Adipic acid

Adipic acid, also known as E355, is an organic compound widely used in the food industry. It is a white, crystalline powder with a slightly sour taste. Adipic acid is a dicarboxylic acid, which means that it has two carboxylic groups (-COOH) in its molecular structure. This compound is soluble in water and has a melting point of approximately 152°C (306°F).

Origin

Adipic acid is mainly of artificial origin. It is synthesised industrially by a chemical process involving the oxidation of cyclohexanol or cyclohexanone with nitric acid. Although it may occur naturally in some plants and beets, the quantities are too small for commercial extraction, making synthetic production the main method of its availability.

Characteristics and food uses

Adipic acid is used in food for several reasons, primarily due to its functional properties:

• Acidity control: It helps to maintain the desired pH level in food.
• Taste enhancement: Contributes to the tart taste of foods and beverages.
• Gelling agent: Helps to form and stabilize gels, especially in gelatin products.
• Bulking agent: Acts as a leavening agent in baking powders.
• Preservative: Extends the shelf life of certain foods by acting as a preservative.

Use in ultra‑processed foods

Adipic acid is used extensively in ultra‑processed foods due to its versatility and effectiveness. Here are some of its common applications:

• Beverages: adds tartness and stabilizes the acidity of carbonated beverages. In fruit juices, it enhances flavor and balances sweetness with acidity.
• Baking: It is used in baking powders to aid leavening, resulting in a light and fluffy texture. Maintains proper acidity levels in cookies and cakes, which can affect texture and flavor.
• Gelling agent: Promotes gel formation and stability, ensuring proper texture in desserts.
• Flavour enhancer: Provides a mild tartness that complements sweet flavours.
• Acidity control: Helps achieve the desired pH, which is key to the texture and shelf life of processed cheese.
• Flavor Balancing: Adds a mild acidity that balances the sweetness in sweets and candies.

Impact on human health

Although adipic acid is generally regarded as safe (GRAS) by the FDA and other regulatory bodies, there are some health aspects to keep in mind:

• Digestive problems: high consumption can lead to digestive problems, including nausea and diarrhea.
• Kidney function: There is some evidence to suggest that excessive intake may affect kidney function, particularly in individuals with pre‑existing kidney disease.
• Allergic reactions: Although rare, some individuals may have allergic reactions to adipic acid.
• General considerations: As with other food additives, there is the potential for adipic acid to affect the gut microbiome, especially if consumed in large quantities over a long period of time. The gut microbiota is sensitive to changes in diet and the introduction of various chemicals, which can affect the balance of beneficial and harmful bacteria.

Overall, moderate consumption within established safety guidelines is not associated with significant health risks.

Sources

1. Food and Drug Administration (FDA). (n.d.). Food Additive Status List. Retrieved from FDA website.
2. European Food Safety Authority (EFSA). (2016). Re‑evaluation of adipic acid (E 355) as a food additive. EFSA Journal, 14(6), 4520. DOI:10,2903/j.efsa.2016,4520.
3. National Center for Biotechnology Information (NCBI). PubChem Compound Summary for CID 196, Adipic acid. Retrieved from PubChem.
4. I. Goldberg, J.S. Rokem, Organic and Fatty Acid Production, Microbial, Editor(s): Moselio Schaechter, Encyclopedia of Microbiology (Third Edition), Academic Press, 2009,Pages 421‑442, ISBN 9780123739445, https://doi.org/10,1016/B978‑012373944‑5,00156‑5.