Proper dispersion of Avicel colloidal MCC is the key to obtaining optimum functionality.
Click here for a presentation by Ross White, FMC BioPolymer Applications Manager on Avicel - The value of effective dispersion.
As Avicel is dispersed in water with appropriate shear, the hydrophilic portion is hydrated. This allows the cellulose microcrystals to be released and activated, resulting in a stable colloidal network. Critical factors to consider when dispersing the remaining ingredients include:
Order of Addition – Avicel MCC should ideally be hydrated in water before other ingredients are added. Avicel does not chemically bind water and will not interfere with the subsequent addition of the remaining ingredients.
Type of Shear – the grade or type of Avicel MCC you select depends on the amount of shear available in your process.
pH of Systems – a protective colloid is recommended to prevent flocculation if the pH of your system is less than 3.8. Suggested protective colloids are xanthan gum, carboxymethylcellulose and methylcellulose. The protective colloid is generally used at 10% of the microcrystalline cellulose level.
Hard Water/Electrolytes – a high level of electrolytes present in the system before the addition of Avicel MCC may inhibit proper dispersion and require higher shear for good activation.
Methods of Dispersion
- Add Avicel MCC to water while agitating
- Add protective colloid if pH of system is less than 3.8
- Agitate in a high speed mixer for 5 to 15 minutes (length of dispersion time is dependent on the equipment)
- Add the other ingredients
- Hold the salts and acids until last
- Follow steps as for water dispersion (above)
- Best to use homogenization at greater than 100 bar pressure (2000 psi)