Maple syrup has always been graded using a color standard. Back in your grandfather’s day, color was the single most important characteristic. The original research, conducted by C.O. Willits in the 1950s, tracked the change in color during the boiling process. As the temperature and length of boil increased, the color moved from very light to dark. Flavor was mentioned, but little was known about the chemistry that determined flavor. One of the reasons for color’s importance was establishing the dollar value of the product with Light Amber syrup bringing the highest prices. For the producer, there was little incentive to make darker syrup to sell at a lower dollar value. Fast forward to today’s market – producers typically receive the same dollar amount for the top three grades of syrup.
When a consumer is shopping for maple syrup, they are immediately drawn to an attractive glass bottle of amber-colored maple syrup sitting on a shelf. Nothing can ruin that image faster than opening the bottle and finding out that the syrup has little flavor or, even worse, an objectionable taste. For decades we have been told that color and flavor are interrelated, yet when it comes to flavor, there must be more to the story than the standard color/flavor relationship.
Even though the current maple syrup grading standard includes a flavor descriptor, flavor remains one of the hardest characteristics to standardize. We now realize that multiple factors come together to form the flavor of maple syrup. It is a combination of microbes present in the sap that changes the liquid’s chemistry as it moves through the boiling process. Maple sap coming from the tree is comprised of 2% sucrose sugar, minerals, and other compounds. When microbes interact with sugar, fermentation happens. The fermentation changes a portion of the sucrose into glucose and fructose sugar compounds. These latter two types of sugar are called invert sugars. During the heating process, color is formed through what is known as the Maillard Reaction. Two things happen when sap boils, density (brix level) increases and the pH of the sap initially increases (more alkaline) and then decreases (more acidic). The color is set when the rising brix level crosses the declining pH level. The closer this interaction is to a pH of 7, the lighter the syrup. The higher the pH is above 7, the darker the syrup. This process also releases a broad range of flavor compounds. A 2009 report Maple Syrup-Production, Composition, Chemistry and Sensory Characteristics stated that “over 130 volatile flavor compounds have been identified in maple syrup.” Many of the compounds are desirable; however, others have a negative impact on both color and flavor. This leads to the belief that color and flavor are interrelated. However, this is not always the case.
When we label a syrup by its color alone, the results can be deceiving. A good example is the re-appearance of light color syrup at the end of the season. The light color indicates that the grade is Golden or an Amber, but the flavor indicates that the syrup is sub-standard. Dr. Tim Perkins, in a recent edition of Maple Digest, described the process. Under normal circumstances, boiling sap is increasingly alkaline reaching a pH of 8 or 9. As more water is boiled off, the density (brix) of the liquid increases and pH becomes more acidic. As syrup finishes, pH drops back to around 7.0. However, this is what may occur at the end of a season where warm weather and poor sanitation has taken their toll. Sap’s pH levels drop excessively, and the liquid becomes extremely acidic. As a result, the pH level of boiling sap may never rise above 7.0, and the liquid reaches 66 brix before darkening occurs, causing the syrup to remain light in color. Mother nature can easily deceive producers into thinking their season has just turned round, but the truth is syrup with light color but bad off-flavor that ultimately is not fit for sale.
This is just one of several effects caused by Sour Sap. Sour sap/syrup is the result of excessive microbial buildup and poor sanitation resulting in the formation of a strong objectional flavor and sometimes a thick viscous syrup that is referred to as Ropey Syrup. It can show up at any time during the season, but especially at the end of the season. Sour Sap can be managed with proper sanitation. However, if ignored, it can destroy the value of your product. Producers often blame the end of the season on the emergence of buds when in reality it is the formation of massive microbial colonies in their system that is shutting them down.
Other natural off-flavors include Buddy Syrup, which appears at the end of the season when maple leaves start to emerge. Buddy off-flavor is often confused with Sour Sap; however, the flavor is more of a tootsie roll flavor. It is more readily identified by an overpowering smell caused by sulfur compounds formed in the tree and precipitated out during the boiling process. Metabolism is a true natural off-flavor. It is caused by environmental conditions that cause an increase in dimethylpyrazine amino acids in the tree. There is very little that can be done to change the onset of metabolism, and it is often very hard to detect before the boiling process.
It is up to producers to eliminate the possible sale of syrups containing off-flavors. Producers must realize that every time a bottle of their syrup is placed on a shelf, their reputation is on the line. For the consumer, the choices are simple when it comes to buying a product off the shelf. It comes down to complete product satisfaction and a repeat customer or fool me once and you will not have a second chance to fool me again.
