Persistent off-flavour in gins

[Mackenzie]

Hey everybody,

We have a persistent problem with gins produced on an R&D still (20L copper alembic). After years of using this still successfully to make great product, we have recently found that gin produced on this still has a "wet dog," "skunky," or sulfur-y aroma.

I'm out of ideas for what the source could be so I'd love to get some more suggestions! Our process is as follows:

• Cut neutral from 95% to 40%
• Macerate botanicals for ~24 hours. Total botanical load is approximately 25 grams botanicals per liter of 40% spirit.
• Run pot still with botanicals inside
• Take a small (~0.5% of still charge) heads cut, and collect gin until distillate goes "weak" or bitter at ~65% ABV
• Cut gin to 40%

We made gins very successfully on this still for years. There was no obvious change that led to this problem. The product is not saleable -- and my concern is that if we scale up and do a gin run on our big still, the off-flavour might occur there too. A non-exhaustive list of things we've tried to tackle the problem: 

• Our neutral spirit is clean and lightly fruity, and does not contain this off-aroma before gin distillation
• Our botanical sourcing has been entirely refreshed to make sure we didn't have any stale/problematic botanicals
• The still has been cleaned with a 1% citric acid solution

Any ideas out there? Happy to provide a sample recipe if that would be useful. Thanks for any help!

[FIVE x 5 Consulting]

Some ideas:

You didn't describe the water you're using for cuts. Sulfur might be coming in that way...?

Try a water, vinegar or neutral run to reduce the number of variables at play.

Check/replace gaskets and tubing.

Clean everything again, perhaps with a weak caustic.

[Kindred Spirits]

Have you cleaned the still recently? If you have too much oxidation on the copper of your still, it may not be cleaning up the distillate the way it used to. Also with your botanicals, you said you refreshed them, did you switch sources for them?

[Mackenzie]

Thanks to everyone for your replies! Extremely frustrated with this issue.

• We are cutting to 40% with RO water from a local filtration company.
• All our gin botanicals have been switched to a new source in the past six months.
• The still has been cleaned immediately prior to the run with a 1% citric acid solution. The copper in the still shouldn't be "tired" as it has been relatively lightly used. The neutral we're starting with doesn't have any perceivable "savoury" aroma: it's becoming perceivable post-gin distillation.