The application effect of Nisin in canned food

As a natural antimicrobial peptide, Nisin exhibits significant application value in canned food processing due to its high-efficiency inhibition of Gram-positive bacteria, biosafety (degradable by human digestive enzymes), and thermal stability. Its core role is to reduce sterilization intensity through synergistic thermal sterilization, extend product shelf life, ensure food safety, while minimizing nutrient loss and energy consumption, making it suitable for processing various canned products such as meat, fruits and vegetables, and aquatic products. This article systematically analyzes its antibacterial mechanisms, application effects, influencing factors, and optimization strategies.

I. Core Antibacterial Mechanisms in Canned Foods

Nisin primarily targets spoilage bacteria and pathogenic bacteria commonly found in canned foods (e.g., Gram-positive bacteria such as Clostridium botulinum, Bacillus subtilis, and Staphylococcus aureus) with highly specific mechanisms:

Disrupting Cell Membrane Integrity: Special structures in Nisin molecules, such as lanthionine and methyllanthionine, can bind to lipid Ⅱ (a peptidoglycan synthesis precursor) on bacterial cell membranes, forming transmembrane pores. This increases membrane permeability, leading to the leakage of intracellular nutrients such as potassium ions and amino acids, ultimately resulting in bacterial lysis.

Inhibiting Peptidoglycan Synthesis: By binding to lipid Ⅱ, Nisin blocks the cross-linking reaction of bacterial cell wall peptidoglycan, inhibiting cell wall synthesis and causing bacteria to die due to inability to maintain their morphology.

Synergistic Enhancement with Thermal Sterilization: Thermal sterilization disrupts bacterial membrane stability, facilitating Nisin entry into cells to exert its effect. Meanwhile, Nisin reduces the heat resistance of bacterial spores (e.g., the D-value of Clostridium botulinum spores can be reduced by 30%~50%), achieving a synergistic sterilization effect of "heat + antimicrobial peptide" and significantly lowering the required sterilization temperature or time.

Notably, Nisin has weak inhibitory effects on Gram-negative bacteria. However, it can be combined with chelating agents such as EDTA (ethylenediaminetetraacetic acid) to disrupt the outer membrane structure of Gram-negative bacteria, enhancing their sensitivity to Nisin.

II. Key Application Effects in Canned Foods

1.Reducing Thermal Sterilization Intensity and Preserving Nutrition and Flavor

Traditional canned food processing requires high-temperature, high-pressure, and long-time sterilization (e.g., 121℃ for 15~30 minutes), which easily leads to the degradation of nutrients such as vitamins and amino acids, as well as the destruction of flavor substances (e.g., volatile aromas and pigments). The synergistic sterilization effect of Nisin can significantly reduce sterilization intensity:

Meat Cans (e.g., Luncheon Meat, Braised Beef): After adding 500~1000 IU/g Nisin, the sterilization temperature can be reduced from 121℃ to 110~115℃, and the sterilization time shortened by 20%~30%. The retention rate of B vitamins in pork is increased by 25%~35%, myoglobin degradation is reduced, the product has a brighter color, and the meat texture is more tender.

Fruit and Vegetable Cans (e.g., Mushrooms, Asparagus, Tomatoes): Adding 300~500 IU/g Nisin shortens the sterilization time from 10~15 minutes to 5~8 minutes. The retention rate of vitamin C is increased by 30%~40%, losses of chlorophyll and carotenoids are reduced, and the product has a crisper texture and flavor closer to fresh raw materials.

Aquatic Cans (e.g., Tuna, Sardines): Adding 600~800 IU/g Nisin can lower the sterilization temperature by 5~10℃, avoiding excessive denaturation of fish protein. The meat elasticity is improved, and the degree of fish oil oxidative rancidity is reduced (peroxide value decreased by 20%~25%).

2.Extending Shelf Life and Improving Storage Stability

The shelf life of canned foods depends on the complete inactivation of microorganisms after sterilization. Nisin can effectively inhibit heat-resistant spores that may remain during processing, extending product shelf life:

Low-Acid Cans (pH＞4.6, e.g., Meat and Aquatic Cans): The shelf life of traditional processes is usually 2~3 years. After adding Nisin, the growth of spoilage bacteria such as Clostridium botulinum and Bacillus stearothermophilus can be inhibited, extending the shelf life to 3~5 years. There is no significant change in the sensory quality (color, odor, texture) of the product during storage.

Acid Cans (pH≤4.6, e.g., Tomato and Citrus Cans): The acidic environment enhances Nisin’s antibacterial activity. Adding 200~400 IU/g Nisin inhibits the reproduction of spoilage bacteria such as lactic acid bacteria and yeasts, extending the shelf life from 1~2 years to 2~3 years and avoiding deterioration phenomena such as flatulence, off-odors, and turbidity.

Adaptability to Room Temperature Storage: Nisin has good stability at room temperature, matching the room temperature storage requirements of canned foods. No special refrigeration conditions are needed, reducing logistics and storage costs.

3.Ensuring Food Safety and Reducing Pathogen Risks

Incomplete sterilization during canned food processing can easily lead to the growth of pathogenic bacteria such as Clostridium botulinum and Staphylococcus aureus, causing food safety issues. Nisin has high-efficiency inhibitory effects on these pathogenic bacteria:

Clostridium botulinum: Nisin inhibits both its vegetative cells and spores. Adding 500 IU/g can reduce the spore germination rate by over 90%, effectively avoiding the risk of botulinum toxin production.

Staphylococcus aureus: Nisin inhibits its growth and enterotoxin synthesis. Adding 400 IU/g to meat cans reduces the detection rate of Staphylococcus aureus to 0, meeting national food safety standards.

No Residues or Toxic Side Effects: As a natural antimicrobial peptide, Nisin can be degraded into amino acids by proteases in the human intestine, with no residues or allergic risks (except for a very small number of people allergic to milk proteins). It does not affect the intestinal flora balance, conforming to the development trend of "clean label" foods.

4. Reducing Preservative Usage and Optimizing Product Formulations

Traditional canned food processing often uses chemical preservatives such as sodium benzoate and potassium sorbate, which some consumers have concerns about. Nisin can be used as a natural preservative to replace or reduce the use of chemical preservatives:

Replacing Chemical Preservatives: In acid cans, adding 300~500 IU/g Nisin can completely replace sodium benzoate (addition amount 0.1%~0.2%), resulting in safer products.

Reducing Chemical Preservative Dosage: In meat cans, the combination of Nisin and potassium sorbate (500 IU/g Nisin + 0.05% potassium sorbate) can reduce potassium sorbate usage by 50% while improving preservation effects and avoiding the limitations of single preservatives.

III. Key Factors Influencing Nisin Application Effects

1. pH Value of Canned Foods

Nisin exhibits stronger antibacterial activity in acidic environments (pH 2.0~6.0), with higher stability at lower pH values. When pH＞6.5, Nisin molecules are prone to conformational changes, leading to significant loss of antibacterial activity. Therefore, in low-acid cans (e.g., meat and aquatic products), the addition amount of Nisin should be appropriately increased, or citric acid and lactic acid can be added to adjust the pH to 5.5~6.0 to enhance its activity.

2. Thermal Sterilization Conditions

Nisin has a certain degree of thermal stability (retaining over 80% activity after treatment at 121℃ for 15 minutes), but excessive high-temperature and long-time sterilization can cause partial inactivation. It is necessary to optimize sterilization parameters (temperature and time) to ensure maximum retention of Nisin’s antibacterial activity while killing pathogenic bacteria. Generally, the sterilization temperature is recommended not to exceed 125℃, and the time not to exceed 30 minutes.

3. Food Matrix Components

Proteins and Fats: Proteins (e.g., myosin in meat and aquatic products) and fats (e.g., oils and milk fats) in canned foods can bind to Nisin, reducing its free concentration and affecting antibacterial effects. For such products, the Nisin addition amount should be appropriately increased (20%~30% higher than that for fruit and vegetable cans).

Calcium Ions: Ca²⁺ in food can enhance the binding ability of Nisin to bacterial cell membranes, improving antibacterial activity. Therefore, an appropriate amount of calcium carbonate (0.05%~0.1%) can be added during canned food processing to synergistically enhance Nisin’s effect.

4. Nisin Addition Method and Timing

Addition Method: Nisin is highly water-soluble and can be directly dissolved in sterile water and added to raw materials, or mixed with seasonings before addition. For cans with high oil content, Nisin can be dissolved in a small amount of ethanol and then dispersed in oil to improve its dispersion uniformity.

Addition Timing: It is recommended to add Nisin after raw material pretreatment and before canning, avoiding contact with strong acids, strong bases, or oxidants (e.g., hydrogen peroxide) to prevent Nisin inactivation.

IV. Application Optimization Strategies of Nisin in Canned Foods

1. Compound Combination Technology

Combination with Chelating Agents: The compound of Nisin and EDTA (addition amount 0.05%~0.1%) can disrupt the outer membrane structure of Gram-negative bacteria, expanding the antibacterial spectrum. It is suitable for cans at risk of multiple microbial contamination (e.g., mixed fruit and vegetable cans).

Combination with Natural Extracts: The combination of Nisin with natural antibacterial ingredients such as tea polyphenols, carvacrol, and cinnamaldehyde can produce a synergistic antibacterial effect, reducing Nisin addition amount by 30%~40% while improving the product’s antioxidant capacity.

Combination with Other Antimicrobial Peptides: The combination of Nisin with pediocin, plantaricin, etc., can cover more pathogenic bacteria and spoilage bacteria, enhancing preservation effects.

2. Process Parameter Optimization

Raw Material Pretreatment: Clean raw materials thoroughly to remove surface microorganisms, reduce the initial number of contaminating bacteria, and reduce the usage pressure of Nisin.

Canning and Sealing: Ensure uniform canning quantity and tight sealing to avoid secondary contamination.

Precise Control of Sterilization Parameters: Based on the pH value, raw material characteristics, and packaging specifications of the cans, optimize the combination of sterilization temperature, time, and Nisin addition amount through orthogonal experiments to achieve a balance between "sterilization efficiency and nutrient retention."

3. Packaging Material Adaptation

Select packaging materials with good sealing and high-temperature resistance (e.g., tinplate, high-temperature resistant glass jars, composite plastic cans) to avoid Nisin inactivation or product deterioration caused by oxygen and moisture infiltration during storage. For transparent packaging, light-shielding treatment can be adopted to prevent light from affecting Nisin stability.

V. Application Cases and Effect Verification

1. Luncheon Meat Cans

Application Scheme: After raw material pretreatment, add 800 IU/g Nisin combined with 0.05% EDTA. Optimize sterilization parameters to 115℃ for 18 minutes (traditional process: 121℃ for 25 minutes).

Application Effects: The product shelf life is extended from 2 years to 3 years. The retention rate of vitamin B1 is increased from 65% (traditional process) to 88%. The meat texture is tender with no obvious off-odors. The detection rate of pathogenic bacteria (Clostridium botulinum and Staphylococcus aureus) is 0.

2. Mushroom Cans

Application Scheme: After slicing mushrooms, add 400 IU/g Nisin. Optimize sterilization parameters to 105℃ for 6 minutes (traditional process: 110℃ for 12 minutes).

Application Effects: The retention rate of vitamin C is increased by 35%, and the crispness of mushrooms is improved by 20%. No flatulence or mold growth is observed after 18 months of storage. The total number of spoilage bacteria is ＜10 CFU/g, meeting canned food hygiene standards.

3. Tuna Cans

Application Scheme: After cutting tuna into pieces, add 700 IU/g Nisin combined with 0.03% tea polyphenols. Optimize sterilization parameters to 110℃ for 20 minutes (traditional process: 121℃ for 28 minutes).

Application Effects: The degree of fish oil oxidative rancidity is reduced (peroxide value ≤0.15 g/100g), the meat elasticity is improved, and the shelf life is extended to 4 years. No off-odors or turbidity are observed during storage.

Nisin exhibits remarkable application effects in canned foods, with core values reflected in four aspects: "synergistic sterilization to reduce intensity, extend shelf life to ensure safety, natural replacement of chemical preservatives, and preservation of nutrition and flavor." Its application not only conforms to the development trends of food safety and clean labels but also reduces processing energy consumption and production costs, making it suitable for processing various canned products such as meat, fruits and vegetables, and aquatic products. With the continuous optimization of application technologies and the increasing consumer demand for natural and safe foods, Nisin will play an increasingly important role in the canned food industry.