Most people are familiar with capsules, whether for taking medicine or nutritional fortification supplements, large or small, of all kinds. In fact, its raw materials, HPMC and pullulan polysaccharide, are suitable for vegetarians, but there are quite a few differences in the source, price, oxygen permeability, and other properties. This article focuses on the different dimensions of HPMC and Pullulan Polysaccharide, and by comparing them, it can help one to choose which material is more suitable for their needs.
The main task of the capsule is to protect the drug or active ingredient inside from deterioration, so it is crucial that the nature of the components of the capsule interacts with the elements inside.
Source
Pullulan in capsules is made from corn starch fermentation, while HPMC is made from cotton fiber. Pullulan is completely natural, while HPMC is semi-synthetic.
Pullulan polysaccharide is derived from the fermentation of the sprouting stalk mold, hence the name sprouting stalks polysaccharide, and the main raw material is corn starch. Pullulan polysaccharide is a straight-chain polysaccharide made of maltotriose repeating unit connected by α-1,4 glycosidic bond and polymerized by α-1,6 glycosidic bond, with a molecular weight of 20,000~2 million and polymerization degree of 100~5000. It is composed of about 480 maltotrioses.
HPMC (Hypromellose), also known as hydroxypropyl methylcellulose, is one of the non-ionic cellulose mixed ethers. It is a semi-synthetic, which is made through a variety of chemical reactions and processes such as alkali immersion.
Moisture
The moisture content of pullulan capsules is about 10%-13%, while the moisture content of HPMC capsules is 5%-8%. Because of the high moisture content of pullulan polysaccharide capsules, it is not suitable for filling moisture-sensitive materials and hygroscopic powders and liquids. If filled with hygroscopic powders, it will quickly lose moisture and become brittle, losing the function of protecting the filler. But HPMC is the perfect choice.
Price
The price of pullulan is roughly twice that of HPMC, which also causes the price of pullulan capsules to be much higher than the price of HPMC capsules. This is the main reason why many manufacturers do not choose it, despite its inherently superior properties. However, with the increase and release of the production capacity of Pullulan and the innovation of technology, I think its price will slowly come down, and it will even be comparable to the cost of HMPC.
Certificates
Both Pullulan and HPMC can meet vegetarian, religious, and some special requirements. They both have certificates including Vegetarian, Non-GMO, Halal, Kosher, TSE/BSE free, Gluten/Preservative Free and in addition, pullulan can obtain the organic certificate than HPMC. Because pullulan is 100% naturally fermented, while HPMC is produced through a chemical process.
Safety
There is no safety risk to our body for both pullulan and HPMC capsules. HPMC capsules are approved for use by many national FDA authorities. The source of pullulan capsules is purely natural ingredients without any added chemical or synthetic ingredients, which is safe and healthy for our bodies.
Allergens
Pullulan capsules and HPMC capsules are free of all the most common food allergens, including peanuts, nuts, eggs, milk (milk protein and lactose), fish, shellfish, soy, wheat, barley, sesame, and gluten.
Oxygen Transmission Rate
The oxygen permeability of pullulan capsules is approximately one 300th of the oxygen permeability of HPMC capsules, under the same conditions. The oxygen transfer rate of pullulan capsules is 0.4 cm3/m2-day, while the oxygen transfer rate of HPMC capsules is 127 cm3/m2-day. Therefore, pullulan capsules are the best choice for filling oxygen-sensitive materials.
Hygroscopicity
The hygroscopicity of HPMC capsules is much lower than that of pullulan capsules because of the presence of methoxy and hydroxypropyl in the structure of HPMC, which makes it difficult to form hydrogen bonds with water. However, its water-keeping property is similar to that of Pullulan. The moisture sorption and desorption properties are critical to the drug/component that the capsule is filled with, and the amount of moisture content directly affects the activity, stability, and efficacy of the filled component.
Chemical Stability
Both pullulan and HPMC are inert, do not react with other substances, are quite stable, and are excellent raw materials for capsules.
Summary
Both pullulan and HPMC are excellent raw materials for capsules, both are inert, very stable, harmless to humans, and excellent at protecting the filler.
I believe that sometimes the disadvantages are more important than the advantages. The advantages determine where you do better, while the disadvantages specify what you cannot do without doing more harm.
This leads to the conclusion that the main differences between pullulan capsules and HPMC capsules are as follows: 1. Pullulan capsules are more expensive than HPMC capsules. 2. The oxygen passage rate of HPMC capsules is much higher than that of pullulan, so it is not suitable for oxygen-sensitive filler materials. 3. Because of the high water content and high water absorption of pullulan, it is not suitable for powders with high water absorption to avoid becoming brittle and broken.
By now, I believe you should have a good understanding of your ideal capsule raw material in your mind.
