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Thread: Holding concentrate in a working bulk tank

  1. #21
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    Quote Originally Posted by DrTimPerkins View Post
    Hey Steve ... Not sure exactly what you're looking for, but sap/concentrate spoilage is a function of time, temperature, sugar concentration and initial microbial load. We have done studies on it, with the following general results:

    - warm sap spoils faster than cold sap
    - higher sap sugar spoils faster than lower sap sugar
    - sap spoils more the longer it is left out
    - if sap has a lot of microbes to start with, spoilage will be faster

    The colder it is kept, the longer it will last, but there is no single setpoint that we can say after this it is bad. Somewhat depends upon the types of microbes in the sap and aeration to some degree as well.
    Dr. Tim, I believe that virus, bacteria and fungi are all consider microbes, that said, what types of microbes are you finding in the sap? I should reword that, are you finding more than bacteria and can it be assumed that natural yeast is present? We typically hear of sap containing bacteria but you using the microbes term is throwing me off. I am fairly certain that there are no virus in the sap but after this past year nothing should surprise us about a virus.

    I believe what Steve is looking for and would be great to have is a graphic calculator (I can not remember the correct term for a line graph typy calculator with three axis) saying at a particular sugar concentration and a particular temperature, sap will stay good for this amount of time before the bacteria makes the sap spoil. Sounds easy, I have no idea how to do it though.
    Last edited by minehart gap; 05-22-2021 at 04:07 PM.
    Matt,
    Minehart Gap Maple

  2. #22
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    Quote Originally Posted by WMF View Post
    What type of chiller did the dairy guy recommend? I know it is common for dairies to use a well water powered plate cooler to lower the temp into the 60 degree range and then they use refrigeration to get milk down to upper 30 degree storage.
    For concentrate you will want to be in lower 30 to upper 20 range.
    I have been told that plate type coolers used in dairies will leak between the two fluid paths so you should not use chilled glycol to power one for maple concentrate.
    The type of chiller he's recommending is a self contained refrigeration unit with a small tank containing a water/glycol solution in it. The glycol is cooled by the refrigeration unit and is circulated through a jacketed tank (perhaps a milk tank could be used). Another option is to use a plate heat exchanger to run the glycol solution and the concentrated sap through. Maybe a brazed plate heat exchanger would be less likely to leak. These units are commonly used for beer and wine making. Some are 3 phase and run by VFD. Here is an example https://www.advantageengineering.com...ller_BG-3A.php
    There are used ones for sale on the beer and wine used equipment lists.

    I suspect the dairy guy I talked to suggested the chiller because there refrigerant circuit is simpler and less likely to leak than sending refrigerant into an old milk tank evaporator cooling circuit. The chiller has one or two pumps to move the cold liquid around, probably draws more amperage and costs more.
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    Tim
    2,500 taps on two pipelines
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  3. #23
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    Quote Originally Posted by minehart gap View Post
    I believe what Steve is looking for and would be great to have is a graphic calculator (I can not remember the correct term for a line graph typy calculator with three axis) saying at a particular sugar concentration and a particular temperature, sap will stay good for this amount of time before the bacteria makes the sap spoil. Sounds easy, I have no idea how to do it though.
    Unfortunately there is no simple answer. Spoilage is related to time, temperature, sugar concentration and microbe type and level. Time can be controlled by processing quickly. Temperature can be controlled with a refrigerated bulk tank or other ways (open-top tanks, tanks in the shade, snow, etc.). Sugar concentration means that when you concentrate you'd better plan on either refrigerating it quickly or keeping it very cold. Microbes (a catch-all term for all types of things: bacteria, fungi, molds, yeasts, etc.)...and there are many dozen dominant types that can be found...vary by year, time of season, operation, cleaning procedures, collection methods, storage methods, filtering methods, microbial load upon collection, processing factors (like double-passing or recirculating through the RO), etc. Just too many things going on to be able to provide solid predictive tools. Any tools we could provide would provide a false sense of security for people who might think it was OK to store the sap for a certain time period, then find out it was not OK.

    What we do know is that spoilage tends not to be linear, but rather is exponential, so the longer it goes the faster it gets worse. Sap might seem fine one day, but be bad very soon after. It might be fine sitting around for 2-3 days early in the season, but not even make it a day in the later season.

    There is unlikely to ever be a calculator that will tell you it is OK to keep sap for XX hrs, after that it is too late. In general, the longer it is held, the higher the invert level, the darker the syrup, and the greater the chance of other issues (off-flavors, sour, ferment, etc.) or ropey sap/syrup.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  4. #24
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    I have looked at the brazed heat exchangers and have always been concerned with the inability to clean them. From my research the shell and tube type seem to be the best sanitary style but food grade ones are very expensive.
    There are cheap stainless and titanium ones all over the internet for heating pools but they are not food grade. Not sure if they would be "food acceptable" like some of our other equipment or not.
    A lot of the cheaper glycol chillers out there are not rated to chill down to the mid twenties or to be used in freezing or sub freezing ambient temps so do some research.

  5. #25
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    Yes, I was looking for a chart/graph/calculator/anything saying if your concentrate was at "x" percentage, then your refrigeration should be no higher than "x" temperature. I was trying to gauge if my holding temp. (and anyone else who knew what their exact concentrate and temp. was) was good or not so good. I did not know if any benchmarks were out there or not. And I can see why there isn't anything out there, with all the variables that Dr. Tim listed. I guess I'll have to end on cleanliness is key and colder is better!
    Thanks for the replies, guy's.

    Steve
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    Ford F-350 4x4 sap gatherer
    An assortment of barrels, cage tanks & bulk tanks- with one operational for cooling/holding concentrate
    And a few puzzled neighbors...

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  6. #26
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    My bulk tank cools only to 34F and I had no issues keeping clear 14% concentrated sap for~70 hours this year. That said we went 6 days without a freeze towards the end of this season and I boiled out and cleaned tanks everyday out of concern of sap spoilage. IMO the preloading of bacteria in the sap might be the largest contributing factor to spoilage when using a refrigerated tank. If the sap is bad to begin with freezing it will not make it much better.

    According to the chart a temp of 29F would be ideal for my setup, but I am not going to worry about a few degrees.
    2.5X10 HE
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  7. #27
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    Quote Originally Posted by DrTimPerkins View Post
    In general, the longer it is held, the higher the invert level
    This is an interesting comment. I know that I am only using part of your sentience and I hope by my doing that, I am not taking it out of context.

    It appears that you are saying that invert sugar level is related to quality of sap. Is this true? What level in the sap constitutes bad syrup?

    I believe that invert sugar levels are the measure of12 molecule sugars that have broken. I am assuming that the bacteria is what is breaking them. Am I even remotely correct? And by introducing oxygen, I would think that aerobic bacteria would increase but that doesn't make sense because more bacteria mean faster bad sap. What do I have screwed up in my thought process here?
    Matt,
    Minehart Gap Maple

  8. #28
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    Quote Originally Posted by minehart gap View Post
    It appears that you are saying that invert sugar level is related to quality of sap. Is this true? What level in the sap constitutes bad syrup?

    I believe that invert sugar levels are the measure of12 molecule sugars that have broken. I am assuming that the bacteria is what is breaking them. Am I even remotely correct?
    The "energy" derived by living things is held in the bonds of different chemical structures. You can kind of the energy as rubber bands that are stretched around and holding different elements or groups of elements together. Microbes (or people) add a little energy to that bond to the point where it breaks the bond, releasing the energy and transferring it to other chemical bonds. A rather simple way of looking at it, but close enough.

    Sucrose (by far the dominant sugar in maple sap) is a 12-carbon sugar. It is pretty much two 6-carbon sugars (glucose and fructose, collectively called invert sugars), that are held together by a bond. Microbes consume and break the bond holding the two 6-C sugars, releasing energy in the process.

    What is left by the process are invert sugars (6-C). Only a rather small amount of invert is found even in sap that is quite contaminated with microbes -- generally up to a max of 2-5% invert even in the darkest syrup.

    Invert sugars chemically react quite differently than sucrose with amino/organic acids. Generally these suite of reactions will result in color (darkening) and flavor development.

    When you heat syrup, another darkening/flavor forming process occurs, caramelization. Fructose (a 6-C sugar) has a much lower activation energy than either glucose or fructose, barely above that of boiling sap/syrup. However some fructose can get entrained into niter, where it will brown and form strong flavors.

    So altogether, more microbes = more invert = darker and stronger tasting syrup.

    Unfortunately there isn't a set level where too much is bad and below that is good. It depends on lots of factors that vary considerably.

    That's the simple answer...the reality is much more complex. There are lots of different organisms involved, some do good things, some do bad. It is kind of like with some microbes you get wine and others you get vinegar. Temperature is important in the rate of microbial growth as well -- as is sugar content.

    Abby and I wrote a chapter on the chemistry of maple syrup in 2009. Unfortunately it is not available for free (the publisher needs to make money somehow). The abstract and some of the figures are located at https://www.semanticscholar.org/pape...9#paper-header Basically it is all you NEVER wanted to know about the chemistry of syrup, unless you're: 1) a maple scientist, 2) a real glutton for punishment or 3) maybe just a bit touched in the head.

    If you are in any of those groups, perhaps you'd enjoy grabbing a drink (made possible by happy microbes) and watching https://www.youtube.com/watch?v=Nnan...&index=16&t=1s

    And by introducing oxygen, I would think that aerobic bacteria would increase but that doesn't make sense because more bacteria mean faster bad sap.
    There has not yet been a lot of research on this, however the thinking is that vacuum tubing systems are very anaerobic (low oxygen). By aerating sap you are changing the level of oxygen and shifting the proportion and types of microbes in the sap. Many anaerobic microbes can give rise to poor flavor (fermentation, sour sap) and poor quality (slimy, ropey) sap. Aerating sap also increases the microbial conversion of sucrose to invert, so you do end up with a darker syrup, however the good strong flavors (especially caramelization) can mask or overcome potential poor flavors. Research is ongoing, and there are no strong recommendations as yet.
    Last edited by DrTimPerkins; 05-31-2021 at 04:26 PM.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  9. #29
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    Is there any time before, during or after the RO process that UV sterilization would be of benefit? Would it help in holding concentrate?
    First introduced to making maple syrup in 1969
    Making syrup every year since 1979
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    Bought first Marcland drawoff in 1997, still going strong.

  10. #30
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    Quote Originally Posted by bill m View Post
    Is there any time before, during or after the RO process that UV sterilization would be of benefit? Would it help in holding concentrate?
    Sure, but units that are really effective are also really expensive, so few producers use them. UV units made for water have very limited effectiveness. The thickness of the water (or sap) film around the unit and the flowrates are too high to achieve good kill efficacy.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

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