Citric acid

Introduction

Anhydrous citric acid is a natural component and metabolic intermediate in plants and animals. It is also one of the most widely used organic acids in the food, pharmaceutical, and chemical industries. It occurs as colorless, transparent, or translucent crystals, or as granular or microparticle powder. It is odorless and has a pleasant, slightly astringent aftertaste despite its sharp sourness. It gradually dissolves in warm air and is slightly deliquescent in humid air.

Distribution in Nature

Citric acid is widely distributed in nature, found in fruits such as lemons, oranges, pineapples, currants, raspberries, and grape juice, as well as in the bones, muscles, and blood of animals. Synthetic citric acid is produced by fermenting sugars such as sugar, molasses, starch, and grapes. It can be found in both anhydrous and hydrated forms. Pure citric acid is odorless and appears as colorless, transparent crystals or a white powder with an appealing sour taste. The translucent, colorless crystals obtained from a hot, concentrated aqueous solution are the anhydrous form, with a melting point of 153°C. The translucent, colorless crystals obtained from cold water solution are the monohydrate, with a density of 1.542. They soften at 75°C and melt at approximately 100°C. The monohydrate loses water in dry air. It is a strong organic acid, soluble in water, ethanol, and ether. It is used in the manufacture of pharmaceuticals, soft drinks, candies, and as a metal cleaner and mordant. Many fruits and vegetables, especially citrus fruits, contain significant amounts of citric acid, particularly lemons and limes, which contain significant amounts, reaching up to 8% after drying (approximately 47 g/L in juice). The citric acid content in citrus fruits ranges from 0.005 mol/L in oranges and grapes to 0.30 mol/L in lemons and limes. This content varies with different cultivars and plant growth conditions.

Chemical Properties

White, translucent crystals or powder. Freely soluble in water and ethanol, and soluble in ether.

Uses

Primarily used as a food acidifier, it is also used in the preparation of pharmaceutical cooling agents and detergent additives.

Uses

It is used as a laboratory reagent, chromatographic analysis reagent, biochemical reagent, and in the preparation of buffer solutions. It is used in the food industry, particularly as an acidifier, pH buffer, and, along with other compounds, as a preservative. In the detergent industry, it is an ideal substitute for phosphates. It is also used as a chemical pickling agent and rinse agent for boiler cleaning. Primarily used as a food acidifier, it is also used in the preparation of pharmaceutical cooling agents and detergents.

Uses

Citric acid is the most versatile and versatile acidifier. It has high solubility and strong metal chelating ability, making it suitable for a variety of foods, with appropriate dosages tailored to production needs. It can also be used as an antioxidant synergist, a synergist for compound potato starch bleaching agents, and a preservative.

Uses

It is widely used as an acidifier for food and beverages and as a pharmaceutical additive. It can also be used as a raw material and additive in cosmetics, metal cleaners, mordants, non-toxic plasticizers, and boiler anti-scaling agents. Its main salt products include sodium citrate, calcium citrate, and ammonium citrate. Sodium citrate is a blood anticoagulant, while ammonium ferric citrate is used as a blood tonic.

Uses

Its uses as an analytical reagent are similar to those of citric acid.