What affects Syrup colour?

[Tapper705]

Looking for some input on what affects maple syrup colour. In years past we have mostly produced amber. This year the first boil was light, next couple of boils were very dark then things turned back to amber. We are pretty consistent in what we do when boiling sap. Is it the weather? Appreciate any input and opinions.

[Bucket Head]

The weather does affect it. The changes in temperature affect the sap. The warmer the sap, the more bacteria it has. The amount of time its boiled along with how much invert sugar in the sap will change the color. Even dirty evaporator pans will change the color.

There are many variables when it comes to syrup color. Dr. Tim would be the guy to explain this science. He will have more details than I could give!

Steve

[TunbridgeDave]

Bucket hit the nail on the head. Those pesky invert sugars. I believe it's glucose and sucrose that come out of the tree, and they get converted into fructose by bacteria more rapidly when it's warmer. That type of sugar darkens much quicker when heated.

[DrTimPerkins]

Dr. Tim would be the guy to explain this science. He will have more details than I could give!

Do you want the full-length book version, or just the quick science version? :D

Assuming it is the second....

Maple trees produce predominantly (~99.5%+) one form of sugar, sucrose. Sucrose is a large 12-carbon molecule (C12H22O11). As soon as it comes out of the tree vessels into the taphole, spout, and tubing, it encounters microbes. The microbes feed on this sugar by breaking the chemical bond that attaches its two parts together. Essentially you can think of that bond as being a spring or rubber band. When the microbes cut (hydrolyze) that bond, they are releasing (and utilizing) the energy stored in that bond. The hydrolysis of sucrose forms two 6-carbon sugars, glucose and fructose, collectively called "invert sugars".

So when things are very clean (few microbes) and cold (low microbial activity), then sap is mostly sucrose + water. When it is warmer (more microbial activity) and typically later in the season (more microbes), or during a low flow (less sap movement to flush out the microbes), then you have sucrose plus some invert sugar, although the amount of invert sugar is still typically less than 5% of the total carbohydrate in sap.

Different types of sugars undergo different chemical processes both before and during the boiling process. Both enzymatic (like when you cut an apple and leave it on the shelf for a few hours) and non-enzymatic browning (Maillard and caramelization) reactions occur at different rates and times. One of the non-enzymatic browning reactions is caramelization, which occurs when sugar solutions are heated. Caramelization is basically a complex series of chemical reactions that begin to occur when the sugar hits it's activation energy, resulting in the solution browning (toast is an example of browning). Sucrose and glucose brown at fairly high temperatures, around 320 deg F, well above the boiling point of syrup. However fructose browns at around 230 deg F, which is pretty close to the boiling point of syrup, and some of the syrup, especially in contact with impurities in the sap or on the pan (scale/niter) can hit those temperatures. When that occurs, the syrup browns. The more invert there is, and the longer you boil the sap (more time to fully caramelize any fructose in the sap), the darker the syrup will become.

There are other complications, such as air injection and sap pH (resulting in alkaline degradation processes), but we'll save that for another time.

So this is why you want to keep things clean and process sap quickly to produce the lightest syrup possible.

[Ghs57]

Thank you Dr. Tim. I like dark syrup, even though the science makes it sound of lower quality. I know that is not the case, it is just different components reacting to heat in their own way.

Is there any any science which shows that sucrose is more desirable for human consumption than syrup from invert sugars?

btw, I get asked about color right after the question about whether tapping hurts the tree.

[Tapper705]

Thank you for your responses. Most folks around here also say they prefer the taste of dark syrup. I second your question Ghs57.

[GeneralStark]

Thank you Dr. Tim. I like dark syrup, even though the science makes it sound of lower quality. I know that is not the case, it is just different components reacting to heat in their own way.

Is there any any science which shows that sucrose is more desirable for human consumption than syrup from invert sugars?

btw, I get asked about color right after the question about whether tapping hurts the tree.

There is a great deal of science regarding human health impacts of sugar consumption. There is also a body of research related to maple syrup specifically. In terms of sucrose vs. invert sugars in maple syrup, maple syrup is mostly sucrose and I believe rarely contains more than 5% invert and typically considerably less.

Human blood sugar is glucose, so this is the most readily metabolized sugar. Sucrose is broken down to fructose and glucose and can then be readily absorbed into the blood stream. Fructose has the most limited metabolic pathway in humans so generally is thought of as the least "healthy" sugar.

Generally speaking, maple syrup is considered a more "complex" form sugar than say table sugar (pure sucrose) or high fructose sweeteners because we metabolize it more slowly and it is less likely to cause dramatic spikes in blood sugar. Other health benefits of maple arise out of the other compounds found in maple syrup.

We all know there are certainly health risks associated with eating sugar in any form in excess.

[DrTimPerkins]

Generally speaking, maple syrup is considered a more "complex" form sugar than say table sugar (pure sucrose) or high fructose sweeteners because we metabolize it more slowly and it is less likely to cause dramatic spikes in blood sugar. Other health benefits of maple arise out of the other compounds found in maple syrup.

It is somewhat interesting to see how different industries approach these issues and the marketing methods used. The cane/beet sugar industry works hard to remove all traces of color and other compounds from their sugar, and consider these things to be impurities that must be "refined" out of the sugar. They use a number of processes and chemicals to produce very white sugar with very uniform characteristics and no taste other than sweet. Maple syrup on the other hand is considered "pure", although in reality it contains a wide variety of compounds that give it color and a range of flavors. These same "impurities", largely phenolic compounds that provide anti-stress (disease resistance, etc.) benefits to the plants themselves, also produce some anti-mutagenic, anti-oxidant, anti-cancer, and anti-bacterial properties (at least in some testing). Quite ironic in some ways.

Disclaimer....I'm not a medical doctor, so please don't misconstrue this as medical advice.