grade changing ?

[ejmaple]

i can never seem to get a definative answer on what causes syrup grade change. this question is probley the most common one i get asked at the local farmers market. from what i've read there seems to be two answers. first, as the season progreses the sugar content diminishes so the sap is in the evaporator cooking longer making it darker.. second, bactiria growth in lines, storage tanks ect... increasing throughout the season eat the sugar, resulting in low sugar contant and longer boiles.

[Thompson's Tree Farm]

It also has to do with the levels of various types of sugars. Glucose, Fructose, and Sucrose. Increased bacteria changes the levels of each of these. I think sucrose is converted to fructose and glucose by the bacteria but I might have that switched around (Dr. Tim?). The resulting sugars are influenced by the browning reaction at a slightly lower temp, hence darker syrup.

[lmathews]

Doesn't it have to do with mineral change as well?

[brookledge]

Another key thing to grade is the temperatures. The hotter the sap gets while in transit or storage the quicker the sap deteriates. So keeping it cool and boiling it as fast as possible will make better grades

[red maples]

Thompson's I think your right glucose is the invert sugar which is more pressent in the darker grades. which is what happens if you let your tanks and releaser and what ever else become bacteria infested.

What I usually tell customers is...

as the season progresses and temps begin to warm the trees need different minerals and natural chemicals at different points during the spring growth and rejuvination. So as the season continues there are different chemical pressent in the sap. Also as the season progresses some sugars increase and othes decrease, other minerals and water increase creating the different grades of syrup. this is all by the needs of the tree. with the added amount of water and changing of of the sugars a longer boil is needed o condense the sugars resulting in darker the syrup.

So I sorta circle around a little bit and some of that may be true hopefully more than not. I have looked around as well and tried to read on it it seems to basically come down to sugars and the different types of, water, minerals, and natural chemicals found at different times of the spring.

Hopefully Dr perkins can chime in and give us a link to read for more info.

I am gonna look around here in the reasearch threads.

[DrTimPerkins]

...what causes syrup grade change.

If by that you mean what causes the typical change from light to dark syrup (generally) over a season, then Thompson's got it right. That would be your best and simplest explanation.

If you want a more detailed picture....read below...otherwise, feel free to ignore what is below.

Nearly all the sugar in sap coming right from the tree is sucrose (a big 12-carbon sugar). When microbes (bacteria, yeast, fungi, etc) feed upon this sugar, they break it into two 6-carbon sugars, glucose and fructose (primarily), also called "invert" sugars. Essentially what the microbes are doing is using the energy in the bond holding those two sugars together, sort of like the energy in a drawn bow. By breaking that bond (like releasing the bowstring), it frees the energy for them to use in some way.

OK...so back to syrup darkening. The more microrganisms around in the sap, the faster the darkening because more of the conversion of sucrose to invert sugars is going on. Temperature also plays role, because it controls how fast the microbes will grow and reproduce (basic rule of thumb is that microbial growth/reproduction doubles for each 10 deg C (about 20 deg F) rise in temperature). So good filtering, the use of a UV system, keeping sap cool, and rapid processing of sap will all help to make lighter syrup.

So how/why does invert sugar affect syrup color and flavor. During processing of sap to syrup, there are two dominant mechanisms happening. One is a series of chemical reactions called the Maillard (pronounced "May-ard) reactions. These are very complex (hundreds of chemical pathways), and involve amino acids reacting to the sugars in solution. These are sort of similar to what happens when you cut an apple and put it down for a few hours. It turns a bit brown and makes flavors different from the apple itself. Invert sugars and sucrose have very different sets of Maillard reaction pathways. The Maillard reactions involving invert sugars tend to produce color body and flavor precursors (so they end up making lots of color and heavy flavor compounds).

During heating, sucrose and invert sugars brown (caramelize) are very different temperatures. Caramelization is like what happens when you make toast, or when you put sugar in a pan and heat it...the sugars brown (and make flavor compounds). The temperature for sucrose caramelization is very high, much higher than the draw-off temperature of syrup. So with pure sucrose solutions (sap early in the season with few microbes), you get almost no browning due to either the Maillaird reactions or through caramelization. Basically with just sucrose, you don't get much browning until you scorch your pans (at which point you get a lot of browning very fast). Later in the season (or during a warm spell, or if you store your sap for a while before boiling) when you have a higher invert sugar level in the solution (and it may be only a small amount of invert, 0.1-2% total), these invert sugars will caramelize at temperatures the solution reaches in the evaporator (213-217 deg F), resulting in color development (browning) along with strong flavor development.

There are other things going on too that are quite a bit more complicated (Amadori rearrangement and alkaline degradation) that depend upon the sap pH (acidity) -- which is also fairly strongly influenced by microbial action, as well as temperature effects, scorching of sugars (sometimes within the scale/sugar sand matrix), and oxidative reactions (for syrup packed in plastic jugs or if you use an air injector in your evaporator).

Dr. van den Berg and I wrote a review article about this a little while back. Citation is below:

Perkins, T.D. and A.K. van den Berg. 2009. Maple Syrup - Production, Composition, Chemistry, and Sensory Characteristics. pp. 102-144. In: S.L. Taylor (Ed.) Advances in Food and Nutrition Research. Volume 56. Elsevier, New York

Unfortunately we can't give this away, as it was done for a book (Advances in Food and Nutrition Research) that the publishers want peopl to buy, but you can see the Table of Contents and abstract at http://www.uvm.edu/~pmrc/syrup_chapter.pdf Basically everything most folks never wanted to know about maple syrup chemistry.

[ejmaple]

thanks everone i now have a handle on this and can sound alittle more knowledgable to customers.

[red maples]

Excellent....thanks for the science behind all that...that is probably one of the most asked questions!!! So unless I get a food chemist that comes by and askes that question then I will keep my answers short and sweet.....pun intended!!!

[Bucket Head]

I have a question regarding the sugars in fresh sap vs. older sap, warm sap, cloudy sap, etc. Does the change in sugar makeup change how a hydrometer reads the sugar content? It does'nt matter what the sucrose/invert ratio is? I could have fresh, clear sap with 2% sugar one day and three days later have warm, cloudy sap and it still measure 2%? It would seem that a change in sugar makeup would affect its density too. Dr. Tim, are you still out there? Any insight on what our hydrometers are working off of?

Thanks,
Steve

[DrTimPerkins]

I have a question regarding the sugars in fresh sap vs. older sap, warm sap, cloudy sap, etc. Does the change in sugar makeup change how a hydrometer reads the sugar content? It does'nt matter what the sucrose/invert ratio is? I could have fresh, clear sap with 2% sugar one day and three days later have warm, cloudy sap and it still measure 2%? It would seem that a change in sugar makeup would affect its density too. Dr. Tim, are you still out there? Any insight on what our hydrometers are working off of?

Well Steve....that's far more than one simple question, but I'll take a stab at it and hope I answer your questions.

A hydrometer measues the "specific gravity" or density of a liquid. Basically it is a measure of the dissolved materials, usually in a solution, typically water. The key concept there is that hydrometers respond to dissolved things, not particles. Particles, including microbes, do NOT affect the density of the liquid (although they can cause some slight measurement errors). Take the example of your jumping in a pool...you (a big solid particle) won't change the density of the liquid, but if you pee in the pool, the dissolved salt in your urine WOULD change the density a little. Put 100 of your friends in the pool, the density still doesn't change. Putting 100 of your beer-drinking, peeing in the pool friends in there, and the hydrometer will respond.

So the second main thing to understand is that the hydrometer can't really tell what the dissolved material in the liquid is, just that there is more or less dissolved stuff in the liquid. If you put salt in syrup, the salt would dissolve and WOULD affect the density, and thus the hydrometer reading (as well as make the syrup taste like crap). Hydrometers are calibrated for certain dissolved things, like sugar or alcohol or salt, and should only be used for liquids where you know the dominant form of dissolved material. You'd get a reading if you measured dissolved salt using a sugar (Brix) hydrometer, but it wouldn't be the correct number, because the scale isn't calibrated properly for that material. Hydrometers generally don't work well for mixed solutions of dissolved materials, only those that are predominantly one thing. But that is OK, you're not usually going to have a whole lot other than sugar+water in your syrup, or salt+water in your pool, or alcohol+water in your liquor bottle. If you do, a hydrometer becomes kind of useless.

So, take your example of microbes changing sucrose to invert (fructose+glucose) sugars. First, the fact that the microbes (particles) are in there won't (greatly) affect the density, although it will affect the turbidity (cloudiness) quite a bit. Second, even with highly contaminated sap only a fraction (maybe up to 5-7% max) of the sucrose is converted to invert sugar (although a little invert goes a long way in terms of producing color and flavor). The fact that there is (slightly) more dissolved invert sugar in there instead of dissolved sucrose won't (greatly) affect the measurement....if it's dissolved, the hydrometer will measure it...and really, it's OK because it's still sugar, not something like salt. However you may find that the sugar content will go down slightly over time as the microbes use some of the sugar for growth/reproduction, thereby consuming some of the dissolved sugar and turning it into biomass (more microbes) particles, which the hydrometer doesn't measure. So basically your 2% sugar will pretty much read 2% regardless of whether it is pure sucrose or sucrose with a little invert in it.

OK, while I'm on the subject, some quick things about hydrometers.
- make sure they are calibrated annually (would you measure something with a ruler that you knew or suspected was wrong?)
- make sure they are very CLEAN when you use them (particles or solid sugar stuck to the side of the hydometer affect its weight and the resulting reading)
- the syrup in the hydrometer cup should not have any foam in it (this can affect the meniscus of the liquid on the hydrometer stem and lead to incorrect readings)
- make sure you read the level correctly
- make sure the temperature is correct (density will change greatly with temp) and that you standardize the temperature after the measurement

I hope I answered all your questions.

[red maples]

speaking of temperature and measuring density. The maple guys have a nice little temp compensation chart that they have laminated its a really nice quick reference when measuring density. I use it religiously. And its very handy.

[DrTimPerkins]

speaking of temperature and measuring density. The maple guys have a nice little temp compensation chart that they have laminated its a really nice quick reference when measuring density. I use it religiously. And its very handy.

We don't normally do much in the way of product endorsement, however the Maple Guys also make a hydrometer Acc-u-cup, which combines a hydrometer cup and thermometer (comes with a temperature compensation chart). Very nice and worth the extra $. Our head sugarmaker (Brian Stowe) here uses it exclusively.

http://www.mapleguys.com/index.php?item=27&ret=http%3A%2F%2Fwww.mapleguys.com%2Findex.php%3Fp age%3D1%26category%3D6

[red maples]

yes I do want one but it was either and acc-u-cup or cv's this year figured I'd go with the cv's so I could make more syrup to sell and get the acc-u-cup next year:)

[Bucket Head]

How does Dr. Tim know my buddies and I pee in swimming pools? Who told him? Lol!

Seriously, thanks Dr. for the info on the hydrometer measurments. I did'nt know the invert sugar amount was so low. I figured the change in sugar was a greater percentage- more like 50/50.

Steve

[Beweller]

Hydrometers will measure the effect of suspended solids just fine. This is used to determine the relative quantities of sand, silt and clay in soils.

Bacteria have a density very close to water, and even millions of bacteria per cc represent a rather small mass. Hence little effect on the hydrometer.

[lafite]

This forum is amazing. With a little research, almost all of my questions can be answered by just reading.

I'm looking forward to the spring even though my wife is already rolling her eyes at me :lol: