How to read a gum acacia certificate of analysis

What is on a gum acacia certificate of analysis?

A gum acacia certificate of analysis reports what one specific lot measured against the agreed specification. The parameters are consistent across suppliers: appearance, loss on drying, total ash, acid-insoluble ash, pH, solution viscosity, specific optical rotation, identity tests for starch and tannins, heavy metals, and a microbiological panel. The document also states the standards the lot conforms to, normally E 414, Ph. Eur., USP and FCC. Some rows carry a number, some carry the word conforms, and the difference between those two cases is where most questions start.

One row on that document is quantitative proof of which species you received. Specific optical rotation is dextrorotatory for Acacia seyal and levorotatory for Acacia senegal, so the sign of the result identifies the material without ambiguity. Most of the other rows describe purity and processing quality.

We answer the same handful of COA questions every month, usually from a QA reviewer looking at gum arabic paperwork for the first time. What follows is how to read the document line by line.

A specification and a COA are two different documents

The specification states the limits the material has to meet. It does not change between shipments. The certificate of analysis reports what a single lot actually measured.

Qualify a material against the specification. Check each delivery against the COA. When the two documents disagree in format, which happens more than you would expect, the specification governs.

Loss on drying

Loss on drying is the moisture figure. The published monographs set a ceiling rather than a target, so a lower number is not a better product.

Consistency matters more than the absolute value. Moisture affects powder flow, the tendency to cake in storage, and the dry weight you are paying for. A lot that arrives noticeably wetter or drier than the ones before it is worth asking about even when it passes.

Total ash and acid-insoluble ash

Total ash is the mineral content left after ignition. Gum acacia carries calcium, magnesium and potassium salts naturally, so ash is expected and a result inside the limit says nothing is wrong.

Acid-insoluble ash is the more informative of the two. It is the fraction of that mineral residue that will not dissolve in acid, which in practice means sand, bark and field debris that survived cleaning. A low result means the raw gum was properly cleaned before it was dissolved and spray dried. Of all the routine parameters, this is the one that tells you the most about processing quality.

pH

Gum acacia solutions sit mildly acidic. Acacia seyal typically runs a little higher than Acacia senegal, though the ranges overlap and pH alone will not identify a species.

The number matters if you are formulating close to a pH boundary, and it matters in beverage systems where the gum contributes to the buffer. In most dry blends it is informational.

Solution viscosity

Gum acacia is prized for staying low in viscosity at concentrations that would turn most hydrocolloids into a gel. That is what lets an emulsion concentrate carry 25 or 30 percent solids and still pour.

A viscosity result is only comparable when the conditions match. Solids concentration, temperature, spindle and speed all have to be the same, which is why they are printed alongside the number. Two lots measured at different concentrations cannot be compared, and neither can two suppliers using different methods.

Viscosity moves lot to lot because gum acacia is a tree exudate. Molecular weight distribution shifts with species, growing conditions and harvest. Movement inside the specification is normal.

Starch, dextrin, agar and tannins

These rows are the adulteration tests, and they are the reason a COA is worth more than a price sheet.

Gum acacia sells at a premium over starches, dextrins and cheaper hydrocolloids, so the economic incentive to cut it runs one way. The starch, dextrin and agar test and the tannin test both report against a requirement rather than as a number, and a passing result says the material is what the label claims.

They matter most when you are qualifying a new supplier or a new origin. A grade that meets every purity limit and fails an identity test is not a borderline lot, it is a different material.

Specific optical rotation, the proof of species

This is the most useful row on a gum acacia COA. Specific optical rotation is quantitative, measured proof of which species you received, and the two species rotate polarized light in opposite directions.

• Dextrorotatory, a positive value, is Acacia seyal.
• Levorotatory, a negative value, is Acacia senegal.

The sign settles it. No other routine parameter separates the two species that cleanly: pH and colour overlap, and viscosity moves with harvest. If a COA reports a negative rotation on material sold as seyal, the species is wrong, and that is worth raising before the lot goes into production.

This row also generates more correspondence than any other, for a reason that has nothing to do with the measurement.

Specifications often write the requirement qualitatively. A seyal specification will say the material must be dextrorotatory and list the test method, polarimetry, instead of a numeric range, because any positive value satisfies the requirement. The COA then reports the measured result, a positive number, with the word conforms in the compliance column.

QA reviewers read that as a mismatch, because the specification row and the COA row do not look alike. They are not in conflict. One field describes how the parameter is tested. The other reports whether the result met the requirement. Both documents are correct and no corrected COA is owed.

Particle size and bulk density

These appear on some COAs and not others, and they matter most for dry-blend and stick-pack work where the gum has to behave on a filling line. Agglomerated grades are engineered for faster wetting and dispersion, which shows up as a coarser particle and a different bulk density than the spray-dried powder of the same species. We covered how that affects line performance in choosing gum acacia for stick packs.

Heavy metals

Lead, arsenic, cadmium and mercury are tested against the limits in the applicable monograph. Those limits tightened substantially in the 2026 specification revision, by a factor of twenty to forty on some elements, without the material itself changing. If your QA file still carries the older limits, the 2026 specification update explains what moved and what to check.

Microbiology

The standard panel covers total plate count, yeast and mold, and the pathogen tests. Gum acacia is a low-water-activity powder, so results are normally well inside limits.

Where this gets specific is in applications with a tighter micro requirement than the monograph sets. Some grades are processed for a lower count and are sold on that basis. If a low micro count is why a particular grade was chosen, say so when you are comparing alternatives, because two grades can match on species and form and still differ here.

What normal variation looks like

Viscosity, color, moisture and ash all move between lots. That is what a natural exudate does. The specification exists to bound that movement, and a result that sits in a different part of the range than last time is still a passing result.

Color is the one that generates the most calls, particularly on seyal grades, where the dry powder runs from cream to beige. Color moves with harvest and with how the gum was processed. It is not a purity measure.

If you are seeing movement that affects your process rather than just your paperwork, that is worth a conversation with whoever supplies the material.

Frequently asked

What is the difference between a specification and a certificate of analysis?

A specification states the limits the material must meet and stays the same from lot to lot. A certificate of analysis reports what a specific lot actually measured. The specification is the contract. The COA is the evidence for one delivery.

Why does my gum acacia COA say conforms instead of a number?

Some parameters are written qualitatively rather than as a numeric range. Specific optical rotation is the usual one: the requirement is that the material is dextrorotatory, so any positive value passes and there is no minimum or maximum to report against. The COA shows the measured result with conforms in the compliance column. That is consistent with a specification that lists the test method rather than a range.

What moisture content should gum acacia have?

Spray-dried gum acacia normally arrives well under the regulatory ceiling for loss on drying. The monographs set an upper limit rather than a target, so a lower result is not a better product. Consistency matters more, because moisture affects flow, caking and the dry weight you are paying for.

Why does viscosity change from one gum acacia lot to the next?

Gum acacia is a tree exudate, so molecular weight distribution varies with species, growing conditions and harvest, and solution viscosity moves with it. A viscosity figure is only comparable when solids concentration, temperature, spindle and speed match.

What does acid-insoluble ash tell you about gum acacia?

It is the cleanliness measure. Acid-insoluble ash captures sand, bark and other field material that survives processing. A low result indicates the raw gum was well cleaned before dissolving and spray drying.

Does a gum acacia COA identify the species?

Yes. Specific optical rotation is quantitative proof of species, and the two rotate polarized light in opposite directions. A dextrorotatory result, a positive value, is Acacia seyal. A levorotatory result, a negative value, is Acacia senegal. The sign settles it, where pH and colour overlap between the two.

Is gum arabic dextrorotatory or levorotatory?

It depends on the species. Acacia seyal is dextrorotatory and gives a positive specific optical rotation. Acacia senegal is levorotatory and gives a negative value. That opposition is what makes the parameter the definitive species identification on a gum acacia certificate of analysis.

If you are reviewing a gum acacia COA and something on it does not read the way you expect, please get in touch.