As far as ordinary hollow capsule shells are concerned, the most common matrix materials are gelatin and hypromellose (HPMC).
| gelatin capsule shell | HPMC capsule shell | |
| category | animal-derived capsule shells | Plant-Based Capsule Shells |
| main ingredient | Gelatin (from animal bone, skin) + water | Hypromellose (from cotton linters, wood pulp) + water |
| Production process | Gelatin is obtained from animal tissue through a series of processes such as degreasing and demineralization under appropriate conditions. Gelatin or HPMC is dissolved in water at a suitable temperature to form a solution, a special mold is immersed in the hot solution, and the solution gels to form a film when cooled, and then undergoes post-processing such as drying and polishing. | |
| water content | 12.5~17.5% | 4%~7% |
| Solubility | Swells up in cold water at 25°C, does not dissolve | Dissolve gradually in cold water at 25°C |
| crumbly | none | Less than 5 in 50 |
| safety | Safe and reliable, it is included in the pharmacopoeia of many countries | There is a risk of excessive preservatives and mad cow disease |
Obvious disadvantages of gelatin capsules:
(1) Because the water content is between 12.5% and 17.5%, it is easy to lose water during the placement process, resulting in poor toughness and softening due to moisture absorption. The temperature and humidity of the storage environment (15~25℃, RH% 35~65%) and the material of the packaging are required to be higher.
(2) The main component of gelatin capsules is gelatin (protein), which undergoes cross-linking reaction when encountering amino acids, aldehydes, reducing sugar-based compounds and vitamins.
In order to overcome the stability problem of gelatin capsules, HPMC capsules were developed, which are mainly made of hypromellose and water, and sometimes contain additives such as plasticizers, surfactants, gelling agents, dispersing agents, flavoring agents , preservatives and sweetening agents, and may also contain opacifying agents, coloring agents and/or processing aids.
