The manufacturing process of softgel capsules
How are soft gel capsules manufactured?
That question is one often asked by many curious people. Delving into the manufacturing process unveils a fascinating journey from concept to capsule.
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 gell 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. 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 on 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 approx. 35-40%.
Drying of softgel capsules
Once formed, the capsules are dried to reduce their moisture content to approx. 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 end point of the drying process is defined during development and can vary for each product.
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.
Want to know more about the common errors in softgel capsule development? Don’t forget to read our free e-book, The 8 Most Common Pitfalls of Soft Capsule Development.
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 which allow strict control of temperature and humidity conditions. Most importantly, skilled personnel, often with years of training, is required in order to ensure consistent product quality.
How we can support your softgel development project
Our team offers the following:
+ Independent technical expertise for softgel manufacturing facilities
+ Structured and systematic approach during troubleshooting
+ State-of-the-art CMC regulatory documentation for soft capsules
+ Analytical expertise for supportive testing