Sodium benzoate, also known as sodium benzoate, is obtained by neutralizing benzoic acid with sodium bicarbonate solution, and then filtered, evaporated and crystallized. It is an acid preservative and has no bactericidal and bacteriostatic effects in alkaline media. The optimum pH value for anti-corrosion is 2.5-4.0; when the pH value is 5.0, even a 5% solution is not very effective in sterilizing bacteria.
【Physical and chemical properties】
This product is white granule, powder or crystalline powder, odorless or slightly benzoin smell, slightly sweet and salty taste. Stable in air, soluble in water, about 53.0g/100mL at room temperature, aqueous solution to weak alkaline pH around 8, also soluble in glycerin, methanol, ethanol.
1. Antiseptic mechanism Benzoic acid preservatives act on their undissociated molecules. Undissociated benzoic acid has strong lipophilicity and is easy to enter the cell through the cell membrane, interfering with the permeability of the cell membrane of microorganisms such as mold and bacteria, and hindering the cell membrane. Absorption of amino acids; the benzoic acid molecule entering the cell can acidify the reserve base in the cell, thereby inhibiting the activity of the respiratory enzyme system in the microbial cell and preventing the condensation reaction of acetyl-CoA, thereby playing an antiseptic effect. Benzoic acid is a broad-spectrum antimicrobial substance, which has a good effect on yeast, mold and some bacteria. Within the maximum allowable use range, the pH value is below 4.5 (the best pH value for antisepsis is 2.5-4.0). All types of fungi are effective.
2. Compound antagonism Benzoic acid also has an antagonistic effect with calcium chloride, and has similar effects with sodium chloride, isobutyric acid, gluconic acid, and cysteine salts.
Although the kidney has the function of detoxification, a safe dose of preservatives can generally be excreted from the body within 1-2 days, but if a variety of foods containing the same preservatives are consumed for a long time and at the same time, it will also produce various toxic effects on the human body.
1. Nervous system damage mechanism Drinking a lot of beverages containing sodium benzoate preservatives can lead to severe brain atrophy. Sodium benzoate reacts with gastric acid to produce benzoic acid, which is toxic to a certain extent, and long-term drinking can cause chronic benzene poisoning in humans. The symptoms of chronic benzene poisoning mainly manifest as neurasthenia, such as headache, dizziness, memory loss, insomnia, fatigue, etc.; at the same time, leukopenia will also occur, and severe aplastic anemia will also occur. Cats are more sensitive to benzoic acid. If the cats were fed with meat containing 2.39% benzoic acid, 17 out of 28 cats showed nervousness, excitement, loss of balance and vision loss. Studies have also shown that long-term drinking of carbonated beverages containing sodium benzoate can lead to ADHD in children.
2. Carcinogenic mechanism For a long time, scientists have suspected that sodium benzoate may induce cancer, because after mixing with the additive Vc in carbonated drinks, sodium benzoate may generate a carcinogen benzene. The researchers tested the effects of sodium benzoate on live yeast cells in the laboratory and found that sodium benzoate seriously harms human cells by damaging mitochondria, known as the cell’s “powerhouses.” Sodium benzoate can effectively inhibit mitochondrial swelling and has obvious protective effect on rat liver ischemia-reperfusion injury. Sodium benzoate is a chromosome disruptor that can cause cancer.
3. Cytotoxicity The results of the study showed that the toxic effects of sodium benzoate and tartrazine, sodium benzoate and sodium saccharin on cells were additive. Sodium benzoate can destroy the ordered structure of the cell membrane, change the structure of the membrane, make the membrane functionally disordered, cause the cell to break destructively, thereby destroying the cell balance mechanism, and combine with the hydroxyl radical in the body to form benzene, which produces poison. Sodium benzoate is a low toxic substance. Large doses of sodium benzoate can reduce white blood cells in rats and significantly damage liver cells.
4. Other side effects Sodium benzoate can induce recurrent acute urticaria and angioedema. Sodium benzoate can cause changes in the conformation of serum albumin, which can damage serum albumin.
Weigh 100g of sodium carbonate decahydrate (NaCO3 10H20) and place it in a glass reactor, add 300ml of water, start stirring and heat to near boiling, then slowly add 86g of benzoic acid dropwise, after all the benzoic acid is added, the solution is Neutral (measured by PH test paper). Continue to react for 0.5 hours, and the reaction is complete. Filter while hot, place the filtrate on a water bath, heat and evaporate to dryness, and obtain 167g of crude sodium benzoate. Weigh 30g of crude sodium benzoate and add it to boiling 300ml In the mixed solvent of water and ethanol of 15:85, filter while hot after dissolving, the filtrate is cooled to room temperature, white crystal appears, then through filtering, washing, drying, obtains 28.5 grams of pure sodium benzoate.