Citric acid is an important organic acid, which is used in many fields such as food, medicine, and the chemical industry. However, there is a clear difference between the use of citric acid in food and industry. So, how to distinguish between food-grade citric acid and cleaning citric acid?

1. Check the Product Label

First, we can judge by looking at the information on the product packaging or label. Citric acid, a food additive, is usually clearly marked as a “food additive” on the packaging, and has detailed instructions for use and limit requirements. Cleaning citric acid may only be marked as “citric acid” or “industrial citric acid”, and the instructions for use are relatively simple.

2. Differences in Color and Purity

Food grade citric acid is a colorless crystal or powder with a melting point as high as 153℃, while industrial citric acid is a colorless semi-transparent crystal, white granules, or white crystalline powder.

Cleaning citric acid belongs to industrial citric acid, with a relatively low purity, usually ranging from 70% to 99%, and also contains other organic acids and impurities. The purity of edible citric acid must meet food safety standards, with a purity as high as 99.9%, and pure edible citric acid does not contain other organic acids and impurities.

3. Origin

The chemical composition of clean citric acid and food-grade citric acid is basically the same, and both are citric acid molecules obtained through fermentation or chemical synthesis. However, clean citric acid is a chemical raw material that contains a considerable amount of impurities, such as metal ions like iron, magnesium, and cobalt, and is widely used in industrial production.

The molecular formula of industrial citric acid is C6H8O7, with a molecular weight of 192.12. It is obtained through microbial fermentation or chemical synthesis. Most of them are produced by deep fermentation, using Aspergillus Niger as the strain. By adding sugar raw materials to the culture medium, citric acid is generated. The production cost is low, and the yield is high. However, it may contain a small amount of impurities and microorganisms, such as metal ions like iron, magnesium, and cobalt. It has wide applications in the field of industrial production, which is unacceptable in food-grade citric acid.
Food-grade citric acid mainly comes from natural fruits, such as lemons and limes.

4. Applications 

Food-grade citric acid requires a relatively high purity and is limited to use in food processing, preservation and anti-corrosion, and flavoring, etc. For instance, food-grade citric acid can be used in beverages, canned foods, jams, and other foods. It can also be used as an acidulant and preservative in the production of baked goods such as cakes, bread, dough, and biscuits. It not only provides a unique sour taste, but also regulates the pH value of food and promotes the release of other flavor substances. The purity and safety of edible citric acid are strictly regulated to ensure that its application in food processing does not hurt human health. In addition, since food citric acid is extracted from natural plant raw materials or produced through fermentation, it has a higher nutritional value and is more easily absorbed by the human body.

Due to its easy solubility in cold water, clean citric acid is widely used in the production of various chemical products and the treatment of industrial wastewater, residential and commercial water pipeline cleaning, etc. For instance, in the textile industry, industrial citric acid can be used as an auxiliary component of detergents to enhance the decontamination effect. Its chelating effect can soften water quality, but it poses safety risks.

5. Safety

Food-grade citric acid has undergone strict safety assessment and approval and is regarded as a safe additive. When used in accordance with standards, it will not pose a threat to health. However, patients with gastric ulcers need to control their intake to avoid irritating the digestive tract.
However, the by-products and impurities of cleaning citric acid, that is, industrial citric acid, may affect human health. Accidental ingestion may lead to heavy metal poisoning, and bittering agents and other substances may be added to prevent misuse.

It is worth noting that concentrated citric acid solution is irritating to mucous membranes, and long-term exposure may cause eczema. In addition, citric acid is flammable, and its powder can form explosive mixtures when mixed with air. Citric acid cannot be directly added to pure milk; otherwise, it will cause the milk to coagulate. In dairy product processing, citric acid is usually prepared into a solution of about 10% and added to a low-concentration milk solution. At the same time, it needs to be stirred rapidly to prevent solidification.

6. Price

Food-grade citric acid, due to its strict control over impurities, heavy metal ions, and solvent residues, is usually more expensive than clean citric acid.

Conclusion

To sum up, food-grade citric acid and clean citric acid (industrial-grade citric acid), although both are members of the citric acid family, are like day and night, each playing a distinct role. The differences between them cannot be ignored.
Food-grade citric acid, like a fairy in the food industry, adds luster to various beverages, candies, pastries, and even dairy products with its mild and refreshing sourness. It is not only the source of sourness, but also the guardian of safety. Under the strict supervision of national food safety standards, the impurities and harmful components contained in food-grade citric acid are strictly limited. For instance, the arsenic content must not exceed 1mg/kg, and the lead content must not exceed 0.5mg/kg, ensuring the safety of consumers’ food on their plates.

In contrast, industrial-grade citric acid is more like a warrior in the chemical world, widely used in multiple fields such as chemical engineering, pharmaceuticals, and textiles, playing multiple roles including chelating agent, dispersant, and antioxidant. However, since it is not designed for human consumption, the restrictions on harmful substances are relatively lenient, and the content of harmful components such as heavy metals may be significantly higher than that of food-grade citric acid. If it is accidentally used in food processing, it will undoubtedly pose a potential threat to consumers’ health.
What is particularly alarming is that some unscrupulous vendors, to cut costs, use industrial citric acid to soak easily Browning foods such as lotus roots. This not only spoils the natural flavor and texture of the food but also casts a shadow over consumers’ health. Therefore, when purchasing food, we should learn to distinguish and choose those that have not been overly processed and retain their original color, allowing health and deliciousness to go hand in hand.