In the century-old history of capsules, gelatin has always maintained its position as the mainstream capsule material due to its wide range of sources, stable physical and chemical properties, and excellent processing performance. With the increase of people’s preference for capsules, hollow capsules are more widely used in the fields of food, medicine and health care products.

However, the occurrence and spread of mad cow disease and foot-and-mouth disease have raised concerns about animal-derived products. The most commonly used raw materials for gelatin are cattle and pig bones and skins, and its risks have gradually attracted people’s attention. In order to reduce the safety risk of empty capsule raw materials, experts in the industry continue to research and develop suitable plant-derived capsule materials.

In addition, as the variety of capsules increases, the diversity of their contents gradually makes people realize that gelatin hollow capsules have compatibility problems with some contents with special properties. For example, content containing aldehyde groups or reacting to form aldehyde groups under certain conditions may lead to cross-linking of gelatin; highly reducing content may undergo Maillard reaction (Mailard reaction) with gelatin Reaction); the hygroscopic content will cause the shell of the gelatin capsule to lose water and lose its original toughness. The above-mentioned stability problems of gelatin hollow capsules have drawn more attention to the development of new capsule materials.

Many attempts have been made. Chinese patent literature application number 200810061238.X applied for the use of sodium cellulose sulfate as the main capsule material; 200510013285.3 applied for the use of starch or starch composition as the main capsule material; Wang GM[1] reported the manufacture of chitosan capsule raw materials Hollow capsules; Xiaoju Zhang et al [2] reported that konjac-soybean protein is the main capsule material. Of course, the most studied ones are cellulose materials. Among them, hollow capsules made of hydroxypropyl methyl cellulose (HPMC) have been mass-produced.

HPMC is widely used in the field of food and medicine, and is a commonly used pharmaceutical excipient, which is recorded in the pharmacopoeias of various countries; FDA and the European Union have approved HPMC as a direct or indirect food additive; GRAS is recorded as a safe substance, No. GRN 000213; included in the JECFA database, INS No.464, does not limit the maximum daily dosage of HPMC; in 1997, the Ministry of Health of China approved it as a food additive and thickener (No. 20), suitable for all kinds of food , according to production needs to add [2-9]. Due to the difference in properties with gelatin, the prescription of HPMC empty capsules is more complicated, and some gelling agents need to be added, such as acacia, carrageenan (seaweed gum), starch, etc.

HPMC hollow capsule is a product with a natural concept. Its material and production process are recognized by Judaism, Islam and Vegetarian Associations. It can meet the needs of people with various religions and dietary habits, and has a high degree of acceptance. In addition, HPMC hollow capsules also have the following unique properties:

Low water content – about 60% lower than gelatin empty capsules

The water content of gelatin hollow capsules is generally 12.5%-17.5%. The temperature and humidity of the environment should be controlled within an appropriate range during the production, transportation, use and storage of empty capsules. The suitable temperature is 15-25°C and the relative humidity is 35%-65%, so that the performance of the product can be maintained for a long time. The water content of HPMC film is very low, generally 4%-5%, which is about 60% lower than that of gelatin hollow capsules. The water exchange with the environment during long-term storage will increase the water content of HPMC empty capsules in the specified packaging, but it will not exceed 9% within 5 years.