Often, the first person to notice a cracked and broken capsule is the consumer—obviously the worst-case scenario for any quality manufacturer. If the consumer tastes leaking product, the negative impression left may be long lasting. This begs the questions: Why wasn’t this observed during manufacturing process or quality checks? And where did the capsule lose moisture along the way?
When manufacturers hear of brittleness in two-piece capsules, their general inquiries turn to capsule storage conditions or empty capsule manufacturing. While these are both critical players in the stability of capsule shells, many other factors play a role and may cause problems. Manufacturers need to understand how to prevent brittleness from the cradle of the supply chain to the consumer purchase point.
Maintaining optimal moisture in capsule shells is key to preventing brittle capsules. Shell moisture must be maintained above 13 percent in two-piece gelatin capsules to prevent breakage. For some hypromellose (“veggie") capsules, especially those that meet USP dissolution requirements, brittleness can occur when moisture falls below 4 percent. Loss of moisture can combine with other physical factors, such as filling pressures and impact points.
Following are areas along the supply chain where capsules commonly become brittle and crack:
Warehousing & Transportation
Storing capsules in areas that are too hot or cold will affect the moisture level of the capsules. In all storage areas, make sure capsules are kept within the recommended temperature range listed on the capsule cartons. If the humidity in the warehouse area cannot be controlled, make certain temperature ranges are adhered to. The capsule bag liner will provide some protection against low humidity until the capsule bag has been opened; optimum humidity is very important in the capsule filling room. In warehousing, remember rising heat is trapped near the ceiling levels; as such, it is best to keep capsules away from high rack locations. Hot spots are also found near ceiling lights and HVAC vents. Capsule cartons wrapped in excessive plastic and kept in hot or humid locations can cause a greenhouse effect, trapping heat and moisture around capsules. When transporting either empty or filled capsules, treat them as if they were chocolate, being careful to maintain ideal conditions.