The manufacturing process of softgel capsules
How are soft gel capsules manufactured?
That question is one often asked by many curious people. Before diving into the manufacturing journey from concept to capsule, it helps to understand what softgel capsules actually are and why they have become such a versatile dosage form.
Soft capsules are commercially manufactured applying the rotary-die technology, a technique that traces its roots back to the 19th century with the innovations of the pharmacist Robert P. Scherer. It involves a series of operations that are performed in parallel to each other and are typically highly standardized at each manufacturer: gel mass preparation, fill mass preparation, encapsulation, drying, inspection, and (bulk) packaging.
We’ll outline the whole process from start to finish in this short blog article.
Gel mass preparation
The process begins with gel mass preparation. The unique property of gelatin for thermoreversible transition between its sol and gel state is used throughout the manufacturing process of softgel capsules. Gelatin is initially dissolved in a hot mixture of water and plasticizers to form a viscous and clear solution. After an optional coloration step, it is supplied for encapsulation while stored at elevated temperatures.
Encapsulation process of softgel capsules
After the mass preparation, the gelatin mass is then spread onto cooled drums to form two thin, continuous ribbons of gelatin, which will become the shell of the capsule. The composition of this shell is the result of careful shell formulation development, where gelatin type, plasticizers, and other excipients are selected to ensure compatibility with the fill.
During the rotary-die encapsulation process, the cast gelatin ribbons are fed between two rotating die rolls. The capsule fill is dosed volumetrically and is injected precisely into the pockets that form each capsule. A ribbon lubricant is applied to the wet gelatin ribbon for easier transport on the metal parts of the encapsulation machine. The rotary dies, seals, and then cuts individual capsules from the ribbons. At this stage, the water content of the capsule shell is approximately 35-40%.
Drying of softgel capsules
Once formed, the capsules are dried to reduce their moisture content to approximately. 10%. The drying takes place in conditioned rooms or chambers, either on trays or in rotating perforated tumblers. It is discontinued once the target endpoint is reached. The appropriate endpoint of the drying process is defined during development and can vary for each product.
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Die rolls of a softgel encapsulation machine
Final steps
The final step sees the capsules then go through inspection for size, shape, and potential defects, after which they are sorted, optionally printed, polished, and packed for distribution. Some products may be coated with a functional coat, e.g,. with gastro-resistant properties.
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Equipment and batch sizes
Specific equipment and room conditions are required for each operation of softgel manufacture. The commonly employed equipment types are listed in Table 1.
Batch sizes for softgel manufacturing can vary widely, based on the production capacity of the manufacturer and the market demand for the product. Small-scale production could range from a few thousand to hundreds of thousands of capsules, while large-scale commercial production can exceed millions of capsules per batch.
Table 1: Commonly used equipment for manufacture of softgel capsules
What are the advantages of the soft gel capsule process?
Softgel manufacturing offers a variety of advantages, including the ability to encapsulate a wide range of fills, from liquids to semi-solids. They provide an excellent option for improving the bioavailability of poorly soluble drugs, masking unpleasant tastes and odors, and ensuring a precise dosage. The flexibility of softgel capsules allows for a broad spectrum of shapes, sizes, and colors, enhancing their aesthetic appeal and facilitating patient compliance.
However, the manufacture of softgel capsules requires significant investment in specialised equipment and premises that allow strict control of temperature and humidity conditions. Most importantly, skilled personnel, often with years of training, are required in order to ensure consistent product quality. This is where independent expertise can be invaluable. Our softgel capsule development consulting draws on 30+ years of CDMO experience to help teams navigate exactly these challenges, from process design to CMC documentation.
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FAQs: Manufacturing of softgel capsules
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Softgel capsules are commercially produced using rotary-die technology, a method developed in the 19th century by pharmacist Robert P. Scherer. The process involves six parallel operations: gel mass preparation, fill mass preparation, encapsulation, drying, inspection, and bulk packaging. Each step is highly standardised within a given manufacturer to ensure consistent quality.
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Two cooled drums spread the gelatin mass into thin, continuous ribbons that become the capsule shell. These ribbons are fed between two rotating die rolls, where the fill is volumetrically dosed and injected into pockets that form each capsule. A ribbon lubricant is applied to ease transport on the machine, and the rotary dies simultaneously form, seal, and cut individual capsules from the ribbons. At this stage, shell water content is around 35 to 40%.
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Freshly encapsulated softgels have a shell water content of approximately 35 to 40%, which must be reduced to around 10% for physical stability. Drying takes place in conditioned rooms or chambers, either on trays or in rotating perforated tumblers. The exact endpoint is defined during development and varies for each product, since drying too little or too much can both compromise stability.
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Batch sizes vary widely based on production capacity and market demand. Small-scale production can range from a few thousand to hundreds of thousands of capsules, while large-scale commercial production can exceed millions of capsules per batch. The continuous nature of rotary-die manufacturing allows efficient scaling from clinical batches to commercial volumes.
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Softgels can encapsulate a wide range of fills from liquids to semi-solids, improve bioavailability of poorly soluble drugs, mask unpleasant tastes and odours, and ensure precise dosing. They also offer flexibility in shape, size, and colour. The main challenges are the significant investment required in specialised equipment and premises with strict temperature and humidity control, and the need for skilled personnel, often with years of training, to maintain consistent product quality.