Don’t get mixed up about mixers – make more dough by being well-equipped

The art of pizza meets the science of food

The art of pizza meets the science of food.

We’ve covered a number of ingredient topics over the last months, and hopefully some of the information has been of use. This time we turn our focus to physical processes rather than ingredients, and discuss the mixing of pizza dough.

Pizza dough can be, as I’m sure you’re all very aware, quite a complex and temperamental thing. Transforming flour, water, living yeast and other basic ingredients into a dough can be greatly simplified by proper and efficient mixing and sheeting.

Of course, the original approach to mixing and sheeting is strictly manual. While it can be therapeutic to hand-mix and manipulate small amounts of dough, any commercial operation typically employs at least some form of mixer, and many utilize one or more sheeting methods beyond traditional hand tossing.

Mixing
Two steps comprise dough mixing. The first involves a uniform physical dispersal of ingredients by mechanical blending, and then absorbing the added water into the dry ingredients. The second stage involves a series of reactions in which the added water now associated with the proteins (gluten) and carbohydrates (starch and fibre) cause the formation of an elastic protein structure incorporating large numbers of starch granules and fibre bits. The mixing actually provides the energy to stretch and twist the gluten protein, kneading it into forming a somewhat elastic texture capable of holding onto bubbles of air. It is these mechanically formed bubbles that are inflated by yeast-
produced carbon dioxide during dough proofing.

Different types of crust demand different degrees of mixing, and differing amounts of water and ingredients. All require adequate mixing to disperse and hydrate ingredients, but the amount of dough development desired (amount of kneading) varies by crust type. Thin, crispy crusts are typically produced from quite dry dough with very little gluten development (short blend times). Softer, more bread-like crusts, such as pan pizza or deep-dish, result from wetter doughs with more gluten development. Mid-thickness crusts derive from intermediate mixing and water levels.

The six general types of mixer used for small and large-scale pizza dough manufacture are characterized below.

Planetary (formerly called Upright)
This is the most common mixer used by pizza operators, and the class is typified by the Hobart products familiar to many as one of the earliest manufacturers. Today Rondo, Berkel, AMF and many other brands are available. The name comes from the fact that the mixing shaft revolves around a circular track (like a planetary orbit) while also rotating. It was the original upright mixer, but as other types of upright mixer now exist, “planetary” is a more specific name for this type.

Thousands of these mixers, from a few quarts to enormous 300+ quart (75+ US Gallon) bowl-capacity mixers are in use worldwide. The mixing ability of this device is adequate for most pizza doughs, although it tends to be slow to achieve mixing uniformity and slow to achieve adequately developed dough versus other types. This is especially apparent with very tight thin crust doughs, or low-carb doughs. Key advantages are that by using various attachments, one machine can mix bread, pizza and cake dough and sauce, as well as slice mushrooms, sausage and vegetables, and even shred cheese. Since there are so many in use, second-hand planetary mixers are reasonably priced, as are repairs and parts. These machines are hard to kill – durability is a real plus. Just remember to change speeds in the prescribed manner, or you will dramatically reduce your mixer’s life. Traditionally, mixing hooks called J-hooks were used. These were partially supplanted by S-hooks, held by some to offer superior kneading characteristics. The most dough-friendly bowl and mixing hook system available today for small-capacity planetary mixers consists of a modified bowl and hook arrangement termed a “McDuffie” bowl. As the key disadvantage of this arrangement is a reduced batch capacity, it is more typically used for research and testing purposes.

Cutting mixers
Looking like large bowls with spinning knives on a vertical shaft that comes into the bowl from the bottom, these are very similar to domestic food processors in function. With the high rotating speed of the shaft, the mixing or dough attachments can produce dough many times faster than the planetary mixers. This is useful, as the size range of cutter-mixers is smaller than the planetary mixers. Remember that you can cause yourself problems many times as fast as well, so make sure you adhere to established procedure and don’t over or under process your doughs. These devices also use a cutting attachment, which can rapidly chop toppings and cheese, as well as pureeing tomatoes or mixing spices into sauce. Disadvantages include complex cleaning procedures, high initial cost, and a potentially more detailed training process for use. Some believe the rapidly produced dough to be inferior to a slower kneaded dough.

Spiral mixers
These look like a large corkscrew hanging into a wide bowl, and rotating to mix material in the bowl. The action of this mixer type is generally held to be gentler than the former two types, and the make speeds are midway between. This mixer is just a mixer, and won’t do all the other things the previous two will do. Also, the smallest spirals available tend to be equivalent to a mid-size planetary, so usually only higher volume operations can reasonably afford one. Balancing this is the spiral’s unique ability to produce batches down to a fraction of full-batch size. Whereas a cutter or planetary is largely ineffective below 50-60 per cent of full capacity, spirals mixers can often produce well-made dough at 20 per cent or less of full capacity. Twin and other customized mixing tolls are sometimes available for more unique crust types. Spiral mixers are much more common in Europe.
 
Reciprocating arm mixers
Imagine the way a person would bend from the waist and pick up a handful of fallen leaves, lift them to belt level and then open their hands and let them drop. The arms of this mixer scoop together, and then release and reach back to scoop again. This is the action traditionally used in hand-mixing dry ingredients, mixing dough and even salting cheese curds before electrification of many food plants. It is also the action of the reciprocating arm mixer designed to mimic these traditional motions. While very visually interesting, and important from a traditional point of view, dough mixing and development is very slow, and these devices are seldom found in modern pizzerias.

Horizontal mixers
This one’s tough. Imagine the rear paddle wheel of a sternwheeler steamboat. That paddle wheel, if mounted inside a cylindrical tank, would form a very efficient yet gentle means of mixing as it revolved inside the tank. Replace the flat paddles with round bars, and drop the number of bars to perhaps three, and in addition to gentle mixing, any thick and viscous material in the tank would be gently stretched and worked. Horizontal mixers are the workhorses of North American bakeries, and are extremely common in frozen dough plants as well. They enjoy throughput speed advantages as a result of their large capacities, though mix times are closer to planetary mixers than spiral mixers. A few smaller (50-150 lb.) models are available, but they tend to be many times more expensive than planetary mixers. Various bar designs exist, for sweet doughs, bread-style doughs, and high protein thin crust doughs.
 
High speed enclosed vacuum mixers
Almost exclusively used in large production facilities, these look a little like armoured blenders. Under a partial vacuum, relatively wet, soft dough can be ready for further processing in extremely short periods of time. High uniformity and consistency are the key benefits of this mixing approach. In the pizza universe, these devices have been used successfully for frozen dough, pizza pocket-style items and frozen retail pre-topped pies.
Whatever mixer you have available to you, the most important factor is the operator. Optimizing a recipe for a specific mixer type (and even size) can pay big dividends in terms of quality and consistency.

A series of mixing time tests, varying nothing but mix time, by one and two minutes less and one and two minutes more, can be highly revealing.

After optimizing your mixing, try your current recipe, together with a total mix that’s 20 per cent larger and one 20 per cent smaller. Mix them identically as per your best mix time determined above. Proof and process them all the same way, and bake them off as cheese pizzas in a well-heated oven.

Repeat this test nearing the end of your desired shelf life for these three doughs. If there are differences between the three when fresh, try investigating the uniformity of your mixing, and the effectiveness of the dough development. If variations show up late in the window of use, the resiliency and resistance of your dough may need some fine tuning. If they appear identical, repeat with a tougher test, like a vegetarian pizza. If you still see no difference, you now have the proven ability to scale your batches up 1/5 or down 1/5 without quality issues. Use that to reduce your waste by tuning batch sizes to sales needs.
By learning more about pizza making, and changing one thing at a time until you reach the “sweet spot” or optimum, we can all advance the art of pizza and the science of food.