The safety of Nisin in dairy processing

Nisin, a natural bacteriocin, is widely used as a preservative in dairy processing. Its safety has been evaluated and certified by regulatory authorities in many countries, and relevant studies have verified the rationality of its application from multiple dimensions, including toxicology, metabolic pathways, and residual effects.

I. Toxicological Safety: No Significant Toxicity or Teratogenicity

Toxicological studies on Nisin have shown extremely low acute and subchronic toxicity to humans. In acute toxicity tests, no obvious toxic reactions were observed even at extremely high doses (e.g., the oral LD₅₀ in mice exceeds 10g/kg body weight). In subchronic toxicity studies, long-term intake of a certain dose of nisin (e.g., rats ingesting 500mg/kg body weight daily) did not cause abnormal liver or kidney function, abnormal blood indicators, or histopathological changes.

In addition, teratogenicity, mutagenicity, and carcinogenicity tests have found no associated risks with nisin. Essentially, it is a polypeptide substance produced by the fermentation of Streptococcus lactis, which has no cross-reaction with the target sites of human cells (such as bacterial cell membranes), and thus will not cause damage to normal human cells, laying the foundation for its safety.

II. Metabolic Pathway: Naturally Degradable by the Human Body, No Residue Risk

Nisin is rapidly degraded into amino acids by proteases (such as trypsin) in the human digestive system and cannot be absorbed by the intestines into the blood or tissues, thus eliminating the problem of in vivo accumulation. This is completely different from the metabolic pathway of chemically synthesized preservatives (such as sodium benzoate) — the latter may be metabolized by the liver, and excessive intake poses a potential burden. In contrast, the degradation products of Nisin are consistent with the digestive products of dietary proteins, belonging to nutrients that can be utilized by the human body, further reducing safety hazards.

Studies have shown that even with high-dose intake, nisin is completely decomposed in the digestive tract and does not interfere with the balance of intestinal flora (its bacteriostatic effect is only against Gram-positive bacteria and it is rapidly inactivated in the digestive environment), avoiding adverse effects on the human intestinal microecology.

III. Regulatory Certification and Dosage Control: Compliance with Global Safety Standards

Nisin has been recognized as a "GRAS" (Generally Recognized As Safe) substance by the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), allowing its reasonable use in food. Various countries have clear regulations on its addition amount. For example, the European Union stipulates that the maximum addition amount in dairy products is 0.5g/kg, and China's GB 2760 standard also limits its scope of use in different dairy products (such as milk drinks, cheese, etc.), ensuring that the dosage in practical applications is far below the safety threshold in toxicological tests.

In dairy processing, the concentration of nisin used is usually 0.02-0.2g/kg. This dosage can effectively inhibit spoilage bacteria (such as Clostridium botulinum and Listeria), while being far lower than the no-observed-adverse-effect level (NOAEL) in safety assessments, further ensuring the safety of its application.

IV. Applicability to Special Populations: No Additional Risks for Sensitive Groups

The safety of Nisin has also been verified for special populations such as children, pregnant women, and the elderly. Due to its mild metabolic pathway and no residue, even groups with weak digestive functions will not experience adverse reactions when ingesting dairy products containing Nisin. Compared with traditional preservatives, it does not irritate the gastrointestinal mucosa nor affect the absorption of key nutrients in dairy products such as calcium and protein, making it particularly suitable as a preservative ingredient in special dairy products such as infant formula milk powder and pregnant women's milk powder.

The safety of nisin in dairy processing has been fully confirmed. Its natural origin, degradability, low toxicity, and clear regulatory control make it an ideal alternative to chemical preservatives. It not only meets the preservative needs of dairy products but also aligns with consumers' pursuit of "clean labels" and food safety.