Properties of nisin
Nisin, produced by Streptococcus lactis, is a polypeptide compound composed of a variety of amino acids.
Characteristic: White to light yellow free flowing powder, slightly salty (sodium chloride content).
Sensitive: Particularly sensitive to proteolytic enzymes
(trypsin, pancreatic enzymes, salivary enzymes, digestive enzymes)
Storage: Store in a cool, dry and sealed condition at 4-15°C, avoid direct sunlight.
Safety: Absorbed and utilized by the human body as a nutrient, it is a non-toxic natural preservative.
It has no adverse effect on the color, aroma, taste and taste of food.
It can be decomposed by intestinal digestive enzymes and has high safety.
Antibacterial pH value: 6.5-6.8
Nisin Solubility
1. It needs to be dissolved in water or liquid when used, and insoluble in non-polar solution
2. Nisin within the allowable usage range can be well miscible with water or other processing liquids
3. The actual use concentration is generally not more than 0.25‰, so the solubility will not be an obstacle to its use in various foods
4. The solubility depends on the pH value, and the solubility in water decreases with the increase of the pH value
❶When PH=2.5, the solubility is 12%
❷When PH=5.0, the solubility is 4%
❸When PH>7 (under neutral or alkaline conditions), it is almost insoluble
5. When Nisin is added for anti-corrosion, the food must be acidic, and it is stable at room temperature and acid during processing and storage
6. Nisin's industrial products contain a certain amount of denatured milk protein, its insolubility will cause the solution to appear misty suspension, but it will not affect its antiseptic effect
7. Nisin is particularly sensitive to proteolytic enzymes (such as pancreatic enzymes, sleeping fluid enzymes and digestive enzymes, etc.), so it can be hydrolyzed into amino acids by proteolytic enzymes in the digestive tract after eating. After inhaling Nisin-containing liquid for 10 minutes, Nisin cannot be detected in saliva
Stability of nisin
1. The best antibacterial pH value is 6.5-6.8
2. Nisin has extremely stable activity under acidic conditions. The stability mainly depends on factors such as temperature, pH, and matrix. The activity decreases with the increase of pH
If heated at 121°C for 15 minutes, its activity decreased by 29%, 69%, 86% and 99.7% at pH 4, 5, 6 and 7, respectively.
❶When PH<2.0, it can be sterilized at 116℃ without loss of activity
❷When pH=2, it is still active after high temperature sterilization at 121°C for 30 minutes, and has good heat resistance
❸When pH=3, the maximum activity (97.5%) is still retained after heat sterilization at 121°C for 20 minutes
It has excellent acid and heat resistance, and its activity will decrease if the pH value is lower or higher than this value.
❹When pH>4, heating will speed up its decomposition and reduce its antibacterial activity
❺When PH=5.0, after heating to 115.6℃ for sterilization, 40% of the activity will be lost
❻When PH>5, the heat resistance decreases, and after pasteurization at 85°C for 15 minutes, the activity only loses 15%
❼ In skimmed milk with PH=6.5, 90% of the activity will be lost when heated to 115.6°C
❽When PH>6.8, 90% of the activity will be lost after sterilization
❾It is not suitable to heat for too long under neutral conditions, otherwise the activity will be greatly reduced
Inactivation occurs at room temperature at pH = 7.0
⑩When pH=11, after sterilizing at 63°C for 30 minutes, inactivate immediately
3. In foods such as milk, macromolecular proteins can provide protection for Nisin, making it less decomposed and less likely to lose antibacterial activity when heated.
Compatibility of nisin
1. The combination of Nisin and sorbic acid or nitrite can broaden the antibacterial spectrum; with irradiation or pasteurization treatment, it has better effect.
2. When Nisin is used in combination with chelating agents such as disodium EDTA, citrate, and phosphate, the cell membrane is destroyed due to the chelating agent combined with magnesium ions in the phospholipid bilayer of the cell membrane of Gram-negative bacteria, resulting in membrane permeability Strengthened, making the milk chain easy to enter the cytoplasm, strengthening the inhibitory effect on Gram-negative bacteria.
3. The combination of Nisin and chelating agent (disodium EDTA) can inhibit some Gram-negative bacteria, such as Salmonella, Shigella and Escherichia coli, etc.
4. Nisin can also be used in conjunction with other preservatives such as sorbic acid to complement and promote each other.
Effective amount of nisin to inhibit bacteria
1. A prominent feature of Nisin in terms of antibacterial: it has a strong inhibitory effect on Bacillus. For example, the concentrations required to inhibit botulinum type A, B, and C vegetative cells in broth medium are: 200ug/mL, 80ug/mL, and 20ug/mL (0.02-0.2g/kg).
2. The inhibitory concentration of Nisin to Clostridium sporogenes in pork with a pH value of 6.5-6.6 is: 5-75ug/mL (0.005g-0.075g/kg).
3. When Nisin is used in combination with chelating agents (such as disodium EDTA, sodium tripolyphosphate), the antibacterial spectrum can be extended to Gram-negative bacteria. Chelating agents (such as EDTA, citrate, phosphate) can enhance Activity of Nisin against Gram-negative bacteria.
4. Nisin can prevent the bubble production of Swiss cheese caused by Clostridium tyrobutyricum and Clostridium butyricum.
5. Nisin can prevent the growth of spoilage bacteria and pathogenic bacteria in liquid milk.
6. After adding 2.5ug/mL (0.0025g/kg) Nisin to canned chocolate milk, the sterilization time is reduced from 12min to 3.3min, which can still prevent the growth of Bacillus stearothermophilus and Clostridium sporogenes.
7. After adding Nisin (0.25ug/ml and 1.25ug/mL) [0.00025g/kg and 0.00123g/kg] to skim milk for 24 hours, the number of Listeria monocytogenes colonies can be greatly reduced, but with the fat content increased, Nisin activity decreased.
8. Nisin reduces Listeria monocytogenes cells to undetectable levels in 3% and 10% fat ice cream stored at -18°C.
9. 0.4g/kg Nisin together with 1g/kg sorbic acid and 2.5% polyphosphate delayed the spoilage of fresh sausage at 5℃.
10. Soaking meat in Nisin solution (250ug/ml) [0.25g/kg] for 10min significantly reduced the number of Lactococcus lactis, Staphylococcus aureus and Listeria monocytogenes attached to the meat.
11.Nisin at 0.075g/kg is more effective in inhibiting branching of Clostridium sporogenes spores in pork, beef and turkey pulp than nitrite at 0.150g/kg.
12. Canned brine lobster combined with 0.025g/kg Nisin can be sterilized at 60°C or 65°C for 5min or 2min respectively, which can greatly reduce Listeria monocytogenes.
13. The use of Nisin in low-acid canned products can reduce the commercial sterilization intensity of equivalent lethality and maintain the texture and flavor of food.
14. Use Nisin instead of nitrite, 0.075g/kg of Nisin is equivalent to the effect of 0.15g/kg of nitrite. A small amount of nitrite can be used as a coloring agent, combined with the antiseptic effect of Nisin, so as to reduce nitrite For the purpose of dosage, it needs to be dissolved in water or liquid when used, and then added to food.
Antibacterial effect of nisin
1. Nisin can effectively inhibit many Gram-positive bacteria that cause food spoilage.For example, it can inhibit the growth and reproduction of Lactobacillus, Leuconostoc, Pediococcus, Staphylococcus, Listeria, Clostridium botulinum, Staphylococcus aureus, Streptococcus hemolyticus, Bacillus stearothermophilus
2. Nisin has a strong inhibitory effect on spore-producing bacteria, such as Bacillus and Clostridium.
3. Nisin has a strong inhibitory effect on Bacillus spores.
❶Generally, spore-producing bacteria are highly resistant to heat. For example, if fresh milk is sterilized at 135°C for 2 seconds, the mortality rate of non-spore bacteria is 100%, and that of spore bacteria is 90%. % of spore bacteria cannot be killed.
❷ If 0.03-0.05g/kg Nisin is added to fresh milk, it can inhibit the germination and reproduction of Bacillus and Clostridium spores.
4. Nisin mainly inhibits most G+ bacteria, especially bacterial spores.
5. Nisin can inhibit certain strains of Staphylococcus, Streptococcus, Pediococcus and Lactobacillus, and most of the spores of Clostridium and Bacillus.
7. Nisin can effectively inhibit food spoilage caused by Clostridium botulinum, Staphylococcus aureus, hemolytic streptococcus Bacillus subtilis, Bacillus stearothermophilus, etc.
8. Nisin is generally ineffective against mold, yeast and G-bacteria, but under certain conditions (such as freezing, heating, lowering PH and EDTA treatment), some G-bacteria (such as Salmonella, Escherichia coli, Pseudomonas etc.) Sensitive to Nisin.
9. The effect of Nisin on spores is to destroy their membranes in the early germination and expansion stages to inhibit their germination process.
10.0.05g/kg of Nisin and 0.2g/kg of EDTA are used in combination, which can also inhibit Salmonella and other Gram-negative bacteria. If there is non-positive bacteria contamination in production, it must be used in combination with other preservatives.
11. The amount of preservative used is related to the original bacterial count of the product, the type of contaminated bacteria, the character of the product, the required shelf life, and the sterilization intensity.
