The safety of Nisin in pickled foods

Nisin is a natural peptide bacteriostatic agent approved by food safety authorities in multiple countries, and its safety for application in pickled foods has been fully verified. Its safety characteristics are reflected in multiple dimensions including toxicological safety, metabolic safety, and compliance. Meanwhile, attention should be paid to the boundary conditions for rational use, which are detailed as follows:

I. High Toxicological Safety

1. Natural Origin and Component Characteristics

Nisin is produced by the fermentation of Lactococcus lactis and is a small-molecule polypeptide composed of 34 amino acids, rather than a chemically synthesized preservative. Its structure is similar to that of natural antimicrobial peptides in the human intestinal tract, featuring good biocompatibility with no teratogenic, mutagenic, or carcinogenic risks. Acute toxicity tests have shown that the median lethal dose (LD₅₀) of Nisin is greater than 7000 mg/kg (oral administration in mice), classifying it as a practically non-toxic substance, which is far higher than its addition level in foods (typically 20–500 mg/kg in pickled foods).

2. No Cumulative or Chronic Toxicity

Long-term feeding experiments have demonstrated that continuous intake of Nisin by animals does not cause chronic toxic reactions such as organ damage or growth inhibition, nor does it lead to drug accumulation. This is because after entering the human digestive tract, Nisin is decomposed into amino acids by trypsin, pepsin, and other proteases, participates in the normal protein metabolism of the human body, and is ultimately absorbed or excreted from the body without residual accumulation.

II. Edible Safety and Applicability to Populations

1. Safety for General Populations

For healthy individuals, consuming pickled foods containing Nisin will not trigger allergies, intestinal flora disorders, or other issues. The antibacterial spectrum of Nisin only targets Gram-positive bacteria; it has no inhibitory effect on beneficial intestinal flora such as Bifidobacterium and lactobacilli, thus not disrupting the balance of the intestinal microecology. In addition, Nisin maintains good stability during the processing of pickled foods (e.g., steaming, sterilization) and does not react with ingredients such as salt, sugar, and spices to produce toxic by-products, ensuring the safety of the final products.

2. Applicability to Special Populations

Infants and Children: The decomposition products of Nisin are amino acids, which can be absorbed as nutrients, and Nisin has no hormone-like effects. Infants can safely consume pickled foods that comply with the addition limits.

Pregnant and Lactating Women: There is no evidence indicating that Nisin exerts adverse effects on fetuses or infants, and its safety has been recognized by the Codex Alimentarius Commission (CAC).

Allergic Populations: Nisin has extremely low allergenicity. Only a very small number of people allergic to Lactococcus lactis need to avoid it, accounting for less than 0.01% of the total population. Moreover, related allergic reactions are mostly manifested as mild skin itching, with no risk of severe allergies.

III. Compliance and Addition Level Restrictions

1. Recognition by International and National Regulations

Nisin has been listed as a Class A food additive by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), with an acceptable daily intake (ADI) of 0–33 mg/kg body weight. In China, the National Food Safety Standard for the Use of Food Additives (GB 2760-2021) clearly specifies the scope and limits of Nisin application in pickled foods:

Pickled meat products (e.g., cured meat, ham): Maximum addition level of 0.5 g/kg;

Pickled vegetables (e.g., preserved vegetables, pickles): Maximum addition level of 0.1 g/kg;

Pickled aquatic products (e.g., salted fish, pickled shrimp): Maximum addition level of 0.3 g/kg.

Based on these limits, the daily intake of Nisin by adults is far below the ADI value, posing no safety risks.

2. Potential Impacts of Excessive Addition

Although Nisin has extremely low toxicity, excessive addition may cause mild side effects—for instance, one-time ingestion of a large amount of Nisin may produce transient irritation to the oral and esophageal mucosa, causing a slight burning sensation. However, such a situation is almost impossible to occur during normal consumption of pickled foods. In addition, excessive addition will increase production costs without significantly enhancing the bacteriostatic effect, thus having no practical application value.

IV. Safety Assurance Measures

1. Quality Control in the Production Process

Compliant Nisin products must meet the requirements of the National Food Safety Standard for Food Additive - Nisin (GB 1886.234-2016). During production, contamination by miscellaneous bacteria should be controlled to avoid introducing allergenic impurities; meanwhile, finished products must pass purity testing (with an active ingredient content of ≥90%) to ensure no residual fermentation by-products.

2. Rational Use in the Application Process

Avoid mixing with strong alkaline substances: Nisin is prone to inactivation under alkaline conditions and may produce trace decomposition products, so it should be added to acidic or neutral pickling systems.

Safety in compound application: When Nisin is used in combination with EDTA, ε-polylysine, and other additives, each additive must comply with the respective limits to prevent excessive total additive intake caused by synergistic effects.

The application of Nisin in pickled foods is characterized by high safety, no residue, and broad applicability to populations, making it an ideal alternative to some chemical preservatives. As long as the addition level is strictly controlled in accordance with national standards and production and application processes are standardized, pickled foods containing Nisin can be consumed with confidence.