plant based protein manufacturing extruder

Plant-based protein manufacturing: Scaling-up extrusion

A recipe for success to industrialize your plant-based protein manufacturing.

Whether or not you subscribe to a vegetarian diet, it’s impossible not to notice plant-based products springing up in every conceivable form. From meatloaf to cupcakes, hot dogs to granola bars, plant-based foods are grabbing a corner of the market that is growing at a rate five times that of total food sales. This is most evident in the way meatless burgers have found their way out of the health food aisle and onto restaurant menus. While plant-based protein manufacturing companies are eager to give consumers what they want, they are also challenged to produce large-scale offerings.

Extrusion is central to the production of these innovative foods, a process that mixes novel ingredients and cooks them in a matter of seconds. It is complex, requiring expensive equipment with an endless variety of possible calibrations. Whether you are an established manufacturer with a history of large-scale food processing or a startup developing a new recipe, you’ll need the right process for plant-based protein extrusion to move from the test kitchen to commercial production while managing quality, safety and cost.

Here are the key ingredients to consider when industrializing plant-based protein manufacturing.

Extrusion: Making plant-based meat substitutes

Extrusion uses moisture, high heat and mechanical energy to produce meat substitutes in a matter of seconds. There are three steps in the extrusion process, used as part of turning plant-based proteins into marketable meat substitutes.

Diagram of extruder components used for plant based protein manufacturing

The first step is mixing and pre-conditioning protein powders. This typically involves proteins made from pulses such as soy, lentils or chickpeas or, in one innovative case, from mushroom fermentation, with water, steam and/or oil. This pre-mixing brings the ingredients into contact with each other before they are discharged into the extruder, where further mixing occurs. It can be used to begin hydrating protein powders, to ensure a more uniform product, or to pre-heat the powder blend.

The ingredient mixture is fed into a twin-screw extruder, essentially a metal barrel where it is sheared and mixed by two rotating screws while being heated via a steam jacket surrounding the cylinder. The screws push the mixture along the barrel, compressing and mixing it as it moves toward a die at the end of the cylinder. The proteins in the mixture are denatured by the heat provided by the steam, and by the mechanical energy generated by the screws in the cylinder and friction. The semi-solid product may be extruded through a thermoregulated die, giving the operator control to cool or puff the product, to create the desired muscle fiber-like texture. It may also be cut as it exits the die.

The extruded product undergoes further processing that is similar to the meat industry—cutting, grinding, shredding, marinating, coating and/or further cooking. Heat pasteurization, UV irradiation or the use of preservatives can be used to extend the shelf life or enhance the food safety of the final product.

Plant-based protein scale-up

Extrusion is much more complex than typical food processing because you only have seconds to get it right, during which large amounts of heat and mass transfer occur. And you can’t just take a small recipe from a test kitchen and make it bigger—it takes specialized equipment and knowledge to scale up the extrusion process. While the chemistry is identical at any scale, we need to determine how quickly the ingredients can be mixed and how quickly we can heat and cool the mixture.

The need for heat in plant-based protein manufacturing

The application of thermal and mechanical energy is unique to extrusion and makes it different than, say, cooking a pot of spaghetti sauce. In that case, the thermal energy comes from the burner and the mechanical energy is applied by stirring with a spoon over relatively long periods of time. In extrusion, there is a need for a lot of heat and for it to be transferred to the mixture as quickly as possible. The combination of thermal energy, mechanical energy and mixing is affected by the specifics of the extrusion equipment, such as die design, screw speed, back pressure, dwell time and formulation. Thus, the quality of product depends on the processing conditions, which, in turn, are sensitive to the size of the equipment.

Thermal energy

Thermal energy is used during pre-conditioning to raise the temperature of the mixture before it enters the extruder. It is further applied to heat the product as it passes through the cylinder. Heat transfer becomes more difficult at larger scales since the surface area to volume ratio is reduced. Though commercial extruders maximize the heat transfer area—the circumference of the twin screws—that can still be heated by high-pressure steam, they have reduced heat transfer compared to the amount of material to be heated. It’s critical to test a process with a relevant-sized extruder that is geared for industrial use.

Mechanical energy

The mechanical energy of the rotating screws and the compression of the mixture being forced toward the die is unique in food production. Typically, increased pressure within the cylinder is indicative of more mechanical energy being generated.

The need to partner with an academic food science lab or equipment vendor

Once a company has established a target production rate, you need to understand how your process runs on appropriately sized equipment and ensure it can be scaled. Given processing considerations, the expense of commercial-scale extrusion equipment and the expertise required to run it, many companies seek outside support and advice. Ideally, companies that don’t fully understand how to scale up their manufacturing process should partner with an organization that has extensive experience in food product manufacturing. Choose a partner with experience designing and building according to good manufacturing practices (GMP) requirements of both the FDA and USDA, depending on the final application.

Extruder used for processing plant based protein

The North Carolina Food Innovation Lab gives growing companies access to equipment like their twin-screw extruder to help them scale their process.

Most extruder vendors will want to demonstrate that a company’s process can be run on their extrusion equipment before the company makes this expensive purchase. This can typically be done at either an equipment manufacturer’s pilot plant or a university’s food science lab that has the appropriate scale equipment. It is an expense to run these tests, but vendors may apply a discount to offset the cost if equipment is purchased.

Some companies are more comfortable going to a university food processing center, partly because of the impression that they will be unbiased and are not trying to sell a particular brand of million-dollar equipment. A good example is the North Carolina Food Innovation Lab, the only such academic facility in the US built to GMP standards and regulated by the FDA.

Choose the right equipment

Due to the complexity of the extrusion process, it can be a challenge to choose equipment with the appropriate specifications, scale up the process and design a facility into which this fits, especially if you’re new to the game. The twin-screw extruder is unique in the food industry because of its short residence time, which makes controlling mixing, heat transfer and mass transfer especially complex during scale-up. Commercial production is challenging because of the need to learn how to use bigger equipment, handle much larger volumes of ingredients and tweak process conditions to manufacture the same quality of product. It requires translating the process from a benchtop extruder to commercial-scale extruders that can be 50 feet long and 20 feet tall. It’s common to have multiple extruders in a production space.

Once a startup has determined its hoped-for production rate in kilos per hour, we can assess the type of equipment that will help them reach this. You will need to ask equipment manufacturers the right questions about equipment specifications, such as:

  • What is the ideal screw design? The screw design can impact how much mechanical energy can be applied, as it generates friction.
  • What is the ideal diameter of the screws?
  • What is the temperature profile needed?
  • What kind of thermal and mechanical energy input is needed?
  • Is the equipment easy to clean and maintain?

Define production parameters

A startup needs to ensure their plant-based protein extrusion process will run on equipment that can meet their target production volume. To do so, you need to evaluate the equipment for your product and learn how to run your process on that equipment with maximum efficiency and effectiveness. Your product experts can work with experienced process engineers, along with a university or equipment manufacturer, to define production parameters.

Different product characteristics can be obtained by manipulating variables. For example, this could include:

  • Altering an equipment configuration to increase mixing and speed up throughput;
  • Pre-hydrating ingredients with steam before they go into the mixer, which allows for a faster flow rate through the extruder;
  • Changing the temperature at the die to alter the density of the final product; or
  • Adding a plate at the end of the cylinder to restrict the opening, thus increasing the heat caused by a buildup of pressure.

Plant-based protein manufacturing facility and process design

Here are some of the considerations that need to be considered in determining how an extruder fits into a plant-based protein manufacturing facility.

Facility design for plant-based foods

Safely handling ingredients as they scale

Receiving, transporting and handling large amounts of ingredients during commercial production poses significant challenges that don’t exist during process development. The dust created during production, the threat of allergen cross-contamination and ergonomic considerations are all different at scale.

When a company is using different formulations or plans to in the future, the appropriate controls must be in place to prevent mixing allergens or other types of ingredients that may affect a product label or food safety. Product innovation can be hampered by the presence of allergens in a facility. Think of a bakery that handles conventional flour and cannot produce truly gluten-free products because of wheat dust spreading throughout the bakery. Facility architects need to design the processing area so it is isolated from other parts of the facility.

Consider allergens and segregation in the early phases of facility design so that allergen-free spaces can be isolated from the rest of the plant. In some cases, allergen contamination in parts of the facility dictates the need for a separate HVAC system or electrical supply, as was done in this bakery. Cleaning should also be considered during facility design.

The fine dust from protein isolate powders is hard to control because it is light enough that it infiltrates HVAC systems, electrical components and throughout a plant. Since powdered organic ingredients are combustible, perform a dust hazard analysis to identify and mitigate the risk of explosion due to dust buildup. Housekeeping, which includes cleaning and containment, must be done in a way to handle dust to prevent explosions.

To minimize the risk of ignition, designers take into account:

  • The way powders need to be transferred, including from bulk bags into mixers and extruders.
  • Electrical elements that could serve as an ignition source.
  • Building codes that ensure worker safety.

It is not a trivial logistical issue to consider how ingredients are handled during commercial production. For example, workers will no longer be tearing bags and dumping ingredients into a mixer. Instead, the design must take into account ceiling height so one-ton bags of powder can be lifted on a hoist and dumped into the mixer from above.

Producing—and dissipating—steam

In addition to the standard air-handling systems that keep a facility comfortable for workers, extrusion requires the generation and removal of surplus steam. Significant amounts of steam are often consumed and generated as a by-product during extrusion. A boiler system, which can be quite expensive, can be overlooked when acquiring an existing facility. Off-gassing at the extruder outlet and the dissipation of excess steam from the building requires adequate ventilation. Ancillary utilities, such as an adequate boiler, HVAC system and electrical power, are vital to production.

Food safety plan

Including food safety experts on the design team helps to develop a manufacturing facility that supports a food safety plan to protect consumers and prevent food recalls. They have to be aware of a wide range of safety considerations that apply to all food processing facilities, such as bakeries (dust mitigation and allergen contamination) and meat plants (raw vs. ready-to-eat). Some considerations include the segregation of materials, equipment cleaning and the flow of materials and personnel. Architectural considerations include unidirectional flow from raw rooms to cooked product spaces and where to gown up and wash footwear.

Future-proofing a plant-based protein manufacturing facility

Think about future opportunities and product innovations when designing a plant-based protein manufacturing facility. Consider future flexibility that will allow you to expand into other spaces within a facility when you are ready. This may include leaving some empty space in the plant into which you can grow or designing a process for a space you can lease in the future.

This flexibility allows you to consider new product lines—say, a shift from a chicken substitute to beef—which may require entirely different ingredients and processes. Or you might want to make a shelf-stable product, requiring different downstream and packaging capabilities.

Expansion considerations from an equipment standpoint include:

  • Are there adequate utilities—natural gas, electricity, water—to support an expansion?
  • Are the boilers sufficient to produce the steam heat needed for more extruders?
  • Can the HVAC system ventilate additional excess steam?
  • Are the roof and ceiling structural supports adequate to house the additional weight of an expanded HVAC system?
  • Is the ceiling height sufficient to handle the movement of large amounts of ingredients?

The design and construction of plant-based protein manufacturing facilities and process lines can be managed properly with the help of a proficient and experienced design-build firm. CRB designs to the highest standards, using food industry experts who consider food safety in every project. CRB has experience working with food processors—from startups new to food manufacturing to established companies with a history of large-scale food processing. Our expertise spans all aspects of extrusion, including architecture, layout design, mechanical systems, dust mitigation and equipment specs and procurement to ensure that safety, flexibility and efficiency are taken into account.

Let’s talk about how to design and build your plant-based protein extrusion facility.

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