Plant-Based Protein Extraction Using Air Classification

NC Food Innovation Lab (NCFIL) Executive Director Bill Aimutis and Food Scientist Chloe Soliman led a new initiative at NC State University this year and co-authored this blog to reveal the initiative.

In 2023, NCFIL partnered with Netzsch Premier Technologies, LLC to add an additional extraction component to their extraction core competency. Netzsch is a German company, with offices in Exeter, PA, offering multiple manufacturing products and equipment to a variety of industries, including food manufacturing. 

One product line important to protein extraction is their milling and air classifying equipment. Netzsch collaborated with NCFIL to place a LabCompactPlus™ Mill and Air Classifier module plant in NCFIL’s Pilot Plant. This piece of equipment was innovatively designed by Netzsch engineers to mimic technology used in full production-size plants for protein extraction from a variety of raw materials including peas, lentils, pulses and defatted oilseeds. 

Protein Extraction at its Best 

NCFIL personnel are trained on this piece of equipment and have used it for several months to air classify a wide variety of materials, including those mentioned above plus other unique agricultural products. For more information on this equipment, visit Netzsch LabCompact.

Dry fractionation is not a new technology. Dry, or air, classification has historically been used in the food industry for precision milling of spices, sugar and flour. As a technology for protein extraction and concentration, air classification is an emerging field with potential benefits. 

First reported in 1979, the technology was slow to be accepted over wet fractionation. Today, air fractionation is increasingly being investigated by research scientists in the protein industry because of several benefits over protein wet fractionation and concentration. 

This method offers multiple environmental advantages over wet extraction and results in less damaged protein concentrates, which offer improved physical functionality, for example, foaming, gelation and emulsification. Another added feature is fractions enriched in fiber or starches are also less damaged and are finding new uses in higher-quality and innovative food formulations.

A Sustainable + Economical Method

Air classification is the latest addition to NCFIL’s protein technology arsenal. The high-level basis for extraction is particle separation by size and density. This method begins and ends with dry material. Therefore, it eliminates the need for solvents and the high energy cost of drying. 

A very sustainable and economical method, air classification can be used for protein extraction and concentration. Because materials are not exposed to heat or solvents, native-state proteins are retained, which is an added benefit for protein technology. 

All foods contain some portion of macronutrients—carbohydrates, proteins and lipids. Each of these macronutrients has unique physical properties, like size and density. Proteins are smaller and lower density than some carbohydrates, such as starch granules and fiber. This opens the door to physically separate starch and fiber from protein, which is the typical goal of plant protein extraction and concentration. This is exactly what the air classifier does.

The process has two phases: precision milling and air classification. Whole, dried materials, such as rice or pulses, are fed into the machine and conveyed into the mill head. The mill reduces the particle size of the material to a specified range. The milled material is then sent through a spinning classifier wheel, which uses a combination of centrifugal force and air flow to allow fine particles, typically proteins, to leave the chamber in the air stream while coarser particles, like starches and fibers, drop down into a separate stream. 

It works like a revolving door. In this analogy, the classifier wheel is the door, and its rotation speed is a parameter controlled by the operator. Milled material can be visualized as a mixture of bowling balls, tennis balls and marbles being thrown into the revolving door. When the door spins slowly, everything can pass through. As the door spins faster only the tennis balls and marbles make it to the other side. At the fastest speeds, only marbles can exit to the other side. This is how we concentrate small protein molecules from the heavier particles in a milled flour. 

More Investigation Needed 

Several papers have been published the last few years focused on the process itself (see Allotey et al., 2022; Pulivarthi et al., 2023; or Rivera et al., 2022). However, after surveying the papers, it is apparent multiple factors must be further investigated and potential intellectual property obtained. 

One important area to review is the initial preparation of the raw material being air classified. NCFIL added another analytical instrument to our protein characterization lab by purchasing an Anton Paar wet/dry particle size analyzer. 

Future blogs will communicate more details about the benefits of air classification in extracting and concentrating plant-based proteins. If you would like to learn more or work with NCFIL to extract proteins from your raw materials, please contact us.

References:

Allotey, D.K. et al. 2022. A meta-analysis of pulse-protein extraction technologies: Impact on recovery and purity. J. Food Engineering 327, 11048. 

Pulivarthi, M.K. et al. 2023. Dry fractionation process operations in the production of protein concentrates: A review. Comp. Rev. Food Sci Food Safety 22:4670. 

Rivera, J., et al. 2022. A comprehensive review on pulse protein fractionation and extraction: Processes, functionality, and food applications. Crit. Rev. Food Sci Nutr. 64:4179.