Guidelines for Choosing the Suitable Grade and Specification of Citric Acid CAS#77-92-9
As a widely used organic acid in the food, pharmaceutical, chemical, detergent, and other industries, the key to choosing the right specification and grade of citric acid lies in matching the requirements of the specific application scenario. Different fields place very different demands on factors such as purity, particle size, anhydrous or hydrated form, and impurity limits. The following explains how to select suitable citric acid specifications and grades from three perspectives: core classification dimensions, application-based selection logic, and key considerations.
I. Core Classification Dimensions of Citric Acid Specifications (Basic Understanding)
Before making a selection, it is essential to understand the main specification parameters of citric acid, as these form the foundation for matching product performance to application needs:
Form and Water Content:
Citric acid is available as monohydrate citric acid (C₆H₈O₇·H₂O) and anhydrous citric acid (C₆H₈O₇). Monohydrate citric acid contains one molecule of crystal water, has a lower melting point (around 100 °C), dissolves easily, and exhibits low hygroscopicity. Anhydrous citric acid contains no crystal water, has a higher melting point (about 153 °C), and stronger moisture absorption, making it suitable for applications sensitive to water content.
Purity Grade:
According to usage, citric acid is classified as food grade, pharmaceutical grade, industrial grade, and reagent grade (such as analytical reagent AR and chemical pure CP). In general, purity and impurity control requirements decrease in the following order: reagent grade > pharmaceutical grade > food grade > industrial grade. Correspondingly, limits on impurities such as heavy metals, sulfates, and chlorides become progressively less strict.
Particle Size and Appearance:
Common physical forms include powder and crystalline products, with crystals further divided into fine, medium, and coarse grades. Particle size affects dissolution speed and mixing uniformity. Powders dissolve rapidly and are suitable for applications requiring quick dispersion, while crystalline products offer better flowability and are easier to measure and feed accurately.
Applicable Standards:
Different industries follow specific national or industry standards. For example, food-grade citric acid complies with GB 1886.235-2016, pharmaceutical grade follows pharmacopoeia standards (such as ChP), and industrial grade adheres to relevant chemical industry standards. Compliance with the appropriate standard is a fundamental criterion for specification selection.
II. Guidelines for Selecting Citric Acid Specifications and Grades by Industry
(1) Food Industry (Most Common Application; Key Requirements: Safety, Qualified Purity, Process Compatibility)
Food-grade citric acid is the primary choice in this sector and must strictly meet the requirements of GB 1886.235-2016. Selection mainly focuses on form and particle size:
Beverage Industry (Carbonated Drinks, Fruit Juices, Tea Beverages, etc.):
Food-grade monohydrate citric acid in fine crystal or powder form is generally preferred. Monohydrate citric acid dissolves quickly, allowing rapid adjustment of beverage pH to inhibit microbial growth and enhance flavor stability. Its low hygroscopicity also supports accurate dosing during storage and formulation. For concentrated beverages or products requiring long-term high-temperature storage, food-grade anhydrous citric acid may be selected to minimize the impact of moisture on product stability.
