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How to handle difficult powders when making plant-based meat substitutes

Many protein powders have challenging flow characteristics that can have a substantial negative impact on product quality

The market for plant-based meat substitutes is expanding rapidly in size as well as diversity. As a result, researchers are continuously seeking new raw materials to add to the available product range for the production of TVP (Texturized Vegetable Protein) and HMMA (High-Moisture Meat Analogues). The suitability of a protein source for plant-based meat substitutes depends on several factors like protein and fat content, as well as its properties when mixed with water. At the same time, the powder’s flow characteristics are a critical factor for successful manufacturing.

Protein powders and their difficult flow characteristics
Plant-based meat substitutes such as TVP and HMMA use protein powders as a raw material. Unfortunately, many protein powders like pea and lupine-based powders have challenging flow characteristics. Inconsistent flow can have a substantial negative impact on product quality because the manufacturing process depends on an accurate, continuous supply of raw materials to the extruder.

While some causes of poor material flow are related to the powder’s own characteristics, others are related to the environment or the transfer and handling system. High humidity in the air, for example, can cause the powder to absorb moisture and aggregate, making it more difficult to transfer.

Solutions for challenging flow characteristics in TVP and HMMA production
Solutions for difficult flow characteristics impact most process steps, from raw material handling all the way through to feeding the extruder. This includes equipment design of hoppers and pneumatic transfer systems, as well as adding extra elements designed to aid powder flow. Gravimetric feeders with flow aid devices such as the Coperion K-Tron ActiFlowTM system play a vital role in continuous supply of protein powder to the manufacturing process.

Gravimetric feeders
Gravimetric feeders discharge powders into the extruder while measuring the discharge rate. Loss-in-weight feeders are the most common, consisting of hoppers mounted on load cells or a weigh scale with screw feeders to move the product from the hopper to the production extruder. Coperion K-Tron offers a wide range of gravimetric feeders. Generally, single screw feeders are suitable for free-flowing powders or granular ingredients, but sticky or poorly flowing ingredients need twin screw feeders.

As the powder flows out, the hopper’s weight decreases. This loss in weight gives an accurate measure of material flow, even if there are changes in the bulk density of the material. A controller adjusts the flow rate to the desired setpoint. However, bridging or ratholing can occur in hoppers due to material flow problems, which may prevent the controller from maintaining the desired rate. Under these conditions, flow aid devices can help restore the material flow into the feed section.

Coperion K-Tron feeders range in capacity from 32 g/h to several tons per hour. They can be outfitted with ActiFlow, a smart non-product-contact device that applies gentle vibrations to the hopper wall, hereby carefully activating the bulk material with the optimal amplitude and frequency. It communicates with the feeder controller to automatically adjust vibration when it detects a material flow issue. In this way, the vibration is limited to the amplitude and duration necessary to restore the flow. The feeder controller compensates for the effect of vibrations on weight measurement, and reducing the vibration ensures that the impact on flow rate is kept to a minimum.

Pneumatic transfer systems
Raw materials for TVP or HMMA production are delivered in several different methods including boxes, bags, bulk bags, or super sacks. Bag dump stations have small hoppers for receiving the material, and may have dust extraction installed to protect operators.

From the receiving hoppers, pneumatic conveying systems are often used to transfer dry materials to the gravimetric feeders. They use positive pressure or vacuum conditions depending on the design parameters. Typical systems include an air source, a material feed device, a conveying line, and an air material separator, such as the Coperion K-Tron filter receiver.  

Vacuum systems have the advantage of containing dust, but their capacity is limited to about 7,500 kg/h (15,000 lb/h). Pneumatic systems typically have inline check sieves or strainers installed to remove packing materials, insects, or hard lumps of agglomerated product. This will reduce flow problems downstream.

Elimination of moisture is a critical factor to keep powders flowing easily. Some installations use a desiccant bed dryer (DBD) to provide a cushion of dry air on the top of silos for this purpose. Exclusive blowers or compressed air sources can also help by fluidizing the powder in silos and hoppers.

Equipment design and coatings
Stainless steel offers the best non-stick performance for vessels storing protein powders. This material is also easier to sterilize and clean than other options. However, a lower cost solution is an epoxy coating with an FDA approved paint, which is common in large silos or storage vessels.

Best practice for equipment design includes using steep hopper angles and flow aids. These features promote the flow of powders through the system and help avoid bottlenecks during transfer.

Filters used in hoppers and on pneumatic receivers should have quick release properties, which can be achieved using superior non-stick fluoropolymer coatings. This is vital to prevent filters from clogging and reducing the flow rate, which can cause challenging powders to agglomerate together, making the problem worse.

Coperion offers Clean-In-Place (CIP) designs for many components, which are preferred for plant-based meat substitute manufacturing. This means that pipes, control units, gate valves, rotary, and diverter valves can all be cleaned without removing them from the processing system. A CIP design saves time when switching between products while maintaining the sanitary requirements of the food industry.

Help with design and troubleshooting
Coperion is a globally represented high-quality supplier of complete systems for the manufacture of plant-based meat substitutes. Coperion equipment design takes challenging powders into account and offers advanced technology, such as the ActiFlow smart flow aid device for gravimetric feeders. Experienced experts in compounding, extrusion, feeding, weighing and bulk material handling are available with technical support that includes help with the design of new systems as well as troubleshooting difficult applications.

Contact Coperion to find out more about how we can help you overcome the challenges of your protein powders with difficult flow characteristics.

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