A guar gum certificate of analysis (CoA) should show viscosity with its full method, moisture, mesh size, ash, acid-insoluble residue, protein and pH. For food grade it should also show microbiology. Pesticides, ethylene oxide, heavy metals and aflatoxin are often reported on separate lab reports.
The CoA should match your specification line by line, with the same units and methods. If it does not, you cannot tell whether the lot passes.
Agree the CoA format before the first order. Send the supplier your spec as a table and ask them to report against it in the same order. That small step saves a lot of back and forth later.
Core physical and chemical tests
- Viscosity: at a stated concentration, temperature, instrument, spindle, speed and time.
- Moisture (loss on drying): affects shelf life and viscosity basis.
- Particle size: percentage passing a named mesh.
- Total ash: a sign of mineral matter and husk.
- Acid-insoluble residue or matter: shows husk and other insoluble material.
- Protein: higher protein suggests germ left in the split.
- pH of a solution.
- Gum or galactomannan content, where your market's purity criteria require it.
- A simple starch check, such as an iodine test, to screen for added starch.
- Appearance, colour and odour.
Microbiology for food grade
More on this in what microbiological specs apply to food-grade guar gum.
- Total plate count.
- Yeast and mould.
- Coliforms and E. coli.
- Salmonella, usually absent in 25 g.
- Any further organisms your use requires.
Contaminants
These tests are usually done by an outside lab, either per batch or at agreed intervals. Ask which, and make sure the frequency suits your risk.
- Pesticide residues: a multi-residue screen against your market's limits.
- Ethylene oxide and 2-chloroethanol: especially for the EU.
- Heavy metals: lead, arsenic, cadmium and mercury.
- Aflatoxins, where your customers ask.
- Other contaminants your market or customers set limits for, such as dioxins or pentachlorophenol, which have affected guar in the past.
What a good CoA looks like
For general advice, see how to read a lab certificate. A supplier's in-house CoA is useful, but verify it with an independent lab, at least on early shipments and then at regular intervals.
- Plant name, address and batch number that matches the bag marking.
- Production date and best-before or retest date.
- Each result shown with the specification limit and the method.
- Signed by a named person, with the lab named.
- Results given as actual figures, not just "complies" or "passes".
- Accredited lab reports attached for tests the plant does not run in-house.
How Creston & Co handles this
We review each CoA against your spec, draw independent samples during inspection and have them tested at an NABL-accredited lab. You get the original reports with the plant's name on them. Ask for a free sourcing review.