strain (something) off of (something else)
To extract, separate, or remove some substance from something else. Strain most of the water off of the pasta, leaving a little bit in the pot to mix with your sauce. Be sure to strain the excess fat off the soup before returning it to a boil.
strain something off of something
and strain something offto remove the excess or unwanted liquid from something. The cook strained the grease off the cooking juices. The cook strained off the grease.