Taken from a thread on a madsci.org:
"According to the label on the containers, Sodium Ascorbate is made by combining Ascorbic Acid with Sodium Bicarbonate (aka Baking Soda) Calcium Ascorbate is made by combining Ascorbic Acid with Calcium Carbonate (aka ground limestone)..."
"2) Ascorbic acid, being monobasic, would take one equivalent of base to neutralize. I leave it to you to calculate the proportions
The process is most probably easy to set up at home, and would include mixing ascorbic acid and sodium bicarbonate solutions, and drinking or evaporating the resulting salt solution. Long storage of salts is not recommended though..."
So I take it from this that in order to get to Calcium Ascorbate you would combine equimolar solutions of Ascorbic Acid (Vitamin C) and Calcium Carbonate (ground limestone, CaCO
3) then evaporate them?
I've yet to find a good source on the web which actually explains the precipitation of tannins, but I'm still looking.