Why Activity, Not Purity, Defines Bromelain
Bromelain (CAS 9001-00-7) is a mixture of cysteine proteases from pineapple, not a single chemical. That single fact drives how the product is bought and sold: a bromelain grade is defined by its enzymatic activity, and two powders that look identical can behave very differently if one has lost activity during processing or storage. This article explains the units, the grades and the quality parameters behind a typical specification. For the wider picture, see the bromelain technical article.
What Is a GDU?
GDU stands for gelatin digesting unit. In the standard assay, a defined quantity of the enzyme is allowed to digest a gelatin substrate under controlled temperature, pH and time, and the result is expressed as GDU per gram. Because the assay is enzymatic rather than gravimetric, it measures what the material can do, not just what it weighs.
Other units appear in the market and in older literature:
- GDU/g – the most common commercial unit for bromelain, often quoted as a minimum (for example 2400 GDU/g).
- mcu – milk-clotting unit, based on the clotting of milk protein.
- FCC PU – the papain unit used in FCC-style specifications for related plant proteases.
When a specification states an activity in one unit, ask whether the test method is stated as well. A number without a method is difficult to compare across suppliers.
Common Bromelain Grades
Bromelain is traded as a family of activity grades rather than a single product. Typical thinking when selecting a grade:
| Grade (activity) | Typical positioning |
|---|---|
| About 2400 GDU/g | Common food-grade / supplement grade; strong activity per unit mass |
| Lower-activity powders | Cost-sensitive food-processing and tenderising blends |
| Higher-activity / purified fractions | Applications that need high specific activity or a narrow enzyme profile |
Higher activity per gram is not automatically “better” – it means less powder is needed to reach a target activity, which matters when the enzyme is a small part of a formulation and the carrier or excipient load has to stay low.
Reading a Bromelain Specification
A complete specification pairs the activity value with limits that decide the grade’s suitability for food, supplement or cosmetic use.
| Parameter | Typical specification | Why it matters |
|---|---|---|
| Appearance | Light yellow color | Indicates a clean, consistent powder |
| Odor | Light pineapple smell | Characteristic of the pineapple source |
| Activity (GDU/g) | ≥2400 | The headline functional parameter |
| Moisture (%) | ≤8 | High moisture shortens shelf life and can lower activity |
| Mesh (%) | 100% pass 80 mesh | Particle size affects blending and dissolution |
| Pb / As (mg/kg) | ≤5 / ≤3 | Heavy-metal limits for food and nutrition use |
| Total plate count | ≤10000 CFU/g | Microbiological quality |
| Salmonella / E. coli | Absent | Safety for food and supplement use |
| Coliform group | ≤30 MPN/g | Hygiene indicator |
| Molds & Yeasts | ≤100 CFU/g | Shelf-life and hygiene indicator |
Activity Loss: What to Watch
Because bromelain is a protein, activity is lost through denaturation. The main risks are heat (prolonged exposure above about 60 C), extreme pH, and high moisture during storage. Practical consequences:
- Re-test activity if the material has been stored warm or for a long time before use.
- Choose a moisture limit that matches your storage and shelf-life requirements.
- Handle powders with dust control, both for activity retention and because enzyme dusts can be respiratory sensitisers.
Frequently Asked Questions
What activity should I specify for bromelain?
2400 GDU/g minimum is a common food and supplement grade; the right value depends on how much carrier load your formulation can accept.
Is higher GDU/g always better?
No. Higher activity means less powder is needed, but the grade should match the application, the cost target and the required enzyme profile.
Why does bromelain lose activity over time?
It is a protein, so heat, extreme pH and moisture denature it and reduce activity; controlled cool, dry storage preserves it.
Where can I buy bromelain?
PolyBlueChem supplies bromelain (CAS 9001-00-7) with COA and MSDS. See also our bromelain buying guide.
References
- PubChem and enzyme database entries for bromelain (CAS 9001-00-7), EC 3.4.22.32.
- Supplier specification sheets for food-grade bromelain standardised at 2400 GDU/g.
- General reference material on enzyme activity units (GDU, mcu, FCC PU).
Disclaimer: This article is provided for general informational purposes only and does not constitute technical, medical, regulatory or safety advice. Always refer to the current safety data sheet and applicable regulations before handling this material.