Excluding bacteria that can eat malic acid and turn it into lactic acid is the only way to make sure you don’t get refermentation in the bottle.
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Perfecting Pyment, Vinifera Vines, and Over-Yeasting
. . . you could also buy some powdered grape tannin, use oak chips, or even use a cup of strong black tea to add some tannin backbone to the wine if it’d be tough for you to obtain grape skins.
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Remember, every time you open your barrel, you introduce air and potentially some undesirable spoilage organisms.