Consumers are increasingly choosing plant-based foods because of environmental concerns, animal welfare, and health reasons. However, surveys reveal that the available products often do not meet customer expectations when it comes to texture and taste. As a result, manufacturers are making an effort to meet expectations by tailoring the properties of plant-based products to meet the consumer’s demands.
The Extrusion Recipe
The source of most plant-based meats is a mixture made from pea, wheat, or soy protein, a type of fat, and some sort of binder. In order for the substitute ingredients to taste like real animal protein, natural and artificial flavors are usually added. But taste is only one factor. Texture and appearance are others. And those factors are influenced by the extrusion process.
We previously wrote about how extrusion methods can change texture. Extrusion in food production is the process where soft mixed ingredients are forced through an opening in a perforated plate or die designed to produce the required shape. Think of different types of pasta. The dough is pushed, or extruded, through a die or plate that forms bow ties, elbows, spaghetti, and many other shapes. For plant-based proteins, the mixture is extruded through dies to form the same shapes as ground beef, bacon strips, and other meat products.
Two different types of plant-based food products are usually used in extrusion: High Moisture Meat Analog (HMMA) and texturized vegetable protein (texturized proteins).
HMMAs are soft and moist products with a directly visible fibrous, muscle-meat-like texture. Texturized proteins (TVP®s) are defined as dry and brittle products that have a porous structure that transforms into a fibrous, meat-like texture upon rehydration. After extrusion, HMMAs and texturized proteins are further processed with conventional meat processing operations such as marinating, shredding, and blending and can be used as a plant-based meat alternative in many different types of convenience products.
Twin-screw extrusion processing is considered a key technology for the continuous production of plant-based meat products. Twin-screw extruders are well-established tools for the mixing, compounding, and processing of materials. They are used in a wide variety of polymer, pharmaceutical, battery, as well as food applications to efficiently develop and produce high-quality products using a continuous process.
Influencing the Properties of Extrudates
In order to better replicate the texture of real meat, scientists have conducted analyses to find if the addition of oils would have any influence on the mechanical properties of materials that are being extruded. This research was driven by that growing consumer demand for plant-based products, which often fail to meet expectations regarding texture, taste, and protein sourcing.
Meat is complex — a system composed of muscle fibers and intramuscular fat. The microstructure of meat and its mechanical properties significantly affect the sensory experience of consumers. Plant-based alternatives aim to mimic the anisotropic structure of meat via high moisture extrusion cooking, altering the raw proteins to create a fibrous protein matrix resembling meat’s muscle structure.
The presence of fat in meat, which can make up to 30% of its total composition, plays a crucial role in determining the meat’s tenderness and juiciness. Therefore, plant-based alternatives often add oils and fats to enhance the sensory characteristics of these products. However, this addition can influence the extrusion process parameters and affect the textural properties of the plant-based alternatives.
The Study Results
The study involved a pea protein isolate (a covalent crosslinking protein) and soy protein concentrate (a noncovalent crosslinking protein) as model systems. Both proteins were found to have almost identical interfacial activities, and the oil concentration was maintained as the primary parameter under investigation.
The study revealed that while the addition of oil affected the visual structure of the extrudates, it did not significantly impact the soy protein samples. However, the pea protein samples displayed a noticeable difference with the addition of oil, with the highest concentration appearing mushy and dough-like.
Upon microscopic examination, the pea protein samples displayed oil lagoons under the surface, indicating oil droplet coalescence during the extraction process. In contrast, soy protein samples did not display these large droplets, possibly due to better emulsifying properties.
The amount of unencapsulated oil was determined, and it was found that soy protein meat analogs retained oil droplets inside the matrix better than pea protein samples. This suggests that oil droplets are not well embedded in the pea protein matrix.
The rheological properties of the extrudates, such as deformability and viscosity, were also examined. The results showed that the addition of rapeseed oil to soy protein concentrate had little effect on the linear viscoelastic region and maximal deformation of the samples. However, the cross-linking density of the pea protein matrix decreased with the addition of oil.
Oil Can Make a Difference
The study demonstrated the important role of oil in the production of plant-based meat alternatives. The research highlighted the differences in the behavior of pea and soy proteins when oil is added, suggesting that the type of protein used in the production of plant-based alternatives can significantly affect the product’s texture and mouthfeel. This study provides valuable insights for improving the texture and sensory properties of plant-based meat alternatives.
Additional Resources
- Food Solutions Through Rheology & Extrusion
- Twin-screw extrusion of plant-based meat: HMMA & Texturized vegetable proteins
- Structure analysis of plant-based meat
Videos
- Webinar: The influence of oils on plant-based meat analogues
- High moisture meat analog extrusion
- Low moisture meat analog extrusion
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