Is there an alternative to cornstarch when used to thicken a pie filling I made a some pies a couple of days ago. The recipe called for cornstarch and it thicken the filling after it came out of the oven. The only thing is I could taste a bit of the cornstarch when I was eating the pies. I would just use less of it but I am afraid of making my pies to runny without the cornstarch. 

Is there an alternative to cornstarch to thicken the pie filling or should I just use less and hope I still use enough?
There are several alternatives, but the most common I know of are tapioca flour and arrowroot powder/flour.

That said, most cornstarch substitutes aren't appropriate for pies, because they break down under high heat.  The only substitutes for corn starch that I'd use in a pie are potato starch and tapioca.  Tapioca powder can be hard to find in some areas though; I usually get it at Asian grocery stores.