What ICUMSA means, and what the number on a sugar offer measures.

What ICUMSA is

ICUMSA describes itself as the only international organisation concerned solely with analytical methods for the sugar industry. It works through national committees in more than twenty countries, and its methods are recognised by Codex Alimentarius, the International Organization of Legal Metrology, the European Union and the US Food Chemicals Codex. Its Methods Book holds all 126 adopted methods; the latest edition is from 2026.

Each method has a status. “Official” methods have normally been through full collaborative testing between laboratories; “Accepted” methods are useful in practice but have not been, or cannot be, validated by a full collaborative test; “Tentative” methods are fully developed but still await a full collaborative test. Methods are numbered by subject (GS1 raw sugar, GS2 white sugar, GS9 plantation white sugar), and ICUMSA asks that contracts cite them with their year, for example “GS1-13 (2004)”.

How colour is measured

ICUMSA defines colour as the absorption coefficient of a filtered sugar solution at 420 nm, at pH 7.0, multiplied by 1,000, and reports it in ICUMSA units. GS2-10 skips the pH adjustment because, as ICUMSA explains in that method, it isn’t needed for sugars below 50 IU. Different methods cover different colour ranges:

If a contract under Refined Sugar Association rules sets a colour but names no method, the rules use ICUMSA Method GS9/1/2/3-8 (2011), the 2011 edition of the method now numbered GS9-8.

Two labs can disagree, and both be right

Every method has a margin. Under GS9-8, two laboratories testing the same white sugar should differ by no more than 8 ICUMSA units in 95% of cases (the method’s reproducibility); under GS2-10 the figure is 7. So a dispute over 45 against 48 can sit inside measurement error. That is why the contract should name the method and its year, and the inspector whose certificate decides.

The other tests on a sugar specification

45, 60, 150: where the numbers come from

• 45. The ICE No. 5 white sugar contract sets colour at 45 ICUMSA units maximum, with polarisation of at least 99.8° and moisture of no more than 0.06%. The EU’s standard quality for white sugar caps colour in solution at 6 points of 7.5 ICUMSA units each, which is 45.
• 60 and 150. The Codex standard for sugars sets white sugar at 60 ICUMSA units maximum and plantation or mill white at 150, in an annex intended for voluntary use by commercial partners, not governments.

More on the grades in ICUMSA 45 vs ICUMSA 150 vs VHP and ICUMSA 150 sugar from Brazil.

Colour charts and “RBU”

ICUMSA colour is measured with an instrument, not by eye. We found no official chart that shows ICUMSA units. ICUMSA’s only visual method, GS2-11, grades white sugar against Braunschweig colour types on a separate scale from 0 to 6. India’s standard grades plantation white sugar against sealed reference samples. You will also see “RBU” on some offers; it does not appear in the ICUMSA, ICE, Refined Sugar Association or Codex texts. Ask for colour in ICUMSA units, with the method.

What to write into your contract

• colour, as a maximum in ICUMSA units, with the method and its year;
• polarisation, moisture, ash, invert sugar and sulphite limits, each with its method;
• the independent inspector whose certificate decides, and that certificate as a document your bank requires. See what protects you if sugar arrives off-spec.