Boston Apothecary's Arroyo & Rum library

Research sources, reviews and links to information relating to distillation.

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Single Malt Yinzer
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Boston Apothecary's Arroyo & Rum library

Post by Single Malt Yinzer » Thu Sep 27, 2018 6:01 am

Arroyo's Library

These articles are a great read for all distillers, not just you rumheads. Arroyo's focus is on the fermentation side. Most of this is pretty easy reading though some get super science-y. There is also some stuff is hard to understand as he was on the very cutting edge and the words he used to name/describe things has evolved.

https://www.bostonapothecary.com/arroyo/" onclick="window.open(this.href);return false;" rel="nofollow

Rum Library

Aka the Rum "Babel Fish". Collection of works focused on Rum. Widely varying from easy reads to what feels like quantum physics. Lots of older stuff from the beginning of real scientific investigations of fermentation and distilling. Lots of insight that we can implement. Same warning here - the language has evolved.

https://www.bostonapothecary.com/rum-babel-fish/" onclick="window.open(this.href);return false;" rel="nofollow

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8Ball
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Re: Boston Apothecary's Arroyo & Rum library

Post by 8Ball » Sat Jun 22, 2019 8:09 am

https://www.bostonapothecary.com/tradit ... -antilles/" onclick="window.open(this.href);return false;" rel="nofollow
Traditional Fermentations of Molasses and Cane Juice in the French Antilles

1.2.2. The pH.

“The pH of the molasses is about 6, that of the cane juice 5. The pH values found in the fermentations are of the order of 4.5. They are acquired by addition of sulfuric acid and by the action of the acids contained in the yeast starter. Molasses has a high buffering capacity. In the laboratory, we found that for molasses concentrations of 200 g/l, 2 g/l of pure, concentrated sulfuric acid was required to increase the pH of the solution from 5.8 to 4.6. At the end of the fermentation, the ph drop is about one unit. These values of ph theoretically should protect fermentations against bacterial attack. This is not the case, as is shown by the amounts of volatile acids produced during the fermentation and the microscopic presence of many bacteria, even if they are not all active.”

So what I gather from this study is you don’t want your rum ferment to drop below pH 4.5 due to the risk of crashing due to volatile acids produced and active & INACTIVE bacteria. The pH drop over the course of the ferment is one unit. My limited experience in rums have had initial pH of around 5.35-5.46 and finish around 4.62-4.78. My OG’s usually are around 1.074 and finish at 1.010.

There was also a mention of the benefit of low alcohol by volume percentage washes in that they resulted in healthy, FAST ferments of 36-48 hours. Increased alcohol yield and aromas.

Good stuff and interesting read.

8B
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Kareltje
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Re: Boston Apothecary's Arroyo & Rum library

Post by Kareltje » Sat Jun 22, 2019 8:52 am

Thanks for posting! :thumbup:

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Re: Boston Apothecary's Arroyo & Rum library

Post by johnnyv » Tue Jul 02, 2019 2:50 pm

8Ball wrote:https://www.bostonapothecary.com/tradit ... -antilles/
Traditional Fermentations of Molasses and Cane Juice in the French Antilles

1.2.2. The pH.

“The pH of the molasses is about 6, that of the cane juice 5. The pH values found in the fermentations are of the order of 4.5. They are acquired by addition of sulfuric acid and by the action of the acids contained in the yeast starter. Molasses has a high buffering capacity. In the laboratory, we found that for molasses concentrations of 200 g/l, 2 g/l of pure, concentrated sulfuric acid was required to increase the pH of the solution from 5.8 to 4.6. At the end of the fermentation, the ph drop is about one unit. These values of ph theoretically should protect fermentations against bacterial attack. This is not the case, as is shown by the amounts of volatile acids produced during the fermentation and the microscopic presence of many bacteria, even if they are not all active.”

So what I gather from this study is you don’t want your rum ferment to drop below pH 4.5 due to the risk of crashing due to volatile acids produced and active & INACTIVE bacteria. The pH drop over the course of the ferment is one unit. My limited experience in rums have had initial pH of around 5.35-5.46 and finish around 4.62-4.78. My OG’s usually are around 1.074 and finish at 1.010.

There was also a mention of the benefit of low alcohol by volume percentage washes in that they resulted in healthy, FAST ferments of 36-48 hours. Increased alcohol yield and aromas.

Good stuff and interesting read.

8B
Yeasts can produce large amounts of volatile acids, no need for bacteria.
Mostly acetic acid but also smaller amounts of longer chain fatty acids, more than enough to bring the pH below 4 if not buffered.
Even 0.1 g/L of Acetic acid would be pH 3.79 and five to ten times that molarity wouldn't be uncommon at the end of a ferment.

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Re: Boston Apothecary's Arroyo & Rum library

Post by johnnyv » Tue Jul 02, 2019 7:00 pm

johnnyv wrote: Yeasts can produce large amounts of volatile acids, no need for bacteria.
Mostly acetic acid but also smaller amounts of longer chain fatty acids, more than enough to bring the pH below 4 if not buffered.
Even 0.1 g/L of Acetic acid would be pH 3.79 and five to ten times that molarity wouldn't be uncommon at the end of a ferment.
Looking into this a little further it seems there is a massive variation in acetic acid production via saccharomyces cerevisiae and in wine production at least a lot of the acetic acid is via acetic acid bacteria.
Found some info on saccharomyces cerevisiae more applicable to rum production.
https://www.hindawi.com/journals/bmri/2010/419586/" onclick="window.open(this.href);return false;" rel="nofollow

With Lactrol antibiotic S. cerevisiae Saf-Instant (Baker’s yeast) produced 0.3537 g/L acetic acid which is significantly lower than without Lactrol at 0.7532 g/L so other microbial contamination caused a doubling in acetic acid production.

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