Vertical Hot Melt Extrusion: A Cutting Edge Technology for Personalized and Sustainable Food Systems

HME Provides Solutions for the Following Issues in Food Processing

HME has been tested/used in various shapes such as pellets, pastes, and for various purposes, e.g., masking the bitter taste, shaping, additives, etc. Additionally, HME significantly improves texture and organoleptic properties in food products, offering solutions that meet consumer expectations for both taste and texture, while also improving functionality through encapsulation of active ingredients, such as nutrients and flavors.

However, many food ingredients remain difficult to process, sometimes sticky, temperature-sensitive, and shear- sensitive materials. This requires working on all process parameters (screw configuration, screw speed, melt pressure, etc.) or ingredients in order to reduce the shear forces needed or lower the temperatures required to properly mix the final product, while avoiding thermal degradation:

On top of lowering those process parameters, controlling them with the smallest possible deviation is crucial to optimize the interference of some components with the functionality of other components in the recipe. Therefore, it requires precise dosing of all product ingredients and metering of all process parameters.

Food processing extruders must be compliant with the regulatory guidelines ─ the metallurgy of the contact parts must not be reactive, additive or absorptive with the product and the equipment must be configured for the cleaning and validation requirements associated with a food environment – see HACCP International Certification of Food Safe Equipment, Materials and Services [11]. This requires among other things that parts be made in special stainless steel alloys and be processed in order to reach specific surface finish in order to avoid contamination.

Vertical Extrusion as a New Technology with Positive Impact

Back in 2012, we estimated that the horizontal format was a bottleneck to various improvements:

• Contamination issues: The equipment footprint of horizontal extrusion machines is quite large for industrial scale production, and it is subjected to high risks of contaminations from the work environment to the production, and vice versa.
• Cleaning issues: A horizontal extruder is quite big, especially with a 40:1 or more Length to Diameter barrel, which makes the cleaning both long and fastidious. Cleaning is a central item in the food processes as both the equipment and the manufacturing room must be fully cleaned after every production run, therefore has a huge impact on efficiency and cost basis.
• Operator interface: Big footprint also means more complex operator interface due to numerous moves along the extrusion line, e.g., along the in-feed of the filler via the control panel to the die and the downstreams.

Based on a market analysis and a vision for the future of HME, we concluded that the preferred process flow direction needed to be changed from the horizontal position to top- down in the vertical axis.

All Technical Issues were Addressed One After the Other:

• The necessity to design a generic extruder capable of integrating by easy ‘plug in’ mechanism all types of top and side feeders for the pellets, powders and further solids, liquids and gases.
• The work on all screw elements design and configuration is essential to ensure smooth additive transportation through the secondary feeders, which are now horizontal. The versatility of changing screw elements allows for mixing at different intensities, conveying, chaotic mixing, and the use of various screw pitches, homogenization elements, and discharges. All these components are fully interchangeable along a single shaft, enabling precise control and customization of the extrusion process to meet specific product requirements.
• The simplification of the extruder ‘easy clean’ system
• The integration of a high-performance cooling systems for strand cooling.
• The integration of downstream equipment with versatile technical constraints (temperature control for the calendar, cutting precision for the pelletizer, tensile force, and size control for the haul-off winders).
• The coordination of all process parameters thanks to an integrated, user friendly and reliable automation system.

In more details, the following steps were achieved in order to develop the 10.5 mm 40:1 Length to Diameter twin screw vertical extruder starting from a ‘classical’ horizontal 10.5 mm 20:1 Length to Diameter extruder [5]:

• Lengthened the barrel in order to smoothen the mixing process for ingredients that are fragile.
• Positioned eight heating/cooling zones all along the barrel in order to better monitor the processing temperature of ingredients that have a narrow range between melting and degradation.
• Changed metals used to manufacture parts (high-grade stainless-steel precision engineered).
• Redesigned many external parts (for easier feed or to avoid contamination between lots due to powder that would remain stuck in notches) and many internal parts (to make ‘change over’ easy in between lots).
• Made the extruder vertical to further reduce the contamination risk (thanks to gravitation) and to further decrease footprint of the process.
• Optimized the settings between screw configuration and speed, motor power and torque in order to start the mixing quicker/smoother and extract the filament with strong/stable pressure for easier downstream steps.

The vertical twin-screw extruder has already been installed for various applications – aeronautics and pharma – both in France, UK and the USA – see presentation of the vertical extrusion line to Seqens Scientific Committee in Boston in June 2023 [12]:

Comparative Advantages of Vertical Twin-Screw Extrusion in Food Processing

The vertical twin-screw extrusion system represents a significant technological leap over traditional horizontal extrusion methods. The vertical configuration introduces several enhanced features that are critically important in food manufacturing, where efficiency, precision, and space optimization are essential. This comparative analysis highlights the key advantages of vertical extrusion, focusing on process control, mixing efficiency, and temperature regulation.

One of the most evident advantages of vertical twin- screw extrusion is its enhanced  process control. Vertical systems benefit from gravity-assisted material flow, which significantly reduces the risk of feed blockages that can occur in horizontal systems. By utilizing gravity to move materials through each stage of the extrusion process, vertical systems allow for more consistent and predictable processing. This results in smoother operations, particularly when dealing with bulk materials or recipes requiring precise control over ingredient flow. The minimized risk of feed interruptions not only improves overall efficiency but also enhances the consistency of the final product, an essential factor in industries where product uniformity is critical, such as in the production of functional foods, gluten-free products, and meat analogues.

The mixing efficiency of vertical twin-screw extruders also surpasses that of their horizontal counterparts. The vertical orientation allows for better integration of ingredients during processing, as the materials are continuously mixed and transported downward through the screws. This configuration ensures that ingredients are more evenly distributed throughout the extrusion process, which is particularly beneficial when working with complex formulations or sensitive bioactive compounds. In addition, the vertical layout supports the integration of advanced mixing techniques that can handle a wider range of ingredient viscosities, from pastes to powders. This is particularly important in the development of products such as high-protein snacks or plant-based meats, where texture and ingredient incorporation are crucial to the final product’s quality.

Another key advantage of vertical twin-screw extrusion is its temperature regulation. The design of vertical systems allows for more precise control over temperature gradients throughout the extrusion process. Vertical systems are often equipped with multiple heating and cooling zones that can be independently controlled, ensuring that each stage of the process is maintained at the optimal temperature for ingredient processing. This is especially important for temperature-sensitive materials, such as certain proteins, bioactive compounds, or nutraceuticals, which can degrade or lose their functional properties if exposed to excessive heat. In comparison, horizontal extruders may face challenges in maintaining consistent temperatures, leading to potential variations in product quality and increased waste. The ability to finely tune the temperature at each stage of the extrusion process in vertical systems ensures better retention of nutritional and sensory qualities, which is essential for the development of premium functional foods.

In addition to these technical advantages, the  space- saving design  of vertical twin-screw extruders offers a practical benefit in industrial settings where floor space is at a premium. Vertical systems are typically more compact than horizontal extruders, as they stack components vertically rather than spreading them across a wide footprint. This makes vertical extrusion particularly well-suited for facilities looking to maximize production capacity without the need for extensive floor space. The reduced footprint also simplifies the integration of ancillary equipment, such as pelletizers, cooling units, or packaging systems, which can be positioned directly below the extruder. This not only improves the overall efficiency of the production line but also reduces the risk of contamination by limiting the number of open conveyors or transfer points between processing stages.

Energy efficiency is another critical factor where vertical twin-screw extrusion has an edge over traditional horizontal methods. The gravity-assisted material flow inherent in vertical systems reduces the mechanical effort required to move materials through the extruder, thereby lowering energy consumption. In a horizontal system, more energy is required to convey materials horizontally, especially when dealing with dense or viscous formulations. The verticality thus provides a more sustainable option, as it reduces both energy costs and the environmental impact of the production process.

Maintenance and cleaning procedures are also simplified in vertical twin-screw extruders. The vertical design minimizes the number of horizontal surfaces where materials can accumulate, reducing the risk of cross- contamination between production batches. Moreover, vertical systems often incorporate ‘easy-clean’ features, such as removable screws and quick-access panels, which make it easier to thoroughly clean the extruder between runs. This is especially important in food processing environments where hygiene standards are stringent, and any residue from previous batches could lead to contamination or quality control issues. Horizontal extruders can be more challenging to clean thoroughly, especially when handling sticky or hard- to-remove materials.

Finally, vertical twin-screw extrusion plays a crucial role in the development of  novel food products  that cater to emerging consumer demands for health, sustainability, and personalization. As consumers increasingly seek out products that align with specific dietary preferences or health goals, such as plant-based meat alternatives, gluten- free snacks, or fortified functional foods, vertical extrusion offers the flexibility needed to meet these demands wherever needed.

From Micro Scale to Industrial Scale

From the start of our “Vertical project” we have integrated all characteristics that we considered essential to successful scale-up for industrialization purposes and our Patent covers extruders up to 42 mm twin screw extruders [5]. Designed for pharmaceutical applications, the vertical extruder considers the well-known technical and economical constraints linked to pharmaceutical applications that are also very applicable to food applications (capability to produce small lots and necessary ‘soft’ extrusion process).

The design of the vertical extrusion system also allows modular integration of all ancillary equipment necessary for final product processing and shaping (pelletizers, calendars, millers and so on) below the extruder. In the traditional horizontal extrusion technology, an array of ancillary equipment is used for further downstream processing, comprising a conveyor belt combined plus a pelletizer. This typically results in a long process chain.

Operator working conditions are also improved as there will be no need to move around the equipment to control process performance – and the small footprint makes the extruder easy to cover and seal to protect operators and the working environment from any hazardous vapors/dusts.

Last but not least, the operational system of the vertical extruder is based on the same design geometry as its horizontal homologues so that the positive conveying mechanism of the fully intermeshing co-rotating twin- screws provides predictable scale-up from vertical small- scale machines to horizontal large-scale extruders, as long as both machines are of the same geometry, e.g., co-rotating and fully intermeshing.

This design allows for a seamless transition from R&D or small-scale individualized production to large-scale industrial production (Figure 1, Table 1) [13, 14]. However, each extrusion process scale up has its own specificities and special care will need to be given to allow for enough time for trials and training in doing so [15, 16].

Sustainability and Future Trends in Personalized and Extruded Food Products

The future of food production is being shaped by the growing demand for personalized nutrition, sustainability, and efficiency. Vertical Hot Melt Extrusion (HME) can play a pivotal role in addressing these demands while becoming not only energy-efficient but also capable of supporting waste reduction and personalized food products  [2, 3, 8, 10], nutrient preservation, and advanced bioactive  packaging solutions  [9, 16, 17].  In particular, the ability of HME to encapsulate bioactive ingredients ensures that nutrients are preserved during processing and released efficiently during consumption, enhancing the nutritional value of food [2, 9]. See Table 2.

Energy Efficiency of Vertical HME: Energy efficiency is particularly important in the context of global food production, where manufacturers are under increasing pressure to reduce their environmental impact. HME’s capacity to streamline production while maintaining high- quality output positions it as a critical technology for the future of sustainable food systems. As mentioned before, the gravity-assisted material flow inherent in vertical systems reduces the mechanical effort required to move materials through the extruder, thereby lowering energy consumption.

In a horizontal system, more energy is required to convey materials horizontally, especially when dealing with dense or viscous formulations. The vertical configuration thus provides a more sustainable option, as it reduces both energy costs and the environmental impact of the production process.

By optimizing the use of energy, Vertical HME can therefore help companies meet sustainability goals and regulatory requirements related to energy consumption and greenhouse gas emissions [2, 9].

Vertical Extrusion with Plug in Downstream for BioActive Films and Packaging that can Reduce Food and Packaging Waste

As the global population continues to grow, the reduction of food waste will become increasingly important for maintaining food security and reducing the environmental impact of food production. By extending shelf life and minimizing waste, Vertical HME can help mitigate these challenges, making it a vital tool for the future of food sustainability [9, 16].

Through the encapsulation of bioactive ingredients, HME protects sensitive nutrients from oxidation and degradation during storage. This encapsulation technology allows nutrients such as vitamins, minerals, and probiotics to remain stable over extended periods, ensuring that food products retain their nutritional value until they are consumed.

Vertical HME together with Plug in Downstream Equipment will also make it easier to develop bioactive films and bioactive packaging materials that further extend shelf life. These films can be infused with antimicrobial agents or antioxidants, which actively interact with the food product to inhibit microbial growth and prevent spoilage. By slowing down the natural processes that lead to food degradation, bioactive packaging reduces the need for artificial preservatives while simultaneously decreasing food waste. One of the major advantages of bioactive packaging is its ability to maintain food freshness without relying on synthetic preservatives, which aligns with consumer preferences for natural, clean-label products. Moreover, by preserving nutrients and preventing degradation, bioactive packaging supports the overall health and well-being of consumers, ensuring that they receive the full nutritional benefits of the food they purchase. This combination of extended shelf life and enhanced nutrient preservation makes bioactive packaging an essential component of the future food system​. Beyond its immediate benefits for food preservation, bioactive packaging also plays a critical role in reducing packaging waste as many bioactive films are designed to be biodegradable or recyclable. As the food industry continues to prioritize sustainability, the integration of bioactive packaging will likely become more widespread, helping to reduce food and packaging waste simultaneously [9, 16].

AI and Digitalization in Food Extrusion Technologies

Looking to the future, AI and digitalization also offer new opportunities for precision, customization, and efficiency, allowing manufacturers to produce highly personalized food products at scale while also maintaining sustainability and efficiency [18, 20, 27, 28].

Artificial Intelligence (AI): AI is playing an increasingly important role in the food industry by enabling predictive analytics, process optimization, and quality control. In the context of extrusion, AI can be used to analyze data from the production process and make real-time adjustments to optimize performance. For example, AI algorithms can predict how different ingredient combinations will behave during extrusion, allowing manufacturers to fine-tune recipes for personalized food products. AI can also be used to predict maintenance needs, reducing downtime and improving overall equipment efficiency.

Digitalization: Digitalization is transforming the way food manufacturers manage and track production processes. Through the use of sensors and connected devices, digital platforms can provide real-time insights into the extrusion process, from ingredient input to final product output. This level of transparency allows manufacturers to monitor quality, track production efficiency, and ensure that personalized nutrition goals are met. Digitalization also supports traceability, enabling manufacturers to track each batch of food from production to consumption, ensuring food safety and quality at every step.