Oaking in Stainless Steel - Metallic Taste in long term storage?

Hi - I've been reading the forum and can see some folks are using SS kegs to oak their spirits. I've also read material elsewhere on the internet that stainless steel might / will impart metallic flavours into spirit - especially if it's left in the stainless steel for a lengthy time e.g. 1 year +

So far I've been oaking my rum in 23L glass carboys. That's ok, but I've come across some 100L stainless steel vessels (rated AISI 304) at a good price (£139 GBP) which would be more space efficient and easier to handle.

Since the shipment costs mean I would need to purchase a few at a time to make it cost-effective, I'm undecided what to do because any taste transfer from the metal would render the purchase useless. Does anyone have any experience of these sort of issues please?

Comments

  • Difficult to answer because SS304 properties vary especially from China where just about all originates as of today. In principal NO, there ought be no "expart" of metallic flavours.

  • @richard - I should have said the SS vessel I'm considering is the Italian Sansone 100L "Stainless Steel Fusti Drum"

  • Glass can corrode as well, and contain impurities. Just sayin...

  • @jaytee. A couple of other guys here are doing it and so have I. Look what I have found is this that in these vessels you can get a lot of great oak flavor or wood flavor as I am using alternative woods, in a very short period of time. But one of the things that I have also found out it still takes time for these flavors to mellow. If you read about wood and whiskey interactions most of the research indicates that the aging process takes place inside the wood with the presence of oxygen, the wood compounds and whiskey. In a close stainless vessel you dont get the oxygen, even if you bubble it wiht a bubbling machine regularly. My latest round of experiments I put whiskey and my woods in the SS vessels, heat cycled them for 6 weeks ( put them in the sun and then in the shade ) and then decant them and put them in a french oak barrel that had a relatively neutral oak flavor. What I found was that inside hte oak barrel as it breaths the wood compounds and flavors from the other woods do age out and mellow and you can get some very interesting flavor combinations. The latest whiskey I made that everyone who has tried it loves is called a multgrain, multiwood. It has 4 grains, barley, smoked barley, wheat, oats and a touch of quinoa, and it was aged first in SS barrels with two brazillian woods, Jequetibia and Amburana, ( the first for soft honey notes the second for florals), American oak chips ( for vanilla) and then it was put in a 50l french oak barrel for 5 months, The result is a very complex whiskey with lots of things for your tastebuds to look for. In retrospect I think I overwooded it in teh first stage in the SS barrels and not enough time in the oak barrels. It was all becoming too complex. But over time out of the oak barrel it is still breathing a bit and mellowing out.
    As for a SS flavor I havent been able to taste any and I have really tried. ha ha ha. If your going to use these barrels add oxygen periodically and have a couple of normal oak barrels for finishing.

  • Forget who in the bourbon world that said it, but it goes something like.

    You pick up an incredible amount of oak flavor in the first year, the most you'll ever extract during the entire aging process. You'll then spend the next several years, trying to get rid of the oak flavor.

  • Thanks guys - some really helpful comments.

    @DonMateo - When you say "add oxygen periodically" with reference to stainless steel, are you meaning that you open the lid of the vessel for 1 day per week (for example) or are you using a tool to bubble air through the spirit?

  • @jaytee. Yes your right. I add oxygen with a little aquarium air pump. About 20 minutes every week. But as I said and @grim correctly ads. Its very easy to over wood in the SS barrels and the only way out is to blend with the same whiskey either un wooded or underwooded.
    When I put it in the barrels I put it in a place on my patio that gets about 4 horus sun a day. So the sun hits the SS and heats it up, alcohol is very heat sensitive so that creates a large amount of pressure in the vessel which forces the whiskey into the wood and then as it cools down it creates a partial vacuum and the whiskey goes out. @grim is correct using this method its easy to get a lot of wood and then hard to get rid of it. My first couple of attempts I used 10g/litre of wood which was waaayyyyy too much. THe last try was 2 grams per litre and after 6 weeks it was too much wood and time to rest it in the oak. But I did have 3 woods in the SS barrel so the total was about 4grams per litre.
    In the future I think I will have some 3rd use barrels that I use for aging out whiskey that have been wooded with the accelerated aging in the SS tanks. I do really like the result as you can get some interesting flavor combinations fast but you still need to age on oak in a barrel. I did a charter whiskey, which is corn whiskey and I put that on the 3 woods and hten in a french oak but with this one I took it off early ie after 4 weeks and the put it in a normal barrel. THe result was very nice actually.

  • edited April 14

    Cheers @DonMateo, @grim & @richard. From my point of view oaking seems to be the trickiest part of the process. I've got much to learn :-)

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