The Application of Nisin in canned food

Nisin, a natural antibacterial peptide produced by the fermentation of Lactococcus lactis, demonstrates significant application value in canned food processing due to its highly efficient inhibitory effect on Gram-positive bacteria (especially spore-forming pathogenic and spoilage bacteria such as Bacillus and Clostridium), as well as its characteristics of high safety, degradability by human digestive enzymes, and no toxic residues. Its core value lies in two dimensions: extending product shelf life and reducing heat treatment intensity, providing crucial technical support for balancing "high quality" and "long shelf life" in canned foods.

I. Extending the Shelf Life of Canned Foods

From the perspective of extending shelf life, nisin’s core role is to precisely target and inhibit "heat-resistant spoilage bacteria" that are difficult to completely eliminate through conventional processing in canned food production. The shelf life of canned foods relies on the establishment of a "commercially sterile" state, which involves killing pathogenic bacteria and most spoilage bacteria in food through heat treatment and inhibiting spore germination. However, the spores of some Gram-positive bacteria (such as certain strains of Bacillus cereus and Clostridium botulinum) exhibit extremely strong heat resistance and cannot be completely inactivated by conventional heat treatment (e.g., pasteurization). If subsequent storage conditions are improper (e.g., temperature fluctuations), these spores easily germinate into viable bacteria and multiply in large quantities, leading to spoilage of canned contents (e.g., swollen cans, flavor deterioration, abnormal texture).

Nisin achieves inhibition by disrupting the cell membrane structure of such Gram-positive bacteria and their spores: its molecules can insert into bacterial cell membranes to form pores, causing the leakage of important substances such as amino acids and ions from the cells, while destroying the osmotic balance of the cell membrane. Ultimately, this results in the killing of viable bacteria and the inhibition of spore germination. After adding Nisin to canned food production, even if heat treatment fails to completely kill all heat-resistant spores, the residual Nisin can continue to function in the sealed canned system, preventing spores from germinating into metabolically active bacteria, thereby blocking the spoilage pathway and significantly extending the shelf life of canned products.

For example:

In meat cans (e.g., beef cans, luncheon meat cans), adding an appropriate amount of Nisin can effectively inhibit "sulfide spoilage" (off-odors, sticky meat texture) caused by spore-forming spoilage bacteria.

In vegetable cans (e.g., mushroom cans, pea cans), it can reduce "acidic spoilage" (sour contents, turbid soup) caused by Bacillus, extending the shelf life of canned products from 6–12 months to 18–24 months or even longer under room temperature storage.

II. Reducing Heat Treatment Intensity

On the other hand, the application of nisin can significantly reduce the intensity of heat treatment in canned food processing—an advantage that is crucial for preserving the nutrition, flavor, and texture of food. Traditional canned food processing typically requires high-intensity heat treatment (e.g., 121℃ high-pressure sterilization for 30–60 minutes) to achieve commercial sterility. However, prolonged high temperatures lead to massive loss of heat-sensitive nutrients in food (e.g., vitamin C, B vitamins, carotenoids), destroy the natural flavor substances of food (e.g., fruity components in fruit cans, umami substances in meat cans), and may even deteriorate food texture (e.g., mushy vegetables, tough meat fibers).

Nisin and heat treatment exhibit a "synergistic bactericidal effect": heat treatment damages the integrity of bacterial and spore cell membranes, reducing their resistance to nisin and enabling nisin to penetrate the cell membrane more easily to exert its effect; at the same time, nisin inhibits the recovery of bacteria not completely killed by heat treatment and the germination of spores. The combination of the two significantly improves bactericidal efficiency. Based on this effect, after adding nisin to canned food production, the heat treatment temperature can be reduced from 121℃ to 105–115℃, or the treatment time can be shortened at the same temperature (e.g., from 30 minutes to 10–15 minutes). This minimizes the damage of high temperatures to food quality while ensuring commercial sterility.

For example:

In fruit cans (e.g., orange cans, peach cans), reducing heat treatment intensity can reduce the loss of vitamin C in fruits (retention rate can be increased by 15%–30%), while preserving the original crisp texture and fresh fruity aroma of the fruits, avoiding over-softened pulp and bland flavor.

In dairy cans (e.g., concentrated milk cans), lower-temperature heat treatment can reduce milk protein denaturation and lactose caramelization, maintaining the product’s smooth texture and natural milk aroma.

In aquatic cans (e.g., tuna cans), shortening high-temperature treatment time can prevent oxidative deterioration of unsaturated fatty acids in fish meat (reducing the formation of fishy substances) while maintaining the firm texture of the fish.

III. Practical Application Considerations

In practical applications, the method of adding nisin to canned foods needs to be flexibly adjusted based on product characteristics and processing technology to maximize its activity. Common addition methods include:

Addition during raw material pretreatment: Dissolving nisin and spraying it on the surface of meat or vegetable raw materials, or adding it to the soaking solution for fruits and grains.

Addition to soup or sauce before canning: Adding nisin to the seasoned soup or tomato sauce of canned foods to ensure uniform dispersion in the food system.

Synergistic use with other preservation technologies: Combining with mild acidification, vacuum packaging, etc., to further expand the antibacterial spectrum—since Nisin has weak inhibitory effect on Gram-negative bacteria, combining it with organic acids can enhance the inhibitory effect on such bacteria.

Meanwhile, the addition amount of nisin must strictly comply with food additive usage standards (usually 0.002%–0.01%). Excessive addition not only fails to improve the preservation effect but may also cause a slight bitter or metallic taste in canned foods, affecting the eating experience.

IV. Industrial Value and Limitations

In addition, the application of nisin in canned foods also has significant industrial value: reducing heat treatment intensity means reducing energy consumption during processing (e.g., less steam usage, shorter heating time), thereby lowering production costs; at the same time, due to more complete nutrient retention and more natural flavor, canned products added with nisin are more in line with consumers’ demand for "healthy food," enhancing product market competitiveness.

However, it should be noted that the activity of nisin is easily affected by certain components in the canned food system. For example, high concentrations of proteins and fats can bind to nisin, reducing its free content and thus weakening its antibacterial effect. Therefore, in high-protein (e.g., meat, soybean product cans) and high-fat (e.g., fish cans) canned foods, it is necessary to appropriately adjust the addition amount of nisin or optimize the addition method (e.g., using microencapsulation technology to reduce non-specific binding with other components) to ensure its stable effect.