4 Advice to Choose a food extruder machines

Extruders can be thought of as high temperature short time cooking (HTST) equipment, that can transform various raw ingredients by forcing through a die to create the desired final product shape during new product development in the food development companies. A food extruder accelerates the restructuring process for food ingredients, compared to other traditional food processing methods. Extruders are highly multi purposed as they can be used to cook, form, mix, and texturize food products with added flavour, quality retention and increased productivity at a low-cost.

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Process in brief:

During the extrusion process[u1] , raw materials are ground to the preferred size, which then passes through a preconditioner. At this stage, steam may be injected into the raw materials and finally reaches the die assembly at a defined throughput. Extruder feeds both solid and liquid ingredients, mostly grain pulse, root-based foods, water, oil, sweeteners, colours, and added vitamins and minerals.

Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section. The extrusion process can be done with the material hot or cold.

Extruder&#;s design and specification can be tailored for the ideal and intended manufacturing application of food products. There is a complex interaction between feed ingredients, extruder design and operating conditions, affecting product development, quality improvement, consistency, and optimum operation efficiency (1).

Extruders can generally be classified based on the build type, such as single screw extruder, twin screw extruder, parallel twin screw extruder, pelletizing Extruder and dry Extruder. The following variables affect the efficiency of the extrusion process. Firstly, raw material&#;s physical and chemical properties, such as viscosity, moisture content etc. The dough&#;s rheological behaviour can greatly influence the final product quality, process time, and heat transfer. Secondly, thermomechanical cooking factors[u2] , such as the design of the equipment including the type of screw, variable screw diameters (D) and lengths (L) and barrel section of the machine, die design and opening shape and section (2).

The die plate assembly design is a crucial part of the operation as it is responsible for forming the desired product shape and adds flow resistance to achieve a final output of transformed materials. Bronze dies produce better quality pasta compared to stainless steel dies. Finally, operating conditions of the equipment such as screw speed, temperature and overall water content contribute to the process&#;s efficiency.

For instance, during the extrusion process, caution must be given to the heat generated from screw elements, the heating system and the self-heat gained by the barrel&#;s viscosity. Water is greatly used in combination with the extrusion process to characterize the melting behaviour and overall final dough rheology. Moreover, it is also used in the form of steam to impact the total extruder energy output. Such usage can significantly impact the extruder selection, design and performance and mainly on the product quality. The remaining water is evaporated during the venting stage to achieve accelerated cooling to form the final product (3).

There are different categories of extruders, such as cold, hot, steam-induced and co-extrusion. Cold extrusion is mainly used for gentle mixing and shapes the dough without heating or cooking, such as pasta. Hot extrusion converts the raw materials under high temperature and pressure in a short time. This type is considered for textured foods such as pet food. Steam-induced extrusion is used for determining the textural attributes of highly expanded products, such as expanded breakfast cereals. Co-extrusion can be very helpful for products with dual textures, such as crispy shell and soft filling. Co-extrusion combines stem induced expansion as well as injection filling.

Global leaders:

There are several types of extruders available in the market, confusion for food manufacturers, based on the product type. Some manufacturers who supply single-screw extruders are American Extrusion International, Wenger, Extru-Tech, and Schaaf Technologie. Companies such as Buhler, Baker Perkins, Clextral and Coperion offer twin-screw extruders.

Brabender CW offers extruders at a pilot scale level. Extruder KE 19 is a single screw extruder with a screw diameter of 19mm and has an output of 5kg/hr. Single screw extruders are open channel extruders, which can be thought of as a drag flow pump, with the final output delivery controlled by the pressure flow.

Syringe Extruder

Screw Extruder

Filament-Fed Extruder

This Extruder comes in handy for product development, specifically to test the extrusion properties of different raw materials and develop the processing characteristics. Process stimulation could be done with ease under low R&D costs. Stimulations such as cold forming, shaping, gelatinization, plasticization and expansion. This Extruder also aids in increasing the time efficiency to characterize the sensory and rheological characteristics.

Brabender CW also offer a twin screw variety, TwinLab-F 20/40. Twin screw extruders contain two screw as the name suggests which counter-rotate forming closed channels. The output from this type of Extruder is less vulnerable to pressure flow and can be considered as a positive displacement pump (2). The TwinLab-F20/40 model has been designed for lab scale applications at different L/D ratios. New product developments in snack, breakfast cereals, sweets, and pet food category can be prepared on a lab scale. It contains either a 600 or rpm motor and horizontally divided barrel that can be opened to observe and clean. It also contains 4 different heating zones and water cooling.

Alternatively, Buhler group offer twin screw extruders. ECOtwin variety is specifically tailored for the pet and sea food industry. It offers a screw diameter of 5 to 7 inches and produces 20,000kg/hr. Whereas the POLYtwin option is a parallel twin screw extruder. Its screw diameter ranges from 2 to 7 inches and offers up to 450 kg/hr. Due to its modular design, it is highly flexible. It can be used for food ingredients, breakfast cereals, sea food and pet food. POLYtwin also offers a robust and fully automated screw ejection unit, thus reducing the risk of damaging the elements. Knife heads can be changed easily without disrupting the production process. Flexible cutter for a consistently high quality end product is yet another advantage.

References:

1. Riaz, Mian. (). Extruders in food applications.
2. Yacu, W. (). Extruder screw, barrel, and die assembly: General design principles and operation. Extrusion Cooking: Cereal Grains Processing, 73.
3. Kokini, J. L. (). The effect of processing history on chemical changes in single-and twin-screw extruders. Trends in Food Science & Technology, 4(10), 324-329.

                                                                chuangbo twin screw extruder

The first factor to consider when choosing a twin screw extruder is the application. Twin screw extruders are used for a variety of applications, including compounding, reactive extrusion, devolatilization and so on. Make sure you choose a twin screw extruder that is designed for your specific application. Below is a basic application of the twin screw extruder. When you want to buy a machine, you need to make your requirement for the machine clear.

Application

1. Compounding: Twin screw extruders are used to mix and compound different ingredients, such as polymers, additives, and fillers, to create a homogenous material with consistent properties.

2. Reactive extrusion: Twin screw extruders are used to carry out chemical reactions, such as polymerization and grafting, in a continuous process. This allows for precise control over the reaction conditions and can improve the properties of the final product.

3. Devolatilization: Twin screw extruders are used to remove volatile components, such as water, solvents, and monomers, from a material. This is important in the production of high-quality polymers and other materials.

4. Recycling: Twin screw extruders are used to process and recycle different types of waste materials, such as plastics, and rubber, etc. The extrusion process can help reduce waste and create new products from recycled materials.

Screw configuration

Twin screw extruders come in different screw configurations, including co-rotating, counter-rotating, and intermeshing. Each configuration has its advantages and disadvantages, so choose the one that suits your needs.

1. Co-rotating: In a co-rotating twin screw extruder, the screws rotate in the same direction, either in a parallel or conical arrangement. This configuration is suitable for high shear and mixing applications, such as compounding and reactive extrusion.

2. Counter-rotating: In a counter-rotating twin screw extruder, the screws rotate in opposite directions, which creates a kneading and mixing action. This configuration is suitable for processing materials with high viscosity and for devolatilization applications.

Contact us to discuss your requirements of food extruder machines. Our experienced sales team can help you identify the options that best suit your needs.

3. Intermeshing: In an intermeshing twin screw extruder, the screws have interlocking teeth that mesh together as they rotate. This configuration is suitable for processing materials with low viscosity and for food processing applications.

4. Non-intermeshing: In a non-intermeshing twin screw extruder, the screws do not have interlocking teeth and rotate independently of each other. This configuration is suitable for processing materials with high viscosity and for devolatilization applications.

Size

Twin screw extruders come in different sizes, ranging from small laboratory units to large industrial machines. Choose a size that fits your production needs. The size of a twin screw extruder is typically determined by the diameter of the screws and the length of the barrel. The diameter of the screws can range from 18mm to over 200mm, while the length of the barrel can range from a few hundred millimeters to nearly one meter.

Small-scale twin screw extruders with screw diameters of 18mm are commonly used for research and development purposes or for small-scale production of specialty products. Mid-range twin screw extruders with screw diameters of 30-70mm are used for medium-scale production of a variety of products. Large-scale twin screw extruders with screw diameters of over 100mm are used for high-volume production of products. It is important to select the appropriate size of twin screw extruder based on the specific application and production requirements to ensure optimal performance and efficiency.

Material compatibility

Twin screw extruders can process a wide range of materials, including plastics, rubber, and chemicals.  However, not all materials are compatible with all types of twin screw extruders. For example, materials that are highly abrasive or corrosive may require specialized screw designs or materials to prevent damage to the extruder.  So Make sure you choose a twin screw extruder that is compatible with the material you plan to process.

The design of the twin screw extruder also plays a role in material compatibility. Different screw designs and barrel configurations are better suited for processing different types of materials.

Finally, the processing conditions, such as temperature, pressure, and residence time, can also affect material compatibility. Some materials may require specific processing conditions to prevent degradation or chemical reactions during processing.

Throughput capacity

The throughput capacity of a twin screw extruder is the amount of material that can be processed per hour. Choose a twin screw extruder with a throughput capacity that meets your production needs. The throughput capacity of a twin screw extruder is typically measured in pounds per hour (lb/hr) or kilograms per hour (kg/hr). Small laboratory-scale twin-screw extruders may have a throughput capacity of a few pounds per hour, while large industrial-scale twin-screw extruders can process several tons of material per hour.

The screw design plays a crucial role in determining the throughput capacity of a twin screw extruder. Screws with a greater number of flights and a higher pitch can increase the shear and mixing forces, resulting in higher throughput capacity. Additionally, the use of multiple screw elements and barrel sections can further increase the throughput capacity.

The material being processed also affects the throughput capacity of a twin screw extruder. Materials with higher viscosities or higher melting points may require more energy and longer residence times to process, resulting in lower throughput capacity. Overall, the throughput capacity of a twin screw extruder can range from a few pounds per hour to several tons per hour, depending on the specific application and processing conditions.

Budget

Twin screw extruders come in different price ranges, so choose one that fits your budget. Generally, the cost of a twin screw extruder can range from $20,000 to $200,000 or more.

Small-scale twin screw extruders with a capacity of up to 50 kg/hour can cost between $30,000 to $40,000. Mid-range twin screw extruders with a capacity of 50-500 kg/hour can cost between $50,000 to $70,000. Larger twin screw extruders with a capacity of over 500 kg/hour can cost up to $70,000 or more.

In addition to the initial cost of the machine, there are also other factors to consider such as installation, training, and maintenance costs. These costs can vary depending on the manufacturer and the location of the buyer. It is important to carefully consider the budget and requirements of your specific application when selecting a twin screw extruder to ensure that you get the best value for your investment.

Brand and reviews

Choose a reputable brand and read reviews from other users to ensure you are getting a quality twin screw extruder.

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