Left on Gross Lees - Too Late?

[1galbrewer2]

I forgot to rack my cab franc and cab sauvignon off the gross lees after MLF was complete. Fast forward a few weeks and they smell as awful as you can imagine. I used Renaissance yeast which doesn’t produce H2S, so I guess I got over confident and didn’t check.

Any hopes in getting rid of the H2S? I splash racked twice, letting it flow down a copper tube the second time. Should I continue doing so? I’m afraid of oxidizing the wine post fermentation, and I’m not comfortable using copper sulfate.

 

[winemaker81]

Add a double dose of K-meta and stir well.

 

[David Violante]

Bryan, when you say stir well, I envision a few different scenarios, and having had H2S occur for me can you clarify a smidge?

1. Is the ‘stirring well’ to get the SO2 dissolved and into solution or is it to agitate the solution to get the H2S out? (Or both)

2. I see the below scenarios of stirring:

a. Gentle swirls of the wine below with a calm surface​

b. Swirling that picks up lees and the surface swirls a little​

c. Strong movement and the beginning of an air vortex​

d. What looks to be a small tornado touching down in the vessel​

​

The Journal of Introductory Biology Investigations published a paper on the Effect of Agitation on CO2 Output in Saccharomyces cerevisiae Yeast with three levels of movement, finding the highest level of agitation producing the most CO2. They describe the levels in terms of RPMs, but not necessarily in lay terms. Also, there are other factors in our scenario, such as oxygen ingress that we may not want at vortex levels, but that may be what’s needed for H2S egress.

Other options include splash racking, sparging with an inert gas, lees / sediment management and use of copper sulfate.

 

[winemaker81]

Bryan, when you say stir well, I envision a few different scenarios, and having had H2S occur for me can you clarify a smidge?

Ahhh ... your telepathy is not working this morning. Ok, I can clarify!

Note -- this is a long one. Get a fresh cup of coffee (or wine) before continuing ...

When doing normal degassing, I run the drill-mounted stirring rod until it builds a small vortex (roughly between C and D in your list) then run it for 20 to 30 seconds. Then reverse the drill and do the same thing,. I typically say "1 minute" as that's the rough time frame for the process, and I've found it's sufficient.

The 1 minute stir is sufficient to disperse K-meta.

I've had 3 personal encounters with H2S, all slightly different. The general treatment was the same, but the details varied. Stirring varied, so I'll explain that first.

2020 Red Blend second run -- This was in 54 liters of wine. We were racking it the first time out of the demijohn when the stench of H2S hit us. My notes state we stirred for 5 minutes. I had a fan running so it blew the stench away. When the wine stopped reeking, I stopped stirring.

2022 Tempranillo -- This one had been in the warehouse too long and had mold. We discarded the worst clusters, hit it with a double dose of K-meta to address remaining mold, and started fermentation using RC-212. Two days later we caught a slight whiff of H2S. So we hit it with another triple-dose of K-meta. This was a grape must, so there was no "stirring". I punched down and mixed the best I could for probably 8 minutes (this is a guess, I didn't time it).

2023 Sangiovese -- Last year caught H2S early in a juice bucket that started fermenting ahead of time. For that one I stirred for probably 2 minutes, and as it was caught very early, 1 minute may have been enough.

Treatment

The exact treatment for each differed because they were caught at different stages.

2020 Red Blend second run -- This one was caught way late, so we added a double dose of K-meta and stirred. That took care of the H2S, but mercaptans had formed, giving the wine an off taste, not exactly bitter, but not good. I ordered Reduless and used the median dosage. 4 days later I fined with K&C.

There was still a residual off-flavor that didn't go away (mercaptans). 4 months later I added 3/4 tsp ascorbic acid to each of three affected 19 liter carboys. The calculation I used said 1-1/4 tsp, but I went with less. As I often say, it's easier to add more than to take some out. It took about 4 months, but the off taste went away and the wine was good.

2022 Tempranillo -- This one was caught early, in the initial part of fermentation, so I added K-meta and nutrient. Then did the punch down as described above. The stench went quickly away, it was caught early to mercaptans didn't form, and the wine was (and still is) good.

Two lessons from this. One -- when using a yeast with high nutrient requirements, use 50% more nutrient than the directions call for. If the wine is still fermenting, regardless of where it is in the process, add nutrient, as stressed yeast is the source of the problem.

Two -- don't go nuts on K-meta. We had already double dosed because of mold, and I added a full teaspoon to the fermenter, which was probably another double dose. This produced a burned match smell. This is not a fatal problem; we didn't add more K-meta to that wine until it had been in barrel for a while.

2023 Sangiovese -- We added pomace from grapes to a pair of juice buckets, and I had to keep the buckets cold enough to not ferment for a week. This didn't quite work, and both buckets started fermenting, even if slowly. One smelled of H2S so I stirred, added 1/4 tsp K-meta and nutrient to each, and sprinkled in 2 tsp Avante yeast. I don't normally inoculate in that fashion, but I figured it would not hurt.

 

[1galbrewer2]

Thanks so much for the responses. There was no sulfur smell during fermentation, I think it’s purely because I forgot them on the lees.

The K-meta you’re suggesting to add is just to fight off oxidation from splash racking/stirring? How much of a dose do you recommend.

I hadn’t heard of ascorbic acid being used to combat mercaptans. Is this something that can be done? I fear I may have mercaptans already. Not sure how long they take to form, but the smell is quite strong. It definitely smells strongly of rotten eggs and butter (from MLF), but I might be getting the rotten vegetable smell as well.

Would trying to add a small amount of sugar and yeast starter perhaps process some of this out?

 

[David Violante]

Ahhh ... your telepathy is not working this morning. Ok, I can clarify!

Bryan, thank you for your thoughtful reply, it was really quite helpful to hear the components in context and why you did what you did. And, no, no telepathy today I'm afraid... perhaps I need another cup of coffee on this second Monday of the week.

As a quick answer to @1galbrewer2 the typical / usual dose of KMETA is 1/4 tsp per 5-6 gallons of wine/must.

Using ascorbic acid was a great question that I looked up and found (an) answer as per the Australian Wine Research Institute. Bryan and the collective will have to give us their actual experiential take.

If a wine containing sulfhydryls (mercaptans) is aerated to remove a suspected ‘reductive aroma’ fault, these compounds can be oxidised to disulfides, which do not react with copper and therefore cannot be removed by copper fining. Removal of disulfides requires the creation of reducing conditions, by the addition of ascorbic acid and SO2, in order to reduce these compounds back to the reactive species (MeSH and EtSH ), which may then be removed by treatment with copper.​

​

I'm not sure restarting a fermentation would be helpful, but more experienced folks will have to chime in to confirm.

 

[winemaker81]

The K-meta you’re suggesting to add is just to fight off oxidation from splash racking/stirring? How much of a dose do you recommend.
...
It definitely smells strongly of rotten eggs and butter (from MLF), but I might be getting the rotten vegetable smell as well.

If you're smelling rotten eggs, then it's H2S. Add a dose of K-meta (as David said, 1/4 tsp per 19-23 liters) and stir for 5 minutes or so. Rack back into a secondary container.

Sniff the wine the next day -- if you smell rotten eggs, then you probably need something like Reduless.

If you smell cabbage or burnt rubber, and/or the wine has a strong off-flavor (hard to describe), that is mercaptan, and you'll need ascorbic acid.

Restarting fermentation will not address the problem.

 

[1galbrewer2]

If you're smelling rotten eggs, then it's H2S. Add a dose of K-meta (as David said, 1/4 tsp per 19-23 liters) and stir for 5 minutes or so. Rack back into a secondary container.

Sniff the wine the next day -- if you smell rotten eggs, then you probably need something like Reduless.

If you smell cabbage or burnt rubber, and/or the wine has a strong off-flavor (hard to describe), that is mercaptan, and you'll need ascorbic acid.

Restarting fermentation will not address the problem.

Thanks again. It smells like if you covered burnt popcorn with movie theater butter and rotten eggs. I think the mercaptans have likely started to form.

I’m going to try purging with co2 tonight and maybe sticking a copper pipe in there longer. If that doesn’t work I’ll add ascorbic acid. Leaving it a sample alone in a glass for a while seemed to help a good amount, so I’m cautiously hopeful. Thanks again for the help.

 

[winemaker81]

I’m going to try purging with co2 tonight and maybe sticking a copper pipe in there longer.

Use of copper in this fashion is a bad idea, as you have no idea how much you're introducing into the wine.