The Application of Nisin in the Preservation of Dairy Products

As a natural biological preservative certified by FAO/WHO, Nisin is widely used in dairy product preservation due to its high safety and easy digestibility by the human body. Current research progress focuses on the optimization of single applications, the development of composite preservation systems, and breakthroughs in modification technologies such as nanonization, which have effectively addressed inherent limitations such as a narrow antimicrobial spectrum and poor stability. Detailed elaboration is as follows:

Optimization of Single Applications in the Preservation of Various Dairy Products

Nisin exhibits significant inhibitory effects on common Gram-positive spoilage and pathogenic bacteria in dairy products. Mature application schemes have been established for various dairy products including fresh milk, yogurt, cheese, and condensed milk, with continuous refinement of application parameters:

Fresh Milk and Cream: Adding 0.05 g/kg Nisin to ultra-high temperature (UHT) sterilized aseptically filled milk reduces the spoilage rate from 0.04% to 0. For low-fat milk and unsalted cream, supplementation with 0.08 g/kg Nisin followed by heat treatment at 121℃ for 3 minutes enables storage at 40℃ for six weeks.

Yogurt: Adding 0.05 g/kg Nisin to yogurt (pH ~4) and sterilizing at 90℃ for 20 minutes extends the room-temperature shelf life from 6 days to over 1 month. When Nisin nanoparticles are added to yogurt, a concentration of 0.125 mg/mL efficiently inhibits methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli O157:H7—completely eliminating the former within 24 hours while significantly prolonging yogurt shelf life.

Cheese and Condensed Milk: Adding 0.05–0.1 g/kg Nisin inhibits the growth of heat-resistant Gram-positive bacterial spores (e.g., Clostridium botulinum) in cheese. In cottage cheese, Nisin reduces the count of Listeria monocytogenes by approximately 3 log cycles within 3 days. For canned unsweetened condensed milk, supplementation with 0.08–0.1 g/kg Nisin suppresses the growth of heat-resistant spores and shortens heat treatment time by 10 minutes.

Research on Synergistic Enhancement of Composite Preservation Systems

To address Nisin’s weak inhibitory effects on Gram-negative bacteria and fungi, the scientific and industrial communities have extensively developed composite preservation schemes, broadening the antimicrobial spectrum and enhancing efficacy through synergistic effects:

Combination with Preservatives: Experiments by Jin Mingxiao show that the optimal inhibitory effects are achieved with either 1000 ppm Nisin + 4% EDTA + 0.5% sorbic acid or 1000 ppm Nisin + 4% EDTA + 5 μg/mL natamycin. In the preservation of Turkish white cheese, combining Nisin with protective cultures such as Lactobacillus plantarum and Lactobacillus rhamnosus exhibits far superior inhibitory effects on microorganisms like coliforms compared to single Nisin treatment, without affecting basic quality parameters such as fat and protein content.

Integration with Enzymes and Natural Systems: In cheese production, the combination of Nisin and lysozyme causes more severe cell damage to Bacillus spp. In pasteurized milk, their synergy inhibits Bacillus and psychrophilic bacteria, extending shelf life to 15 days. The combination of Nisin and the lactoperoxidase system inhibits Listeria monocytogenes in skim milk through a synergistic mechanism of "pore formation + protein inactivation," ensuring the pathogen remains undetectable after 15 days of storage at 25℃.

Coordination with Physical Treatments: When combined with heat treatment, Nisin reduces the average thermal D-value of Bacillus cereus in milk by 40% at 80–100℃. Synergy with high hydrostatic pressure processing enhances inhibitory effects on Gram-positive bacteria such as Listeria spp., as Nisin-induced membrane disruption increases bacterial sensitivity to pressure.

Breakthroughs in Modification Technologies to Improve Stability and Applicability

Nisin tends to bind to components such as fat globules and casein in dairy products and exhibits poor stability under neutral pH conditions. Modification technologies such as nanoencapsulation have addressed these issues, with significant progress achieved in related research:

Nanoparticle Encapsulation: Nisin/chitosan nanoparticles prepared via electrostatic self-assembly technology achieve an encapsulation efficiency of 48.6% at a Nisin concentration of 5 mg/mL, demonstrating good storage stability at both 25℃ and 4℃. When applied to condensed milk, these nanoparticles sustain anti-Listeria activity through controlled release of Nisin. Additionally, Nisin nanoparticles prepared via acetic acid nanoprecipitation have been confirmed safe through cytotoxicity testing, posing no additional safety risks in dairy applications.

Other Modification Directions: Beyond nanonization, research explores encapsulating Nisin into active packaging materials to reduce direct contact with food matrices and minimize activity loss. Simultaneously, structural modification of Nisin via bioengineering and optimization of formulation enhance its stability under varying pH and temperature conditions, further expanding its application scenarios in dairy products.