I am beginning to think that an HRI pizza is more prone to gum lines than other types of pizzas, and it may be more pronounced for the HRI pizzas made in its pizzerias than for the frozen HRI pizzas. I think part of the explanation has to do with the amount of "stuff" that is put on the HRI pizzas. For example, when I dissected one of the 12" HRI frozen pepperoni pizzas and weighed the pepperoni slices, the cheese and the sauce, the total weight was 14.64 ounces. Notably, the weight of the cheese alone was 10.33 ounces. Later, when I did the same thing with two 12" HRI sausage pizzas, which weigh about two ounces more than the pepperoni pizzas, the total weights of the cheese, sauce and sausage were 15.2 ounces and 15.52 ounces (see Reply 307 at http://www.pizzamaking.com/forum/index.php/topic,6112.msg242492.html#msg242492
). Remember, these weights were for pizzas that had already been partially baked and gave up some water content in the process. Also, it appears that some of the HRI frozen pizzas have more sauce than others. So, by my estimate, the above numbers may be a few percent on the low side.
If we now assume that the dough ball weight for a 12" HRI pizza is 15 ounces, which I deem to be a plausible number from my analysis, it can easily be seen from the above numbers, especially when they are adjusted for water loss during the par-bake, are higher than the weight of the dough itself. Even though the HRI dough is a sturdy and fairly dense dough (with its high oil content, low hydration value, and an estimated thickness factor of a bit over 0.13) and capable of holding everything that is put on it, I think these weights impose a burden on the way that the end pizza is baked, in terms of the type of oven used, the oven positioning, the type of carrier used (e.g., disk, cutter pan or their equivalent), bake temperature, and bake time. The balance between these factors has to be just right to be able to bake the crust to the right final color and to melt the cheese to the desired degree, and especially so if there is an above average amount of cheese on the skin. If there are a lot of toppings, these factors become even more critical because more things have to be baked. Under the circumstances, I can see how it might be easy to end up with a gum line. I don't think that it happens very often where what is put on a skin or crust for a flat profile pizza weighs more than the skin or crust itself. Maybe when this happens, a gum line is more probable.
As a cross check, I went to the Burke guide at Reply 4 at http://www.pizzamaking.com/forum/index.php/topic,14822.msg147190.html#msg147190
to check out typical amounts of cheese used on 12" pizzas. As can be seen there, a typical 12" pizza has a maximum Burke guide cheese quantity of 7.5 ounces. The HRI pepperoni pizza that I mentioned above had 10.33 ounces, and that weight was after some loss of water content. For sausage, the maximum Burke guide weight for a typical 12" pizza is 7.5 ounces for raw sausage and 5.75 ounces for cooked sausage. A typical, or generic, raw, fresh pork sausage contains about 56% water (http://nutritiondata.self.com/facts/sausages-and-luncheon-meats/1375/2
). On this basis, HRI appears to be above the Burke guide numbers, and in some cases perhaps considerably higher than the Burke guide numbers. In fact, HRI has said that it uses more sausage than what the USDA specifies as the minimum for pizza (see the article at Reply 9 at http://www.pizzamaking.com/forum/index.php/topic,6009.msg51738.html#msg51738
As a further cross check, the other day while I was at my local supermarket, I examined the Nutrition Facts for several types and brands of frozen pizzas. I was looking for numbers other than pizza weights but it seemed to me that most 12" frozen cheese and pepperoni pizzas weighed less than the HRI frozen pizzas. I didn't do a rigorous analysis but that was my impression. Even a 12" Papa John's pizza, whose dough skin has a comparable thickness factor, weighs less than a typical frozen HRI cheese pizza.