【Overview】
Sodium benzoate (Sodium benzoate), also known as sodium benzoate, is produced by neutralizing benzoic acid with sodium bicarbonate solution, and then filtering, evaporating and crystallizing it. Acidic preservatives have no bactericidal or bacteriostatic effects in alkaline media. The optimal pH value for antisepsis is 2.5 to 4.0. When the pH value is 5.0, even a 5% solution does not have a very good bactericidal effect.
[Physical and chemical properties]
This product is white granules, powder or crystalline powder, odorless or slightly smelling of benzoin, and tastes slightly sweet and salty. It is stable in the air and soluble in water, about 53.0g/100mL at room temperature. The aqueous solution reaches a slightly alkaline pH of about 8. It is also soluble in glycerin, methanol and ethanol.
Figure 1 shows sodium benzoate
【Mechanism of action】
1. Preservative mechanism: Benzoic acid preservatives act on their undissociated molecules. Undissociated benzoic acid is highly lipophilic and easily enters cells through the cell membrane, interfering with the permeability of the cell membranes of microorganisms such as molds and bacteria. , hindering the absorption of amino acids by the cell membrane; the benzoic acid molecules entering the cells can acidify the reserve base in the cells, thereby inhibiting the activity of respiratory enzymes in the microbial cells and preventing the condensation reaction of acetyl-CoA, thus playing an antiseptic role. Benzoic acid is a broad-spectrum antimicrobial substance that is very effective against yeasts, molds and some bacteria. Within the maximum allowable range of use, the pH value is below 4.5 (the best anti-corrosion pH value is 2.5 to 4.0). All 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, cysteine salts, etc.
[Toxicity mechanism]
Although the kidneys have a detoxification function and can generally excrete a safe dose of preservatives from the body within 1 to 2 days, if you eat a variety of foods containing the same preservatives for a long time and at the same time, it will also have a variety of toxic effects on the human body.
1. Mechanism of damage to the nervous system: Drinking large amounts of drinks containing sodium benzoate preservatives can cause severe brain atrophy. Sodium benzoate reacts with gastric acid to form benzoic acid, which has a certain degree of toxicity. Long-term drinking can cause chronic benzene poisoning in humans. The main symptoms of chronic benzene poisoning are neurasthenia, such as headache, dizziness, memory loss, insomnia, fatigue, etc.; at the same time, leukopenia can also occur, and in severe cases, aplastic anemia can occur. Cats are relatively sensitive to benzoic acid. When cats were fed meat containing 2.39% benzoic acid, 17 out of 28 cats showed nervousness, excitement, loss of balance and decreased vision. Some studies have also shown that long-term consumption of carbonated drinks containing sodium benzoate can cause ADHD in children.
2. Carcinogenic mechanism: Scientists have long suspected that sodium benzoate may induce cancer, because when mixed with the additive Vc in carbonated drinks, sodium benzoate may generate benzene, a carcinogen. Researchers tested the effects of sodium benzoate on live yeast cells in the laboratory and found that sodium benzoate seriously harms human cells by destroying mitochondria, known as the “power stations” of cells. Sodium benzoate can effectively inhibit mitochondrial swelling and have a significant protective effect on rat liver ischemia-reperfusion injury. Sodium benzoate is a chromosome-breaking agent and can cause cancer.
3. Cytotoxicity: Research results show that the toxic effects of sodium benzoate and tartrazine as well as sodium benzoate and sodium saccharin on cells are additive. Sodium benzoate can destroy the orderly structure of cell membranes, change the structure of the membrane, cause functional disorder of the membrane, and cause destructive rupture of cells, thereby destroying the cell balance mechanism, and combines with hydrogen and oxygen free radicals in the body to generate benzene and produce poisons. Sodium benzoate is a low-toxic substance. Large doses of sodium benzoate will reduce leukocytes in rats and cause significant damage to liver cells.
4. Other side effects: Sodium benzoate can induce recurring acute urticaria and angioedema. Sodium benzoate can cause conformational changes in serum albumin, thereby damaging serum albumin.
[Preparation method]
Weigh 100g of sodium carbonate decahydrate (NaCO3·10H20) and place it in a glass reactor, add 300ml of water, start stirring and heat to nearly boiling, then slowly add 86g of benzoic acid dropwise, until all the benzoic acid is added , the solution is neutral (as measured by pH test paper). Continue the reaction for 0.5 hours, and the reaction is completed. Filter while hot, place the filtrate on a water bath, heat and evaporate to dryness to obtain 167g of crude sodium benzoate. Weigh 30g of crude sodium benzoate and add to the boiling Dissolve in 300 ml of a 15:85 mixed solvent of water and ethanol and filter while it is hot. Cool the filtrate to room temperature and white crystals will appear. Then filter, wash and dry to obtain 28.5 grams of pure sodium benzoate.
【Application】
Sodium benzoate has inhibitory effects on a variety of bacteria, molds and yeasts, so it is widely used to preserve highly acidic fruits, berries, juices, jellies, jams, beverages, margarine, table olives, syrups, pickles and others Acidic foods are also used as preservatives in medicines and cosmetics, antifreeze for automobiles, rust inhibitors for steel, and plastic ingredients.
[Application status]
Sodium benzoate is widely used in oral liquids, so the stability of sodium benzoate needs to be tested in oral liquids. Sodium benzoate can effectively inhibit endotoxin toxicity that may be produced in food. In my country, the preservative in vinegar and soy sauce is mainly sodium benzoate, and the sodium benzoate content of soy sauce is significantly higher than that of edible vinegar. This is because sodium benzoate has a good preservative effect under acidic conditions, so the amount of sodium benzoate used in edible vinegar is smaller, while in soy sauce, in order to achieve the preservative effect, a higher amount is used. larger. Sorbic acid and potassium sorbate are less toxic than sodium benzoate and have better antiseptic effects than sodium benzoate.
The advantages of benzoic acid and sodium benzoate are that they are relatively stable in the air and have low cost. However, in the sealed state, sorbic acid and potassium sorbate are also very stable. Potassium sorbate has better thermal stability and its decomposition temperature is as high as 270°C. Since the amount of food additives added is very small, it will not significantly increase the cost of meat products. Many countries have gradually replaced benzoic acid and sodium benzoate with sorbic acid and potassium sorbate. The use of natural preservatives (Nisin, chitosan, spice extracts, etc.) can also achieve antibacterial and preservation effects, which is a development direction of the meat products industry. For example, the minimum inhibitory concentration of chitosan against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Streptococcus is 0.025%, while the minimum inhibitory concentration of sodium benzoate is ≥0.04%. Preservation and preservation can also be achieved by improving processing conditions, improving food packaging, heat treatment or irradiation sterilization of products, and low-temperature storage. In addition, the toxicity of paraben is much lower than that of sodium benzoate, and its application pH range is wide. Its antibacterial effect is almost not affected by the pH value at pH 4 to 8, and it has a wide range of antibacterial properties against molds, yeasts, and bacteria. Function, can be widely used in food, beverage, cosmetics and pharmaceutical industries. It is reported that the preservative effect of paraben on vinegar and soy sauce is significantly better than that of sodium benzoate. When a small amount of benzoic acid or sodium benzoate is added to food, it is not harmful to the human body. The key is to control its dosage. The state clearly stipulates that benzoic acid cannot be used in milk powder foods or soy products.
[Main reference materials]
[1] Shi Jiangong, Liu Zhijian, Zhang Minhong, Zhao Guiliang, Shi Qinzhi, Yang Wantai, Zhao Limei. Research and application progress of sodium benzoate as a nucleating agent for thermoplastic materials [J]. Science and Technology Herald, 2009, 27(16):110 -115.
[2] Lü Na. Toxicological research on food preservative sodium benzoate[D]. Jilin Agricultural University, 2006.
[3] Mou Yue. Molecular level study on the toxic effects of sodium benzoate[D]. Shandong University, 2012.
[4] Wang Siwen, Gong Jiang, Gao Gao, Zhao Ting, Luo Rongfang, Wang Shao, Ni Shifeng, Chen Qianliang. Pharmacological and toxicological research on the preservative sodium benzoate [J]. Anhui Agricultural Sciences, 2010, 38(30) :16724+16846.
[5]Lin Yubin, Wang Lei, Wang Dong. Synthesis and purification of sodium benzoate[J]. Shandong Science, 1991(01):68-70.
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