The Application of Nisin in the Preservation of Meat Products

Nisin (nisin), a natural food preservative, is widely used in the preservation of meat products due to its advantages of high safety, targeted antibacterial spectrum, and easy metabolism by the human body. Meat products are rich in protein, fat, and moisture, making them susceptible to microbial contamination (such as Gram-positive bacteria like Clostridium botulinum, Listeria monocytogenes, and Staphylococcus aureus), which leads to spoilage. Nisin can extend the shelf life of products by inhibiting the growth of these pathogenic and spoilage bacteria.

I. Antibacterial Mechanism of Nisin and Its Adaptability to Meat Preservation

Nisin exerts its antibacterial effect mainly by disrupting bacterial cell membranes: it binds to lipid Ⅱ (a key precursor for bacterial cell wall synthesis) on the membrane of Gram-positive bacteria, forming transmembrane channels that cause the leakage of intracellular potassium ions, amino acids, and other substances, ultimately inhibiting bacterial proliferation or causing death. This mechanism has a significant inhibitory effect on common spoilage and pathogenic bacteria in meat, such as streptococci (which cause meat to become sticky and produce off-odors) and Listeria monocytogenes (which may cause food poisoning).

Meanwhile, the characteristics of Nisin are highly compatible with the processing and storage needs of meat products:

It has good thermal stability and is not easily inactivated during heating processes such as cooking and smoking of meat products (e.g., retaining over 80% activity after heating at 121°C for 15 minutes under pH 2.0–6.0 conditions);

It is safe for humans, recognized as a GRAS (Generally Recognized as Safe) substance by the Food and Agriculture Organization/World Health Organization (FAO/WHO), with no strict restrictions on the acceptable daily intake;

It does not affect the flavor, color, or texture of meat, avoiding the off-odors or texture changes that may be caused by chemical preservatives.

II. Application Methods and Effects in Different Meat Products

The application of nisin in meat products requires selecting appropriate addition methods based on product characteristics. Common forms include direct addition, soaking/spraying, and synergistic use with other preservation technologies, with specific effects varying by product type:

Low-temperature meat products (e.g., sausages, ham, bacon):

Low-temperature meat products are processed at relatively low temperatures (usually ≤70°C), which cannot completely kill microorganisms, making them prone to bacterial growth during refrigeration. Adding nisin directly to meat fillings or marinades at a concentration of 0.5–2 g/kg can effectively inhibit the growth of Listeria monocytogenes, Staphylococcus aureus, etc. For example, adding 1 g/kg Nisin to Frankfurt sausages, combined with refrigeration at 4°C, can extend the shelf life from 7 days (traditional process) to 14–21 days. Additionally, it can reduce the use of nitrites (though nitrites have preservative effects, excessive amounts may produce nitrosamines; the synergy of Nisin can reduce their addition by 30%–50%).

High-temperature meat products (e.g., canned meat, high-temperature sterilized ham):

High-temperature sterilization can kill most microorganisms, but some heat-resistant spores (such as Clostridium botulinum spores) may survive. Adding Nisin (0.2–1 g/kg) during processing can enhance the sterilization effect, reduce the sterilization temperature or shorten the time, and minimize texture deterioration of meat caused by high temperatures (such as hardening of muscle fibers). For example, adding 0.5 g/kg Nisin to canned meat allows the sterilization temperature to be reduced from 121°C to 115°C, ensuring thorough sterilization while retaining the juiciness of the meat.

Fresh meat (e.g., chilled meat, cut meat):

The surface of fresh meat is easily contaminated by environmental microorganisms. Treatment with a Nisin solution (concentration 0.1%–0.5%) via soaking or spraying can form an antibacterial protective layer on the meat surface. Studies have shown that after soaking chilled meat in a 0.3% Nisin solution for 30 seconds and vacuum packaging, the growth rate of the total bacterial count under 4°C refrigeration is reduced by more than 50% compared to the control group, extending the shelf life by 3–5 days.

III. Application of Synergistic Preservation Technologies

When used alone, nisin has a limited antibacterial spectrum, with weak inhibitory effects on Gram-negative bacteria (e.g., Escherichia coli) and fungi. Therefore, it is often combined with other preservation technologies to enhance overall antiseptic effect:

Combination with natural preservatives: For example, compounding Nisin with lysozyme (targeting Gram-negative bacteria) or plant extracts (such as cinnamaldehyde and eugenol, which have both antibacterial and antioxidant effects) can expand the antibacterial range. In beef meatballs, the combination of 0.5 g/kg nisin and 0.3% cinnamaldehyde not only inhibits bacterial growth but also delays fat oxidation, extending the shelf life at 25°C from 2 days to 5 days.

Integration with physical preservation technologies: Vacuum packaging and modified atmosphere packaging (MAP) can reduce oxygen content and inhibit the growth of aerobic bacteria, showing significant synergy with Nisin. For example, chilled meat treated with Nisin and packaged in a modified atmosphere of 70% CO₂ + 30% N₂ can have a shelf life of up to 21 days at 4°C, far exceeding that of single Nisin treatment (12 days) or single modified atmosphere packaging (10 days).

Coordination with hurdle technology: By adjusting pH (e.g., adding organic acids to lower pH to 5.5–6.0) and controlling water activity (Aw ≤0.95), a "multiple hurdle" system is formed with Nisin to enhance microbial inhibition. In pork sausages, the combination of nisin (1 g/kg) + lactic acid (0.2%) + reducing Aw to 0.94 can extend the shelf life at room temperature (25°C) from 1 week to 3 weeks.

IV. Challenges in Application and Solutions

Nisin also has certain limitations in meat applications:

Its antibacterial spectrum is narrow, with limited effects on Gram-negative bacteria and fungi. This can be addressed by compounding with other preservatives or physical technologies;

Its stability decreases in meat products with high pH (e.g., pH >7.0). This can be improved by adding organic acids to adjust pH to 5.0–6.5 or using microencapsulation technology (e.g., encapsulating Nisin with chitosan);

The cost is relatively high. This can be mitigated by optimizing the addition amount (determining the minimum effective concentration through pre-experiments) or compounding with low-cost natural preservatives (such as plant essential oils) to ensure effectiveness while reducing costs.

As a natural preservative, nisin shows significant advantages in the preservation of meat products. Through reasonable addition methods and synergistic technologies, it can effectively inhibit pathogenic and spoilage bacteria, extend shelf life, and ensure product safety and quality. Future research will focus on the development of efficient delivery systems for nisin (such as nano-encapsulation), broader synergistic formulations, and application expansion in new meat products (e.g., plant-based mixed meat), further promoting the green preservation process in the meat industry.