A soft gel capsule is a one piece, hermetically sealed soft gelatin shell containing a liquid, a suspension or a semisolid; referred to as a fill. The soft gel shell is usually comprised of a film-forming material such as gelatin, and a water-dispersible or water-soluble plasticizer (to impart flexibility). The soft gel shell could also include minor additives such as coloring agents, flavors, sweeteners, opacifying agent, medicaments, acid and preservatives. Soft gel capsules can also be enteric coated for certain applications.

Capsule shell composition:
  • Water : 45% w/w. The ratio by weight of water to dry gelatin can vary depending from 0.7-1.3 (water) to 1.0 (dry gelatin) depending on the viscosity of the gelatin being used.
  • Plasticizer. Used to make the soft gel shell elastic & pliable. Ration used is between 0.3- 1.8 for soft to hard shell on dry basis. Plasticizer usually used : Glycerin and sorbitol.
  • Coloring Agent. Colour used in shell has to be darker than color of encapsulating material. Color may be natural or synthetic.
  • Opacifier. Usually used is titanium dioxide, may be added to produce an opaque shell, when the fill formulation is a suspension or to prevent photo degradation of light sensitive fill ingredients. Concentration of oacifier may be up to 0.5%.
  • Chelating agents. Iron is always present in raw gelatin & should not contain iron more than 15 ppm. Additionally chelating agent may be used for preventing the reaction of iron with materials or colors.
  • Gelatin

Soft Capsule’s Gelatin

Gelatin is derived mostly from collagen by thermal denaturing with the aid of diluted acid or alkali. Gelatin contains a mixture of water-soluble proteins (84-90 percent), mineral salts (1-2 percent), and water (8-15 percent). These proteins contain a significant amount of the amino acids: glycine, proline, hydroxyproline, glutamic acid, alanine, arginine, aspartic acid, lysine; in addition to other amino acids in smaller amounts.

There are two types of gelatins:
1. type A : derived from pork skin by hydrolysis with an acid
2. type B : derived from bones and animal skin by hydrolysis with an alkaline solution.
Gelatin used in soft gels is a blend of both types, or used individually.

Gelatin is odorless, tasteless, colorless, and insoluble in most organic solvents, but soluble in glycerin, diluted acids and alkalis. Gelatin swells and absorbs room-temperature water, up to five to 10 times its weight. It dissolves in hot water, and forms a gel upon cooling.

The main source of gelatin is collagen, which is found in the skin and bones of animals such as deep-water fish. Most of the soft gel capsules on the market are made from an animal source, bovine or porcine.
There are non-animal based forms of gelatin to meet the needs of those wishing alternatives to meat products for vegetarian, ethical or religious reasons. A vegetarian gelatin made from Irish moss, which is derived from seaweed and grows off the coast of Ireland, is available but is costlier than the animal-sourced gelatins. The brand name called Vegicap soft capsule.

Typical Formula of Soft Gelatin Capsule Shell for 1 batch = 120 L

Ingredients/MaterialsAmount (kg)Function
Propylmethyl Paraben0.512Preservative
Methyl Parabe0.128Preservative
Gelatin 120 Bloom152Basis of gelatin
Briliant Blue Ponceau0.3Coloring agent
Sunset Yellow0.3Coloring agent
Titanium Dioxide16Opacifier
Water120 LSolvent
Sorbitol Liquid16Plasticizer

Preparation of Soft Gelation Capsule Solution:
The gel is prepared in a 100 liter stainless steel vessel:
  1. Gelatin Powder is mixed with water and glycerin, then heat and stir it.
  2. After the molten gelatin mass is formed, decanted into 200 kg mobile vessels.
  3. Mix the molten gelatin mass using turbine mixer then add color and flavors agent.
  4. It ensure consistency of gelatin mass
  5. This mass is kept at a constant temperature until it is needed for the next stage of the process