Reclaim Memory After FullText Catalog Execution On SQL Server 2008

I have a server that has 16 Gigs RAM and having Windows 2003Enterprise Server with SQL Server 2008 Enterprise Edition Sp2.
Now I have 6 FullText Catalogs each approx. size of 2 GB, and I use them separatelyfrom different stored procedures and I am not executing stored procedures simultaneously.
Now I want to know that is there any way i reclaim the memory which isoccupied by Fulltext Catalog before executing second stored procedure?

I had a problem before when we got 8 GB RAM at our server now we upgrade it to 16 GB, but I want to know can i reclaim that memory which is taken by FullText Catalog because i want as Minimal Memory Usage as possible.