Citric acid is found naturally in citrus fruits and generated by all living cells. It's used in cuisine, medicine, science and industry. In the human body it's integral to biological processes and health.
About Citric Acid
Citric acid (C6H8O7) is a weak organic acid. It naturally occurs in citrus fruits like lemons, limes, oranges, and grapefruit. It's an intermediate in the citric acid cycle or the Krebs cycle, an essential metabolic pathway.
This cycle generates energy by oxidizing acetyl-CoA, derived from carbohydrates, fats, and proteins, into carbon dioxide and chemical energy in the form of ATP, driving cellular respiration.
A colorless, crystalline substance, citric acid has a sharp, sour taste and is a popular ingredient in foods and beverages. It enhances flavors and is also a natural preservative.
Creation of Citric Acid
Citrus fruits are pressed to yield juice. The juice goes through purification techniques to isolate citric acid. While this method is suited for small-scale production, it can't meet high demands of industries.
The citric acid in processed foods and industrial applications is made by fermentation. It uses Aspergillus niger, a common mold, to ferment sugary substrates like molasses or corn steep liquor.
The mold consumes sugar and, as a byproduct, produces large quantities of citric acid. The citric acid is extracted, purified and dried to a crystalline form.
For a ton of citric acid, about 2000 kilograms of sugar are needed to feed the mold. This method is favored for large scale production due to maximum yield for minimum cost.
Properties of Citric Acid
Sour Taste: Its tart acidic taste is well known in food and beverages.
Water-Soluble: Citric acid readily dissolves in water.
Chelating Agent: It can bind to metal ions as a stabilizer.
Antioxidant: Citric acid has antioxidant properties.
pH: 2-3 lowers pH of food and inhibits bacterial growth
Buffering Agent: It helps maintain a stable pH in solutions
The chemical formula for citric acid is C6H8O7. Its structure features three carboxyl groups, enabling it to donate protons and function as a weak acid.
Citric Acid in Nature
The Citric Acid Cycle (Krebs Cycle): A critical component of cellular respiration, the way cells produce energy from food.
Plant Metabolism: Citric acid helps plant growth and development, regulation of nutrient uptake and transport. It aids in metabolism of carbohydrates, fats, and proteins to creating ecosystem balance.
Soil Amendment: Improves soil quality by increasing availability of nutrients to plants.
In the environment, citric acid is biodegradable. It's used in cleaning products as a natural disinfectant. It can bind to heavy metals in the soil, reducing their bioavailability and enhancing soil health.
Citric Acid in Health
Kidney Stone Prevention: Citric acid, as in the form of potassium citrate, can help prevent calcium oxalate kidney stones by binding to calcium, a metal, in urine.
Citric acid also improves calcium absorption by organisms. In animals it's crucial for maintaining strong bones.
Digestion: Citric acid can stimulate the secretion of gastric juices, promoting smoother digestion and reducing issues like bloating.
Skin Care: It's used in cosmetic products as an exfoliant, helping to remove dead skin cells and improve skin texture.
Pharmaceutical: Citric acid finds uses in pharmaceutical formulations as an excipient, enhancing the stability and bioavailability of drugs.
Citric Acid in Science
Laboratory Reagent: It's a common reagent in chemical reactions, often used to adjust pH or as a buffer.
Metallurgy: It can be used in cleaning and descaling metal surfaces.
Textile Industry: Used in dyeing and finishing processes.
Photography: A developer in photographic solutions.
Facts About Citric Acid
World War I: During World War I, the demand for citric acid skyrocketed when Italy, the main source of citrus fruits, was blockaded. This led to the industrial development of citric acid fermentation using Aspergillus niger.
While strongly associated with lemon flavor, citric acid is used in a wide array of products beyond lemonade, including jams, jellies, soft drinks, candies, and even some medications.
Citric acid is generally recognized as safe in food products.
China is the largest producers of citric acid
Citric acid is used in bioplastics.
On ingestion, citric acid is metabolized into bicarbonate, which can help reduce acidity in the body.
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