vegetables are immersed for no more than a few minutes. Despite the name (and Webster 1913's definition), they should only lose color if overcooked. When properly blanched, green vegetables (notably
broccoli) will actually look brighter. I believe this is due to
chloroplast membranes rupturing and spilling out
chlorophyll.
Blanched
vegetables will be firm and a little plump, but less crunchy. Their
flavor will improve, becoming less
bitter but not stinky or
sulfurous.