To go a little further, calcium ascorbate is actually a form of Vitamin C so it's outright good for you, providing not only the vitamin but a good dose of calcium as well. This is a great example of how many ingredients with funny names are not the monsters we've been told we must fear.

http://lpi.oregonstate.edu/ss01/bioavailability.html

....so it serve the same purpose as squeezing lemon juice on the fruit -- no harm done.

It's to keep the fruit from turning brown quickly. it's the calcium salt of ascorbic acid (vitamin C).