Glutamic acid is the amino acid behind glutamate, the savoury, umami signal in foods, seasonings, and fermentation broths. It is reported either as free glutamic acid, already present as eaten or in solution, or as total glutamic acid after hydrolysis breaks proteins apart. Those numbers answer different questions. This page explains the difference, shows how a free result converts to a monosodium glutamate (MSG) equivalent on a stated basis using verified molar masses, and names which panel reports each version. Taste and formulation decisions are usually free questions. Protein composition may be a total question.
Chemistry in plain terms
Glutamic acid is an acidic amino acid. In foods and most near-neutral solutions it is present mainly in its ionised form, glutamate, which is why reports switch between the two words. They describe the same amino acid in different chemical states, not two ingredients. MSG is its sodium salt, supplied dry either without added water in its crystal structure (anhydrous) or with one water per unit (monohydrate). The salt weighs more per unit of glutamate than glutamic acid itself, so converting between them is molar-mass arithmetic, not guesswork.
Glutamic acid differs from glutamine by one amide group, a small difference that matters in total analysis, below. No health or safety claim is made here.
Where glutamic acid occurs
Free glutamate occurs naturally in savoury foods and ingredients including tomatoes, aged cheeses, fermented sauces, yeast extracts, and protein hydrolysates, and in seasoning blends where MSG or a glutamate-rich ingredient was added. Bound glutamic acid occurs in almost every protein, built into protein chains. Fermentation and cell culture media can also contain it, as a remainder of microbial or cellular activity.
A result measures the combined amount from all sources at once. It cannot tell you how much MSG powder was added, which ingredient contributed what, or whether a product meets a labelling rule.
Free vs total for glutamic acid
Free glutamic acid is measured without hydrolysis: the as-eaten question. Use it for savoury strength, comparing formulations as eaten, and an MSG equivalent for a serving as consumed.
Total glutamic acid is measured after acid hydrolysis breaks protein chains, so it is free plus formerly bound glutamic acid. It will be larger where a sample has substantial protein, by an amount depending on the sample. No free-to-total ratio is given for any food, because no general ratio is valid.
Hydrolysis is special here. During acid hydrolysis, glutamine converts to glutamic acid, qualitatively, and asparagine converts to aspartic acid. A total result therefore includes glutamate that was originally glutamine. It is a hydrolysed-sample measurement, not a photograph of native glutamic acid alone. That is the British Journal of Nutrition (2023) point, with no conversion percentage stated.
Reporting bases and the MSG conversion. Name the basis before comparing: glutamic acid, glutamate, MSG anhydrous equivalent, or MSG monohydrate equivalent. Verified PubChem molar masses: glutamic acid 147.13, MSG anhydrous 169.11, MSG monohydrate 187.13 (CIDs 33032 and 23672308). As MSG anhydrous equivalent, multiply a glutamic acid result by 169.11 / 147.13, about 1.149. As MSG monohydrate equivalent, multiply by 187.13 / 147.13, about 1.272. Worked shape only, no sample data: 100 units as glutamic acid are about 114.9 units as MSG anhydrous equivalent, or about 127.2 units as MSG monohydrate equivalent. State which form you used; mixing bases creates a false difference.
Method notes: AQC AccQ-Tag HPLC-UV
Free glutamic acid is measured inside AA-1 by AQC (AccQ-Tag) pre-column derivatization with HPLC-UV: tagged, separated by high-performance liquid chromatography, and measured by ultraviolet detection against calibrated standards. Total glutamic acid is measured after hydrolysis, then the same way. No performance number is stated: no detection limit, precision, or recovery figure. For salty, dark, or oily matrices, matrix-effect qualification, checking distortion with a known spike in your sample, may be needed and is priced on inquiry.
Which panel includes it
AA-1 free panel includes glutamic acid: 19 amino acids plus ammonia by AQC HPLC-UV. Cysteine is excluded and needs a separate AA-3 workup. Prices: $150 per sample for liquids, $180 for powders ($150 plus $30 powder preparation), $150 flat for first-time customers, $125 at 25 or more samples per month.
AA-T total analysis includes total glutamic acid, with the glutamine caveat above, at $230 per sample.
Pilot: $250 for 5 samples, credited in full against a first contract signed within 90 days.
OpenChemWorks is validating now and reserving pilot slots. It is not GLP, GMP, or ISO/IEC 17025 accredited. No turnaround is promised here. Email info@openchemworks.com with whether your question ends with "as eaten" or "as protein," plus a sample description.
Frequently asked questions
Is glutamate the same as glutamic acid?
They describe the same amino acid in different chemical states. What matters is the stated reporting basis, especially for an MSG equivalent.
Which MSG form should I use?
The form matching the ingredient you actually use, stated on every comparison. Factors: about 1.149 for anhydrous, about 1.272 for monohydrate.
Will total glutamic acid tell me how savoury a food is?
No. Savoury impact as eaten follows the free fraction. Total includes bound glutamate not free to taste until digestion or hydrolysis.
Why is total higher than the recipe suggests?
Bound glutamic acid, plus glutamine converted during hydrolysis, both feed the total. That is expected method behaviour, not by itself evidence of added MSG.
Can a result prove how much MSG was added?
No. Glutamate has many sources. A result measures the combined amount on the stated basis.
References
- PubChem — L-Glutamic acid (CID 33032) — Molar mass reference for glutamate / MSG-equivalent conversions.
- PubChem — Monosodium glutamate (CID 23672308) — Molar mass reference for the MSG forms named on this page.
- Waters — Derivatization of Amino Acids Using Waters AccQ-Tag Chemistry — Method background for AQC derivatization and HPLC-UV amino acid analysis.
- British Journal of Nutrition (2023) — Asparagine and glutamine lose an amide residue during acid hydrolysis and are measured with aspartate and glutamate respectively.
- OpenChemWorks — Pricing — Published service and pricing copy (2026).
OpenChemWorks Laboratory · Reviewed by the laboratory director, PhD chemist · Published October 26, 2026