If you've set the temperature too high, or the temperature crept up without you realizing it, then it's likely that you'll be left with a tough brisket. You'll find that the brisket will reach the internal temperature of 190-210°F before all the connective tissue has broken down leaving you with a tough brisket.

What do I do if my brisket is tough?

Often, tough brisket comes about as a result of undercooking. The meat needs to be subjected to low temperatures for many hours in order to achieve that prized tenderness. If the brisket does turn out too tough, you may be able to salvage it by returning it to low heat for a few hours.

Why did my brisket turn out tough?

Brisket contains a lot of connective tissue, which can make it tough. The type of connective tissue in brisket is called collagen. Cook the meat quickly and you get tough, dry meat. Cook a brisket slowly, with some liquid, and the collagen turns into gelatin.