Sulfur off-odors question

[Stressbaby]

I have a batch of country wine, Lemongrass Mint. It has a grape base, Alexander's Sauv Blanc concentrate. I've made this wine before and it was really pretty good. This time I got a nasty off-odor.

The wine was started 10/15/2016; pH 3.48, SG 1.085. The yeast was QA 23, rehydrated with GoFerm. Step fed Fermaid K, and at 1.009 noted an off odor which seemed to resolve with splash racking to secondary. It got Kmeta preferment, again postferment, then a third dose 2 weeks later (about 2 weeks ago) when I found the SO2 level to be 19 by titrette method.

I went back to the wine last weekend and the odor was horrible. It was not rotten eggs or burnt matches. I can't quite decide if it was disulfide/onion/burnt rubber or more like methyl mercaptan/rotten cabbage, possibly more the latter. Also reminded a bit of bandaids. It was the exact smell I have gotten on citrus wines in the past. I vacuum racked twice with the Ai1 using the sheet film technique with no apparent effect. I dropped a bit of copper into a glass with about 30ml of wine and this seemed to help some. So, I ordered some copper sulfate (along with some Reduless) with a plan to trial copper +/- ascorbic acid to see if it helped.

I went back to it today and lo and behold, the smell is practically gone. My only intervention was the racking x 2.

Questions:
1. Does the treatment of reductive odors with racking have a delayed effect?
2. Can I expect this off-odor to return, and if so, what preventive measures should I take?

 

[cimbaliw]

Completely unscientific but I've found through trial and error, with RC212 yeast, that racking by itself may be enough to rid off odors, as with your situation. Specifically, the lees alone seem contain the off odors. This has been the case when I have fed the RC212. When the RC212 was not fed, the undesired odors are more challenging to get rid of. In this instance I used multiple rackings, additional KMeta and the tincture of time. Lastly, the couple of times I've tried adding dried mangos after fermentation did not produce the desired result, unless you like eau du burning tire.

I am doubtful the odors will return.

 

[NorCal]

I found splash racking can help a mild case and it is best to not judge right away. If you have clean wine, off the lees now and keep on the SO2 levels up, you should be out of the H2S woods.

 

[Stressbaby]

Thanks, folks! I appreciate the feedback.