The safety of Nisin application in infant and toddler food

As a natural antimicrobial peptide produced by the fermentation of Streptococcus lactis, nisin is commonly used in the food industry to inhibit the growth of Gram-positive bacteria (e.g., Listeria, Staphylococcus) and extend food shelf life. The safety of its application in infant food requires a comprehensive analysis integrating toxicological research, evaluations by authoritative institutions, the physiological characteristics of infants, and practical application scenarios. The specific analysis can be conducted from the following dimensions:

I. Toxicological Basis: Natural Origin and Low Toxicity Characteristics

Nisin’s molecular structure determines its metabolic pathway and safety in the human body. As a polypeptide, it is degraded into amino acids or small-molecule peptides by proteases in the gastrointestinal tract (e.g., pepsin, trypsin) after ingestion—consistent with the digestion process of ordinary proteins—without accumulating in the body.

Multiple acute toxicity tests have shown that nisin has an extremely high median lethal dose (LD₅₀): the oral LD₅₀ in mice is >2000 mg/kg body weight, far exceeding the potential additive dose in food. Long-term chronic toxicity tests (e.g., 90-day rat feeding tests, reproductive and developmental toxicity tests) have also not observed clear toxic reactions, including no adverse effects on liver and kidney function, blood indicators, or reproductive development. In addition, mutagenicity tests (e.g., the AMES test) indicate that nisin has no mutagenic activity, further eliminating the risk of potential genotoxicity. This "digestible, non-accumulative, low-toxicity" property forms the core toxicological basis for its application in infant food.

II. Safety Certification and Usage Standards by Authoritative Institutions

Mainstream global food safety regulatory institutions have recognized the safety of nisin in infant food through systematic evaluations and formulated clear scope of use and limit standards:

For example, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) has classified nisin’s acceptable daily intake (ADI) as "Not Specified" (ANS), meaning that long-term intake within a reasonable range will not pose risks to human health.

China’s National Food Safety Standard for the Use of Food Additives (GB 2760) explicitly permits the use of Nisin in infant formula and complementary foods for infants (e.g., cereal supplements, fruit purees, meat purees), with no strict limits (only requiring "appropriate use according to production needs"). However, it emphasizes compliance with product quality specifications (e.g., purity, microbial indicators).

The core basis for these certifications lies in nisin’s natural fermentation origin and human-metabolizable properties, which make it compatible with the delicate digestive systems of infants. Additionally, it does not disrupt the normal intestinal flora balance of infants (exerting no inhibitory effect on beneficial intestinal bacteria such as Bifidobacterium and lactic acid bacteria).

III. Compatibility with Infant Physiological Characteristics: Targeted Risk Control

Infants (especially those aged 0–3 years) have underdeveloped digestive systems and liver metabolic functions, resulting in lower tolerance to food additives than adults. Therefore, the application of nisin in infant food requires extra attention to "compatibility risks." However, existing research and practice have confirmed its targeted safety:

On one hand, nisin has a specific antibacterial spectrum, only targeting Gram-positive bacteria that cause food spoilage or pathogenesis. It does not inhibit beneficial Gram-negative bacteria essential for the infant intestinal tract (e.g., beneficial strains of E. coli), thus avoiding disruption of the intestinal microecological balance. This distinguishes it from some chemical preservatives (e.g., benzoates), which may exert non-specific effects on intestinal flora.

On the other hand, the use of nisin can reduce the occurrence of other potential risks in infant food. For instance, by inhibiting pathogenic bacteria such as Listeria and Bacillus cereus, it lowers the risk of diseases (e.g., diarrhea, sepsis) in infants caused by food contamination, indirectly enhancing food safety.

It is important to note that there is currently no evidence indicating that nisin triggers allergic reactions in infants. Its fermentation source is Streptococcus lactis (a food-grade safe strain closely related to yogurt-fermenting strains), and its polypeptide structure contains no known allergenic fragments. However, considering the variability of individual allergic constitutions in infants, some regulatory institutions recommend that when infants are first exposed to food containing nisin, the principle of "small-dose trial and reaction observation" should be followed to rule out the possibility of rare allergic reactions (though such cases are extremely uncommon in practice).

IV. Safety Boundaries in Practical Application: Dosage and Scenario Control

Despite its high safety, the application of nisin in infant food must still adhere to the principles of "necessity" and "appropriateness" to avoid unnecessary addition:

From the perspective of "necessity," nisin is mainly used in infant food at risk of Gram-positive bacterial contamination, such as canned infant complementary foods and ready-to-eat cereal purees requiring room-temperature storage. Without antimicrobial agents, such foods are prone to spoilage due to the proliferation of residual spore-forming bacteria (e.g., Bacillus cereus) during processing. For low-temperature refrigerated infant food with a short shelf life (e.g., freshly prepared complementary food purees), if microbial growth can be controlled through cold chain management, nisin addition is unnecessary, reducing unnecessary intake of additives.

From the perspective of "appropriateness," food enterprises must determine the minimum effective additive dose (usually 0.005%–0.02%, i.e., 50–200 mg/kg food) based on the type of infant food, processing technology, and shelf life requirements. Excessive addition not only provides no additional antibacterial effect but may also increase the digestive burden on the infant gastrointestinal tract (though polypeptides are easily degraded, high concentrations may temporarily irritate the intestinal mucosa). Therefore, enterprises must strictly follow the standard of "appropriate use according to production needs" to avoid dosage out of control.

V. Summary and Outlook

Based on comprehensive analysis of toxicological research, authoritative certification, compatibility with infant physiology, and practical application control, the rational application of nisin in infant food exhibits high safety. Its natural origin, metabolizable properties, and specific antibacterial effects enable it to meet the preservation needs of infant food while avoiding potential risks of chemical preservatives.

Future safety research can further focus on "compatibility with special populations," such as conducting targeted safety verification for more physiologically vulnerable groups (e.g., premature infants, low-birth-weight infants). Meanwhile, it is necessary to strengthen supervision and testing of nisin addition levels in infant food to prevent excessive dosage caused by irregular enterprise processes, further consolidating the safety barrier for its application.