Gelatin in Hard Capsule Manufacturing

Key Considerations for Selecting Gelatin in Hard Capsule Manufacturing

The production of hard gelatin capsules (HGC) is a high-precision process that relies on the "dip-molding" technique. To ensure consistent shell quality, mechanical strength, and rapid dissolution, selecting the appropriate grade of gelatin is paramount. Below are the essential technical criteria for manufacturers.

1. High Bloom Strength (Gel Strength)

Hard capsules require a significantly higher Bloom strength than softgels to ensure structural rigidity.

·         Standard Range: Typically between 220 and 280 Bloom.

·         Purpose: High Bloom gelatin provides the necessary mechanical "snap" and prevents the capsules from deforming during high-speed filling or blister packaging. It also ensures the shells are brittle enough to be opened by machinery but tough enough to resist cracking.

2. Strict Viscosity Control

Viscosity is perhaps the most critical parameter in hard capsule production because it determines the thickness of the capsule wall during the dipping process.

·         Ideal Range: Usually maintained between 40 and 50 mps (at 6.67% concentration, 60°C).

·         Impact: If the viscosity is too low, the gelatin film will be too thin; if it is too high, the film will be too thick. Consistency is key to ensuring that the cap and body of the capsule fit together perfectly with a secure "click."

3. Low Viscosity Breakdown (Thermal Stability)

Hard capsule production involves keeping the gelatin mass in a liquid state for extended periods in dipping tanks.

·         Requirement: The gelatin must have excellent thermal stability.

·         Selection Tip: Choose gelatin with a low "viscosity breakdown" rate. This ensures that the dipping solution remains stable over 24–48 hours of continuous production without losing its film-forming properties.

4. Raw Material Type (Type B vs. Type A)

·         Type B (Alkali-processed bovine bone): This is the industry standard for hard capsules. Bovine bone gelatin provides superior film clarity, high gel strength, and the specific rheological properties needed for dipping.

·         Type A (Acid-processed porcine skin): Less commonly used as a primary source for hard capsules due to different setting speeds, but sometimes blended to adjust dissolution profiles.

5. Transparency and Color

Since hard capsules are often clear or vibrantly colored, the raw gelatin must have:

·         Low Turbidity: High clarity is essential for "clear" capsules to ensure a premium look.

·         Low Natural Pigmentation: The gelatin should be light in color so that it does not interfere with the added dyes or opacifiers (like Titanium Dioxide or Calcium Carbonate).

6. Cross-linking Resistance

Hard capsules are prone to "cross-linking"—a chemical reaction that makes the shell insoluble, often caused by exposure to heat, humidity, or certain fill materials (aldehydes).

·         Selection Tip: Select gelatin with high purity and low reactive impurities to minimize the risk of dissolution failure during the product's shelf life.

Conclusion

For hard capsule manufacturing, the priority lies in Bloom-to-viscosity ratios and batch-to-batch consistency. By sourcing high-bloom, bovine-bone Type B gelatin, manufacturers can ensure a smooth encapsulation process and a final product that meets stringent pharmacopeia dissolution standards.