Specifications
Psyllium Husk Purity Grades Explained: 85% to 99%
TL;DR. Psyllium husk purity is measured by swell volume in water, not by chemical assay. The standard B2B grades are 85%, 90%, 95%, 98%, and 99%, corresponding to swell volumes of ≥28, ≥32, ≥36, ≥38, and ≥40 ml/g respectively. 99% is the only grade that meets USP, EP, BP, and IP pharmacopoeial requirements. Below we explain what each grade actually delivers, when to use it, and where buyers typically over-spec.
What “purity” means in psyllium husk
Unlike chemical APIs, psyllium husk purity is not a chromatographic assay. The industry-standard test is the USP swell volume method: 1 g of husk is hydrated in 100 ml of water at 25 °C for 24 hours, and the volume of the resulting gel is measured.
The “%” grading reflects the proportion of high-mucilage seed-coat fragments versus low-fibre fines, broken seed, and inert matter. Higher purity = more soluble fibre per kilo of finished product.
Grade-by-grade comparison
| Grade | Min. Swell Volume | Light Foreign Matter | Pharmacopoeia | Typical Use |
|---|---|---|---|---|
| 85% | 28 ml/g | ≤ 5% | – | Animal feed, low-cost food fortification |
| 90% | 32 ml/g | ≤ 3% | – | Bakery flour blends, generic fibre |
| 95% | 36 ml/g | ≤ 2% | – | Mid-tier supplements, beverage premixes |
| 98% | 38 ml/g | ≤ 1% | – | Premium capsule fill, retail private-label |
| 99% | 40 ml/g | ≤ 0.5% | USP / EP / BP / IP | Pharmaceutical, OTC laxatives, FDA heart-health-claim formulations |
When 99% pharma grade pays off
You should specify 99% only if at least one of these is true:
- Your end-product references a USP, EP, BP, or IP monograph on the label or in the regulatory filing.
- You’re filing for an FDA-authorised heart-health claim (which references 7 g psyllium fibre/day from soluble-fibre sources meeting USP).
- The destination market’s regulator (e.g. Drug Authority of Saudi Arabia, AESAN in Spain) requires pharmacopoeial-grade fibre.
- Your buyer’s QC team specifies USP swell volume in the supplier qualification protocol.
If none of the above apply, 95% or 98% delivers the same in-product fibre experience at 12-18% lower landed cost.
Common buyer mistakes
- Over-spec’ing 99% for a generic fibre powder. The end-consumer cannot distinguish between 95% and 99% in a stick-pack. Save the margin.
- Conflating purity with mesh. A 99% purity powder at mesh 40 is wrong for a capsule fill regardless of swell volume, particle size is a separate axis. See our grade & mesh guide.
- Not asking for the swell-volume test report. Some suppliers grade by visual inspection of fines content, which under-reports purity in dusty lots. Always request the USP swell volume number on the COA.
- Switching grades mid-formulation. Purity drives swell volume, which drives gelling kinetics, which drives capsule fill density and beverage mouthfeel. Pilot every grade change.
How to verify purity in-house
Two practical methods your QC team can run without specialised equipment:
- Swell volume: 1 g sample + 100 ml water, 24 h at 25 °C, measure gel volume in a graduated cylinder. Repeats < 5% variance indicate consistent purity grade.
- Light foreign matter: 10 g sample, sieve through 40 mesh, weigh residue. Anything > 0.5% in a “99%” lot means the supplier is mis-grading.
For audit-grade verification, send a sample to a NABL or ISO 17025 lab for an independent USP <785> swell volume report.
Frequently asked questions
Is 99% purity always better than 95%?
Not in functional terms for most retail supplements. 99% is “better” only if your buyer or regulator requires pharmacopoeial-grade material. Otherwise 95% or 98% is the better economics.
What does “99% purity” actually mean?
It means the lot meets a swell volume of ≥40 ml/g (USP method) and ≤0.5% light foreign matter. The “99%” is a market-standard grading, not a chemical assay percentage.
Does organic certification affect purity?
No. Organic and conventional psyllium are graded on the same swell-volume scale. Organic psyllium is available across the full 85-99% range.
What is the price spread between grades?
From 85% to 99%, expect roughly a 35-50% price spread on FOB India terms, depending on harvest year and organic premium. The biggest jump is 95% → 99% as the fines-removal yield drops sharply at the top end.
Want a side-by-side sample of two purity grades to pilot internally? Request a comparative sample, we’ll ship two lots with COAs at no charge for qualified B2B buyers.