Grades and Uses of Food-Grade CMC
Applications：
Uses and Functions：
1. Thickening: Achieves viscosity at low concentrations, allowing control over the viscosity during food processing while providing a smooth texture.
2. Water Retention: Reduces dehydration and shrinkage in foods, extending shelf life.
3. Dispersant Stability: Maintains food quality stability, prevents oil-water separation (emulsification), and controls crystal size in frozen foods (reduces ice crystals).
4. Film Formation: Forms a gel film in fried foods to prevent excessive oil absorption.
5. Chemical Stability: Stable against chemicals, heat, and light, with some resistance to mold.
6. Metabolic Inertness： As a food additive, it is not metabolized and does not provide calories in food.
Structural Characteristics of CMC
Sodium Carboxymethyl Cellulose (CMC) is an anionic cellulose ether, commonly found as a white or slightly yellow fibrous powder or granules, with a density of 0.5-0.7 g/cm³. It is nearly odorless and tasteless, with strong hygroscopic properties. CMC dissolves easily in water to form a clear, gel-like solution but remains insoluble in organic solvents like ethanol. A 1% aqueous solution typically has a pH between 6.5 and 8.5, performing best at pH 7. The viscosity decreases significantly when the pH is above 10 or below 5.
CMC is heat stable, with viscosity increasing rapidly below 20°C and changing more slowly between 25°C and 55°C. However, prolonged heating above 80°C can denature the gel, reducing its viscosity and effectiveness. High-temperature boiling above 100°C or extended ultra-high temperature sterilization can significantly degrade CMC, leading to a rapid loss of viscosity. CMC is stable in weak alkaline solutions but hydrolyzes easily in acidic environments. It remains stable above pH 3.5, but precipitation can occur at pH levels of 2-3 and in the presence of multivalent metal salts.
Quality of CMC is gauged by degree of substitution (DS) and purity.
The properties of Sodium Carboxymethyl Cellulose (CMC) depend on its degree of substitution (DS). As the DS increases, so do the solubility, transparency, and stability of the solution. When the DS is between 0.7 and 0.9, CMC solutions exhibit some transparency and pseudoplastic behavior. With a DS greater than 0.90, the solution becomes more transparent and its rheological properties improve. Factors influencing DS include the ratio of alkali to etherifying agent, etherification time, water content, temperature, pH, solution concentration, and the presence of salts.
High-purity CMC products demonstrate more distinct characteristics and greater stability. The FAO and WHO have approved pure CMC for use in food, following extensive biological and toxicological testing. The internationally accepted daily intake (ADI) is 25 mg per kg of body weight, which is about 1.5 grams per person per day. Some studies have reported no toxic effects even at intake levels as high as 10 kg.
For optimal results, consider these factors when using CMC to ensure its effectiveness and safety in various applications.
