L-Arginine improves texture in plant-based meat products

Plant-based meat products simulate the texture and mouthfeel of animal meat using plant proteins such as soy protein, pea protein, and wheat protein. However, their inherent limitations—including loose texture, poor chewiness, and insufficient juiciness—remain core bottlenecks restricting product quality.

L-Arginine, a natural basic amino acid, not only offers nutritional benefits (e.g., participating in protein synthesis and regulating physiological metabolism) but also addresses the texture defects of plant-based meat products through three key pathways: "regulating protein-protein interactions," "improving thermal processing properties," and "optimizing microstructures." A deep understanding of its mechanisms and application strategies is crucial for developing highly realistic plant-based meat products. This article explores the working principles of L-arginine, analyzes its effects on improving the gelling properties, water-holding capacity, and chewiness of plant proteins, and outlines key parameter controls for practical applications.

I. Core Mechanisms of L-Arginine in Improving Plant-Based Meat Texture

The texture of plant-based meat products (e.g., elasticity, chewiness, juiciness) essentially depends on the gel network structure of plant proteins. Protein molecules form a three-dimensional network via hydrogen bonds, hydrophobic interactions, and disulfide bonds, entrapping water and oil to mimic the muscle fiber structure of animal meat. L-arginine optimizes this network by regulating the charge state of protein molecules, their aggregation behavior, and cross-linking reactions during thermal processing, ultimately improving texture. The core mechanisms are categorized as follows:

(I) Regulating Protein Charge State to Promote Uniform Gel Network Formation

Most plant proteins (e.g., soy protein isolate, pea protein) have an isoelectric point (pI) between 4.0 and 5.5. Under neutral or weakly alkaline conditions (pH 6.5–7.5, commonly used in plant-based meat products), protein molecules carry negative surface charges. Excessive electrostatic repulsion between molecules leads to poor aggregation, preventing the formation of a dense, uniform gel network.

L-arginine contains a guanidino group (-C(NH₂)₂⁺) and an amino group (-NH₂), which dissociate to release positive charges in solution. Its mechanisms of action include:

Neutralizing negative surface charges: The positive charges of L-arginine bind to the carboxyl groups (-COOH, dissociated as -COO⁻) on plant protein surfaces, reducing electrostatic repulsion between molecules. This allows proteins to aggregate more easily, laying the "molecular foundation" for gel network formation.

Expanding the pH range for protein solubility: Conventional plant proteins tend to denature and precipitate when the pH deviates significantly from their pI (e.g., pH > 8.0). L-arginine forms "charge complexes" with proteins, enhancing their solubility under alkaline conditions. For example, adding 1% L-arginine increases the solubility of soy protein isolate at pH 8.0 from 65% to over 90%, preventing gel coarsening caused by excessive protein aggregation.

Enhancing network uniformity: After charge neutralization, protein aggregation slows down, enabling the gradual formation of a uniform gel network with "small nodes and dense cross-links" (instead of disordered, coarse particles). This uniform network traps water and oil more stably, reducing moisture loss during thermal processing and improving product juiciness and elasticity.

(II) Activating Protein Cross-Linking Reactions to Enhance Gel Strength and Elasticity

During the thermal processing of plant-based meat products (e.g., boiling, extrusion), plant proteins require intermolecular cross-linking to form stable gels. L-arginine strengthens protein cross-linking and improves gel strength/elasticity by "promoting disulfide bond formation" and "activating transglutaminase (TG enzyme) activity":

Promoting disulfide bond (-S-S-) formation: The guanidino group of L-arginine has strong nucleophilicity, attacking the thiol groups (-SH) in plant protein molecules and promoting the oxidation of -SH to form disulfide bonds. As the "core cross-linking bonds" of the protein gel network, disulfide bonds significantly enhance mechanical strength. Experiments show that adding 0.8% L-arginine to a soy protein isolate system increases the disulfide bond content of the gel by 25%–30% after thermal processing; gel hardness rises from 1500 g to 2200 g, and elasticity increases from 0.65 to 0.80 (elasticity values closer to 1 indicate textures more similar to animal meat).

Activating endogenous/exogenous TG enzymes: TG enzymes are commonly used texture modifiers in plant-based meat products. They catalyze the formation of isopeptide bonds between the γ-carboxamide group of glutamine and the ε-amino group of lysine in proteins, strengthening gel cross-linking. The guanidino group of L-arginine binds to the active site of TG enzymes, increasing their catalytic efficiency (e.g., adding 0.5% L-arginine boosts TG enzyme catalytic rate by 15%–20%). Additionally, the alkaline environment of L-arginine (pH ~10.0 for aqueous solutions) extends the activity duration of TG enzymes (from 2 hours to 3.5 hours), ensuring sufficient protein cross-linking during processing.

Reducing protein denaturation loss from heat: High-temperature processing easily causes excessive denaturation of plant proteins, damaging the gel network. L-arginine binds to the hydrophobic regions of protein molecules, forming a "protective shell" that lowers the rate of protein thermal denaturation (e.g., the thermal denaturation temperature of soy protein increases from 75°C to 82°C). This minimizes gel network damage from heat and maintains gel integrity and elasticity.

(III) Optimizing Microstructures to Improve Water-Holding Capacity and Chewiness

The "juiciness" of plant-based meat products depends on the water-holding capacity of the gel network, while "chewiness" is related to the density of the microstructure. L-arginine improves both water-holding capacity and chewiness by optimizing the microtopography of protein gels and regulating the state of water in the system:

Constructing a "porous-dense" composite microstructure: Without L-arginine, plant protein gels typically have a microstructure of "coarse pores + loose cross-links," leading to easy moisture loss during processing or storage. With L-arginine, protein molecules aggregate uniformly to form a structure of "small pores (1–5 μm in diameter) + dense cross-linked walls." This structure traps water and oil in pores while preventing moisture seepage via dense walls, increasing product water-holding capacity from 65% to over 85% and reducing cooking loss from 18% to below 8%.

Regulating water binding states: Water in food exists in three forms: free water (easily lost), bound water (stably bound to proteins), and immobilized water (trapped in the gel network, contributing to juiciness). L-arginine binds to protein molecules via hydrogen bonds, increasing the "water-binding sites" on proteins and converting free water to immobilized water. For example, adding 1% L-arginine to a soy protein system increases the proportion of immobilized water from 35% to 55%, enhancing juiciness and reducing moisture evaporation during storage.

Simulating the fibrous structure of animal meat: The chewiness of animal meat stems from the oriented arrangement of muscle fibers, whereas plant protein gels typically form disordered networks. L-arginine binds to the α-helical structure of plant proteins, inducing protein molecules to align along the processing direction (e.g., extrusion direction) and form muscle fiber-like "bundled structures." Through the synergistic effect of extrusion processing and L-arginine, the fiber degree of plant-based meat products increases from 2.0 (disordered structure) to 4.5 (bundled structure; animal meat has a fiber degree of ~5.0), significantly improving chewiness and avoiding the "soft, non-chewy" defect.

II. Application Strategies and Effects of L-Arginine in Plant-Based Meat Products

The texture-improving effect of L-arginine is influenced by its addition level, application scenario (different plant protein systems), and processing technology. Targeted protocols must be developed based on product requirements (e.g., simulating beef, pork, or chicken). Key application strategies and effects are as follows:

(I) Optimization of Addition Levels: Balancing Texture and Flavor

The addition level of L-arginine must be controlled within an "effective improvement range": too low, and texture improvement is negligible; too high, and it may cause a "bitter alkaline taste" (L-arginine has a mild alkaline flavor), reducing palatability. Optimal addition levels for different plant protein systems are:

Soy protein systems (simulating beef meatballs, beef patties): Soy protein has strong gelling properties but tends to be "overly hard and less elastic." The optimal L-arginine addition level is 0.6%–0.9% (based on the mass of protein raw materials). At this level, product hardness decreases from 2000 g to 1800 g (closer to the hardness of beef: 1700–1900 g), elasticity increases from 0.70 to 0.85, and no obvious alkaline taste is detected.

Pea protein systems (simulating chicken chunks, chicken sausages): Pea protein has a loose texture and poor water-holding capacity. The optimal addition level is 0.8%–1.2%. After addition, gel water-holding capacity increases from 55% to 80%, and chewiness rises from 1000 g·mm to 1800 g·mm (close to the chewiness of chicken: 1600–2000 g·mm). Additionally, the "beany flavor" of pea protein is neutralized by the mild umami of L-arginine, resulting in a more balanced flavor.

Composite protein systems (soy protein + wheat protein, simulating pork filling, bacon): Composite proteins tend to form layered gels due to uneven intermolecular interactions. The optimal addition level is 0.5%–0.7%. This promotes cross-linking and fusion of different protein molecules, preventing layering. Product sliceability (no crumbling) improves by 40%, and texture uniformity is significantly enhanced.

(II) Synergistic Application with Different Processing Technologies

Processing technologies for plant-based meat products (e.g., hot pressing, extrusion, boiling) affect the interaction efficiency between L-arginine and proteins. Adjusting process parameters maximizes texture improvement:

Hot pressing (for hamburger patties): At 110–120°C for 15–20 minutes, L-arginine more efficiently promotes disulfide bond formation. Gel strength increases by 30% compared to conventional hot pressing (100°C for 10 minutes), and the pressed product has no surface cracking, no internal pores, and a dense texture.

Extrusion (for plant-based sausages, shredded meat): With an extruder screw speed of 300–400 rpm and a die temperature of 130–140°C, L-arginine induces protein molecules to align along the screw direction, forming fibrous structures. The fiber detection rate (observed via microscopy) of extruded products increases from 30% to 75%, and the "fiber breaking sensation" during chewing is more similar to animal meat.

TG enzyme synergy (for high-end plant-based steaks): First, add 0.5% L-arginine and 0.3% TG enzyme, incubate at 35–40°C for 2 hours (to activate TG enzymes), then boil at 100°C for 30 minutes. This process increases the isopeptide bond content of the protein gel by 50%. The product’s elasticity and tenderness reach over 80% of animal steaks, with no moisture seepage after thermal processing and prominent juiciness.

(III) Synergistic Enhancement with Other Modifiers

Combining L-arginine with modifiers such as polysaccharides (e.g., carrageenan, pectin), oils (e.g., vegetable cream, olive oil), and phosphates achieves synergistic optimization of "texture, flavor, and nutrition":

Synergy with polysaccharides: The positive charges of L-arginine form "protein-polysaccharide-arginine" complexes with negatively charged polysaccharides (e.g., carrageenan), further enhancing gel network stability. Adding 0.6% L-arginine + 0.3% carrageenan increases the water-holding capacity of plant-based patties from 85% to 90%, and reduces the hardness change rate after 7 days of storage from 25% to 10%, significantly improving texture stability.

Synergy with vegetable oils: L-arginine reduces the surface tension of vegetable oils, enabling more uniform dispersion of oil in the protein gel network and preventing oil exudation. Adding 1% L-arginine + 5% olive oil decreases the oil exudation rate of plant-based sausages from 12% to 3%, resulting in a smoother mouthfeel without "greasiness."

Synergy with phosphates: Phosphates are common water-holding agents, but excessive use causes a "metallic taste." L-arginine can replace 30%–40% of phosphates, maintaining water-holding capacity while reducing off-flavors. Adding 0.7% L-arginine + 0.4% sodium tripolyphosphate achieves water-holding capacity equivalent to adding 0.6% sodium tripolyphosphate alone, but the off-flavor score decreases from 3.0 (obvious off-flavor) to 1.5 (no obvious off-flavor), improving palatability.

III. Application Considerations: Avoiding Potential Issues

The application of L-arginine in plant-based meat products requires attention to three key issues—"flavor coordination," "processing compatibility," and "nutritional stability"—to prevent product quality degradation from improper use:

Flavor masking and coordination: High addition levels (>1.2%) of L-arginine easily cause an alkaline taste. Natural flavorings (e.g., yeast extract, shiitake powder, beef essence) can mask this: adding 0.3% yeast extract reduces the alkaline taste score of 1.0% L-arginine from 4.0 (obvious alkaline taste) to 1.0 (no perception) while enhancing the "meaty umami" of the product.

Processing temperature control: L-arginine decomposes easily at high temperatures (>150°C), producing ammonia and pyrrole compounds that damage flavor and nutrition. In extrusion or baking, control die/oven temperatures below 140°C, or use "low-temperature, long-duration" processing (e.g., boiling at 80°C for 60 minutes) to reduce L-arginine decomposition loss (from 25% to below 5%).

Compatibility with acidic ingredients: Acidic ingredients (e.g., tomato powder, vinegar) in plant-based meat products react with L-arginine, reducing its texture-improving effect. Adjust the order of ingredient addition: first mix L-arginine fully with proteins, then add acidic ingredients. Alternatively, use buffers (e.g., sodium citrate) to adjust the system pH to 7.0–7.5, maintaining L-arginine activity.

As a natural amino acid-based texture modifier, L-arginine targets the core defects of plant-based meat products (looseness, poor chewiness, insufficient juiciness) by "regulating protein charge, activating cross-linking reactions, and optimizing microstructures." It also offers nutritional benefits and safety, aligning with consumer demand for "clean labels."

In practical applications, L-arginine addition levels (0.5%–1.2%) must be adjusted based on plant protein type (soy, pea, composite proteins). Synergy with processing technologies (hot pressing, extrusion, TG enzyme) and other modifiers (polysaccharides, oils) is essential, while flavor and processing compatibility issues must be avoided to maximize texture improvement.

Future research into the interaction mechanisms between L-arginine and plant proteins will enable more precise applications in "highly realistic plant-based meat products" (e.g., plant-based steaks, bacon), providing key technical support for quality upgrading in the plant-based food industry.