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Is MLF testing necessary?


Robert Outenreath — San Rafael, California asks,

I’ve read a lot about malolactic fermentation (MLF) and think I know the basic principles. What I do not understand is the constant recommendation to test for the end of MLF with a relatively expensive chromatography kit.

Obviously, if one is going to bottle within a few months after starting MLF, you want to confirm the end of MLF to avoid exploding bottles later.

However, and this is my question: if you are going to age your wine in a carboy for many months before bottling, won’t it be certain that MLF will be over after sitting in a carboy after six or eight months, and there is no need for testing?

You are absolutely right that most wines, especially those that are inoculated and have favorable conditions, will go malolactic (ML) complete within six or eight months of harvest. Even if your area gets cold and your ML bacteria have to take a bit of a “long winter’s nap,” it’s likely they’ll wake up when the weather gets warmer and will tick your fermentation down to completion. This is especially true for big reds that age even longer, like Cabernets and Merlots. There are two problems with just inoculating and assuming that your ML fermentation will be fine: 1) It’s possible conditions aren’t favorable and your MLF will stick, and 2) You want to know when MLF is complete so you can rack and start adding SO2 right away in order to protect your wine. I’ll tackle the second point first. Basically, when wine is undergoing an active primary or secondary (MLF) fermentation, it’s protected by the carbon dioxide gas being released by the microbes. When the ML fermentation goes complete, however, your wine becomes extremely vulnerable to oxygen and spoilage
Response by Alison Crowe.