Benzoic Acid
Molecular formula: C6H5COOH
Benzoic acid has no odor or a slight benzoin odor. It is widely used as a food preservative and exists naturally in cranberries, prunes, cinnamon, and cloves. It is an aromatic acid and can also be added as a spice. The undissociated acid has antibacterial activity and shows the best activity within the pH range of 2.5 – 4.0. Toxicological basis: LD50 for rats by oral administration is 2530 mg·kg-1 (bw). Generally Recognized as Safe (GRAS) by FDA – 21CFR 184.1021. Acceptable Daily Intake (ADI) is 0 – 5 mg·kg-1 (bw) (the total amount of benzoic acid and its salts, calculated as benzoic acid) (FAO/WHO, 1994).
Sodium Benzoate
Molecular formula: C7H5O2Na
It is the sodium salt of benzoic acid, has no odor or a slight benzoin odor. In acidic foods, it can be partially converted into active benzoic acid, and its preservation mechanism is the same as that of benzoic acid. Since it is more soluble in water than benzoic acid and is stable in the air, and has a strong effect on inhibiting yeasts and bacteria, it is more commonly used than benzoic acid. Toxicological basis: LD50 for rats by oral administration is 4070 mg·kg-1 (bw). GRAS by FDA – 21CFR 184.23, 181.733. ADI is 0 – 5 mg·kg-1 (bw) (the total amount of benzoic acid and its salts, calculated as benzoic acid) (FAO/WHO, 1994).
Preservation Mechanism
Benzoic acid preservatives act through their undissociated molecules. The undissociated benzoic acid is highly lipophilic, easily penetrates cell membranes, enters cells, interferes with the permeability of cell membranes of molds, bacteria and other microorganisms, hinders the absorption of amino acids by cell membranes. The benzoic acid molecules that enter the cells acidify the intracellular storage bases and inhibit the activity of the respiratory enzyme systems in microbial cells, thus playing a preservative role (Hou Zhenjian, 2004).
Benzoic acid is a broad-spectrum antimicrobial agent and has a good effect on yeasts, molds, and some bacteria. Within the allowable maximum usage range and below pH 4.5, it has an inhibitory effect on various bacteria.
Toxicity and Safety
To ensure the absolutely safe use of food additives, countries all over the world have strict regulations on whether various food additives can be used, their applicable scopes, and maximum usage amounts, which are restricted by laws and regulations. Internationally recognized safety indicators for food additives include LD50, GRAS, and ADI (Ling Guanting, 2003). LD50 (rats, oral administration) is a commonly used indicator for judging the safety of food additives and is also the first-stage acute toxicity test indicator in the toxicological evaluation that any food additive must undergo. The larger the LD50 value is, the lower the toxicity is, and the higher the safety in food use is. According to the toxicity classification regulations of the “Food Safety Toxicological Evaluation Standards” (1994) of the Ministry of Health of China, benzoic acid and sodium benzoate belong to the practically non-toxic category. While sodium nitrite, which is commonly used as a coloring agent in meat products, has an LD50 of 220 mg·kg-1 and belongs to the moderately toxic category.
GRAS is a safety indicator for food additives evaluated by the US FDA. According to FDA regulations, benzoic acid (FDA. § 184.1021, 2000) is classified as a Generally Recognized as Safe (GRAS) food additive. The ADI (Acceptable Daily Intakes) value is the number of milligrams allowed to be ingested per kilogram of body weight per day by humans, and the value is stipulated by FAO/WHO (1994). The usage amount of benzoic acid in food is 0.2 – 1 g/kg. As long as it is used in accordance with the addition amount stipulated by national standards, there will be no safety problems.
Human Detoxification Mechanism
When a small amount of benzoic acid is added to food, it is not harmful to the human body. Years of application and toxicity tests in countries all over the world have shown that when added at 0.06 g/kg, benzoic acid has no cumulative, carcinogenic, teratogenic, mutagenic, or antigenic effects. Benzoic acid can be quickly absorbed in the body. Benzoic acid will combine with glycine to form hippuric acid (benzoyl glycine), and the rest will combine with glucuronic acid to form 1-benzoyl glucuronic acid. 75 – 80% of benzoic acid is excreted from the human body within 6 hours, and all of it can be excreted from the body after 10 – 14 hours (FAO, 1974). This detoxification effect prevents benzoic acid from accumulating in the body. It should be pointed out that cats are relatively sensitive to benzoic acid, and attention should be paid when producing pet food. When cats were fed with meat containing 2.39% benzoic acid, 17 out of 28 cats showed symptoms such as nervousness, excitement, loss of balance, and vision problems (FAO, 1974).
In addition, sodium benzoate reacts with vitamin C to generate benzene (benzene is a carcinogen), so it is harmful to use sodium benzoate in vitamin C-rich foods such as preserved fruits. Sodium benzoate is commonly found in beverages, so we should pay attention when purchasing beverages. Sodium citrate will not react with vitamin C, and beverages containing sodium citrate can be chosen. Note: The sugar-free zero-calorie carbonated beverage produced by The Coca-Cola Company contains sodium benzoate in its ingredients, and it should be chosen and consumed with caution.
Foreign Usage Issues
Discussion on the Use of Benzoic Acid and Sodium Benzoate in Meat Product Processing
In Europe and Australia, benzoic acid and sodium benzoate can be present in meat products, but their consumption by children is not recommended (E210, E211). In Canada, benzoic acid and sodium benzoate can be used in packaged fish and meat products. In India, sodium benzoate is considered to exist widely in nature and is close to a natural additive, and it can be used as a food preservative in meat products. However, in many countries, such as Japan and the United States, benzoic acid and sodium benzoate are not allowed to be used in meat products. In Japan, the production of benzoic acid and sodium benzoate has been stopped, and there are also some restrictions on imported foods (Ling Guanting, 2003).
According to the regulations of the US FAO, benzoic acid and sodium benzoate can be used in quick-frozen fish sticks, fish pieces, and fish filling products, but meat products are not included in the usage range. In addition, in the countries where the use of benzoic acid and sodium benzoate is allowed as mentioned above, these two additives are also not recommended as preservatives for meat products.
Domestic Usage Issues
Sodium Benzoate
In China, some literatures on meat product science and processing technology also mention that benzoic acid and sodium benzoate can be used as preservatives (Kong Baohua, 2003; Ge Changrong, 2002). At an exchange conference of the China Food Additives Association in 2004, an enterprise put forward the “Proposal on Amending the ‘Hygienic Standards for the Use of Food Additives’ to Prohibit the Use of Flour Whitening Agent (Benzoyl Peroxide)”. The proposal attracted the attention of the participants (Chemical Industry, 2004). Since benzoyl peroxide will eventually form benzoic acid in flour, some domestic enterprises have also questioned the prohibition of the use of benzoic acid and sodium benzoate in meat products, which has caused disputes.
So, is it necessary to amend the “Hygienic Standards for the Use of Food Additives” to expand its usage range? First of all, from the preservation mechanism of benzoic acid and sodium benzoate, we know that benzoic acid preservatives act through their undissociated molecules, and the pH value of food has a great impact on the percentage content of undissociated benzoic acid in food, that is, the pH value of food has a great impact on the preservation effect of benzoic acid preservatives. As can be seen from Table 1, under the same acidity, different additives have different effects. When the pH value is 5, the undissociated molecules of benzoic acid are one-third of those of sorbic acid, that is, in foods with a pH value of 5, the antibacterial effect of sorbic acid is three times that of benzoic acid (Hou Zhenjian, 2004). However, when the pH value is below 4, the difference in the effect is not significant. Therefore, benzoic acid preservatives are generally used in acidic foods such as soft drinks, jams, and pickles. The pH value of meat products is generally 5.3 – 6.5. Even for fermented meat products, such as Italian salami and German salami, the pH value is only between 4.7 – 5.3 (Kong Baohua, 2003), and the preservation effect of benzoic acid is also limited. Therefore, except for having some effect in fermented meat products, it is difficult for benzoic acid to play a preservative role in general meat products.
