The gem citric acid

This article seeks to look at the chemistry and industrial background of Citric acid and its advantages and disadvantages to humans as it is being used in almost all foods and beverages.

What is an acid, as defined in chemistry?

An acid is any substance that in a water solution tastes sour, changes blue litmus paper to red, reacts with some metals to liberate hydrogen, reacts with bases to form salts, and promotes chemical reactions (acid catalysis).

Sources of acids

There are two main sources of acids namely Organic (Natural) source and contains carbon-hydrogen bonds in their structure. The reason is that carbon is present in the living and non-living parts of the earth. Carbon makes up approximately 50 percent of all living tissue. Carbon is found in rocks, water, and atmospheric gases and inorganic (prepared at the Laboratory) sources and contains no carbon. The Organic ones are the weakest as compared to the inorganic ones.

Examples of some common acids and their sources

Lactic acids from animal milk (Organic), citric acids from citrus fruits (Organic), nitric acid from ammonia (inorganic), Sulphuric acid from car batteries(inorganic), etc.

Citric acid with the chemical formula C₆H₈O₇ is a weak organic (natural) acid.

Here are some examples of citrus fruits:

Oranges: Oranges are one of the most popular citrus fruits. They come in various varieties, including navel oranges, Valencia oranges, and blood oranges. Oranges are known for their sweet and tangy flavour.


Lemons: Lemons are sour citrus fruits that are commonly used for their juice and zest. They have a bright yellow colour and are known for their high vitamin ‘C’ content.

Limes: Limes are small, green citrus fruits with a tangy and acidic flavour. They are often used in cooking, beverages, and as a garnish.

Grapefruits: Grapefruits are large citrus fruits with a tart and slightly bitter taste. They come in different varieties, including white, pink, and red grapefruits.

Tangerines: Tangerines are small, sweet citrus fruits with a bright orange colour. They are easy to peel and have a refreshing flavour.

Mandarins: Mandarins are similar to tangerines and are often used interchangeably. They are small, sweet, and easy to peel.

Pomelos: Pomelos are large citrus fruits with a thick rind and a sweet, mild flavor. They are often compared to grapefruits but have a milder taste.

Kumquats: Kumquats are small, oval-shaped citrus fruits that are eaten whole, including the skin. They have a sweet and tangy flavor.

Citrus fruits are known for their juicy flesh, high vitamin C content, and refreshing flavors.

Physical and chemical properties of citric acid

Physical properties

Appearance: Citric acid is a white crystalline powder or granules.

Odour: It has a slightly acidic and citrus-like odor.

Solubility: Citric acid is highly soluble in water, with a solubility of approximately 59 g/100 mL at room temperature.

Melting point: The melting point of citric acid is around 153-159°C (307-318°F).

Density: The density of citric acid is approximately 1.665 g/cm³.

Chemical properties

Acidity: Citric acid is a weak acid with a pKa value of 3.13, meaning it can donate a hydrogen ion (H+) to a solution but only partially dissociates.

pH: In its solid form, citric acid is slightly acidic, with a pH of around 2.2. However, when dissolved in water, it acts as a buffer and can adjust the pH of a solution.

Chelating agent: Citric acid has chelating properties, meaning it can bind to metal ions and form stable complexes. This property is useful in various industrial applications, such as cleaning and water treatment.

Reducing agent: Citric acid can act as a reducing agent, meaning it can donate electrons to another substance during a chemical reaction.

Biodegradability: Citric acid is biodegradable and environmentally friendly.

These properties contribute to the wide range of applications of citric acid in various industries.

The industrial uses of citric acid

Citric acid, a natural acid found in citrus fruits, has a wide range of industrial uses. Here are some
common industrial applications of citric acid:

Food and beverage industry: Citric acid is widely used as a food additive and flavoring agent in various food and beverage products. It acts as a natural preservative, and pH adjuster, and enhances the flavor and tartness of food and drinks.

Pharmaceutical industry: Citric acid is used in the pharmaceutical industry as an excipient in the formulation of medicines, particularly in effervescent tablets and syrups. It helps in improving the taste, stability, and solubility of medications.

Cleaning and detergent industry: Citric acid is an effective chelating agent, meaning it can bind to metal ions and prevent them from interfering with the cleaning process. It is used in household cleaners, dishwasher detergents, and descaling agents for removing mineral deposits.

Personal care products: Citric acid is used in various personal care products, such as shampoos, soaps, lotions, and cosmetics. It acts as a pH adjuster, and preservative, and can help in exfoliating and brightening the skin.

Water treatment: Citric acid is used in water treatment processes to remove metals and scale deposits from pipes and equipment. It is also used in some water softeners to prevent the formation of limescale.

Textile industry: Citric acid is used as a dye-fixing agent in the textile industry. It helps in enhancing the colour fastness of dyes on fabrics.

Industrial cleaning: Citric acid is used in industrial cleaning applications, such as descaling boilers, heat exchangers, and other equipment. It helps in removing mineral deposits and rust.

Metal cleaning and polishing: Citric acid is used in metal cleaning and polishing products to remove tarnish, rust, and scale from various metal surfaces.

These are just a few examples of the industrial uses of citric acid. Its versatility, low toxicity, and eco-friendly nature make it a popular choice in various industries.

Advantages of citric acid in foods and beverages:

Flavour enhancement: Citric acid provides a pleasant and refreshing tartness to foods and beverages, enhancing their overall taste. It is commonly used in carbonated drinks, jams, and candies for this purpose.

Preservative properties: Citric acid has antimicrobial properties that can help extend the shelf life of certain food products. It inhibits the growth of bacteria, yeast, and mold, making it a natural and effective preservative.

Antioxidant properties: Citric acid acts as an antioxidant, which helps prevent oxidation and spoilage of food and beverages. It can delay the degradation of products, such as delaying the browning of fruits and vegetables.

pH regulation: Citric acid is commonly used as a pH regulator, as it can decrease the acidity of food products, making them less acidic. This is particularly important in the preservation of canned and jarred food
Disadvantages of citric acid in foods and beverages

Allergenic potential: Citric acid is derived from fruits such as lemons and oranges, which can trigger allergies in some individuals. People with sensitivities or allergies to citrus fruits may need to avoid products containing citric acid.

Dental erosion: The acidic nature of citric acid can erode tooth enamel when consumed in excess or improper oral hygiene is maintained. This can lead to tooth sensitivity and cavities over time.

Digestive issues: In some individuals, citric acid can cause stomach discomfort, heartburn, or acid reflux. People suffering from digestive issues or gastroesophageal reflux disease (GERD) should limit their intake of citric acid.

Industrial manufacturing concerns: While natural citric acid is derived from fruits, the majority of citric acid used in the food industry is produced synthetically through fermentation processes. Concerns have been raised regarding the purity and safety of industrially produced citric acid.

It is important to note that the potential disadvantages of citric acid are typically associated with excessive consumption or specific individual sensitivities. In moderation, citric acid is generally recognized as safe by regulatory bodies.