Gelatin capsules are made by extracting collagen from animal bones and hides, dissolving it into a warm liquid solution, then dipping or molding metal pins into that solution to form the familiar two-piece shell. The process is surprisingly mechanical, relying on precision-engineered machines that can produce millions of capsules per day. Hard capsules and soft gel capsules follow different manufacturing paths, but both start with the same core ingredient.
Where the Gelatin Comes From
Gelatin is a protein derived from collagen, the structural material in animal skin, bones, and connective tissue. Manufacturers typically source it from cattle (bovine) or pigs (porcine), with mammalian collagen preferred over fish or other animal sources because it produces a more stable gel. The raw hides or bones arrive at processing plants where they undergo one of two treatments to break down the collagen into usable gelatin.
Acid hydrolysis soaks the raw material in acid to break the collagen apart, producing what’s known as Type A gelatin (most often from pigskin). Alkaline hydrolysis uses a lime or base solution over a longer period and yields Type B gelatin (typically from cattle bones and hides). Both methods dissolve the collagen into a solution that, once purified and dried, becomes the powdered gelatin shipped to capsule factories. Alkaline processing has an added safety benefit: it further reduces the already low risk of transmissible diseases like BSE (mad cow disease). Regulators also require that bovine materials come from countries free of BSE.
How Hard Capsules Are Formed
Hard gelatin capsules, the two-piece shells you twist apart to see powder inside, are made using a dipping method on automated machines. The process follows a consistent sequence.
First, the gelatin powder is dissolved in purified water at a carefully controlled temperature to create a warm, viscous solution called a “gel mass.” Manufacturers measure two key properties of this solution: bloom strength, which indicates how firm the gel sets, and viscosity, which determines how evenly it coats the molds. Bloom strength for pharmaceutical gelatin ranges from 30 to 300, with higher values producing stiffer, more rigid shells. Colorants, opacifiers like titanium dioxide (which gives capsules their opaque white appearance), and sometimes flavoring agents are stirred into the gel mass at this stage.
Rows of stainless steel pins, shaped precisely like the body and cap of the capsule, are then dipped into the warm gelatin solution. The pins are at a cooler temperature than the liquid, so a thin, uniform film of gelatin solidifies around each pin as it’s withdrawn. The coated pins pass through a series of drying chambers where controlled airflow removes moisture gradually. Drying too fast would cause cracking; too slow would leave the shells sticky. The target is a residual moisture content that keeps the shells flexible enough to handle without becoming brittle or soft. Even small shifts in moisture, whether from storage conditions or from the capsule’s own contents, can cause brittleness or stickiness down the line.
Once dried, the capsule halves are stripped off the pins by mechanical arms. Each shell is trimmed to a precise length, then the body (the longer half) and cap (the shorter half) are loosely joined together. At this point, the empty capsules are sorted by size, inspected for defects like dents, thin spots, or uneven edges, and packed for shipment to pharmaceutical or supplement companies that will fill them with their product.
How Softgels Are Made Differently
Softgels, the one-piece oval capsules that hold liquid or oil-based fills, are manufactured in a completely different way. Instead of dipping pins, softgel production uses a rotary die process that forms, fills, and seals the capsule in a single continuous step.
The gelatin solution for softgels includes a plasticizer, typically glycerin, sorbitol, or a blend of both. These plasticizers are what give softgels their characteristic flexibility. The ratio matters: a 1:1 blend of sorbitol to glycerin (at about 30% of the water weight) tends to produce the best balance of flexibility and structural integrity, meeting pharmacopeia standards for both brittleness and disintegration time. The preferred bloom strength for softgel gelatin falls in the medium range of 150 to 220, and viscosity is held between about 2.8 and 4.5 millipascal-seconds at 60°C.
In the rotary die machine, this plasticized gelatin is spread into two thin, continuous ribbons on rotating drums. The ribbons feed down either side of a pair of rotating dies, metal cylinders with capsule-shaped pockets carved into their surface. As the two ribbons meet between the dies, a precisely metered dose of liquid fill is injected between them by a pump called a “wedge.” The dies press together, cutting and heat-sealing the gelatin ribbons around the fill in one motion. Freshly formed softgels drop into a collection basket and then move to drying tunnels, where they lose excess moisture over several days until they reach a stable, firm texture.
What Goes Into the Shell Besides Gelatin
Pure gelatin and water alone would produce a clear, colorless capsule. Most commercial capsules contain several additional ingredients to control appearance, stability, and performance.
- Titanium dioxide is the most widely used opacifier, present in the majority of tablet and capsule products on the market. It provides a bright white base that blocks light, which helps protect light-sensitive medications inside. The European Union has moved toward restricting its use as a food additive (E171), but finding replacements has proven difficult. No current alternative matches its whiteness, light-blocking ability, or consistency at manufacturing scale.
- Colorants such as iron oxides or food-grade dyes give capsules their distinctive colors, both for branding and to help patients tell medications apart.
- Plasticizers like glycerin and sorbitol are essential in softgels but sometimes added in small amounts to hard capsules to fine-tune flexibility.
- Water remains a critical component even in the finished product. Hard capsule shells typically need to retain a specific equilibrium moisture level. Too dry and they crack during filling or handling; too moist and they become tacky or deform.
Quality Testing Before Capsules Ship
Every batch of capsules goes through a series of quality checks before reaching a pharmacy shelf. One of the most important is the disintegration test, which confirms that the capsule will break apart fast enough in your stomach for the contents to be absorbed. The United States Pharmacopeia sets the standard: capsules must disintegrate in less than 30 minutes under test conditions that simulate the digestive environment. Capsules that fail this threshold, whether because of excess moisture loss during storage, cross-linking of the gelatin, or formulation problems, are rejected.
Manufacturers also test for uniform wall thickness (which affects both strength and dissolution), dimensional accuracy so the caps and bodies fit together with the right amount of resistance, and moisture content of the finished shells. Capsules are sampled from production runs and checked for visual defects like bubbles, splits, or color inconsistency. Because gelatin is hygroscopic, meaning it readily absorbs or releases moisture depending on its surroundings, finished capsules are packaged in moisture-controlled containers to maintain stability through distribution and storage.
Vegetarian Alternatives
For people who avoid animal products, capsules made from hydroxypropyl methylcellulose (HPMC), a plant-derived cellulose, or from pullulan, a polysaccharide produced by fermentation, serve as alternatives. These shells are manufactured using similar dipping or die processes but require different formulation adjustments because plant-based polymers don’t gel the same way collagen does. They tend to be more sensitive to humidity and can behave differently in dissolution testing. Still, they’ve become increasingly common in the supplement industry, and most major capsule manufacturers now offer both gelatin and vegetarian product lines.