YAN, FAN and the rest of the clan...

by Karien O'Kennedy - 05 Apr 2016

I was recently part of a conversation between a group of winemakers and the issue of measuring YAN and managing yeast nutrition came up. It seems that there are many different ways to skin this cat but the one comment that caught my attention (or had me almost hyperventilating) was from a young winemaker:

“I never measure YAN. I just make a standard addition of 30 g/hL DAP at the start of fermentation to every single tank before yeast inoculation. I have never had problems.”

I was under the impression that this practice died out along with new plantings of Hárslevelu0171 in South Africa? Clearly not in this winemaker’s case. In general, most South African winemakers have moved away from just blindly adding a heap of DAP before the start of fermentation. Many measure YAN and do additions accordingly, either with just DAP or with complex nutrition or a combination of the two depending on various factors. They also add it in increments during fermentation, with the majority of additions made in the first half of fermentation.

In the past, winemakers added nitrogenous compounds (mostly DAP) to juice or fermenting must to ensure fermentation completion and prevention of the formation of sulphur-like off odours, especially H2S. In the past decade, various researchers and companies such as Anchor Yeast, Laffort and Lallemand (who sell yeast and nutrients) communicated the importance of measuring YAN, the type of nutrition used, the timing of nutrition addition, the role of the specific yeast, etc. to ensure optimal yeast vitality and viability. More recently researchers started to communicate about the effect of YAN and yeast nutrition on wine aroma.

I do get it that due to various practical, financial and timing constraints,  it is not always possible to measure the YAN of every load of grapes entering the cellar. One must at least have the desire to do so because of the scientific significance of knowing what you are dealing with before making additions. One could end up adding too much nitrogen, which can have various negative effects.

The Institute for Wine Biotechnology (IWBT) in the Department of Viticulture and Oenology (DVO), Stellenbosch University, under the leadership of Prof. Florian Bauer, has been doing extensive research in the field of yeast nutrition and wine aroma. A new project proposal to continue research in this field has just been awarded funding from the Department of Science and Technology (DST) via Winetech, the South African wine industry’s research funding body. If you are serious about producing good quality wines, you need to be serious about nutrition management. Otherwise nature’s - as well as your viticulturist’s - work can be undone in seconds.  

The whole concept of YAN, FAN and the CLAN of nutrient options accompanying it, is too complex to cover in a single blog. Here are some useful open source links on the topic:


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