HPMC (Hypromellose)

HPMC grades and forms

HPMC (hydroxypropyl methylcellulose, also called hypromellose) is a semi-synthetic cellulose ether. Food supplement manufacturers use it as a capsule-shell polymer, tablet binder, film-coating polymer and thickener. In the EU it is the food additive E464. It adds no nutrient to a formula and is bought only for its technological function.

HPMC powder grades differ in three main ways:

• Viscosity: the nominal viscosity of a standard aqueous solution. Low-viscosity grades suit film coating and binder solutions. High-viscosity grades suit thickening and matrix tablets.
• Substitution type: the balance of methoxy and hydroxypropoxy groups. It sets solubility behaviour and the temperature at which solutions gel.
• Particle size: finer powders hydrate faster. Coarser powders disperse with fewer lumps and flow better in direct compression.

The application decides the grade. A coating line needs a grade that sprays at a workable solids content. A matrix tablet needs a high-viscosity grade. Whether you need food grade or pharmacopoeia grade depends on your own specification and markets. SoleChem supplies HPMC to supplement manufacturers in Europe and sends the specification sheet and certificate of analysis with its quote. State the viscosity and grade you need in the quote form.

EU regulatory status

HPMC is a food additive, not a source of a vitamin or mineral. It is therefore governed by Regulation (EC) No 1333/2008, not by the nutrient-form lists of Directive 2002/46/EC. E464 belongs to Group I of the additives in Annex II of that regulation. Group I additives are listed at quantum satis in Annex II Part C. Check the conditions of use for food supplements (food category 17) in Annex II Part E.

Specifications for food additives are set in Regulation (EU) No 231/2012; check the purity criteria in its E464 entry. Material used as an additive must meet that specification. The certificate of analysis should confirm conformity.

Food additives within the scope of Regulation (EC) No 1333/2008 are excluded from Regulation (EU) 2015/2283 on novel foods. The novel food guide explains how that exclusion works. Conditions of use for E464 are set at EU level in Annex II of Regulation (EC) No 1333/2008.

On the label, additives are declared in the ingredients list under Regulation (EU) No 1169/2011. This includes HPMC in a capsule shell or film coat. Check the declaration format in the labelling guide.

Formulation notes

HPMC dissolves in cold water but not in hot water. Its solutions gel reversibly on heating, at a temperature set by the substitution type. To avoid lumps, disperse the powder in hot water, then cool or add cold water while stirring. Dry blending with other powders before adding water also prevents clumping.

HPMC is non-ionic. It does not form salts with mineral ions or charged actives, so it is compatible with most vitamin, mineral and botanical ingredients. It takes up moisture from air, so keep containers closed between uses.

• Capsules: HPMC shells are the usual plant-derived alternative to gelatin. They hold less water than gelatin shells and do not turn brittle when dry, which suits hygroscopic fills. Shell opening can start more slowly than with gelatin, so test dissolution on the finished product. See ingredients for capsules.
• Tablets: low-viscosity grades act as binders in wet granulation and as the main polymer in film coats, usually with a plasticiser. High-viscosity grades form a gel layer that slows release from matrix tablets. See ingredients for tablets.
• Powders and liquids: HPMC thickens and stabilises suspensions. Its cold-water solubility suits drink powders if it is pre-blended with the other dry ingredients. See ingredients for powders and sports nutrition.

For flow agents, fillers and other binders, see Excipients & Processing Aids.