Gummy pizzas can be caused by a number of things. One, the pizza may not be thoroughly baked. If the oven temperature is too high, the outer portion of the crust can be nice and brown, but the center has not been fully baked. In these cases, the crust is generally said to be more "doughy" than just gummy. This characteristic is also accompanied by a strong “yeasty” taste and aroma in the baked crust.

A second cause might be due to the soaking of moisture from the sauce into the dough before baking. This can result from a pre-sauced pizza. What happens is that the water is absorbed into the dough immediately beneath the sauce, creating a sticky, gummy layer. With the addition of the cheese and other toppings, it is all but impossible to bake out this portion of the crust, which results in the classic "gum line" often reported just beneath the sauce layer.

A third cause might be due to the release of water from the vegetable toppings. This usually happens as the pizza is being baked. The underlying cause can be due to an excessive amount of vegetable topping, or possibly, the use of improperly frozen vegetable toppings. In either case, the toppings can release a significant amount of water during baking.

The solution here is to reduce the quantity of vegetable topping used, and to make sure any frozen toppings haven't been subjected to thaw conditions prior to application to the pizza. In some cases, the use of impingement baking can help to alleviate the problem, too. The highly focused/directed air of the impingement oven can increase the evaporative loss of the water as it is released from the toppings, so less of it finds its way to the crust.

Finally, there are some specialized ingredients available designed to help absorb the water as it’s released from the toppings, thus preventing its being absorbed into the crust.