As the world's population continues to grow, food demand increases, particularly for foods containing protein essential for human health. While animal protein has traditionally been an essential element in many people's diets worldwide – particularly Western-style diets – the land and water needed to raise livestock make raising it increasingly unsustainable to produce enough protein for the world's population. 

Alternative protein sources – including various high-protein plants,  algae, mushrooms, and even insects – have been touted as alternative means to provide sufficient protein for the world's growing population. Within this, size reduction and air classifying equipment for fractionating cultivated crops high in protein  shows great promise in delivering adequate sustenance to humanity in the future.  

Importance of Protein 

Proteins are essential to maintaining the cells within our bodies. Made up of amino acids strings, proteins provide your body with what it requires to repair or build new cells. It’s especially important for growing children, young adults and pregnant women. 

After ingesting, your body breaks these proteins down into the individual amino acids, then uses them to: 

  • Build bones, muscle, cartilage, skin and hair. 
  • Deliver oxygen throughout the body through a protein compound carried by red blood cells. 
  • Make enzymes necessary for digesting food and creating new cells. 
  • Regulate hormones, especially during puberty. 
  • Repair body tissue. 

Though protein is most often associated with meat, dairy products, and eggs, many plants also contain rich amounts.. Plant proteins  are touted as healthier, with studies showing that sprouted grains and seeds are both protein and nutrient-dense, assisting the body with: 

  • Absorbing nutrients 
  • Aiding digestion
  • Healing disease

Plant proteins are increasingly marketed as the future of protein, with an estimated market value of $14.5B USD by the year 2025. 

How Size Reduction and Air Classifying Equipment Extracts Proteins

The most popular plant crops used for protein extraction are varieties of pulses and beans that contain between 20-35% protein. Various extraction methods will concentrate this protein to 50% or better where more specialized techniques can isolate the protein to as high as 90%. Concentration levels are determined by weight on a dry basis.

So how does size reduction and air classification fit into this process?

First off, an efficient extraction  of the protein can only be achieved if the plant material is properly conditioned and milled. This process begins with selection of a high quality crop tempered to a consistent moisture. Harvest product is sent to the cleaning plant for splitting, dehulling and sometimes pre-sizing into a meal before further processing.

The next step is size reduction. Size reduction is critical to proper cell wall disruption, where whole plant cells are crushed to liberate the various nutrients into a homogenous mixture of different particle sizes. Quite naturally, the size reduction process results in protein particles that are smaller than the starch and other nutrients present in plant cells. Past research has proven that impact milling is an ideal means of properly conditioning the plant without breaking down the starch and other nutrients.

The final step is extraction. After properly milling the plant material, the homogenous mixture can be refined by various methods of extracting  the protein from the other nutrients. The predominant methods involve dry or aqueous processes, each with their own benefit.

For concentrated proteins, milled flour is further processed in a dry state by passing it through an air classifier. Air Classifiers are built to efficiently separate smaller protein particles from the other nutrients by utilizing a precisely controlled amount of centrifugal force. The protein particles are then collected separately from the other nutrients for further processing.

Isolated protein levels also require a specific, yet different particle size distribution to prepare the plant material for extraction. Isolated vegetable protein typically involves an aqueous, ph adjusted solution of protein that is precipitated, centrifuged and then dried.  The isolated protein can be further milled, or micronized based on customer preference and end use.

Prater Solutions for Protein Extraction

For 95 years, Prater Industries has offered a variety of size reduction technologies that have become proven in processing plant proteins. For size reduction, Prater manufactures two types of hammermills, fine grinders, and air classifying mills used in the various stages of preparing the plant for extraction.

Prater Full Screen Mills offer an efficient, gentle means of crushing larger varieties of dehulled pulses and beans into a coarse meal. Pre-crushing often improves the efficiency of the downstream processing by performing some of the most energy intensive work.

Prater also manufactures the Mega-Mill Hammermill. The Mega-Mill is a unique, cantilevered style of hammermill that offers unparalleled access for maintenance and cleaning. Its precision tolerances make it ideally suited to bridge the “particle size gap” between traditional hammermills and fine grinders within a dust tight package ideally suited for use in pneumatic systems. Mega-Mills are most often used to manufacture a coarser grind in the 30 to 60 mesh range unique to certain types of wet extraction processes 

For the manufacture of finer flours typically used in dry and wet fractionation, Prater’s Fine Grinders and Air Classifying Mills are purpose built to achieve size reductions as fine as 10 microns while achieving a high degree of particle uniformity. Both technologies use high speed impact to crush and accelerate particles toward the stationary surfaces of screens and jaws fitted precisely around the rotor. These surfaces amplify the size reduction process by creating shear, deceleration and rebound of particles into the rotor’s path. Particles that are small enough to pass the screen are conveyed away from the grinding chamber.

When a finer particle size or further uniformity is required, an Air Classifying Mill is selected over the Fine Grinder. Air Classifying Mills utilize the same methods of size reduction as Prater’s Fine Grinders with the addition of a second, independently controlled rotor that separates the coarser particles and recirculates them back into the grinding chamber for further size reduction.  Air Classifying Mills are ideally suited for cell wall disruption of pulses and beans used in dry fractionation processes.

Both technologies are rich in features and come in various sizes with motors from 3 to 250 horsepower.  Their horizontal, cantilevered design, large access door and outboard mounted bearings result in a clean interior that is easily disassembled for cleaning and maintenance with a minimal of tools. They also come standard with a trapped key door safety interlock, static grounding brush and optional bearing monitoring package to complement existing safety protocols and preventative maintenance programs. Like the Mega-Mill, all designs are dust-tight and built for use within a dedicated vacuum convey circuit. 

Prater’s MAC Series Air Classifiers are an independent unit designed for precise separation of ultra-fine particles. Air Classifiers  create a forced vortex and utilize centrifugal force to process fine particles that would otherwise blind mechanical screens. Capable of making separations as fine as 10 micron, they are proven in separating protein and starch with fractionation processes. Their unique, adjustable secondary air greatly improves protein capture efficiency as compared to other designs. Air Classifiers also come in a variety of sizes with a dust tight design that lines Prater’s mills, and operates with a vacuum convey circuit.