You need free glutamate if your question is about the food as eaten — its savoury taste, its seasoning strength, or how much glutamate is immediately present. You need total glutamate if your question is about the protein itself — its overall amino acid makeup after everything is broken apart. Free glutamate is measured directly. Total glutamate is measured after hydrolysis, a chemical step that releases glutamate bound inside protein, so a total result is larger and answers a different question. Ordering the wrong one is the most common way individuals waste money on glutamate testing, and it is entirely avoidable.
The distinction, in plain terms
Glutamate is the form in food of the amino acid glutamic acid. Some of it is already free: dissolved, unattached, available to taste buds and to a measuring instrument without any further chemistry. The rest is bound: built into protein chains, the way beads are built into a necklace. Bound glutamate contributes to nutrition as protein, but it is not free to taste as glutamate until the protein is digested or chemically broken down.
A free amino acid test measures only the free fraction. A total amino acid test first performs hydrolysis — here, treating the sample with 6 N hydrochloric acid at 110 °C for 24 hours — which snips the protein chains and releases their amino acids, then measures everything: what was free plus what was bound. Total therefore includes free. If you subtract, in principle, you approach the bound fraction, though in practice you should ask the lab whether a direct free-versus-total comparison on your sample is valid rather than assuming the arithmetic is clean.
One further complication deserves plain statement, because honest labs will raise it: harsh acid hydrolysis changes some amino acids. In particular, the related amino acids glutamine and asparagine are converted during hydrolysis, which is one reason total-panel interpretation needs care and why a total result should never be read as a simple photograph of the original food. This draft does not quantify that conversion for any food, because no food-specific sourced figure was available at drafting — treat any total number as a hydrolysed-sample measurement, described by the method, not as the food's native state.
Which question do you actually have?
If you are adjusting a seasoning blend and want to know its savoury strength, you have a free question. If you are comparing two sauce recipes as eaten, you have a free question. If you are asking how much MSG-equivalent a serving delivers as eaten, you have a free question, with the conversion handled on a stated basis — see the reporting-bases companion article for the anhydrous and monohydrate arithmetic, cited to PubChem.
If you are characterising a protein ingredient, checking a protein's amino acid composition, or supplying a total-profile figure someone has specifically requested in writing, you may have a total question. If your question is about protein quality in a nutritional sense, pause: a total amino acid profile is one input to that judgement, not the judgement itself, and this page does not make protein-quality claims for any food.
If you are unsure, the most useful sentence you can send a lab is: "I want to know X, as eaten / as protein — which test is that?" A lab that answers by asking what decision the number feeds is advising you. A lab that simply sells you the larger panel is not.
How each is measured here
Free glutamate sits inside the AA-1 free amino acid panel: 19 amino acids plus ammonia, measured by AQC (AccQ-Tag) pre-column derivatization with HPLC-UV. The sample is prepared without hydrolysis, the amino acids are tagged, separated, and measured against a calibrated standard. Cysteine is excluded from the free panel, needing a separate AA-3 workup. Seeing the whole free profile alongside glutamate is useful: it shows whether glutamate dominates the free fraction or is one contributor among many, which changes how you would reformulate.
Total glutamate sits inside AA-T, total amino acid analysis, at $230 per sample, using the hydrolysis conditions above before the same style of measurement. AA-1 costs $150 per sample for liquids, $180 per sample for powders ($150 plus $30 powder preparation), $150 flat for first-time customers, and $125 per sample at 25 or more samples per month.
For complex matrices — a salty, dark, or oily blend — either test can be distorted by the matrix, meaning everything else in the sample. Matrix-effect qualification checks that distortion with a known spike in your actual sample and is priced per sample and matrix on inquiry. A recent single-sample seasoning project with full matrix-effect qualification was $350. Qualification matters most precisely where individuals most often test: a homemade blend whose recipe they are trying to pin down.
Limits that apply to both numbers
Neither number, free or total, tells you how much MSG powder was added to a recipe, because glutamate arrives from many ingredients and the tests measure the combined result. Neither assesses safety, and neither is a regulatory submission: OpenChemWorks, in Davis, California, is not GLP, GMP, or ISO/IEC 17025 accredited, is validating now and reserving pilot slots, and provides results for your own decisions. No turnaround is promised here. And a single sample describes that sample: a reformulation deserves a retest if the number still carries a claim.
Your next step
Decide whether your question ends with "as eaten" or "as protein." Then email info@openchemworks.com with that sentence and a description of the sample. You will be quoted for the test that matches the question — free, total, or, where a comparison is genuinely needed, both, with the reason stated.
Frequently asked questions
Is total glutamate the "real" amount and free just a portion?
Both are real; they measure different fractions. Total includes free plus protein-bound. Calling total "real" smuggles in the assumption that the protein question is your question.
Will total always be much higher?
It will be higher where the food contains substantial protein. How much higher depends on the food, and this page invents no ratio for any food — measure the sample you care about.
Can I convert free glutamate to MSG?
Yes, with a stated form — anhydrous or monohydrate — using molar-mass ratios. The reporting-bases article works the conversion with PubChem-cited masses.
Do I ever need both?
Occasionally, when you need to know both the as-eaten free level and the protein composition, or to understand a bound fraction. Ask the lab to justify the second test in one sentence before paying for it.
What about glutamine on my report?
Ask the lab how glutamine is handled in each panel, especially after hydrolysis. Do not assume a hydrolysed total figure describes native glutamine or native glutamate separately.
References
- PubChem — L-Glutamic acid (CID 33032) — Molar mass 147.13 g/mol, cited for the MSG-equivalent conversions.
- PubChem — Monosodium glutamate (CID 23672308) — Anhydrous MSG 169.11 g/mol; monohydrate 187.13 g/mol.
- Waters — Derivatization of Amino Acids Using Waters AccQ-Tag Chemistry — Method background for AQC derivatization and HPLC-UV amino acid analysis.
- OpenChemWorks — Pricing — Published service and pricing copy (2026).
- British Journal of Nutrition (2023) — asparagine and glutamine lose an amide residue during acid hydrolysis and are measured with aspartate and glutamate respectively.
OpenChemWorks Laboratory · Reviewed by the laboratory director, PhD chemist · Published October 16, 2026