Two types of capsules
Hard-shelled capsules contain dry, powderedingredients or miniature pellets. Soft-shelled capsules are primarily used for oils and for active ingredients that are dissolved or suspended in oil. Hard capsules normally come in size 000, 00, 0, 1, 2, 3 and 4.
Hard-shelled capsules
Hard capsules are two-piece (body and cap)telescoping structured, made in two parts by dipping pin bars in the melting glue. The capsules are in pre-lock status before being supplied to the pharmaceutical and nutraceutical manufacturers. The two halves are separated on the manual, semi-automatic or automatic filling machines. Then the capsule is filled with powder or more normally pellets and the other half of the capsule is pressed on.
Empty hard capsules fall in two differenttypes: traditional gelatin capsules made from collagen taken from animal body parts and vegetarian capsules, almost 99% vegetarian capsules on the market is HPMC capsules. Both are made from aqueous solutions of gelling agents, such as animal protein (mainly gelatin) or plant derivatives (cellulose).
Gelatin capsules
Gelatin capsules, also called gel caps orgelcaps, are composed of gelatin produced from the collagen of animal skin or bone. It is not suitable for vegans because it is made from animal parts. One advantage of gelatin capsule is lowercost, more than half of vegetarian capsules. They are available in various colors and sizes. Though vegetarian capsules are getting more popular, however, gelatin capsules are still the first option used by pharmaceutical companies to produce medicines. Few reasons, firstly because gelatin capsules have lower oxygen permeability to better protect the active ingredients inside. Secondly, they have shorter disintegration time (4-5 mins) than vegetarian capsules (8-12 mins).
Gelatin capsules have more water content(12.5%-17.5%) than vegetarian capsules (around 6%), making gelatin capsules are more sensitive to changes of temperature and easily turn brittle when humidity drops. In addition, high water content means gelatin capsules are not suitable for hygroscopic substance. In addition, Liquids like oil and gels are not compatible with gelatin capsules.
Vegetarian Capsules
The common vegetarian capsules are eitherHPMC capsules or Pullulan capsules. Hypromellose (HPMC) is a semisynthetic, inert, viscoelastic polymer used as eye drops, as well as an excipient and controlled-delivery component in oral medicaments. HPMC is vegetable cellulose derivative approved by the FDA all over the world. Pullulan is produced from starch by the fungus. Pullulan capsules pricing may triple that of the HPMC capsules. On the market, over 99% vegetarian capsules are HPMC capsules.
Compared with gelatin capsules, HPMCcapsules have Lower Moisture. It is right for stuffing which is easy to absorb moisture and/or react with moisture content. HPMC is a kind of vegetable cellulose which contains no amino acid, so there is no risk of cross linking reaction. The most obvious advantage of vegetarian capsules is plant-based, good choice for vegan consumers and more acceptable for religious reasons.