The Mechanics of Plant-Based Food: Hosokawa Equipment Turns Legumes and Pulses Into Usable Protein

Plant-based food is undeniably the wave of the present, and probably the future, too. It pleases consumers who are concerned about the environment and those who seek a healthier diet, two giant trends that are affecting consumption patterns around the world. Just one statistic sums it up: Demand for plant-based meat is expected to double from 2022 to 2027, reaching more than $35 billion, according to a 2021 report from Global Industry Analysts.

But most plant-based foods don’t go straight from the farm to the table. It takes a detour through the manufacturing process, and that highlights the key role of equipment that can reliably turn sources of plant protein, such as pulses and legumes, into ingredients suitable for commercial food processors.

“The whole thrust of the plant-based food industry is deriving protein from plants,” notes Frank Bernero, food applications manager at Hosokawa Micron Powder Systems. “The goal is to extract as much protein from the plant as possible, given the customer’s parameters and manufacturing requirements.”

Hosokawa makes equipment for food manufacturers that grinds pulses and legumes and separates the protein from the starch and other components. The grinding and separation are two distinct processing lines. This is true for large scale production as well as small lab scale evaluation. Because Hosokawa manufactures both types of equipment, clients can depend on smooth and efficient transitions from one stage of the process to the next.

The first stage in the process is grinding the legumes or pulses. Hosokawa grinders are designed to create particles that match the customer’s manufacturing requirements. For example, a food processor making a smoothie or other beverage may want a fine grind because it is more soluble and results in a smoother end product. On the other hand, a manufacturer of plant-based hamburgers may want a coarser grind that provides a more meat-like mouthfeel.

“The grinding step liberates the starch and the protein so they are separable,” Bernero says. “If you looked at the grains under an electron microscope, you would see that the starch particles look like baked potatoes and the protein looks like little salt granules on the baked potatoes.” Once the peas or beans are ground, the resulting powder stream moves into the classification part of the system. Hosokawa pioneered air classification, a processthat separates the starch from the protein.

The air classifier uses one or more classifier wheels, which are cylinders with specific size slits in them. A downstream fan pulls the powder over the rotating cylinders. The smaller particles – the protein – slip through the slits in the wheels and fall into a container. The larger particles – the starch – don’t fit in the slits, so they drop down into a different container. Voila! The protein is separated from the starch.

The classifier process is called “forced vortex” because of the constant flow of air. The process is not perfect – there is always some starch in the protein container and vice versa. But a well-tuned classifier maximizes the separation.

In low-capacity separators, one wheel is enough to handle the powder flow. But when clients need to classify large quantities – such as several tons of material per hour — they turn to Hosokawa separators with multiple classifier wheels. This technology was developed exclusively by Hosokawa and greatly increases the amount of flow that can be handled.

“The multiple-head classifier wheels use a series of smaller wheels to accurately handle large volumes,” Bernero explains. “They are unique to our design.”

Naturally, an important characteristic of a quality classifier is its ability to accurately separate the particles depending on size. For example, if the operator wants to separate particles that are 20 microns or smaller from particles that are larger than 20 microns, the preciseness by which it does that is an important characteristic. The term used for that is “cut.”

“The preciseness of the cut is very important, and that’s what the Hosokawa ATP Classifier provides,” Bernero says. “It gives a sharp, distinctive separation of coarse going in one direction and fine going in the other.”

The measurements most commonly used in protein fractionation – which is the technical term for isolating the protein from the plant source – are percentage yield (which refers to the percentage of available protein in a legume or pulse that is extracted) and percentage protein fraction (which refers to the concentration level, or purity, of the extracted protein). In general, the higher the yield, the lower the purity.

Bernero says the baseline measurements for protein extraction using the dry method – which is the method Hosokawa equipment uses and which means water is not added during the process – is about 30 percent yield at 55 percent concentration. “That’s kind of middle-of-the-road, and we can adjust that to tweak for a higher protein concentration,” he says.

“But that may influence the yield and bring it a bit lower,” he continues. “It’s a seesaw effect where you can influence one aspect or the other by changing the parameters Obviously, you try to shoot for the maximum amount of protein given the conditions.”

Competing systems that use a wet process can provide a higher concentration of the protein in the extract, Bernero says. But the trade-off is that the resulting product needs to be dried, which requires extra equipment and energy. In fact, a 2021 study at the University of Goias in Brazil noted that “dry fractionation is a more sustainable method of protein extraction, as it uses few resources and preserves the native properties of proteins.”

When a food processor purchases a protein fractionation system from Hosokawa, the company ensures the system meets the client’s needs. They discuss the desired end product, the inputs, the required speed and quantity and other factors. They can even test the material the client proposes to feed into the system and use the information gleaned from that to correctly set the variables before the equipment is delivered.

At installation, technicians test all the components to make sure everything is working as planned, and they train the client on how to adjust parameters and control the equipment. If a Hosokawa system includes components from another manufacturer, technicians from that manufacturer join the process to make sure everything works smoothly together. The bottom line is that when a system is delivered, it works the way the client expects.

“Our technology and support teams collaborate to make sure our clients achieve what they want with our equipment,” Bernero stresses. Often, however, a client’s needs change. Fortunately, the equipment can adapt. “Sometimes we’ll get a call from a client and they’ll need something totally different. Our equipment is flexible, nothing is set in stone,” Bernero explains.

“We have clients, especially on the food side, who will tell us they’re grinding one material but then they come back to us later and say they’re grinding something else. That’s not a problem – our equipment is designed to accommodate a wide range of applications.”

This is especially important considering that even different variations of the same material can require different settings in the equipment. A yellow pea from North Dakota will differ from a yellow pea from Saskatchewan, Bernero says. One may have more protein or starch than the other, and consequently the settings that produce the best yield and concentration may differ. Conditions may even vary by time of year when the plant is harvested.

There are many adjustments to the equipment clients can make themselves, such as the flow of the air and the rate at which the material is delivered. Some other adjustments are made by Hosokawa technicians. In some cases, the client authorizes Hosokawa technicians to monitor and adjust equipment remotely. They can see the trending history of the equipment and determine if adjustments need to be made to ensure optimal performance.

Another characteristic of Hosokawa equipment is longevity. The company was founded nearly 100 years ago and some equipment manufactured more than a half century ago is still in service.

“I get calls from people looking for parts and when I ask them for serial numbers, they’ll give me numbers for equipment that was made in the 1950s or 1960s,” Bernero says. “That equipment is still out there running, and we still support it.”

By Food Processing.

As appeared in Food Processing Special Report: Processing Plant Based Proteins, May 2022

To download the full report, click here.