Is there a way to combat oxidation already started

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Aug 9, 2015
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I probably already know the answer to the question in the subject line, but I figured I'd put it out there and see if any advice/solutions that could help out. The situation is this. I have a Malbec that is about a month away from being bottled. Just did the most recent test and came back with, TA at 6.9 and pH a bit high at 3.7. Free SO2 was low so calculated and added the Meta. Admittedly the 3 gallon carboy was not completely filled for storage. Probably about 2.7-2.8 gallons (estimate). So I know there was more air in there then there should have been and it has had some effect. The last few times I have done tests, (tasted) everything has seen fine, but the one I did today, you can taste the oxidation just beginning. It has a slight hint of a bottle that has been opened for awhile. So my question is, is it to late? Is there a way to slow it down or stop the oxidation? Thanks.
I'm not sure what you are detecting, but the usual oxidized aroma starts as acetaldehyde, though it could be other compounds. Acetaldehyde reacts quickly with sulfite, so the aroma should have already improved. You should probably retest free sulfite as the amount of acetaldehyde present before the addition is unknown, so the free sulfite may not rise as high as calculated. You could consider adding a small dose of tannin FT Rouge, I said small dose, preferably before adding sulfite, as it may help tie up acetaldehyde reducing the amount that binds with your sulfite addition.
I looked into the PVPP from Scott labs. Looks like it is what I need, but it's wine uses seem to list just whites and rose'. I have some polycel that I used on a white i did recently, so I might do a bench trial just to see what happens. Good to know about the acetaldehye. Hopefully it helped when I put in the SO2. I mixed it in and closed the carboy, so I did not note if any aroma changes happened right away. I will retest the SO2 again in a couple days and see where I am at. What I am detecting is the raisin (casis?) smell and taste. Not to strong, but an underlining hint of it. Reminds me of a bottle that's been open awhile. Hopefully it's not to far gone. Thanks for the help.

Not to be a jerk, but I am glad that you have determined the cause of the oxidation and have learned your lesson..

Keep them filled up, and maintain the proper PH and SO2 levels.
As they say, live and learn. So there is about 3 weeks left before bottling so for the remainder of the time I got some marbles to off set the air space. The marbles are clear glass, but are from china. So I put them in some Zip lock sandwhich bags and worked them into the carboy. (Sanitized everything of course). Thoughts??
Thanks for the link. Very interesting. I will try this or use the polypol, hopefully in the next couple of days and report back once the process is done.
I finally got around to adding the polycacel about 4 days ago. Racked this morning and added some bentonite and going to wait about 10 days before I rack again and let it store again. The results were pretty good. The off "bottle has been open for awhile" flavor has pretty much disappeared. The wine did get a bit "harsher" then it was before, but I am hoping that time will mellow it out again. I will report after I rack off the bentonite. Happy New Year everyone. Peace.
Update. Racked the Malbec off the bentonite and very happy with results. Tastes pretty darn good and the oxidation taste is no where to be found. Did so2, TA, and pH tests. TA at 7.2 but pH still high at 3.68. I added a little TA to try to get pH lower (since I have some TA room) and got the so2 levels up as well. Put some inert gas (CO2) on top and closed it up. The process work very well in my humble opinion. Thanks to everyone for their insight. Peace