Extrusion of meat substitutes
Meat substitutes could be part of the solution for feeding a rapidly growing world population. Clextral, a French manufacturer of food extrusion equipment, who has been in this market for many years has recently successfully partnered with Brabender Technologie.
One of the greatest challenges of the 21st century will be to feed the growing world population while protecting the environment and animal welfare. Global meat consumption has more than doubled in the last 50 years. This substantial increase in industrial livestock production has had a serious environmental impact and raises ethical questions in relation to animal welfare. In addition, excessive meat consumption has a negative impact on human health.
Flexitarians and meat substitutes
These worrisome developments have given rise to a new food trend: a conscious reduction in personal meat consumption. Flexitarians regularly eat meat but are mindful of nutrition and the environment. They try to incorporate healthy, plant-based, protein-rich alternatives to traditional meat products in their diets. Plant-based meat substitutes resemble real meat in terms of flavor, appearance, and texture, but consist of plant-based proteins. These meat substitutes are rich in protein, fiber and nutrients and contain highly effective essential amino acids, that are cholesterol-free, and low in fat. The most important sources of plant-based proteins include wheat gluten, soya beans, peas, lentils, fava beans, chickpeas, green beans, and lupins.
Clextral: the food extrusion expert
Since the late 1990s, Clextral, a French manufacturer of food extrusion equipment, has been working together with food processors and food research centers to develop convenience foods made of fibrated protein products, which consist of extruded fibrous proteins. Jérôme Mottaz, Head of Engineering and R&D at Clextral, explains: “In the past few years, the sales figures for texturized or fibrated vegetable protein in Europe, Asia, America and Australia have increased steadily. Since 2001, we have held a patent for High Moisture Extrusion Cooking (HMEC) – one of the two twin-screw extrusion processes used to manufacture meat substitute products from proteins.”
The two extrusion processes
In addition to the High Moisture Extrusion Cooking process, there is also a “dry” process, called TVP. The two extrusion processes differ from one another in terms of the configuration of the extruder and the die used. In the dry extrusion process, Clextral usually feeds a premix made of soya powder or pea concentrate with a protein content of between 50 and 60 percent into the extruder. Using a simple die produces an extrudate with a spongy texture and a low moisture content of 10 to 23 percent at the exit of the extruder die and around 8% at the exit of the dryer post extrusion. After rehydration, the extrudate is ready for consumption at home.
High Moisture Extrusion Cooking
Plant-based raw materials like peas or soya are also used in the HMEC process, although in the form of isolate or concentrate with a higher protein content of 70 to 80 percent. The difference compared to the dry process is that HMEC involves thermomechanical processing – “cooking” – the proteins at temperatures in excess of 120 degrees Celsius and at a high moisture content of 50 to 70 percent, as well as relatively long dwell times. This process enables fiber formation and takes place in a complex screw and barrel configuration within the twin-screw extruder, where the specific screw configuration features a high length to diameter ratio.
Emmanuel Lavocat, food extrusion process engineer at Clextral, describes it as follows: “In their original state, proteins are like woolen threads that are interwoven. During the cooking process in the extruder, they are disentangled, unfolded and cut into small pieces. In the die, they are then re-crosslinked to produce even filaments of good quality.”
Cooling die influences texture
A long cooling die is positioned behind the screw-barrel configuration, and it plays a key role in the HMEC process. The setup of its cooling channels, the cross-sectional area and aperture dimensions all have a major impact on the texture and quality of fiber formation. For example, both rough surfaces featuring relatively short, thick, cross-sectionally oriented fibers and smoother surfaces with long. thin, laminar-flow-oriented fibers are feasible. Each of these products is used for specific food applications, for example, as analog chicken strips or analog pulled pork. HMEC creates intermediate products, the structure and texture of which closely resembles the muscles found in meat. Further processing also enables flavor, olfactory and visual features to be added.
Look into the future
“The end products of the High Moisture Extrusion Cooking process have the potential to appeal to consumers, who have previously viewed analog meats with skepticism,” says Emmanuel Lavocat with conviction – and they could help to feed the growing world population on a sustainable basis in the future.
(published in FLUX 2/2021)