Citric acid is a weak organic acid that is produced as a white crystalline powder. It is a natural food preservative that is also used to add an acidic, or sour taste to foods and soft drinks. In biochemistry, it is important as an intermediate in the Krebs (citric acid) cycle and therefore occurs in the metabolism of virtually all living things. Citric acid can also be used as an environmentally benign cleaning agent.
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The Chemical Company’s Citric Acid is a white, odorless crystalline powder that is a naturally occurring weak organic acid found in citrus fruits. It is one of the most widely used food-grade acids globally, produced commercially via fermentation of carbohydrate substrates (typically corn or molasses) using Aspergillus niger. Citric acid is available in both anhydrous and monohydrate forms.
Thanks to its Generally Recognized As Safe (GRAS) status, excellent chelating properties, and mild, pleasant acidity, citric acid is indispensable across food and beverage, pharmaceutical, cosmetic, and industrial applications. It functions as an acidulant, preservative, flavor enhancer, pH buffer, and chelating agent, and is increasingly valued in industrial cleaning and green chemistry applications as a biodegradable alternative to phosphate-based compounds.
Global citric acid production exceeds 2 million metric tons annually, with more than 50% produced in China. The modern fermentation process using Aspergillus niger was pioneered by American food chemist James Currie in 1917, and industrial production began at Pfizer by 1919 — a process largely unchanged today. Lemons and limes contain the highest natural concentrations, up to 8% of dry weight.
Citric acid is a tricarboxylic acid, meaning it carries three carboxyl groups (–COOH) and one hydroxyl group, giving it excellent buffering capacity across a wide pH range of approximately 2–8. Its citrate conjugate base plays a central role in the Krebs (citric acid) cycle — the metabolic pathway by which all aerobic organisms generate energy — making it one of the most biologically significant organic acids known.
| Property | Value |
| Molecular Formula | C6H8O7 |
| Molecular Weight | 192.12 g/mol (anhydrous); 210.14 g/mol (monohydrate) |
| Appearance | White odorless crystalline powder |
| Melting Point (anhydrous) | 153°C (307°F) |
| Decomposition Point | ~175°C (loss of CO2) |
| Density | 1.66 g/mL (anhydrous) |
| Solubility in Water | ~1,174 g/L at 10°C; highly soluble and temperature-dependent |
| pH (1% solution) | ~2.2 |
| pKa Values | pKa1: 3.13 / pKa2: 4.76 / pKa3: 6.40 |
| Buffering Range | pH 2–8 |
| Available Forms | Anhydrous (crystallizes from hot water); Monohydrate (crystallizes from cold water) |
| E Number (food) | E330 |
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