Short answer
In the United States, Grade A maple syrup is sold in four colour classes — Golden, Amber, Dark and Very Dark — set by how much light at 560 nm passes through 10 mm of syrup. The class describes colour and the strength of maple flavour that goes with it; it is not a ranking, and all four are the same grade. How dark a syrup turns out depends on how the sap was handled before boiling and on how the syrup was packed and kept afterwards, and it goes on darkening in the bottle.
The US standard grades syrup by the light that gets through it. A sample goes into a square cell with a 10 mm path, and a spectrophotometer reports what fraction of 560 nm light — a yellowish green — emerges, compared with pure glycerol set at 100%. The result is written %Tc. Syrup at 75.0% or more is Golden; 50.0 to 74.9% is Amber; 25.0 to 49.9% is Dark; anything below 25.0% is Very Dark. Each class is paired with a word for the intensity of maple taste: Delicate, Rich, Robust and Strong. The standard allows any method that gives equivalent results, so syrup can also be graded by eye against permanent glass standards in a comparator, which is how the Vermont study described below checked its samples.
The scale runs the opposite way to beer and honey: a bigger number is a paler syrup, because it counts light passed rather than light absorbed.
Under the standard in force since March 2015, every one of the four classes is Grade A. To earn the grade a syrup must sit between 66 and 68.9% solids, have a good uniform colour, taste and smell as expected for its colour class, and be clear and free from off-flavours. A syrup that fails those tests becomes Processing Grade whatever its colour: it may fall in any class, must be packed in containers of 5 US gallons (20 litres) or more, and cannot be sold in retail sizes. So darkness alone never demotes a syrup. What demotes it is a flavour or clarity defect, and those can occur in a pale syrup as readily as a dark one.
The colour is made on the way from sap to syrup. Researchers at the University of Vermont, summarising the production literature, list microbial growth in the raw sap, long holding times before boiling, the temperature of processing and pH as the influences on how colour and flavour develop, and note that sap drawn under aseptic conditions has consistently given lighter syrup while badly installed tubing has given darker, more variable syrup. It is also the likely reason darker syrup is associated with the later part of the season, when warmer weather makes sap harder to keep clean and cold before it reaches the evaporator — an explanation the sources imply without testing it directly. During evaporation itself, sugars, amino acids and minerals react under prolonged heat, which is the same family of non-enzymatic browning that colours toast and caramel.
A class is fixed when the syrup is graded, but the syrup is not. Oxygen passing through a container wall is described as the main cause of darkening in storage: plastic jugs let through far more than glass, uncoated plastic has been reported to darken syrup more than three times as fast as coated plastic, and long-term trials found the worst darkening in plastic kept warm. The Vermont team bought 507 retail syrups online over three years and checked them against the label. Syrup sold as Golden was still light enough to be Golden in only 1.7% of samples in 2021, 26.4% in 2023 and 21.9% in 2024; syrup sold as Dark matched its class in 45.7%, 64.8% and 64.6%. The authors put this down to producers' grading practice and to darkening after packing, not to deliberate mislabelling.
Read the class as a flavour-strength label. Golden is the mildest and the one most likely to have slipped a class by the time it reaches you; Dark and Very Dark carry the strongest maple taste and stand up in baking and glazes. If the colour matters — for a pale dessert, say — buy from a recent season in glass, and keep the bottle cool and out of the light. A fine gritty cloud in the bottom of a bottle is usually what producers call sugar sand, mineral salts that the standard itself describes as harmless; it affects the grade for clarity, not safety. Colour says nothing about whether a syrup has fermented or picked up an off-flavour: smell and taste do.
| Colour class | Taste descriptor | Light transmittance (%Tc) |
|---|---|---|
| Grade A Golden | Delicate | 75.0 or more |
| Grade A Amber | Rich | 50.0–74.9 |
| Grade A Dark | Robust | 25.0–49.9 |
| Grade A Very Dark | Strong | below 25.0 |
| Year | Sold as Golden | Samples | Sold as Dark | Samples |
|---|---|---|---|---|
| 2021 | 1.7% | 116 | 45.7% | 129 |
| 2023 | 26.4% | 91 | 64.8% | 91 |
| 2024 | 21.9% | 32 | 64.6% | 48 |
Why: It has darkened since it was graded, most often in a plastic jug that admits oxygen or after warm storage; borderline grading at the sugarhouse adds to it.
Fix: Buy recent-season syrup in glass if the pale colour matters, and keep it cool and dark.
Why: Class depends on when in the season the sap ran and how quickly it was boiled, not on the producer's recipe.
Fix: Buy by class, not by brand memory, and expect a range within each class.
Why: Darkness is easily mistaken for a lower letter grade.
Fix: Treat class as flavour strength; all four classes meet the same Grade A requirements.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
StandardStrong evidence· United States
The US standard defines maple syrup colour classes by percent light transmittance at 560 nm through a 10 mm cell relative to glycerol at 100%: Golden at 75.0% or more, Amber 50.0–74.9%, Dark 25.0–49.9% and Very Dark below 25.0%.
Caveat: A voluntary US federal standard effective 2 March 2015; other jurisdictions' rules were not checked.
Source: United States Standards for Grades of Maple Syrup (effective 2 March 2015)
StandardStrong evidence· United States
All four colour classes belong to US Grade A; syrup that fails Grade A requirements is Processing Grade, which may be of any colour class and may not be packed in retail-size containers.
Source: United States Standards for Grades of Maple Syrup (effective 2 March 2015)
Observed market dataModerate evidence· Online sellers in ten US states, mainly in the north-east, and one Canadian province· 2021, 2023 and 2024
Among retail maple syrups bought online and tested against their labels, those sold as Golden met the Golden colour class in 1.7% of samples in 2021, 26.4% in 2023 and 21.9% in 2024, while those sold as Dark met their class in 45.7%, 64.8% and 64.6%.
Measured: 507 retail syrups labelled Golden or Dark from about 30 businesses a year (245 in 2021, 182 in 2023, 80 in 2024). Method: Visual colour comparator against permanent glass standards
Caveat: Online purchases only, graded by eye with a comparator. Testing in 2021 was delayed and half the samples were held at room temperature, which the authors say increased darkening that year.
Source: Maple Quality Testing: An Evaluation of Maple Syrup Compliance with Grade A Standards
FactModerate evidence
Microbial growth in sap, delay before boiling, processing temperature and pH influence the colour a syrup develops, and oxygen entering through plastic containers and warm storage darken it after packing.
Caveat: Taken from one research paper's summary of earlier trade and extension studies, which Colourwise did not read individually.
Source: Maple Quality Testing: An Evaluation of Maple Syrup Compliance with Grade A Standards
Colourwise interpretationLimited evidence
Maple syrup colour is produced by non-enzymatic browning during evaporation, so the chemistry is continuous with Maillard browning and caramelisation in other heated sugary foods.
Based on: Colourwise's reading: the cited study says only that sugars, amino acids and minerals react during evaporation, and the classification of those reactions as Maillard-type browning comes from the general browning chemistry on this pillar.
Caveat: No source read for this page identifies which reactions or pigments account for maple syrup colour.
Reviewed 1 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.