Citric acid

Citric acid is a weak organic acid commonly found in citrus fruits like lemons, limes, and oranges. It is known for its tart, sour taste and crystalline form. The chemical formula for citric acid is C₆H₈O₇, and it is highly soluble in water. It acts as a natural preservative and is used to add an acidic or sour taste to foods and beverages. Additionally, citric acid is a key intermediate in the citric acid cycle (Krebs cycle), which is fundamental to cellular metabolism.

Origin

Citric acid occurs naturally in citrus fruits. However, the majority of citric acid used as a food additive is synthetic and is produced through microbial fermentation. In this process, the mold Aspergillus niger is typically used to ferment a carbohydrate source such as corn or sugar beet molasses, resulting in a more efficient and cost‑effective production compared to extracting it from citrus fruits.

Characteristics

Citric acid is widely used in the food industry for several reasons:

• Preservative: Inhibits the growth of bacteria and mold.
• Flavour Enhancer: Adds a sour taste to foods and beverages.
• pH Regulator: Adjusts the acidity or alkalinity of products.
• Chelating Agent: Binds with metal ions to prevent discoloration and oxidation.

Uses in Ultra‑Processed Foods

In ultra‑processed foods, citric acid serves multiple functions:

• Preservation: Citric acid extends the shelf life of products by creating an acidic environment that inhibits the growth of spoilage microorganisms. This is crucial for processed foods that need to remain safe and consumable over long periods.
• Flavour Enhancement: It enhances and balances the flavour profiles of many processed foods. For example, in soft drinks, candies, and snacks, citric acid provides a sharp, tangy taste that is often associated with freshness.
• pH Adjustment: Citric acid is used to maintain the desired pH level in various food products, ensuring consistency in taste and texture. For instance, it helps to stabilize the pH in canned vegetables and fruits, preventing discoloration and maintaining firmness.
• Emulsification: In products like ice cream and mayonnaise, citric acid acts as an emulsifying agent, helping to blend oils and water‑based ingredients, resulting in a smooth and consistent texture.
• Antioxidant Role: Citric acid binds with metal ions that can catalyze oxidation reactions, thereby preventing rancidity and extending the shelf life of fatty and oil‑rich foods.

Health Considerations

While citric acid is generally recognized as safe (GRAS) by regulatory authorities like the FDA, there are some considerations and potential risks associated with its consumption:

• Dental Erosion: Frequent consumption of foods and beverages containing citric acid can lead to the erosion of dental enamel due to its acidic nature.
• Gastrointestinal Issues: In large amounts, citric acid may cause stomach upset or exacerbate symptoms in individuals with sensitive gastrointestinal systems, such as those with acid reflux or GERD.
• Allergic Reactions: Although rare, some individuals may experience allergic reactions to citric acid, presenting as skin irritation or respiratory issues.
• GMO Concerns: Synthetic citric acid is often made using GMO beets or corn.

Further studies need to be done on the effects of synthetic citric acid on human health. 

References

1. U.S. Food and Drug Administration (FDA). (n.d.). "Everything Added to Food in the United States (EAFUS)." Retrieved from FDA EAFUS Database.
2. National Center for Biotechnology Information (NCBI). (n.d.). "Citric Acid." PubChem Compound Summary. Retrieved from PubChem.
3. Echemi. (n.d.). "Is Citric Acid a Preservative: A Comprehensive Guide" Retrieved from Echemi.
4. Healthline. (2019). "Citric Acid: Benefits, Uses, and Side Effects." Retrieved from Healthline.
5. Journal of Dentistry. (2016). "The impact of citric acid on human enamel erosion: a systematic review." Retrieved from ScienceDirect.
6. Sweis, I. E., & Cressey, B. C. (2018). Potential role of the common food additive manufactured citric acid in eliciting significant inflammatory reactions contributing to serious disease states: A series of four case reports. Toxicology Reports, 5, 808–812. Published online 2018 Aug 9. doi: 10.1016/j.toxrep.2018.08.002. PMCID: PMC6097542. PMID: 30128297.