Looks like egg whites are used for resolving overly tannic wine while being gentle on color. I've used gelatin when the need arose for this purpose.
I haven't used egg whites personally but these instructions are from Pambianchi's book.
"... 1-2 egg whites per 100L. First separate the egg white from the yolk, discard the yolk and then add to slightly salted water. Salt prevents the solution from getting cloudy. Alternately, use pure, refrigerated egg whites, the type sold in small cartons in your grocer's dairy section. Typically, approximately 30mL (2 tbsp) of pure egg white is equivalent to 1 large egg white. For each egg white, dissolve a pinch of salt in 100mL of water and then combine with the egg white. Add the saline egg white solution to the wine directly into the barrel and stir gently but thoroughly. Rack the wine in 1-2 weeks, no later."