Solubility: Dissolved in water or liquid, and the solubility is different at different pH values. For example, in water (pH=7), the solubility is 49.0mg/ml (Nisin); in 0.02M hydrochloric acid, the solubility is 118.0mg/ml (Nisin); under alkaline conditions, it is almost insoluble.
Stability: It is related to the pH value of the solution. In the system of pH=6.5, after pasteurization at 85°C for 15 minutes, the activity only lost 15%. In the system of pH=3, the activity of 100% was still maintained after autoclaving at 121°C for 15 minutes, and its acid resistance Excellent heat resistance.
Bacteriostatic: It can effectively inhibit many gram-positive bacteria that cause food spoilage, such as Lactobacillus, Leuconostoc, Pediococcus, Staphylococcus, Listeria, etc., especially for spore-producing bacteria such as Bacillus, Clostridium Bacillus has a strong inhibitory effect. Usually, spore-producing bacteria are very heat-resistant. For example, fresh milk is sterilized by ultra-high temperature at 135°C for 2 seconds. The mortality rate of non-spore bacteria is 100%, the mortality rate of spore bacteria is 90%, and the mortality rate is 10%. The spore bacteria cannot be killed.
Sorbic acid and its salts:
There are three types of sorbic acid: sorbic acid, potassium sorbate and calcium sorbate. Sorbic acid is insoluble in water and must be dissolved in ethanol or potassium hydrogen sulfate before use. It is inconvenient and irritating to use, so it is not commonly used. Calcium sorbate FAO/WHO stipulates that its use range is small, so it is also Not often used; potassium sorbate does not have their shortcomings, is easily soluble in water, and has a wide range of applications.
Potassium sorbate is an acidic preservative with high antibacterial properties and inhibits the growth and reproduction of molds; it mainly inhibits the growth of microorganisms and acts as a preservative by inhibiting the dehydrogenase system in the microorganisms. Yeast has inhibitory effect; its effect weakens with the increase of pH. When pH reaches 3, the bacteriostasis reaches its peak, and when pH reaches 6, it still has bacteriostatic ability.
Sorbic acid (potassium) can effectively inhibit the activity of mold, yeast and aerobic bacteria, and can also prevent the growth and reproduction of harmful microorganisms such as botulinum, staphylococcus, salmonella, etc. Lactobacillus and other beneficial microorganisms are almost ineffective, and their growth inhibition effect is stronger than bactericidal effect, so as to effectively prolong the preservation time of food and maintain the original flavor of food. Its antiseptic effect is 5-10 times that of similar products sodium benzoate.
Sorbic acid (potassium) is stable in a sealed state, easy to absorb water when exposed to humid air, oxidize and change color. Potassium sorbate has good thermal stability, and the decomposition temperature is as high as 270 °C.
Natamycin is a natural antifungal compound produced by the fermentation of Streptomyces. It belongs to the polyene macrolides, which can widely and effectively inhibit the growth of various molds and yeasts, as well as inhibit the production of mycotoxins. It can be widely used in food preservation and antifungal treatment. Natamycin has no inhibitory effect on bacteria, so it does not affect the natural ripening process of yogurt, cheese, raw ham, and dry sausage.
Solubility: Slightly soluble in water, in ethanol, the solvent is relatively large, insoluble in most organic solvents. The solubility in water at room temperature is 30~100mg/L. At pH lower than 3 or higher than 9, the solubility will increase, but the stability of natamycin will be reduced.
Mechanism of action: Natamycin relies on its lactone ring structure to interact with sterol compounds on the fungal cell membrane to form antibiotic-sterol compounds, thereby destroying the structure of the fungal cytoplasmic membrane. The hydrophilic part (polyol part) of macrolide forms water pores on the membrane, which damages the permeability of the cell membrane, which in turn causes the exudation of amino acids, electrolytes and other substances in the bacteria, and the bacteria die. When there is no sterol compound on the cell membrane of some microorganisms, natamycin has no effect on it, so natamycin only inhibits fungi and does not produce antibacterial activity against bacteria and viruses.
Dehydroacetic acid and sodium salts:
Dehydroacetic acid and its sodium salt are white or light yellow crystalline powder, stable to light and heat, degraded into acetic acid in aqueous solution, and non-toxic to human body. It is a broad-spectrum preservative, which has a strong inhibitory effect on bacteria, molds and yeasts in food. It is widely used in the preservation and preservation of meat, fish, vegetables, fruits, beverages, cakes, etc.
Strong inhibitory effect on yeast, mold and bacterial reproduction: Sodium dehydroacetate has strong effect on yeast and mold that often cause food spoilage. The effective inhibitory concentration is 0.05% to 0.1%, and the general dosage is 0.03 %～0.05%. Basically, the bacteriostatic effect of sodium dehydroacetate is not affected by the pH of the food, nor is it affected by heating. In the environment below pH 5, the inhibitory effect of sodium dehydroacetate on yeast is 2 times greater than that of sodium benzoate, and the inhibitory effect on gray-green penicillin bacteria and Aspergillus niger is 2.5 times greater than that of sodium benzoate.
High relative stability: Sodium dehydroacetate has no special requirements for the external environment, and can be used under normal temperature, normal pressure and general humidity; there is no harsh requirement for the production process. In addition to being unaffected by acid-base conditions, sodium dehydroacetate is also quite stable to light and heat. Specifically, it can be used in boiling water or baking food, even if heated at high temperature, it will not be destroyed, deteriorated, or volatile, even under the condition of heating at 120~C for 20 minutes, its antibacterial and antiseptic ability Nor is it affected in any way.
Calcium propionate: prepared by reacting propionic acid with calcium hydroxide and calcium carbonate. Calcium propionate decomposes into propionic acid under acidic conditions. The antibacterial spectrum of propionic acid is narrower than that of benzoic acid and sorbic acid, and its antibacterial effect is slightly weaker. Calcium propionate has special effects on enzymes, but has limited effect on bacteria and no effect on yeast. The minimum inhibitory concentration is 0.01% when the pH value is 5.0, 0.188% when the pH value is 5.8, and the optimum pH value should be lower than 5.5.
Calcium propionate, for bread, has no nutritional value, nor can it keep the bread from becoming moldy for a long time, it can only inhibit the growth of mold in the bread and delay the moldy time of the bread. Therefore, it can solve the problem that the bread quickly becomes moldy in hot summer or rainy rainy season, reduce losses, and ensure people's health. But there are many reasons for moldy bread. There is a lot of mold in the air. Therefore, in addition to adding preservatives - calcium propionate to bread, attention should be paid to the hygiene of production equipment, production environment and operators. Hygiene supervisors must be set up to meet hygiene requirements. Handling and packaging. This will allow the bread to be stored for a long time.