The preservative principle of preservatives is roughly as follows:
1. Interfering with the microbial enzyme system, destroying its normal metabolism and inhibiting the activity of the enzyme.
2. Suspecting and denaturation of microbial proteins, interfere with their survival and reproduction;
3. Change the permeability of the cell serosa to cause its enzymes and metabolites to escape and cause its inactivation.
At present, there are many kinds of food preservatives, which are mainly divided into synthetic and natural preservatives; commonly used synthetic preservatives are represented by sorbic acid and its salts, benzoic acid and its salts and parabens, etc. Brief introduction:
1. Sorbic acid has three types of sorbic acid, potassium sorbate and calcium sorbate. Sorbic acid is insoluble in water. It must be dissolved in ethanol or potassium hydrogen sulfate before use. It is inconvenient and irritating when used. It is generally not used. Calcium sorbate FAO/WHO regulates its use range is small, so it is also Not often used; potassium sorbate has no disadvantages, is easy to dissolve in water, and has a wide range of uses. We can often see it in some beverages, preserves, canned foods, etc. Here I will focus on potassium sorbate: It is unsaturated hexacarbonic acid; the potassium sorbate sold in the market is white or light yellow granules, the content is 98%--102%; no odor, or slightly odor, easy to absorb moisture, easy to oxidize and turn brown It is stable to light and heat, the relative density is 1.363, the melting point is decomposed at 270 °C, and the pH of its 1% solution is 7-8. Potassium sorbate is an acidic preservative, which has high antibacterial property and inhibits the growth and reproduction of mold; it mainly inhibits the growth and antiseptic effect of microorganisms by inhibiting the dehydrogenase system in microorganisms, against bacteria, mold, Yeast has inhibitory effect; its effect is weakened with the increase of PH. When the pH reaches 3, the bacteriostatic peak reaches the peak. When the pH reaches 6, the antibacterial ability remains, but the minimum concentration (MIC) can not be below 0.2%. It is proved that PH: 3.2 is impregnated with potassium sorbate solution of pH 2.4, and the storage period of non-sterilized food is 2-4 times shorter.
The three mechanisms of action of sorbic acid, potassium sorbate and calcium sorbate are the same, the toxicity is smaller than that of benzoic acid and paraben, the daily allowance is 25mg/Kg, the benzoic acid is 5 times, and the paraben is 2.5. It is a relatively safe food preservative; it can be used in soy sauce, vinegar, noodle sauce, jam, pickles, canned foods and some alcoholic beverages.
2, benzoic acid has benzoic acid and sodium benzoate; benzoic acid is also known as benzoic acid, so sodium benzoate is also called sodium benzoate. Benzoic acid is hardly soluble in water at normal temperature, slightly volatile in air (especially hot air), hygroscopic, about 0.34g/100ml at normal temperature; but soluble in hot water; soluble in ethanol, chloroform and non-volatile oil. Sodium benzoate is used in both sodium benzoate; the properties and antiseptic properties of benzoic acid and sodium benzoate are similar. I will briefly introduce sodium benzoate: sodium benzoate is mostly white granules, odorless or slightly benzoin smell, slightly sweet, astringent; soluble in water (normal temperature) 53.0g/100ml, pH around 8; sodium benzoate It is also an acidic preservative. It has no bactericidal or bacteriostatic effect in alkaline medium. The best pH for anti-corrosion is 2.5-4.0. At pH 5.0, the bactericidal effect of 5% solution is not very good. Sodium benzoate is more lipophilic, easily penetrates into the cell membrane, interferes with the permeability of the cell membrane, inhibits the absorption of amino acids by the cell membrane, enters the alkali storage in the ionized acidified cells of the cell, and inhibits the activity of the respiratory enzyme of the cell. The acetyl-CoA condensation reaction is prevented, thereby serving the purpose of food preservation.
Benzoic acid can be used in foods such as noodles, jams, pickles, canned foods and some alcoholic beverages in China. Now the country clearly stipulates that benzoic acid can not be used in jelly foods; benzoic acid is more toxic. The country has restricted the use of benzoic acid and its salts, and many countries have replaced it with potassium sorbate.
3, parabens (ie, parabens) are methyl paraben, ethyl p-hydroxybenzoate, propyl paraben, p-hydroxybenzoate, etc.; Butyl formate has the best antiseptic effect. In China, ethyl p-hydroxybenzoate and propyl ester are mainly used, and the most used in Japan is p-hydroxybenzoate. The biggest feature of parabens is that there are many series of products and a wide spectrum of inhibition. The antiseptic mechanism is to destroy the cell membrane of microorganisms, denature proteins in cells, and inhibit the activity of respiratory enzymes and electron transport enzymes. The antibacterial active ingredient of paraben ester mainly acts in a molecular state. Since the hydroxyl group in the molecule has been lipidated, it is not ionized, and the ionization constant of the para-phenolic group is small. When the solution pH is 8, there is still More than 60% of them are in a molecular state, so the antibacterial action of parabens has a good effect in a wide range of PH4-8.
Since parabens are hardly soluble in water, they are usually dissolved in sodium hydroxide, acetic acid, ethanol, and then used. In order to better exert the antiseptic effect, it is preferable to use two or more kinds of the lipids in combination. Ethyl p-hydroxybenzoate is generally used in soy sauce and vinegar, while p-hydroxybenzoate is generally used in some fruit drinks and fruits and vegetables. It can be added, dipped, coated, sprayed, applied to the surface or adsorbed to the inside. The presence or absence of spores and spores has a great influence on the antiseptic effect of the preservative. Under the condition of using the same amount of preservatives, the more serious the food contamination, the more the original bacteria number, the worse the antiseptic effect. Relevant data show that from the perspective of the proliferation process of microorganisms, the beginning is a slow induction period. After the induction period, it will rush into the logarithmic phase and the proliferation is very strong. Since the role and dosage of food additives are limited in various countries around the world, it usually only inhibits microorganisms and prolongs the induction period during microbial proliferation. If the food is heavily contaminated with micro-organisms, then the use of preservatives will not help. For example, when sorbic acid is seriously polluted by microorganisms, sorbic acid becomes a nutrient for microorganisms, which not only inhibits microbial growth, but also accelerates food spoilage. Therefore, when using food preservatives, attention should be paid to maintaining good sanitary conditions, reducing the number of original bacteria in foods, and other means such as sterilization or packaging, as much as possible to reduce the possibility and extent of microbial contamination of foods. important