The synergistic effect of Nisin and low-temperature sterilization

Extending the shelf life of meat products is a key challenge in the food industry, and the synergistic effect of Nisin (nisin) and low-temperature sterilization offers an efficient solution. This synergy leverages the complementary advantages of both methods to reduce microbial contamination while maximizing the retention of meat product quality, thereby significantly extending shelf life.

I. Fundamental Mechanisms of Nisin and Low-Temperature Sterilization

Nisin is a natural antimicrobial peptide produced by lactic acid bacteria, exhibiting strong inhibitory effects primarily against Gram-positive bacteria (e.g., Clostridium botulinum, Listeria monocytogenes, Staphylococcus aureus). Its mechanism of action involves disrupting the integrity of bacterial cell membranes, forming transmembrane channels that cause leakage of intracellular substances, ultimately inhibiting bacterial growth or inducing death. Due to its natural origin, high safety, and ease of degradation by human digestive enzymes, Nisin is widely used as a food preservative, particularly suitable for meat products—foods highly susceptible to Gram-positive bacterial contamination.

Low-temperature sterilization (e.g., pasteurization, typically at 60–75°C for several minutes) kills pathogenic and most spoilage bacteria in meat products using moderate heat, while avoiding high-temperature damage to texture, flavor, and nutrients. However, its limitation lies in its inability to completely eliminate heat-resistant microorganisms (e.g., spores of certain Bacillus species) and weak efficacy against some Gram-negative bacteria, making long-term preservation difficult when used alone.

II. Core Mechanisms of Synergistic Effects

The synergy between Nisin and low-temperature sterilization is not a simple additive effect but enhances antimicrobial efficacy through multi-layered mechanisms:

Reducing microbial heat resistance: The heat treatment in low-temperature sterilization alters bacterial membrane fluidity and permeability, facilitating Nisin penetration and action. For example, heat-induced loosening of lipid molecule arrangements in bacterial membranes creates favorable conditions for Nisin to bind to membrane receptors (e.g., lipid II, a cell wall precursor), thereby enhancing its bactericidal efficiency.

Expanding antimicrobial spectrum and improving sterilization thoroughness: Low-temperature sterilization eliminates some Nisin-insensitive microorganisms (e.g., certain Gram-negative bacteria), while Nisin specifically inhibits residual Gram-positive bacteria (especially germinated heat-resistant spores) post-sterilization. For instance, Listeria monocytogenes—common in meat products—exhibits partial resistance to low-temperature sterilization, but Nisin effectively suppresses its growth under refrigeration, compensating for the limitations of low-temperature treatment.

Minimizing microbial recovery and reproduction: Residual microorganisms in post-sterilization meat products may recovery during storage (e.g., refrigeration). Nisin retains partial activity at low temperatures, providing "secondary protection" by continuously inhibiting microbial growth. Simultaneously, low temperatures slow microbial metabolism, superimpose with Nisin’s antimicrobial effects to further reduce spoilage risks.

III. Application Advantages in Meat Products

Compared to using Nisin or low-temperature sterilization alone, their synergy offers significant advantages in extending meat product shelf life:

Reducing sterilization intensity while preserving quality: High-temperature sterilization achieves strong microbial reduction but damages meat texture, flavor, and nutrients (e.g., muscle protein denaturation, accelerated fat oxidation). In contrast, Nisin combined with low-temperature sterilization achieves equivalent or superior antimicrobial effects at lower temperatures, minimizing heat-induced damage to sensory and nutritional properties. For example, in sausage processing, 65°C pasteurization combined with Nisin kills most pathogens while maintaining juiciness and elasticity, outperforming traditionally high-temperature-sterilized products.

Synergistic inhibition of spoilage bacteria: Meat spoilage is primarily caused by microorganisms (e.g., lactic acid bacteria, yeasts, Bacillus), which may grow slowly under refrigeration. Nisin’s inhibition of Gram-positive spoilage bacteria complements the metabolic slowdown induced by low temperatures—low temperatures reduce growth rates, while Nisin directly blocks reproduction, jointly delaying spoilage phenomena like acidification, stickiness, and off-odors. For instance, in chilled meat storage, Nisin treatment combined with 4°C refrigeration extends shelf life from 3–5 days (traditional refrigeration) to 7–10 days, while effectively controlling pathogens like Listeria.

Reducing reliance on chemical preservatives: Traditional meat preservation often depends on chemical preservatives such as nitrites, but excessive use may generate harmful substances (e.g., nitrosamines). Nisin, as a natural peptide, synergizes with low-temperature sterilization to reduce chemical additive levels, enhancing product safety and consumer acceptance.

IV. Practical Application Considerations

To maximize synergistic effects, attention to the following points is crucial in practice:

Nisin addition timing and concentration: Nisin should be added before low-temperature sterilization to ensure sufficient microbial contact. Concentrations (typically 0.05–0.2g/kg) are adjusted based on meat type and contamination risk—excess may affect flavor, while insufficient amounts limit efficacy.

Optimizing low-temperature sterilization parameters: Temperature and duration are tailored to meat characteristics (e.g., moisture, pH, fat content). For example, high-moisture products may require slightly higher temperatures (70–75°C) for efficacy, while high-fat products need time control to prevent oxidation.

Coordinating storage conditions: Post-treatment meat products still require low-temperature storage (e.g., 0–4°C) to maintain Nisin activity and microbial inhibition, avoiding temperature fluctuations that may trigger microbial rebound.

The synergy between Nisin and low-temperature sterilization achieves efficient microbial control in meat products through a "physical sterilization + biological inhibition" dual mechanism. This approach overcomes the incomplete antimicrobial effect of standalone low-temperature sterilization, avoids high-temperature-induced quality damage, and reduces chemical preservative use, aligning with modern food industry demands for "safety, quality, and naturalness." Future optimizations—such as Nisin encapsulation to enhance stability, or combining low-temperature sterilization with high-pressure processing—are expected to further expand its application potential in meat preservation.