Log In / Join Now

Ask Dr. Vinny

Do you have a question for Dr. Vinny? Ask it here...

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

Wine Basics

We break down the basics—how to taste, serve, store and more. Plus:
» Maps of major wine regions
» Grape variety characteristics

How-to Videos

Learn to taste wine like a pro, pull a cork with flair, get great wine service in a restaurant and more

Wine Spectator School: All courses are FREE for WineSpectator.com Members

Learn from the experts and get the most out of each sip. Take one of our online courses or take them all—from the ABCs of Tasting to in-depth seminars on Food Pairing, California Cabernet, Bordeaux, Tuscany, Sensory Evaluation and more.

Browse our course catalog
Check out the professional wine sales and service courses
Learn Wine Forum: Got questions? Get answers

WineRatings+ app: Download now for 340,000+ ratings.