Protein alternatives: How plants become artificial meat

Alternative proteins are one of the trend topics in machinery and plant engineering in the food industry, and thus also at POWTECH. But how are they actually produced? And what challenges do product developers and machine designers face? A short deep dive into a fascinating technology segment.

Nothing works without proteins. They are the cornerstone of all living things and provide our bodies with amino acids from which muscles, cells and tissues, as well as antibodies and hormones, are built. Eggs, meat, fish and dairy products are traditionally important sources of protein, but so are plant proteins - and these are becoming increasingly important for the world's food supply. But it is a long way from the soybean, lupin or wheat grain to the vegan sausage substitute, and a lot of technology is involved. The protein must first be extracted from the raw materials and processed before it can be "textured" into a meat or sausage substitute.

The process starts with sorting and cleaning of raw materials, be they pulses, seeds or others, which are then first ground. This still comparatively classic preparation process is then followed by protein extraction, which can be carried out differently depending on the raw material. This is often done in a multi-stage process with water or salt solutions, but organic solvents are also used. The raw materials are first soaked to separate the proteins from the carbohydrates and other components. Then the separated protein is precipitated from the solution (protein coagulation) and separated. Finally, the solution (concentrate or isolate) is processed directly or dried in a spray dryer to generate a powder. This powder forms the starting point for texturising - a process that ultimately leads to the meat-like product.

From the purification of soybeans to protein powder

Even this rough overview indicates that a wide variety of machines and equipment are needed in the various steps. So let's take a closer look at this using the example of the production of soy isolate: The soybeans are cleaned, ground and soaked in water. They are then heated to release the proteins. Centrifuges or decanters make their big appearance during protein extraction: in their conical rotating drums, solid particles are forced outwards by centrifugal force and form a layer on the inner wall of the drum. The liquid collects in the centre and is discharged through an outlet. This continuously separates the protein solution from the plant residues in the first step. After the initially dissolved protein has been "precipitated" into protein flakes by adding acid or salt, these are also concentrated in a decanter. In order to make the protein as completely usable as possible and to reduce the wastewater load, protein flakes that have not been separated in the decanter are separated in an additional plate separator; this works because the machine uses both centrifugal forces and gravity.

Finally, the coagulated proteins are washed and acid residues are neutralised, centrifuged again or filtered. Finally, the soy isolate is dried at low temperature - for example in spray dryers. As the name suggests, the protein-containing liquid is sprayed from above into a drying chamber where it falls towards a stream of hot air, causing the liquid to evaporate and the previously dissolved product to finally fall to the ground as a dry powder.

Texturing is the only way to create a competitive meat substitute

However, all these steps are only the preliminary work on the way to meat substitutes! Because in the end, it is not only the content and taste that are decisive for the consumer, but also the bite and mouth feel. In order to achieve a "customer experience" that is as true to the original as possible, the vegetable proteins must be textured. This is usually done in special extruders, where various raw materials and spices of the recipe are first mixed and ground to achieve a uniform consistency. This mixture is dosed into an extruder and water is added via spray nozzles. One or even two screws rotate in the elongated machine, transporting the material towards an opening (die) at the end of a cylindrical chamber. On this path, the mass is exposed to high pressure as well as defined shear forces and temperatures, whereby the protein denatures - this is referred to as the cooking extrusion process. At the end of the extruder, the product is discharged through a nozzle, producing fine fibres that are cut to a desired length. Depending on the process, either dry textured vegetable proteins (TVP) or those with a high water content (HMMA) can be produced. The latter are most similar to meat, while TVP have to be soaked in water before further processing.

High demands on the machine technology

The demands on the technology used are high: on the one hand, the machines must be flexible enough to process different recipes and raw materials. In addition, hygiene plays a major role - all components should be free of dead space and easy to clean. Because the centrifuges used in the first step have to set large masses in motion, energy efficiency plays an important role here. In addition, it is important to produce solids with the lowest possible moisture content in the separation step, because the subsequent drying is an energy-intensive process.

In texturing, the precision of the components used in terms of dosing accuracy and process parameters such as pressure and temperature is of great importance. With increasing demand and growing production volumes, integrated processes in which the complete line is optimally coordinated are also becoming more and more important. Automation also plays an important role here. It not only ensures high productivity, but also reproducible, consistent processes and complete documentation of the production parameters.

At POWTECH, machines and solutions for the entire process chain - from bean to granulate - will be on show. The new scope, which includes liquids as well as powders and bulk solids, takes into account the integrated, holistic view of the process chains.