E6, E18 and E25 can be useful commercial shorthand—but they are not a complete specification. Buyers should not treat the number as a universal purity percentage or assume that a larger number automatically creates the lowest cost in every application.
Ask the supplier to define E
Request the exact test method, wavelength, sample concentration, dilution, path length, moisture basis and calculation. Two suppliers can use similar grade language while testing under different conditions. Without the method, the number is difficult to compare.
Separate colour strength from purity
An absorbance-based colour value can help describe intensity under stated conditions. It does not by itself identify every protein, sugar, mineral, carrier or impurity in the powder. Ask for identity, composition and contaminant specifications separately. Avoid rewriting an E value as “percent pure” unless the supplier provides a validated definition supporting that statement.
Prepare equal-concentration drawdowns
Make solutions using the same mass, water, temperature, mixing time and container. Photograph them under controlled light, then test graded dosages in the actual formula. This shows both intrinsic colour strength and practical behaviour.
Test process and storage, not only fresh colour
A higher initial blue is not useful if the colour fades, sediments or changes flavour in the finished product. Run the intended pH, heat, light and storage conditions. Published phycocyanin stability research demonstrates why temperature and pH belong in the comparison.
Calculate cost-in-use
For each candidate, calculate the ingredient cost per finished unit at the dose that meets the colour specification after processing and shelf life. Add freight, duties, MOQ, yield, rework and packaging changes. The cheapest kilogram can become the most expensive finished unit.
Use a comparison table
- Supplier and lot
- Declared grade and complete method
- Moisture and composition basis
- Dose needed in the actual formula
- Fresh and aged colour values
- Sensory and sediment observations
- Landed cost per finished unit
- COA and specification completeness
Reject comparisons that cannot be reproduced
If a quotation lists only “E25 premium” with no method, ask for the missing conditions. Do not combine colour values taken at different wavelengths, dilutions or moisture bases in one ranking. Keep original supplier reports in the comparison file so the team can see which numbers are genuinely comparable and which are only descriptive.
Ask for an application recommendation, then verify it
A supplier may recommend a starting dose based on similar products. Treat that as a useful hypothesis, not a guarantee. Ask what formula, pH, process and storage support the recommendation. Run the dose ladder in the buyer’s own product and record both fresh and aged cost-in-use before approving the grade.
Make the next supplier conversation more useful
When contacting AimGrow, include the application, target shade, process and current benchmark. Review AimGrow Blue Spirulina and request the current specification and method definition. Compare verified documents and pilots—not grade names alone.