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Al_The_Chemist

Ferment-able sugars in Molasses?

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I'm prepping to start on a Rum. From my reading it seems that of the sugar content in Molasses only ~52% of it is fermentable.
How should I calculate the gravity of my wash? Should I divide the sugar contribution from the molasses in half or take it as is? 

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Get an assay sheet from your supplier, don't make an assumption on the sugar content.  If you find yourself with a solid quality high-test, it could be as high as ~75% fermentable.  If you are using blackstrap from a really efficient refinery, as low as 40%, and who knows if you can even trust that number.  There is a big difference in fermentable sugars, and a big difference in price.  High test, bakers grade, fancy - you can trust your starting gravity to be mostly predictive of your yield, the bottom grades, you can't.

You can roughly work by weight of molasses (11.6 pounds per gallon) and sugars content.  1000lbs of 70% molasses is roughly equivalent to 700lbs sugar, go from there.

Don't be greedy and make your life miserable, shoot for low starting gravities in your first batches and move up from there.  

Lots of good threads on the topic.

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Thanks for the thorough response Silk City. 

Im using a triple processed byproduct  through a third party. I doubt I can trust the data. I’ll have to run a test batch and see. I’m after a darker, full bodied Rum, so I far from mind the non fermentables and solids. More a matter of planning the batch. 

Ill do some more digging and find these threads. 

 

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On 11/22/2017 at 7:55 PM, Silk City Distillers said:

Get an assay sheet from your supplier, don't make an assumption on the sugar content.

What @SilkCityDistllers said.  You can call your vendor and ask for a cut sheet. The figure you're looking for is "TSAI" -- total sugars as invert; this is the stuff that ferments.  Fancy stuff will be in the 70% range while the brooding / heavy flavors can be in the mid 40s.  "Triple processed" sounds like blackstrap. (they've crystialized and centrifuged three times??)

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It's Blackstrap. I'll ping them about the TSAI. I'm currently blending grade A with Blackstrap in an attempt to get a usable yield combined with heavier flavors. Ran the starting calculations based on Grade A at 70% and Blackstrap at 45% (these ranges seem to be confirmed across the board). Final Brix will give me a better idea. Thanks again for all the information. 

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On 11/22/2017 at 7:55 PM, Silk City Distillers said:

High test, bakers grade, fancy - you can trust your starting gravity to be mostly predictive of your yield, the bottom grades, you can't.

Digging up an old thread... Why do you say this?  I assume because there is less ash and thus fewer dissolved solids to skew the density. 

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Yep.

Compare two grades from the same manufacturer (Fancy and Blackstrap), and the Premium molasses from a third.  This bottom grade isn't the worse I've seen either, it gets worse than that.  (Added high test)

High Test
Brix 80-85%
Ash 2.2-2.5%
Invert 50-65%
Total Sugars 74-79%

Premium (Blend of A Grade and High Test)
Brix 79-80
Ash 3.5% Max
Total Sugars 68-75%

Top Shelf Fancy (A Grade)
Brix 79-80
Ash 5% Max
Invert 25-40%
Total Sugars 63-74%

Not Awful Blackstrap (C Grade or worse)
Brix 79-80
Ash 10-15%
Invert 6-22%
Total Sugars 45-60%

Awful Blackstrap (Substandard, Fertilizer Grade)
Brix 79-80
Ash >10% (Highly optimistic)
Total Sugars 44-52%

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Premium, for example, is a commonly available molasses produced for distilleries.  The Top Shelf Fancy is one that's also commonly used, it's typically sold by the drum/tote as Bakers grade.

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Last sheet we got for a tote of their " Premium" was:

  • Solids - 79 - 80% (I dont even know what this means honestly)
  • Total Sugars 68 - 76%
  • Ash < 3.5%

I was going to gripe about the wide range of TSAI but saw your figures above.  Is it possible for use to empirically determine the exact quantity of fermentables? We're having a slight yield problem I'm trying to run down and it's darn difficult if I don't know the quantity of fermentables I'm starting with.

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There's a more going on than just fermentables for rum production. Are you using nutrients? Monitoring and adjusting your pH? What sort of numbers were you getting for gravities and yield?

Solids are particles in suspension - sugars, acids, minerals, protein, fats, etc. I found a paper from the 40's on the breakdown in molasses. Ash would be the solids that don't burn off. The data sheet the molasses supplier gave you is as good as you'll get without some heavy lab equipment, but you can run a test fermentation under ideal conditions to determine expected yield.

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16 hours ago, Silk City Distillers said:

I would also imagine blackstrap molasses from 80 years ago was a very different animal.

I've thought often about this.  When Arroyo submitted his patent in 1945 I wonder if he would have use blackstrap if a "premium" molasses had been available. 

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Based on his writing, it's clear there were different grades available, but given the economics of rum as a waste product of sugar manufacturing, not sure that less-refined variations really would have taken hold.

There are some really interesting thoughts in one of his later pieces, linked below.  I thought the quote about the unsuitability of Hawaiian blackstrap for rum was very interesting.

The-Arroyo-Fermentation-Process-For-Alco

 

 

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