The role of Nisin in the preservation of cooked chicken wings

Cooked chicken wings, rich in protein, fat, and moisture, are susceptible to microbial contamination and oxidative deterioration after processing. Their shelf life is typically only 1–2 days at room temperature, and even under refrigeration, issues like excessive bacterial counts and flavor deterioration often occur. Nisin (nisin), a natural and safe food preservative, can significantly extend the shelf life of cooked chicken wings by precisely inhibiting spoilage-causing and pathogenic Gram-positive bacteria and delaying quality deterioration. It also eliminates safety concerns associated with chemical preservatives, making it a core preservation solution for cooked chicken wings. This article analyzes the specific role of Nisin in preserving cooked chicken wings from four aspects: antibacterial mechanism, preservation efficacy, application advantages, and practical key points.

I. Core Role in Cooked Chicken Wings: Precise Antibacterial Action to Block Spoilage at the Source

Spoilage of cooked chicken wings is primarily caused by microbial growth, with Gram-positive bacteria (e.g., Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus) being the "main contributors." These bacteria not only decompose proteins and fats in chicken wings to produce off-odors (e.g., putrid smell, rancid smell) but also secrete toxins (e.g., S. aureus enterotoxin) in some cases, posing food safety risks. Nisin blocks the spoilage process at the source by specifically damaging the structure and metabolism of Gram-positive bacteria.

(I) Damaging Bacterial Cell Membranes to Rapidly Kill Spoilage-Causing Bacteria

The core antibacterial mechanism of Nisin involves targeting the cell membrane of Gram-positive bacteria to form "transmembrane pores," leading to bacterial lysis. Specifically, Gram-positive bacteria remaining in cooked chicken wings (either residual or post-processing contaminants) have "lipid II" (a key precursor for cell wall synthesis) on their cell membrane surfaces. Nisin binds specifically to lipid II to form stable Nisin-lipid II complexes; multiple complexes aggregate and penetrate the cell membrane, creating transmembrane pores approximately 2 nm in diameter. This causes massive leakage of intracellular small molecules (e.g., potassium ions, amino acids) and influx of external water, disrupting bacterial osmotic balance and ultimately leading to rapid bacterial lysis and death.

Nisin exhibits significant inhibitory effects against common spoilage-causing bacteria in cooked chicken wings:

Against Staphylococcus aureus: In cooked chicken wings supplemented with 0.15 g/kg Nisin, the growth rate of S. aureus under 4°C refrigeration is 90% lower than that in the non-supplemented group, with bacterial counts remaining <100 CFU/g within 7 days (far below the national standard limit of 1000 CFU/g). Without Nisin, bacterial counts exceed 5000 CFU/g after 3 days, accompanied by obvious off-odors.

Against Bacillus cereus: This bacterium produces heat-resistant spores that are difficult to completely eliminate via conventional heating and tend to germinate and grow during storage of cooked foods. Nisin inhibits spore activity by damaging the cell membrane of germinated spores. In cooked chicken wings supplemented with 0.2 g/kg Nisin, the germination rate of B. cereus spores decreases from 60% to 10%, and no "stickiness" (caused by spore growth) is observed within 10 days of refrigeration.

(II) Inhibiting Toxin Production to Ensure Edible Safety

Some Gram-positive bacteria (e.g., S. aureus, L. monocytogenes) secrete heat-resistant toxins during growth. These toxins cannot be completely inactivated even by reheating, posing major safety hazards for cooked chicken wings. By killing or inhibiting these bacteria in advance, Nisin reduces toxin production at the source.

Experimental data shows:

In cooked chicken wings without Nisin, the content of S. aureus enterotoxin reaches 0.5 μg/kg (exceeding the safety limit of 0.1 μg/kg) after 24 hours of storage at 25°C.

In samples supplemented with 0.1 g/kg Nisin, no enterotoxin is detected even after 48 hours of room-temperature storage.

Studies on L. monocytogenes also indicate that Nisin reduces the secretion of listeriolysin (a virulent toxin) by inhibiting bacterial metabolism, decreasing toxin content by over 85% and preventing food poisoning symptoms (e.g., nausea, diarrhea) after consumption.

II. Protecting the Quality of Cooked Chicken Wings: Delaying Deterioration to Maintain Sensory Properties and Nutrition

In addition to antibacterial action, Nisin indirectly delays oxidative deterioration and nutrient loss in cooked chicken wings. When combined with proper storage conditions, it preserves the color, flavor, and nutritional quality of chicken wings for an extended period, avoiding the issue of "preservation without quality maintenance."

(I) Delaying Lipid Oxidation to Preserve Flavor and Texture

During processing (e.g., frying, roasting) and storage, fats in cooked chicken wings are prone to oxidation, producing small molecules such as aldehydes and ketones that cause a rancid smell. This process also makes the meat tough and compromises texture. Although Nisin does not directly exhibit antioxidant properties, it reduces the production of reactive oxygen species (ROS) from microbial metabolism by inhibiting the growth of oxygen-dependent microorganisms (e.g., some aerobic Gram-positive bacteria), thereby indirectly delaying lipid oxidation.

Comparative experiments show:

In cooked chicken wings without Nisin, the peroxide value (POV, an indicator of lipid oxidation) increases from an initial 0.8 meq/kg to 5.2 meq/kg after 7 days of 4°C refrigeration, with obvious rancidity and a 30% increase in meat hardness.

In samples supplemented with 0.15 g/kg Nisin, the POV is only 3.1 meq/kg after 12 days of refrigeration, with no rancidity and a meat hardness increase of less than 15%, maintaining a tender texture.

When Nisin is combined with antioxidants such as tea polyphenols or vitamin E, the antioxidant effect is further enhanced. For example, cooked chicken wings supplemented with 0.1 g/kg Nisin and 0.08 g/kg tea polyphenols have a POV of <2.5 meq/kg even after 15 days of refrigeration, with minimal flavor difference from freshly processed products.

(II) Protecting Proteins and Pigments to Maintain Nutrition and Color

Proteins in cooked chicken wings are easily decomposed into small peptides or amino acids by microorganisms, leading to nutrient loss. Meanwhile, myoglobin in muscle is prone to oxidation to metmyoglobin, turning the color of chicken wings from an appealing reddish-brown to a dull brown and reducing sensory appeal.

By inhibiting microbial growth, Nisin reduces the production of protein-degrading enzymes (e.g., proteases), thereby protecting proteins and myoglobin:

Nutrient retention: In cooked chicken wings supplemented with Nisin, protein content decreases by only 5% from the initial value after 10 days of refrigeration, compared to a 12% decrease in the non-supplemented group. The retention rate of essential amino acids (e.g., lysine, methionine) is also increased by 10%–15%.

Color maintenance: In non-supplemented samples, metmyoglobin accounts for 45% of total myoglobin after 5 days of refrigeration, with obvious browning. In samples supplemented with 0.2 g/kg Nisin, metmyoglobin accounts for less than 20% even after 10 days, maintaining a bright color and significantly higher consumer acceptance.

III. Application Advantages in Preserving Cooked Chicken Wings: Safety, Efficacy, and Strong Adaptability

Compared to chemical preservatives such as potassium sorbate and sodium dehydroacetate, Nisin offers significant advantages in safety, targeting, and processing adaptability for preserving cooked chicken wings, better aligning with modern consumer demands for "natural, safe, and high-quality" foods.

(I) Natural and Safe, with No Residue or Antibiotic Resistance Concerns

Nisin is a natural bacteriocin produced by fermentation of Lactococcus lactis. After ingestion, it is decomposed into amino acids by digestive enzymes (e.g., trypsin) in the gastrointestinal tract, with no residue, toxicity, or accumulation in the body. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has classified it as "GRAS" (Generally Recognized as Safe) with no restrictions on the Acceptable Daily Intake (ADI).

Furthermore, Nisin exerts its antibacterial effect by physically damaging cell membranes rather than targeting microbial metabolic enzymes, making it difficult for bacteria to develop resistance. Even with long-term use in preserving cooked chicken wings, there is no "decreased antibacterial efficacy," avoiding the risk of resistant bacteria associated with chemical preservatives. This makes it particularly suitable for cooked products requiring long-term refrigeration or circulation.

(II) Highly Targeted, with No Impact on Product Flavor

Chemical preservatives (e.g., potassium sorbate) often impart a bitter or metallic taste to cooked chicken wings at high doses, compromising flavor. In contrast, Nisin has a high flavor threshold; at the recommended dosage (0.1–0.2 g/kg), it barely alters the original flavor of cooked chicken wings (e.g., braised, spicy) and achieves high sensory acceptance.

Experiments show: In blind taste tests, 90% of consumers could not distinguish between braised chicken wings supplemented with 0.2 g/kg Nisin and those without preservatives. In contrast, 65% of consumers detected a distinct bitter taste in samples supplemented with 0.5 g/kg potassium sorbate, leading to significantly reduced acceptance.

(III) Adaptable to Processing Techniques with Good Stability

The processing of cooked chicken wings (e.g., braising, frying, sterilization) often involves high temperatures and acidic environments, and Nisin maintains good stability under these conditions without easy inactivation:

Heat resistance: At a braising temperature of 100°C, Nisin loses only 10%–15% of its activity. Even after high-temperature sterilization at 121°C (used for vacuum-packaged cooked foods), it retains over 60% of its activity, meeting subsequent preservation needs.

Acid resistance: The braising broth for cooked chicken wings is mostly weakly acidic (pH 5.0–6.0), where Nisin exhibits maximum stability with a half-life of over 15 days, avoiding rapid degradation under acidic conditions.

IV. Practical Guidelines for Using Nisin in Preserving Cooked Chicken Wings

To maximize the preservation efficacy of Nisin, it is necessary to reasonably control the dosage, select appropriate application methods, and optimize results through combination with other techniques, based on the processing technology, packaging method, and storage conditions of cooked chicken wings.

(I) Precise Dosage Control to Balance Efficacy and Cost

The recommended dosage of Nisin should be adjusted according to the storage conditions of cooked chicken wings:

Room-temperature circulation (20–25°C): A dosage of 0.15–0.2 g/kg extends the shelf life from 1 day to 3–4 days.

Refrigerated storage (0–4°C): A dosage of 0.1–0.15 g/kg is sufficient, extending the shelf life from 3 days to 10–15 days.

Vacuum packaging + refrigeration: The dosage can be reduced to 0.08–0.1 g/kg, with a maximum shelf life of 20–25 days.

Note: Higher dosage does not equate to better efficacy. Exceeding 0.3 g/kg not only increases costs but may also introduce a slight bitter taste affecting flavor, and the antibacterial effect does not increase proportionally with dosage (due to saturation effects).

(II) Selecting Appropriate Application Methods to Ensure Uniform Distribution

The application method of Nisin in cooked chicken wings should align with the processing workflow to ensure uniform adhesion to the surface and interior of chicken wings, avoiding insufficient local concentration and subsequent preservation failure:

Addition during braising: Dissolve Nisin directly in the braising broth; during braising, it penetrates into the interior of chicken wings with the broth. This method is suitable for braised cooked chicken wings, ensuring the most uniform distribution and optimal preservation efficacy.

Spraying/soaking after cooling: Dissolve Nisin in sterile water (concentration 0.2%–0.3%), then spray or soak cooked chicken wings for 5–10 minutes after processing and cooling. This method is suitable for fried or roasted chicken wings, forming an "antibacterial film" on the surface to block external microbial contamination.

Coating before vacuum packaging: Mix Nisin with a small amount of edible oil and coat the surface of chicken wings before vacuum packaging. This method is suitable for whole or large-cut chicken wings, enhancing antibacterial efficacy inside the package and reducing the growth of residual microorganisms.

(III) Combining with Other Technologies to Enhance Preservation Efficacy

When used in combination with low-temperature storage, vacuum packaging, or antioxidants, Nisin achieves a "1+1>2" effect, further extending shelf life:

Combination with vacuum packaging: A vacuum environment isolates oxygen and inhibits the growth of aerobic bacteria. When combined with Nisin, it inhibits both aerobic and anaerobic Gram-positive bacteria, extending the refrigerated shelf life of cooked chicken wings from 15 days to over 25 days.

Combination with antioxidants: Combining Nisin with 0.05–0.1 g/kg tea polyphenols or vitamin E addresses both microbial spoilage and oxidative deterioration, particularly suitable for high-fat fried chicken wings, extending shelf life by 2–3 times.

Combination with low-temperature sterilization: First reduce initial bacterial counts via pasteurization at 80–85°C, then add Nisin. This reduces the required Nisin dosage (to 0.08 g/kg) while enhancing preservation efficacy, avoiding tough meat texture caused by high-temperature sterilization.

Nisin exerts dual effects in preserving cooked chicken wings—"precise inhibition of Gram-positive bacteria and indirect delay of quality deterioration." It not only effectively extends shelf life and ensures edible safety but also maintains the flavor, texture, and nutrition of chicken wings. With additional advantages of natural safety, no residue, and strong adaptability, it perfectly meets the multiple needs of the cooked food industry for "preservation + quality maintenance + safety."

In practical applications, maximizing Nisin’s preservation efficacy only requires precise dosage control based on storage conditions, selection of appropriate application methods, and further optimization through combination with technologies like vacuum packaging or antioxidants. In the future, with the development of Nisin microencapsulation and composite preservation technologies, its application in preserving cooked chicken wings and other meat products will become more widespread, providing stronger support for quality upgrading in the food industry.