Sodium hydroxide as pH adjuster for rum wash?

[RumFiend]

Scenario: a 4th gen rum wash didn't take off when yeast was pitched so 4 tablespoons of NaOH (sodium hydroxide) were added to bring the pH to 5.10. This pH level was chosen based off the result of a similar batch (3rd gen wash of same dunder lineage) whose pH needed adjusting (up to 5.48) to get the fermentation to take off.

There was a considerable amount of dunder used for this wash, 50% in fact, which is a bit more than the usual.
I couldn't find much on sodium toxicity except for this article on google scholar, http://mmbr.asm.org/content/74/1/95.full, which I couldn't really extract any meaningful information from. There was one thread here which concerned NaOH and listed ppm values but nothing as the details of the toxicity (are toxic byproduct pathogenic to humans produced? is the toxicity to do with the yeast?).

After the pH was adjusted, stirred thoroughly, and left to sit for 3 hours the yeast appeared to spring back into action, creating swirls of activity on the top of the wash. However an unusual smell was noted, slightly 'fishy' and/or pungent, much more so than a Pugirum wash usually would.

I'm going to monitor the wash over the coming days but I was wondering if anyone could provide some safety info regarding sodium hydroxide in washes. Does it suffer a similar ammonia-producing problem that sodium carbonate during distillation of low-wines does?

If NaOH proves troublesome I'm either going to have to use less dunder in each new wash (not ideal as I want to build up flavour quickly), or find a better pH adjustment compound (and it looks like sodium (bi)carbonate is outa the picture as a inconveniently large amount would be needed). I wonder how the commercial distilleries deal with this problem?
If NaOH proves troublesome I'm going to have to either use much less dunder so as not to effect

[Meatheadinc]

Although I have no personal experience with lye- caustic soda. I have heard of its use in distillation.

It has been long time since chemistry class but I believe it will make a great buffer ( sodium citrate) when combined with citric acid, similar to sodium carbonate and citric acid but will require less volume.

[wynnum1]

POTASSIUM BICARBONATE they use for wine but wine may have different acid to rum.

[db1979]

I suspect your problem with the fishy odour is more to do with your dunder or the amount of dunder. Sodium hydroxide will not have any impact on anything other than adjusting pH, unless it isn't stirred in well (at high concentrations it could cause unwanted degradation of esters and other chemicals that you may want to keep in your ferment, but stirring during the addition should prevent that and it would only be minimal and affect only a very small portion of your wash).

It will react with acids to neutralise them and the result will be the sodium salt of the acid and water. The sodium salt of any acid that you currently have in your dunder will not be any more toxic than the acid itself so there shouldn't be any concerns there.

Now the fishy smell is most likely due to an amine that WAS protonated (in its acid form, and far less volatile, or smelly) or acidified prior to the addition of the sodium hydroxide whereupon it then became the free amine (after reacting with the sodium hydroxide) which is much more volatile and hence the smell.

So I think you've already answered your own question... use less dunder if you want to minimise the smell.

Also potassium bicarb and sodium bicarb will have the same result... the smell is not caused by the base that you use, rather that the pH has been adjusted to a point where the smelly chemicals are now volatile.

As meatheadinc said, sodium hydroxide when used with citric acid will buffer your wash.

Hope this makes sense, I've had some beers...

[db1979]

The article you linked to basically says that yeasts are known to have ways of dealing with high concentrations of sodium and potassium ions and it was summarising the research that has taken place to work out how yeasts do this.

[RumFiend]

db1979, fantastic reply, thorough and thought out, and definitely made sense. Cheers mate 8-)

[RumFiend]

Alkali Metal Cation Transport and Homeostasis in Yeasts
Movement of Sodium and Cell Volume Changes in a Sodium-rich Yeast
Effect of salt hyperosmotic stress on yeast cell viability

Full of juicy (read: very dense) information regarding the effects of metal cations (i.e. sodium) on yeast cells.