Stevia: Reb A, Reb M and why the glycoside profile is the product

Two stevia extracts both meeting "95% total steviol glycosides" can taste entirely different. The total is a purity specification; the profile within it is the product.

The main glycosides

• Stevioside — abundant in the leaf and the cheapest to produce, with the most pronounced bitter, liquorice-like aftertaste.
• Rebaudioside A (Reb A) — the long-standing commercial standard. Cleaner than stevioside, still with some lingering aftertaste at higher use levels.
• Rebaudioside M (Reb M) and Rebaudioside D (Reb D) — present at very low levels in the leaf, so they are usually produced by bioconversion or fermentation. Much closer to a sugar-like profile, and priced accordingly.

A material described only as "Stevia 95%" is almost certainly stevioside-dominant. That is a legitimate ingredient at a legitimate price, but it is not interchangeable with Reb M in a formulation, and substituting one for the other will be noticed by consumers immediately.

Production route affects labelling

Reb M produced by enzymatic bioconversion from Reb A, or by fermentation, is a different regulatory and labelling proposition from leaf-extracted material in several markets. If your positioning depends on a "natural" or "leaf-derived" claim, the production route needs to be confirmed and documented before you commit, not assumed from the name.

What to put on the specification

• Total steviol glycosides by HPLC, on a dry basis, per the JECFA specification.
• Individual glycoside breakdown — Reb A, Reb M, Reb D, stevioside, rebaudioside C, at minimum. This is the parameter that defines the material.
• Production route — leaf extraction, enzymatic bioconversion or fermentation.
• Solubility, which falls as Reb content rises and becomes a genuine formulation constraint for high-Reb grades.
• Residual solvents, heavy metals and microbiology, plus pesticide residues on the leaf input.

Taste it in your own matrix

Sweetener performance is matrix-dependent to an unusual degree — acidity, temperature and the rest of the flavour system all interact with the aftertaste. Approve stevia on a bench trial in your actual formulation, at your actual use level. No certificate substitutes for that, and the material that wins the tasting is frequently not the one that won on paper.