From my experience, three of the areas of pizza making that I have found to the most useful to understand as a practitioner to achieve good results in pizza making are the following: 1) gluten and flours, 2) the fermentation process, and 3) the factors that influence fermentation. Almost everything else that technically pertains to dough production will fit somewhere within the framework defined by these three topics. For many of the new members, and especially those who have had limited experience with making pizza doughs, the following discussion may be helpful. I will first address the gluten/flour topic in this post and cover the fermentation topic in another post in due course.
Most people think that gluten is in the flour in the bag they brought home from the local grocery. But if you poke around the flour, or even if you examine the flour under a microscope, you won't find any gluten. The reason for this is that gluten comes into existence only when the flour is combined with water and kneaded (or vigorously stirred). It is then that you will see that the flour/water mixture starts to take on an elastic, somewhat rubbery and stretchy quality. That's due to the gluten that was formed during the kneading process. To be a bit more technical, the gluten is formed when certain long-coiled, tangled insoluble protein molecules of flour, called glutenins and gliadins, unfold and line up in long strands and crosslink with each other when they come into contact with water and are kneaded. The glutenins are believed to be primarily responsible for the strength and stability of the gluten and the gliadins are believed to be primarily responsible for the elasticity (the ability to spring back when stretched) and softness of the gluten. While you can't see the glutenins and gliadens with the naked eye and distinguish between them, they are there in the dough and they are real (there are even tests that can be performed to separate the two).
Another important component of dough production in general is the starch that is present in flours along with the protein. Starch is a complex carbohydrate made from chains of sugar molecules. Within the dough, the starch takes the form of tiny “balls” or granules that are trapped within or cemented with the strands of gluten as the water joins the starch and gluten and as the gluten forms and is developed in the course of producing dough. The starch serves several important functions insofar as pizza dough production is concerned: (1) it provides body and structure for the pizza crust (since there is much more of it than protein, about 68-76%), (2) it is responsible, along with water, for the “crumb”, or internal porosity and texture of the baked crust, (3) it provides food (sugar) for yeast fermentation (in a manner to be discussed in a later post on fermentation), and (4) it dilutes the gluten in the dough to form a crust of acceptable consistency and texture (for example, you wouldn't want to eat a pizza made from protein or gluten alone).
Another useful thing to understand about gluten is that different flours have different amounts of gluten-forming protein. (The reader should note that the terms "gluten" and "protein" are often used interchangeably by writers, even experts on baking, and I often do so also, as a simple short-hand way of talking about protein and gluten even though they are not technically identical).
From a protein and gluten standpoint there is a pecking order that I have found useful to keep the different kinds of flours straight in my mind and how they are likely to behave when used to make doughs. At the bottom of the pecking order is cake flour. It generally contains about 6-8% protein (which converts to about 30-32% gluten when mixed with water). Cake flour is followed in the pecking order, in turn, by pastry flour (the white variety), which generally contains about 7-9.5% protein (which converts to about 33-34% gluten); all-purpose flour, which generally contains about 10-11.7% protein (which converts to about 37-39% gluten), bread flour, which generally contains about 11.5-13.5% protein (which converts to about 40-42% gluten); and high-gluten flour, which generally contains 13.5-14.5% protein (which converts to about 45-47% gluten). (Please note that the above ranges, while typical, are exemplary only and can vary from brand to brand, as may the gluten conversions numbers recited above).
In addition to the above specific flours, there are also others that are not often put into the pecking order but nonetheless play a very useful role in pizza making. For example, much has been written of late at this site about 00 flours, as are imported from Italy. 00 flours are milled differently than domestic flours and have protein contents that overlap the categories mentioned above. They can be as low as 9-10% protein and as high as 12.5% protein. Quite often, the gluten formed from these flours is also lower than domestic flours. This is important to know because it means that you can't treat 00 flours identically to their domestic counterparts with a similar protein level. You will have to learn about the particular idiosynchracies of 00 flour and develop a separate dough management procedure.
Of the above types of basic flours, pizza doughs can be made with all of them, except cake flour and pastry flour, both of which have too little protein and gluten to make a functional pizza dough. However, it is possible to combine either cake flour or pastry flour, or both, with all-purpose flour or bread flour, in suitable ratios, to produce another category of flour blends with their own protein and gluten contents. (These combinations, or "clones", were established in great measure to approximate the 00 flours mentioned above, which are not easily found in the U.S. or as well known in the baking trade as the other types of flours). As regular readers at this forum know, 00 and other flours, most notably, high-gluten flour, can also be combined to create yet another "hybrid" combination, affectionately known as the "Di Fara clone".
What is very important to understand about the protein content and gluten-formation aspects of different flours, is that the protein and gluten will play a major role in the characteristics and textural properties of the doughs and crusts made from the different flours. For example, a dough made from a low-protein, low-gluten flour (such as a 00 flour or one of its "clones") will be soft and easy to knead (the elasticity is low), and the crust will be soft and tender and without a great deal of "heft". As you move up the flour chain, the doughs become tougher to knead (relatively speaking) and have greater elasticity and pliability. The crust texture will also gradually change and, when you reach the other end of the flour chain (high-gluten flour), the crust will be heavier, puffier, with a coarser texture, with small crunchy bubbles (and sometimes large bubbles), a darker and maybe even slightly charred rim, and chewier than most crusts, and with a somewhat more “bready” flavor. The crusts are also more likely to be able to support a lot more toppings than one based on a softer flour, because of their greater "heft" and substance. Another important distinction between low-protein, low-gluten flours and high-protein, high-protein flours, is that, all other things being equal, the crust produced from a low-protein, low-gluten flour will be lighter in color--almost white or tan-colored--than one made from a high-protein, high-gluten flour.
It would be nice if one could easily determine which type of flour to use to make the different styles of pizzas. It's hard to generalize, but the following guidelines might prove useful. 00 flours and their "clone equivalents”, with their relatively low protein levels, lend themselves best to the production of Neapolitan style crusts, with their characteristic soft and chewy textures. Flours with a protein level of around 11% (bread flour) tend to lend themselves best to thick crusts, including crusts for deep-dish pizzas. Flours with a protein level of around 12% tend to be suitable for both thick and thin crusts. And flours with a protein level of around 13% and above (high-gluten flour) are most suitable for cracker-like thin crusts and New York style crusts, with their characteristic tough, chewy, leathery and bubbly crust textures. These are generalizations, of course, and, as anybody who has spent much time on this site already knows, the possibilities are wide and varied and limited only by one's creativity and willingness to experiment.
The discussion to this point has centered on white flours alone. It is possible, of course, to use other flours to make pizzas, such as whole-wheat flour, and various other flours in combination with white flours. Whole-wheat flour is a high-protein flour, containing around 12-14% protein. It can be used alone to make pizzas, but more often it is combined with white flour to provide a softer crust. Some of the more common examples of other flours that can be added to white flour include cornmeal, semolina, and rye. (More recently, soy flour and various high-protein by-products of wheat milling have become popular as ingredients for low-carbohydrate pizza doughs.) These additions generally impart pleasant flavor and texture components, especially where cornmeal and semolina are used. Crusts using cornmeal and semolina will be chewy with a light yellow color (and the doughs are sturdy enough to lend themselves nicely to grilling on an outdoor grill). To avoid an overly tough or stiff crust, the amount of semolina used should be in the range of 15-25% by weight of the total flour mixture (although I have seen ratios much higher).
It will generally be because of a flavor preference or nutrition enhancement that one elects to use whole-wheat flour, or cornmeal, semolina, or rye as an addition to white flours. Usually, the crusts made from whole-wheat flour and the various flour combinations will be a bit heavier, tougher and chewier than the crusts made from the white flours alone. They also do a better job of holding multiple toppings. An important point to keep in mind when using the above flours, however, and especially those that do not themselves have much gluten or have lower quality gluten (such as rye), is not to add too much of such flours in relation to the white flours. This can have the effect of diluting the gluten strength of the white flours and result in a less pronounced rise, and also produce a crust that is too stiff. For this reason, it is generally advised that the low-gluten secondary flours (e.g., rye) be combined with a high-gluten flour that will better be able to stand up to the other flours. Alternatively, vital wheat gluten may be added to compensate for the dilution of the gluten. For those who are unfamiliar with vital wheat gluten, it is a dried wheat protein of high-protein, hard wheat flour that has had all of the starch removed and is then dried. It has a gluten content of around 45% and a protein content of about 75%. The recommended amount to use is at the rate of 1 to 2 teaspoon for each cup of flour used (or 2-3% by weight of flour, in terms of baker’s percentage). Vital wheat gluten is also sometimes added to other flours, such as all-purpose and bread flours, to increase their protein and gluten content.