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Molasses Fermentation

  1. Feb 20, 2012 #1
    A couple of questions regarding the fermentation and distilling of molasses,

    What is the effect of yeast on the fermentation process? Would varying the amount of yeast effect the amount of ethanol produced or purity of it.
    What is the best ratio of molasses:yeast is this worth investigating?
    Does temperature effect this process too?
    What role does the added water play on the fermenting process?

  2. jcsd
  3. Feb 21, 2012 #2


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    Yeast is the machine that converts the sugar into ethanol. Do you think more of it might affect how fast it is produced? Is the speed of fermentation the same as the amount? The purity?

    Yeast will go to sleep when it gets too cold and either just shut down or die if it gets too hot.
  4. Feb 21, 2012 #3
    Yes, we found out today that varying the amount of yeast will just change the rate of fermentation,
    So we have decided to change the concentration of the molasses and water
  5. Feb 21, 2012 #4


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    Different strains of yeast will tolerate different sugar and alcohol concentrations as well.
  6. Mar 7, 2012 #5
    It was found that,
    The higher the concentration of water in the fermentation process, the more pure the ethanol produced is, however the less the yield is.
  7. Mar 14, 2012 #6
    Here are some findings, See attached spreadsheet for graphs and results,

    The first graph is, the amount of water we had in the fermentation process (water is the variable in our experiments), against total ethanol produced in grams.
    To get the total ethanol produced, we first worked out the density of the liquid produced after distill, we put this on a density vs % ethanol curve, to see what percentage of ethanol was produced, This was then multiplied by the mass of the liquid produced, ending up in grams how much ethanol we actually made. It seems that the optimum amount of water is between 200ml-300ml of water in the fermentation process. We are currently working on an explanation for this, we post soon,

    The second graph, shows the amount of water in the fermentation process, against the heat produced per gram of ethanol. We used a % ethanol against heat produced graph, which gave us the heat produced then this was divided by the mass of the total ethanol produced to give heat produced per gram of ethanol. Don't really know whats happening in this graph??, the first free points line up, but from 300ml onwards its a bit bizarre, do you know whats happening?

    In terms of using this process to create ethanol as an alternative energy supply. we are about to conduct another experiment to find out the wattage of the gas tap and to see if this process if worthwhile for the amount of heat we get out of it, or are we using to much heat to get a little amount out of making it completely pointless.

    The 3rd picture shows all the information we have so far. Any suggestions on what extra things we should look out/find with this information (graphing, calculating or conducting another experiment. Or any suggestions on what we should do next?


    Attached Files:

  8. Mar 21, 2012 #7
    At the start our project it was going to be with molasses but we changed it to HONEY after this post was made... SOme additional information we have come up with, any thoughts?
    Yield of ethanol is mostly about survivability of the yeast. Yeast can't survive too high concentrations of sugars (osmotic pressure) and too high concentrations of ethanol (denaturation of proteins). You want them to process as much sugar as possible in as small volume (less processing) as possible.
    So there is an optimum amount to produce the most amount of ethanol as what you would expect. The less water, the more concentrated the honey is, because it is so concentrated it is killing the yeast. Honey keeps, it doesn’t go off. It doesn’t go off because it is so concentrated in sugar that the osmatic pressure in the bacteria cell wall sucks all the water out so it is becomes with lower levels of water, it is more concentrated than the bactiral cell wall so it is much more concentrated than the yeast. So the water inside the yeast just comes out inside the honey drying the yeast out and killing it.

    Alcohol denatures proteins by disrupting the side chain intramolecular hydrogen bonding. New hydrogen bonds are formed instead between the new alcohol molecule and the protein side chains.

    Proteins depend heavily on "hydrophobic" interactions
    Water molecules like to form strong hydrogen bonds with each other, if there's a large surface area of protein in the solution, these interactions are disrupted. In order to minimise exposed surface area, the bits of the protein which aren't able to interact with each other tend to fold over themselves to minimise exposed surface area. In like a ball or coil.
    The more pure the ethanol is, the tendancy for non-interacting regions to stick together is much weaker so proteins tend to unfold.

    The more water that is added, the more pure the ethanol is because it denatures protein too quickly and forms a thin outer layer of denaturated protein beyond which the cell lives on.
    Too much alcohol = dead yeast.
    Hydrogen bonds cause the tertiary structure (ethanol) to stuff up. Only one hydrogen bond needs to stuff up and the whole process is over and the yeast dies.

    All the sugars in honey get fermented into ethanol,
    38% of honey is Fructose, 31% of honey is Glucose, 17% is water, and the rest is other sugars.
    Since fructose and glucose have the same molecular formulas the approximate equation for
    honey->ethanol is
    C6H12O6 --> H3CH2OH + 2CO2
    Using that formula,
    It was estimated that we should get 41g of ethanol out of how much honey we put in.
    This was used to work out the percentage yield and turns out our method wasn't very efficient as the most ethanol that was made was about 5g, so how highest percentage yield was about 10%.
  9. Mar 21, 2012 #8
    Honey is easily fermentable, but as it is mostly sugars, the yeast ferment it slowly.
    My experience is just from homebrewing, but I've used honey a lot.
    Meads take longer if only honey and water are used, and typically I will add yeast nutrient, which is urea and ammonium phosphate to help the process speed up.

    While the sugars are fermented, yeast do require trace minerals/vitamins during fermentation, which honey has low amounts.

    With yeast nutrients, the fermentation can take place in about the same about of time as with malt grains (3-5 days), without it, it can take weeks or even months to ferment completely through.
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