The four Grade A classes
Golden
Amber
Dark
Very Dark
Grade A syrup is sorted into four color classes by light transmittance: how much light at 560 nanometers passes through a 10 mm sample, compared with pure glycerol at 100%. The lighter the syrup, the more light gets through, and the milder the flavor.
Golden
Delicate taste
75% or more
Amber
Rich taste
50–74.9%
Dark
Robust taste
25–49.9%
Very Dark
Strong taste
under 25%
Canada uses the same four classes under the Canadian Food Inspection Agency's grade compendium. In both countries Grade A syrup has to land between 66% and 68.9% solids, which you can check with a hydrometer or refractometer.
Why syrup darkens through the season
Early-season syrup is usually lighter; late-season sap tends to make darker syrup. A big reason is microbes: the Producers Manual names microbial contamination of sap as a major contributor to darker grades, and microbe counts climb as the season warms.
So the same habits that keep sap fresh keep syrup lighter: keep sap cold, boil it promptly, and keep equipment clean. See how long sap can sit. Reheating finished syrup much past 200°F also darkens it.
Processing Grade and off-flavors
Syrup with off-flavors, or that misses Grade A's color and clarity requirements, is Processing Grade. Under the USDA standard it has to be packed in containers of 5 gallons or more and can't go into retail-size containers. Canada has its own Processing Grade too.
Color isn't quality
What happened to Grade B?
The current standard replaced the old names, which you'll still see on older labels and in some state rulebooks. The old bands don't line up one-to-one with the new classes:
| Old name | Light transmittance | Today's class |
|---|---|---|
| Grade A Light Amber | 75% or more | Golden |
| Grade A Medium Amber | 60.5–74.9% | Amber |
| Grade A Dark Amber | 44.0–60.4% | Amber or Dark |
| Extra Dark (Grade B) | 27.0–43.9% | Dark |
| Commercial | under 27% | Dark or Very Dark |
State rules to know
The USDA standard is voluntary at the federal level, but some states make grade labels mandatory, including Maine, New Hampshire, New York, Vermont, and Wisconsin for licensed processors. Vermont also sets a higher density floor (66.9 °Brix) and requires a batch code on Grade A retail containers. Your state's rules are on the selling maple syrup pages.
