Fiber spinning innovations for improved plant protein texturization

Current challenge

Animal skeletal muscles are hierarchical structures consisting of mostly fibrous proteins that form long, flexible fiber bundles. These complex structures contribute to the texture, mouthfeel, and appearance of conventional whole muscle cuts. In contrast, plant proteins are typically globular proteins that are tightly packed, spherical, and require texturization to mimic fibrous proteins. Methods to texturize globular proteins into fibers are classified as “bottom-up” or “top-down” techniques (Dekkers et al. 2018). Bottom-up methods assemble individual components into a larger product, thus building from nano- to macro-scale. Fiber spinning has emerged as the most promising bottom-up technology for plant protein texturization. These techniques form thinner protein fibers with enhanced aspect ratios compared to top-down methods, which texturize biopolymers on larger length scales. Although fiber spinning technologies can create superior plant protein fiber bundles, top-down strategies are currently more affordable and scalable. As a result, top-down strategies like extrusion and molding are more commonly used than fiber spinning technologies. However, there are many opportunities to improve plant protein fiber spinning to be more effective, commercially scalable, and affordable.

Proposed solution

Fiber spinning technologies apply an external force to a polymer solution ejected from a needle or spinneret and then collect the elongated polymers as solid fibers. The external force applied, other environmental conditions, and intrinsic polymer characteristics control the final properties of the resulting fibers. Common types of spinning technologies include wet spinning, electrospinning, jet spinning, and blow spinning. Wet spinning simply extrudes polymer solution through a spinneret and into a non-solvent, causing the polymer to precipitate into a fiber. Electrospinning methods extrude polymer solution through a needle with an electric potential (Nieuwland et al. 2013). Charge repulsive forces ultimately cause the polymers to form thin fibers. Typically, electrospinning is more controlled and yields thinner fibers (~100 nm) than simple wet spinning (~10 μm). Jet spinning and blow spinning are technologies that use high-speed rotation and high-pressure gas, respectively, to force polymers into fibrous structures (Rogalski et al. 2017). 

While these methods have been tested for synthetic polymers and some therapeutic biopolymers, the lack of suitable food-grade conditions for protein spinning has prevented their scalability and use in food science. There have been very few studies on optimizing electrospinning of plant proteins (pea proteins: Kutzli et al. 2019a & 2019b; common bean: Aguilar-Vazquez et al. 2020; zein: Mattice et al. 2020). There is ample room to improve experimental conditions for spinning plant proteins, including optimizing solution type, viscosity, conductivity (for electrospinning), and surface tension. Process parameters for each technology should also be optimized; in the case of electrospinning, this would entail tuning voltage, flow speed, and distance between the ejection needle and fiber collector. 

There is also room to optimize raw ingredient use. Specific proteins, particularly zein and gelatin, have demonstrated better spinning efficacy than other proteins. This is because the spinnability of proteins depends on their solubility (many proteins require harsh, non-food-grade solvents to solubilize) and protein conformation (random coiled structures are best for spinning because of their flexibility). Combining poorlyspinnable proteins with more readily spinnable proteins has been shown to aid their spinning efficacy. More plant proteins and their combinations should be examined for their optimal spinning conditions. 
As spinning technologies develop further, techno-economic models will be necessary to confirm commercial scalability. These models will be helpful to understand the cost drivers and opportunities of texturizing plant proteins with various spinning technologies.

Anticipated impact

Spinning technologies form thin fiber bundles of polymers and have great potential to do the same for food-grade proteins. Creating plant protein fiber bundles from these bottom-up spinning methods will help alternative meats reach sensory parity with conventional meats by improving product texture, mouthfeel, and appearance. Techno-economic models that accompany these spinning innovations will help guide researchers and investors in the best opportunities to improve their cost and scalability.

Related efforts

• Cybercolloids, an Ireland-based contract research firm, is starting to develop a high-shear spinning technology for alternative meat production. 
• Study focused on food-grade electrospinning of proteins with gelatin (Nieuwland et al. 2013).  While gelatin is animal-derived, the study can serve as a guide for those electrospinning with non-animal food-grade proteins.

GFI resources

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