Glycine is the simplest amino acid, and one of the most useful to measure precisely because it is so common. It occurs naturally in protein, is sold on its own as a sweet-tasting powder, and is inexpensive to add to a product. A glycine result alone tells you how much glycine was in that sample. Read alongside the other amino acids in the same sample, it can also help check a pointed question: does this profile look like protein alone, or has extra free glycine been added?
Chemistry in plain terms
Most amino acids have a distinctive side chain. Glycine barely has one: its side chain is a single hydrogen atom. PubChem therefore describes glycine as the smallest of the standard amino acids. It has no left-handed or right-handed form, dissolves readily in water, and tastes noticeably sweet, which is part of why it turns up as an ingredient in its own right. Because it is so small, protein chains can bend where a larger amino acid would not fit — a structural fact, not a health claim. For testing: glycine is measured as itself, with no special test of its own.
Where it occurs
Glycine occurs in protein-containing foods as part of the protein itself, and in collagen-rich materials in particular it is a major building block — stated qualitatively, without a percentage, because the share varies by source. It also occurs free: in broths, sauces, and fermented products where protein has broken down, in glycine powder supplements, and as an added ingredient in some drinks, sweetener blends, and protein products. That last use makes testing sensitive: glycine is cheap compared with intact protein, and it contains nitrogen — the combination behind the spiking question below.
Free vs total glycine
A free result measures glycine already unattached in the sample as received. A total result is measured after hydrolysis — 6 N hydrochloric acid at 110 °C for 24 hours — which breaks protein chains and releases bound glycine. Total therefore includes free plus bound, and will be larger in a protein-rich sample. How much larger depends on the sample; no ratio is given for any food or product.
Glycine has no special hydrolysis behaviour. It is not converted from another amino acid during hydrolysis as glutamine and asparagine are, and it is not destroyed by acid hydrolysis as tryptophan is. It is measured as glycine in both panels. A product as eaten or sold is a free question; the protein ingredient itself is a total question.
The protein-spiking tell, explained qualitatively
Many headline protein figures are not measured as protein directly. Nitrogen-based methods measure nitrogen and convert it to a protein figure using a factor, so any nitrogen-rich ingredient added can raise that figure whether or not it adds intact protein. Adding glycine this way — sometimes called amino spiking or nitrogen spiking — can make a nitrogen-based reading look higher than the intact-protein content alone would support.
An amino acid profile helps because it measures individual amino acids separately. If free glycine has been added, the profile can show glycine out of proportion with the other amino acids in that same sample, in a pattern intact protein alone would not be expected to produce. That is as far as this page goes, deliberately. What proportion glycine "should" be in a whey product, or any other product, depends on the protein source, the blend, and any declared added glycine — so no expected percentage, ideal profile, or pass/fail limit is stated here. A maker may add glycine openly and declare it, in which case a high result confirms the label rather than contradicting it.
Method notes
Glycine is measured here by AQC (AccQ-Tag) pre-column derivatization with HPLC-UV, described in Waters AccQ-Tag method literature (URL to verify at science check). The amino acids are tagged, separated by HPLC, and measured by ultraviolet detection against a calibrated standard. No recovery, precision, or detection-limit number is claimed here, because none is stated from a verified source for your matrix. For complex samples, matrix-effect qualification — checking distortion with a known spike in your actual sample — is available on inquiry, priced per sample and matrix.
Which panel includes it
Glycine is included in AA-1, the free amino acid panel: 19 amino acids plus ammonia by AQC HPLC-UV. Cysteine is excluded from AA-1 and needs a separate AA-3 workup. The extended AA-2 compounds are not routinely included.
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. Total amino acid analysis, AA-T, is $230 per sample. The pilot is $250 for 5 samples, credited in full against a first contract signed within 90 days.
OpenChemWorks, in Davis, California, is validating now and reserving pilot slots. The lab is not GLP, GMP, or ISO/IEC 17025 accredited, and no turnaround is promised. To discuss a sample, email info@openchemworks.com with the product, its form (liquid or powder), and the decision the result will feed.
Frequently asked questions
Is a high glycine result proof of spiking?
No. It is a signal to check against the label and formulation. Declared added glycine, a collagen-rich source, and a blend can all raise glycine legitimately.
Do I need free glycine, total glycine, or both?
Free for the product as sold or eaten. Total for the protein's composition. Both only if the lab can state in one sentence why the second test earns its cost.
Is glycine in the standard panel, or an extra?
In AA-1 as standard, alongside the other 18 amino acids and ammonia, at no extra charge.
References
- 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).
OpenChemWorks Laboratory · Reviewed by the laboratory director, PhD chemist · Published October 26, 2026