The authors of the report Trends in food science & technology 2022 noted that “Animals and plants are the main sources of dietary proteins, and there are important differences in the type of protein that they supply. The differences include molecular structure, amino acid profile, digestibility, and technical functionality in food, i.e. the ability to gel, emulsify, bind water etc…. These fundamental differences mean that designing plant-based foods to mimic animal foods requires much more than simple substitution of one ingredient with another.”
Grand View Research reported that the global plant-based meat market size is projected to reach USD 24.8 billion by 2030. But there are some challenges to building that market, including making sure the products meet customer expectations for texture, taste, and appearance.
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 animal protein to taste like real meat, 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.
Extrusion Methods Can Change Texture
Food extrusion is an established, versatile method for the production of meat analogs. Carefully chosen processing parameters can control and enhance various aspects of food such as texture, shape, color, and flavor.
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.
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. Two different types of plant-based food products are usually addressed by this type of technology: 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.
Texturized protein and HMMA products can be manufactured using the same twin-screw extruder despite their different product characteristics by simply varying the die type and the water content used for the particular production process.
High Moisture Meat Analog Extrusion
During the twin-screw extrusion process for HMMA, water must be fed at certain rates and cooled at the appropriate temperature ranges, while the equipment must be kept at its own specific temperature to avoid structural distortion due to the evaporation of water. The formation of the characteristic product texture is determined by shear-induced structuring of plant protein formulations. The flow characteristics determine the final product texture.
Texturized Vegetable Protein Extrusion
The twin-screw extrusion process for TVP is typically operated at slower water feed rates. Extrusion and nozzle temperatures are similar to HMMA processing, while the temperature in the die nozzle is kept at a warmer temperature to promote the evaporation of water. The formation of the characteristic product texture of texturized proteins is determined by pressure drop at the die exit leading to the evaporation of water and expansion of the product.
Differing temperature, die design, and water feed rate promotes the creation of a wide range of meat-like textures depending on the combination of formulation and other process conditions.
Summary
Taste is in the tongue (and brain) of the beholder, but it looks like with the help of food extruders, companies are getting closer to providing meat substitutes that are satisfying many customers’ taste buds and mouth-feel.
Additional Resources:
- Webinar: Extrusion of Plant-based Meat
- Application Note: Twin-screw extrusion of plant-based meat
- White Paper: An Evaluation of Meat Analog Product Characteristics – Combining Extrusion with Electron Microscopy and Rheological Measurements
- Application Note: Small Scale Extrusion Solution for Meat Analogs
TVP is a registered trademark of Archer-Daniels Midland Co.
