As with all ball valves, you should sanitize the output side before running off or attaching your racking tube.
If you are taking samples from the ball valve (as you should) after each sample you should spray an ample amount of StarSan into the closed valve. This will rinse
This will rinse away any sugars which could offer a source of food for bacteria, and if you mixed the StarSan per the instructions the Ph of the solution will be well beyond levels that bacteria can survive in. One added
One added step of security if you like, is to put a Tap Plug (or even a pipe-cleaner) into the hose barb of the valve after you rinse it with StarSan, this will ensure an extended contact time for maximum protection.