A soft gel or soft gelatin capsule is a solid capsule (outer shell) surrounding a liquid or semi-solid center (inner fill). An active ingredient can be incorporated into the outer shell, the inner fill, or both. They are oral dosage form for medicine similar to capsules. Soft gel shells are a combination of gelatin, water and a plasticizer such as glycerin and/or sorbitol.
Soft gel is composed of a gelatin or potato starch matrix. Gelatin matrix consists of gelatin, plasticizer, solvent and optional ingredients such as flavors and colorants.
GELATIN– bovine, porcine, or piscine (fish) origin. Comes in a variety of bloom strengths, the higher the bloom strength, the more resilient the gel. Most oil based fills are encapsulated using a bloom strength of 150. When polyethylene (PEG) based fills are used, a higher bloom strength is generally used. The limitations of bovine (i.e. bovine-related diseases) and porcine (i.e. not kosher) gelatin may be overcome by piscine (fish) gelatin.
PLASTICIZER– Glycerin and Sorbitol Special are the two most common plasticizers. Glycerin is generally used with oil based fills. Sorbitol Special is used with PEG based fills. Sorbitol is not soluble in PEG and therefore will not leach out of the shell into the PEG based fill like Glycerin would. Sorbitol Special is formulated to inhibit sorbitol from crystallizing out in the gelatin shell. Do not substitute Sorbitol for Sorbitol Special.