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Manufacturing of TVP - texturized vegetable protein

One of the fastest growing global segments in the food industry is the production of TVP or texturized vegetable protein. This alternative protein source provides an economical and ecological option to traditional sources, such as meat and poultry. This article will outline the use and versatility of twin screw extruders for the production of this unique and healthy product.

The extrusion process can be used to transform wheat or legume protein – e.g. from soy, peas or lupines – into a fibrous structure similar to that of meat. If fat, aromas and/or colorings are added, the texturized vegetable protein generated in this way can be processed after soaking in water in order to make stand-alone meat substitutes or various ingredients or extenders used in the food industry. The aim of the extrusion process is to manufacture a product with a consistent color and texture. After being soaked in water, a subtly laminar or fibrous structure should be visible or tangible. The texture of the product must not be too soft, and should be very similar to “original” meat in a tactile or kinesthetic sense. These requirements are fulfilled if the protein is effectively solubilized, and if the starch is completely and consistently embedded in the protein matrix. The Coperion ZSK food extruder offers the ideal conditions for this.

The process
Vegetable protein is texturized with the aid of the ZSK food extruder by means of a typical hot extrusion cooking process. During this process, a protein-rich powder mixture or a vegetable protein concentrate – which usually has around 70% protein content – is mixed with water in the ZSK food extruder and hydrated. The mass is subsequently pulped, melted and denatured in the process section of the ZSK. The fiber and starch components are finely dispersed and worked in. These help to loosen up the texture of the extrudate. The temperatures in the process section are usually very high in order to achieve a well-texturized structure, yet not so high that they brown the product excessively.

The set-up
Powdery vegetable proteins or premixes – and also additives if these are required – are fed into the feeding barrel of the ZSK process section via Coperion K-Tron gravimetric feeders. The water required for the process is injected into the extruder’s process section via injection nozzles, which are also gravimetrically controlled by Coperion K-Tron loss in weight technology. It is possible to assist the thermomechanical extrusion process by directly injecting steam into the ZSK process section. In this manner, particular textures can be achieved, and the process can be run more economically.

Initially, the water and powder are mixed together to form a paste before the mass is warmed up by means of mechanical energy consumption. During this process, the starches are gelatinized, the proteins are denatured, and the entire mixture is worked to form a consistent product. Additional liquids such as aromas or other components can be added to the process section further downstream and worked into the product mass. At the end of the ZSK food extruder, the hot protein mass is discharged through a shaping nozzle in such a way that oriented, fine fibers develop. The product expands as it escapes from the nozzle, causing it to get its light and foamy, fibrous or laminar structure. Using Coperion’s ZGF centric pelletizer the textured product is shaped and cut to the desired size at the nozzle plate itself.

The ZSK food extruder
The ZSK food extruder boasts properties which make it the ideal system for manufacturing texturized vegetable protein. Its process section consists of multiple barrels in which two screws co-rotate. These closely intermeshing screws prevent low-flow zones along the whole length of the process section. The results are outstanding mixing behavior and good self-cleaning of the screws. The process engineers use their comprehensive expertise to tailor the extremely flexible ZSK system to each individual application. All process steps, from raw ingredient handling to ingredient feeding and extrusion, expansion and pelletizing, are all closely interlinked and function seamlessly. They can be designed to fulfill the most stringent hygienic standards, and the system is easy to operate, clean and maintain.

One additional point should be noted specifically in regards to energy efficiency. Coperion ZSK food extruders also offer advantages when it comes to energy requirements. The deeply cut screw flights with a diameter ratio Do/Di of 1.8 result in a very large free screw volume thus enabling energy-saving, gentle product handling and reduced thermal stress on the raw materials.

Kontakt

  • Uta Kühnen

    Process Engineer for Food Technology at Coperion

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