Are there adverse effects to adding diammonium phosphate (DAP) as a yeast nutrient in red wine?

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Dear Dr. Vinny,

Are there adverse effects to adding DAP as a yeast nutrient in red wine?

—Akbar, Pakistan

Dear Akbar,

For those not already familiar, I’ve written before about DAP (diammonium phosphate), a water-soluble ammonium phosphate salt. As you point out, it’s a yeast nutrient in the context of wine. DAP is also commonly used to support cheese cultures, as a soil additive to increase pH levels in agriculture, to purify sugar and even control dyes in wool.

But in wine, DAP and similar products are used to prevent or fix fermentation problems. Yeast is a very important part of the fermentation process, gobbling up the sugar and converting it into alcohol. But sometimes the yeast tires out before all the desired sugar is converted—that’s what’s referred to as a “stuck” fermentation. Yeasts can be old or weak or just not really digging the grapes they are paired with, or something in the environment can be getting in the way, like the temperature is wrong or something wasn’t clean, disrupting the process. And some yeasts just don’t do well without a lot of nitrogen around, which is what DAP brings to the table.

Some winemakers are against this type of intervention, preferring to make wines more naturally, without any performance-enhancing help. When used properly, not only can DAP help make sure fermentation goes smoothly, it can also prevent unwanted characteristics and even boost flavors and aromatics, but some folks call that cheating.

There are a lot of opinions within the winemaking community about when and how much DAP to add. DAP can increase the risk of volatile acidity, and some believe too hearty of a fermentation can mute aromatics and flavors. There’s also a risk that the fermentation will be too robust, creating microbial instability and paving the path for spoilage organisms.

—Dr. Vinny

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