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How to Get Flour Finer with a Rotormill



Flour is generally made from wheat kernels, which have three basic components. These include the bran, endosperm, and germ. The bran and germ contain high amounts of fiber, minerals, natural oils, and nutrients, along with protein. The endosperm is mainly made up of protein and starch. The endosperm is used exclusively when producing refined or all-purpose flours, while bran and germ are removed. The endosperm is milled into small particles, after which protein and starch content are analyzed to create flour blends that have certain properties when used in baking. Stone-ground flours are different, however, as they contain some bran and germ. 

Flours are typically ground into coarse, medium, or fine consistencies. Coarse-grained flours are often used to make heavier breads or dough. Medium-grained flours tend to swell and are typically used in pastas. Fine-ground flours refer to cake or pastry flour. Some flours not made from wheat also must be finely ground. To understand the challenges in making these finely milled flours, it’s important to look at what flour milling entails and the types of fine flours. 

Fine Flours: Milling Challenges & Types 

Flours made at scale use milling machines and sieves to grind and sift first the whole grains, then the coarse meal, into fine flour. Milling with faster, high-speed machines typically creates more heat, however, which can reduce the nutritional content in the end product. For this reason, fine flour milling requires equipment that lowers the amount of heat to which the flour is exposed. Often fine wheat flours use only the endosperm and leave the grain’s bran and germ, which are either blended into other types of wheat flour to make them whole grain.

Types of Fine Flours

With each type of fine flour, milling techniques differ. Wheat flours are typically made from a mix of different parts of the wheat kernels, each having different properties and applications.

Types of fine flours include:

  • 00 flour – referred to as Italian flour – comes from the toughest type of wheat, ground to a super-fine texture so that recipes can roll out dough extremely thin; it’s used for pasta, crackers, and thin-base pizzas.  
  • Almond flour is made with almonds that have been blanched to remove their skins and which are then ground and sifted into a fine, gluten-free flour that’s low in carbohydrates while also high in healthy fats and fiber.  
  • Built flour is a fine flour using only part of the bran, with millers historically “building” the flour by placing whole wheat flour into a coarsely woven bag that acted as a sieve, where only the finest parts of flour came through small holes in the fabric while the bran and groats remained; it was used to make white bread for wealthier people as, due to its original labor-intensive sieving techniques, it was more expensive to produce than whole wheat flour.
  • Cake or pastry flour – known by the Dutch as “zeeuwse” flour – is a very finely milled white flour with low gluten and protein content, made exclusively from the endosperm; with a very fine consistency, it’s used to thicken sauces, as well as in pastries, sponge cakes, cookies, tarts and white bread. 
  • Corn flour comes from whole kernels made into cornmeal, which are then finely ground and used in quick breads, stuffing, and tortillas, or used as a thickener or filler in many recipes. 
  • French flour is a generally fine type of flour with lower gluten that uses only the germ and endosperm, made from a type of wheat grown only in France and numbered according to fineness; type 45 is used for cakes and scones, while types 55 and 65 tend to be used for croissants, French baguettes, and other breads. 
  • Masa corn flour is a dough made from processed corn products used to make many types of foods such as tortillas, tamales, empanadas, and other foods.
  • Patent flour – often referred to by bakers as “baking flour” – is a very fine wheat flour made from the innermost part of the endosperm and without the bran or germ; most commercial grade white flour used for bread, cakes, or pastry is classified as patent flour, with higher quality types referred to as “extra short” or “fancy” patent flours.  
  • Semola rimacinata refers to an exceptionally fine Italian flour used to make pastas, with finely ground grains that are “re-milled” or “twice-milled” from coarser semolina flour, most often from durum wheat. 
  • Soy flour made from finely ground soybeans can be made into finely textured bread with high protein content and is often used in vegan recipes. 
  • Tarwebloem is a Dutch type of finely ground wheat flour, though less fine than patent flours. 

Some other specialty non-wheat flours are also finely ground, though these tend to be used in conjunction with other flours in recipes.

Rotormills: Dealing with Challenges of Fine Flour Milling

Flour manufacturers must look at flour particle size distribution. The fineness of a flour is measurable and requires the flour to have certain properties—various reduction techniques to retain nutrients in the flour. The milling techniques need to consider the heat, as higher heat from grinding reduces the nutritional value of the end product, especially when ground. For this reason, certain mills work better for fine flour milling. 

Particles break apart when elastic stress reaches a certain level. Cracks also emerge when grains are exposed to sufficient local stress. Rotor mills use cutting tools that rotate to create high-speed impacts against the particles. The kinetic energy caused by this impact deforms the contact area and breaks these flour particles. This reduction happens in combination with shear forces between the rotor and sieve rings. High rotational speeds achieve high throughputs, while particles within the grinding chamber only stay for a short time, ensuring more gentle processing. The flour can then be collected for packaging or returned for further processing. 

Rotor mills work well for softer plant-based substances, including the processing of all types of fine flours. Milling materials like wheat kernels, corn for Masa, and other organic substances sensitive to grinding temperatures, rotor mills use rotors moving at extreme speeds to effectively and quickly grind flour finely. This reduces thermal stress, keeping more minerals and nutrients in the final product. As a more energy-efficient means of reducing material, Rotor mills are also capable of high-capacity production. These mills are well-suited for fine flour milling applications, including wheat, soybeans, rice, and corn. They’re also very robust and durable, requiring little maintenance. 

IPEC Rotormills for Fine Flour Milling

The Rotormills manufactured by Prater (formerly manufactured by International Process Equipment Company) (IPEC) are made to finely grind material at a high capacity. Also referred to as “long gap mills’ ‘ due to the long, ring-shaped gap between the mill’s discharge sites and inlet, Prater’s Rotormills enhance reduction during fine flour milling, promoting collisions between flour particles during processing. With grinding done at several stages throughout the mill’s upper section, grinding plates accelerate particles and air against its grooved interior lining. This high level of turbulence causes particles to collide, pulverizing flour into a fine dust as continuous airflow absorbs the heat caused by grinding. 

Our Rotormills include the following benefits and features:

  • Allows easy access for replacement, adjustment or cleaning of components. 
  • Balanced rotor assembly allows for smooth operation. 
  • Comes in eight models that range from 15-750 horsepower. 
  • Enables high capacity and continuous fine flour milling. 
  • Features an intake port for air. 
  • Made from either stainless steel or carbon steel. 
  • No need for multiple systems as Rotormill combines several operations, such as surface coating and de-agglomeraton. 
  • Requires no special foundation. 
  • With the Rotordryer option, it dries while milling. 

Our Rotormills can additionally be installed as standalone machinery or within existing production lines. This makes them extremely versatile, offering multiple configuration capabilities to simplify customization. 

Prater also offers Fine Grinders, Air Classifying Mills, Rotary Sifters, and Rotary Airlock Valves that are often used in flour milling and production.

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