The effect and mechanism of L-Arginine on improving the quality of freeze-thawed meat products

In the processing and storage of meat products, freeze-thaw treatment is a common method to extend shelf life. However, repeated freeze-thaw cycles can lead to quality deterioration of meat products, such as moisture loss, texture deterioration, and intensified oxidation. As a natural amino acid, L-arginine is not only an essential nutrient for the human body but also can alleviate the quality decline of freeze-thawed meat products through multiple mechanisms of action, demonstrating significant application value in the food industry. Its specific functions and mechanisms can be analyzed from the following aspects:

I. Inhibiting Protein Freeze Denaturation to Improve Meat Texture and Water-Holding Capacity

During the freeze-thaw process, water in meat products forms ice crystals. The growth and recrystallization of ice crystals damage the muscle cell structure, causing denaturation of proteins (such as myofibrillar proteins). This is specifically manifested as changes in protein spatial conformation, exposure of hydrophobic groups, and increased aggregation, ultimately resulting in tough texture of meat products and decreased water-holding capacity (increased drip loss rate).

L-arginine inhibits protein freeze denaturation through two core mechanisms: On one hand, its molecular structure contains polar groups such as guanidine and amino groups. These groups can form hydrogen bonds or electrostatic interactions with polar residues (e.g., hydroxyl, carboxyl groups) of myofibrillar proteins, stabilizing the secondary and tertiary structures of proteins, reducing abnormal changes in protein spatial conformation during freezing, and maintaining their original functional properties. On the other hand, L-arginine acts as a "moisture regulator": it enhances the water-retaining capacity of the system by binding to water molecules, while inhibiting the excessive growth and recrystallization of ice crystals. It lowers the freezing point of the frozen system, reduces the probability of large ice crystal formation, and avoids mechanical damage to muscle cells caused by ice crystals. This thereby reduces the loss of intracellular water, improves the water-holding capacity of meat products (e.g., reducing thaw loss rate), and maintains the tenderness and elasticity of meat (e.g., reduced hardness and improved chewiness after cooking). For example, adding an appropriate concentration of L-arginine to freeze-thawed products such as pork meatballs and beef slices can reduce the thaw loss rate by 10%-20% while significantly increasing the sensory texture score of the products.

II. Scavenging Free Radicals to Delay Lipid and Protein Oxidation in Meat Products

During freeze-thaw cycles, unsaturated fatty acids (e.g., linoleic acid, linolenic acid) and proteins in meat products are prone to attack by activated free radicals (e.g., hydroxyl radicals ·OH, superoxide anions O₂⁻), triggering lipid oxidation (producing undesirable flavor substances such as aldehydes and ketones, e.g., malondialdehyde MDA) and protein oxidation (e.g., increased protein carbonyl content, decreased sulfhydryl content). This not only causes off-flavors such as "rancidity" in meat products but also damages protein structures, further exacerbating texture deterioration.

L-arginine is an effective free radical scavenger, with its mechanism of action mainly including two points: First, it directly scavenges free radicals. The guanidine group in the L-arginine molecule has strong electron donor capacity and can react with free radicals, converting them into stable molecules, thereby reducing the attack of free radicals on lipids and proteins. Second, it indirectly enhances the activity of the antioxidant system. L-arginine is a precursor for nitric oxide (NO) synthesis. Appropriate NO can activate the activity of endogenous antioxidant enzymes (e.g., superoxide dismutase SOD, glutathione peroxidase GSH-Px) in meat products, improving the efficiency of these enzymes in scavenging free radicals. At the same time, NO can also bind to metal ions (e.g., Fe²⁺, Cu²⁺, which catalyze lipid oxidation), inhibiting the pro-oxidative effect of metal ions. In practical applications, adding L-arginine to freeze-thawed products such as chicken and mutton can reduce lipid oxidation indicators (e.g., MDA content) by 25%-35% and protein carbonyl content by 15%-25%, effectively delaying flavor deterioration and quality decline of the products.

III. Regulating pH Value to Optimize Sensory Quality and Processing Adaptability of Meat Products

The pH value of muscle tissue has a significant impact on the quality of freeze-thawed meat products: The pH value of normal fresh meat products is approximately 5.5-6.0. During freeze-thaw cycles, the pH value may further decrease due to lactic acid accumulation. A low pH value exacerbates the aggregation and denaturation of myofibrillar proteins, reduces water-holding capacity, and may also cause the color of meat products to darken (e.g., oxidation of myoglobin to metmyoglobin).

As a basic amino acid (isoelectric point approximately 10.76), adding L-arginine to meat products can appropriately increase the pH value of the system, moving it away from the isoelectric point of myofibrillar proteins (approximately 5.0). When the pH value is far from the isoelectric point, the net charge on the protein molecule surface increases, and the electrostatic repulsion between molecules is enhanced, which can effectively reduce protein aggregation and further improve water-holding capacity. At the same time, a suitable pH environment can stabilize the structure of myoglobin, reduce the probability of its oxidation to metmyoglobin, maintain the bright red color of meat products (e.g., increased redness value a* of freeze-thawed beef), and improve the appearance and sensory properties of the products. In addition, pH regulation can also optimize the processing adaptability of meat products. For example, in the processing of freeze-thawed minced meat, a suitable pH value can enhance the binding properties of the minced meat and reduce the breakage rate of products such as sausages and meatballs.

IV. Enhancing the Nutritional Value of Meat Products to Balance Functional and Healthy Attributes

In addition to improving quality, L-arginine itself is a semi-essential amino acid for the human body (essential for infants; adults can synthesize it themselves but have increased demand under stress). Adding it to freeze-thawed meat products can enhance the nutritional value of the products without affecting their flavor and texture—it not only supplements the amino acids needed by the human body but also provides additional health benefits to consumers through its physiological functions (e.g., promoting protein synthesis, improving intestinal health).

Compared with traditional chemical quality improvers (e.g., phosphates), L-arginine, as a natural amino acid, has higher safety and consumer acceptance, conforming to the current development trend of "clean labels" in the food industry. Therefore, it has gradually become a preferred alternative to some chemical improvers in low-temperature meat products (e.g., freeze-thawed sausages, bacon) and quick-frozen prepared meat products (e.g., freeze-thawed chicken cutlets, fish balls).