Measuring YAN

[StimVino]

I attended an Advanced Winemaking Workshop at Penn State over the weekend and the instructor stressed the importance of measuring YAN of the must to determine nutrient needs. Her target was around 220 mg/L for most wines, so if you know your starting YAN then you can add the proper dosage. Fermaid O was the preferred nutrient, although we discussed a few others. We did not get into the process for measuring YAN, so my question is anybody doing this at home and what method are they using?

 

[cmason1957]

If I were to measure YAN (I don't), I would probably investigate using the Vinmetrica system and measure a few other things I don't measure now. It is probably a useful number to know, but I always just assume I need to add some and do.

 

[Rice_Guy]

There is a procedure/ chemistry available from Vinmetrica. It is as easy to run. It is a long procedure titrating two things to pH 8.2 and then a third titration to pH 8.2 to measure how much of the formaldehyde reacted with the nitrogen.

My feel is that with white it is extremely helpful, and knowing your YAN will up your game. >>> I ought to post some examples some time.

 

[StimVino]

Thanks for your input. I watched a video of the testing process on Vinmetrica's website based on your feedback.

The YAN test kit comes with formaldehyde for 25 tests, a few pipettes, and neutralizing powder for discarding liquid. It does require that you have the SC-200 or SC-300 Analyzer and support stand, and as Rice_Guy pointed out requires at least two titrations.

I also found information regarding a spectrophotometer that measures Ammonia and Free Amino Nitrogen. The two are measured separately and then combined to provide a YAN value. This method sounds easier, but the equipment is very expensive - at least new. Maybe there is a used spectrophotometer out there that would be affordable?

If I was doing a large batch, I might also consider sending a sample out to a lab for testing. I assume this is what most wineries do?

 

[BarrelMonkey]

My standard procedure is to add 20g/hL Fermaid-O at 3 brix drop and another 20g/hL at 1/3 brix drop. (So, eg if starting brix = 24, that would be additions at 21 brix and 16 brix). Even if my starting juice/must has sufficient YAN I don't think it hurts the wine to add a bit more nitrogen (particularly in the 'slow release' form of FMO) as long as you don't do it late. I wouldn't add nutrient below 10-12 brix.

I've never measured YAN at home. I have the equipment to measure it in my home lab but the most common method uses formaldehyde which is not nice stuff.

The YAN test kit comes with formaldehyde for 25 tests, a few pipettes, and neutralizing powder for discarding liquid. It does require that you have the SC-200 or SC-300 Analyzer and support stand, and as Rice_Guy pointed out requires at least two titrations.

No need for the Vinmetrica brand analyzer, if you have a pH meter (and some means of titrating - a burette or even maybe a syringe) you're good to go.

I also found information regarding a spectrophotometer that measures Ammonia and Free Amino Nitrogen. The two are measured separately and then combined to provide a YAN value. This method sounds easier, but the equipment is very expensive - at least new. Maybe there is a used spectrophotometer out there that would be affordable?

A spec would be great since there are several other useful tests that can be run with it - but it seems impossible to find anything suitable for under $1000. The other downside (which has dissuaded me from getting more lab instruments) is that everything needs maintenance (eg new bulbs) and stuff breaks, so I like to keep it as simple as possible.

And yes, most wineries (unless they're large with comprehensive lab facilities) send samples out for testing. Fo example, ETS labs runs a juice panel which is helpful and relatively cost effective if you're processing tons of grapes at a time.

 

[StimVino]

BarrelMonkey thanks for the information. I was trying to determine how much your standard nutrient addition would bump the YAN. According to Lallemand's website, a 20g/hL dose (0.75g/gal) will provide a YAN equivalent of 20mg/L, which would be 40mg/L for both doses. Assuming that the target for happy yeast is 225mg/L, then it does seem like a 40mg/L YAN addition would be safe, without going over the recommended dosage.

I know that nutrient needs are yeast dependent, but in general do you treat juice the same as grapes when it comes to nutrient addition? As Rice_Guy indicated, may be more important for whites.

 

[BarrelMonkey]

I know that nutrient needs are yeast dependent, but in general do you treat juice the same as grapes when it comes to nutrient addition? As Rice_Guy indicated, may be more important for whites.

@StimVino, here is a useful guide from Scott Labs:

https://shop.scottlab.com/content/files/documents/fermentation/FermentationManagement.pdf

(BTW Scott Labs has a ton of great information like this - mostly geared towards commercial winemakers but very useful for the home winemaker as well)

In general - higher brix, more YAN. And as you note, different yeasts have different needs, so you can bump up or down accordingly.

One point to note is that some people use must volume as the basis of calculations and some wine volume. For whites, you're working with juice so wine volume = juice volume to a first approximation. (So in answer to your question, yes I'd probably just base my 20g/hL calculation on the volume of juice)

For reds - commercial winemakers use 150-175 gal/ton as the conversion factor. I'd use the lower estimate for home winemaking. So eg if I have 1000lb grapes, that's 75 gal = 2.8hL, 20g/hL = 56g per dose. You'd go a bit higher if basing the addition on must volume, but to be honest I'd probably only add more if I had a particularly high brix must and/or high nutritional need yeast.

 

[Rice_Guy]

* @StimVino ,, a basic question, why did the instructor encourage knowing YAN? and then is that a risk that you / we as a community are willing to take?
My look at it is that we want to know YAN because stressed yeast can produce H2S. If we are unaware and let this in the wine we can produce mercaptans which are sensed at parts per trillion levels and mask fruity aromatics. This can result in a wine that can be described as reductive or skunk or the wife’s hair perm or in my local club as fried chicken and the AWRI as stinky sulfur. ,,,, This may be acceptable in a red where we don’t expect lots of fruit. BUT isn’t acceptable in whites. ,,,, can you taste/ put a name on the defect? If we look at November Winemaker magazine 2022 a contest judge was reflecting that reductive wine was the number two reason wines got docked at their contest. I tend to agree at his frequency observation.

* Next what are the risks of over doing it? With chemical nitrogen/ DAP we pretty much get 100% of what we put in so we increase the risk of bacterial infection by having excess. I am on the same page as @BarrelMonkey , organic YAN as measured in the lab is about 25% of what effect it produces on the yeast so it is safer to over dose, ,,, and ignore the bacterial infection risk if the starting YAN was high and we then add more. I have chemical nitrogen on the shelf but haven’t used it in two years.

* We as a community seem to be low on the learning curve as to what is normal. Example last fall California merlot juice tested at 171ppm. This spring Chilean merlot tested at 138ppm. (half of the needed YAN) ,,, Looking at whites last fall our California Gewurtztraminer tested at 101ppm. This month Chilean Gewurtztraminer came in at 93ppm. (in the same range/ a third if needed YAN) If I widen the field my 2022 Itasca (white) tested at 43ppm (basically I could ignore YAN from the grape just add 100%) This leads to other questions as my Itasca is five years old, do young vines always have extremely low YAN/ should we as a community expect reductive flavor on all young vines? or is it Wisconsin soil? or short growing season? etc etc.
We need to share our learnings, ,,, I don’t have anyone to compare my data with.

* Normal fermentations need 250 to 300ppm nitrogen. A few other data points. Last years apple (my seven year old tree/ first real crop) tested at 88ppm. The pear I juiced for a neighbor winemaker tested at 130ppm. The finished Marquette @wood1954 entered in state fair tested at 24ppm. . . . . WHAT IS NORMAL in juices? ie how important is knowing YAN in preventing off flavor

* Back to the test, the formal titration is based on having excess formaldehyde to react with the nitrogen. If I had a juice with 1000ppm YAN I would need to increase the quantity of formaldehyde. When I first started running I miss read the instructions and didn’t add prescribed formaldehyde, ,, with my low YAN juices the number was the same when I reran the test correctly. ,,, The Vinmetrica instructions specify any pH meter accurate to 0.02 units. ,,,, Formaldehyde forms a white solid at 5C, DO NOT REFRIGERATE THE CHEMICALS. ,,, I haven't run enough duplicates yet but am guessing the test is accurate to ten ppm (+/- 5 ppm). ,,, I may have thirty juice varieties/ buckets to run in fall. I weigh samples example if gravity is 1.089 the sample will be 10.89 grams. ,,, With my pH probe I use a glass vial that fits a #7 cork to adjust the pH of the formaldehyde. ,,,, The test is as easy as running any titration (TA) one just needs to be careful/ run slowly to accurately reach the pH end point.

 

[winemaker81]

Next what are the risks of over doing it? With chemical nitrogen/ DAP we pretty much get 100% of what we put in so we increase the risk of bacterial infection by having excess.

Although I understand what you're saying, I add nutrient according to package directions and the only problem I've had is with high nutrient requirement yeast producing H2S -- not problems from too much nutrient.

This doesn't mean that excess nutrient isn't a problem, just that by following package directions I have not experienced it.

 

[sour_grapes]

And if we use no-H2S yeast, should we even worry about it?

 

[winemaker81]

And if we use no-H2S yeast, should we even worry about it?

Yes. H2S is a highly visible problem with wine-destroying effects, but it's far from the only potential problem. A healthy ferment is best, just to avoid things such as a stuck fermentation.

 

[StimVino]

* @StimVino ,, a basic question, why did the instructor encourage knowing YAN? and then is that a risk that you / we as a community are willing to take?
My look at it is that we want to know YAN because stressed yeast can produce H2S. If we are unaware and let this in the wine we can produce mercaptans which are sensed at parts per trillion levels and mask fruity aromatics. This can result in a wine that can be described as reductive or skunk or the wife’s hair perm or in my local club as fried chicken and the AWRI as stinky sulfur. ,,,, This may be acceptable in a red where we don’t expect lots of fruit. BUT isn’t acceptable in whites. ,,,, can you taste/ put a name on the defect? If we look at November Winemaker magazine 2022 a contest judge was reflecting that reductive wine was the number two reason wines got docked at their contest. I tend to agree at his frequency observation.

@Rice_Guy your comments are spot on. Knowing YAN allows you to make correct adjustments to nutrient deficient must, which can in turn reduce the risk of sluggish or stuck fermentations, which can cause several wine faults. An example that stuck out was that a drop of phenol can be detected in an Olympic sized swimming pool. According to Penn State research, the threshold for many of the common wine faults can be detected in parts per billion and even parts per trillion, so the room for error is very small. Also, making adjustments to must is easier than dealing with faults later on that could result from stressed or nutrient deficient yeast.

* Next what are the risks of over doing it? With chemical nitrogen/ DAP we pretty much get 100% of what we put in so we increase the risk of bacterial infection by having excess. I am on the same page as @BarrelMonkey , organic YAN as measured in the lab is about 25% of what effect it produces on the yeast so it is safer to over dose, ,,, and ignore the bacterial infection risk if the starting YAN was high and we then add more. I have chemical nitrogen on the shelf but haven’t used it in two years.

Again, @Rice_Guy is spot on. The idea of splitting the nitrogen dose into two is to build a less vigorous but healthier fermentation. Dumping in large amounts of DAP at the beginning will lead to a more vigorous fermentation that will likely blow off delicate volatile aromas that are more associated with white and rose wine. The danger in overdosing apparently has more to do with timing than anything. Its better to do the second dose earlier than too late. After the yeast are done reproducing, the nitrogen will only feed bacteria. The preference for Organic nitrogen is to build healthy yeast cells that can last the duration of fermentation without spikes caused by excessive DAP.

Incidentally, a tip that I learned for white wines, not rose, is to add yeast hulls to help keep the yeast in suspension throughout the liquid so that they are more evenly distributed. Rose usually has enough phenolic content so that hulls are not needed. Same with reds.

* We as a community seem to be low on the learning curve as to what is normal. Example last fall California merlot juice tested at 171ppm. This spring Chilean merlot tested at 138ppm. (half of the needed YAN) ,,, Looking at whites last fall our California Gewurtztraminer tested at 101ppm. This month Chilean Gewurtztraminer came in at 93ppm. (in the same range/ a third if needed YAN) If I widen the field my 2022 Itasca (white) tested at 43ppm (basically I could ignore YAN from the grape just add 100%) This leads to other questions as my Itasca is five years old, do young vines always have extremely low YAN/ should we as a community expect reductive flavor on all young vines? or is it Wisconsin soil? or short growing season? etc etc.
We need to share our learnings, ,,, I don’t have anyone to compare my data with.

Having these numbers is very helpful. Without measuring YAN, we are all just guessing that the nutrient addition is correct. Even if you get grapes from the same vineyard every year, I'm sure that environmental factors will effect starting nutrients in the fruit. One of the statements that struck me at the workshop was that in 20 years of laboratory analysis for grapes and juice, she rarely gets a sample that does not require some adjustment to the YAN value.

* Normal fermentations need 250 to 300ppm nitrogen. A few other data points. Last years apple (my seven year old tree/ first real crop) tested at 88ppm. The pear I juiced for a neighbor winemaker tested at 130ppm. The finished Marquette @wood1954 entered in state fair tested at 24ppm. . . . . WHAT IS NORMAL in juices? ie how important is knowing YAN in preventing off flavor

You are correct, the targets are a little higher than I initially thought. Looking back at my notes, I think 250 to 300 is the correct target. Most of the information that I've found for starting nitrogen levels is for grapes, which generally have a lot of the good stuff that yeast already like in them. Knowing the starting nitrogen for fruit may even be more important, since fruit generally lacks the same starting nutrients levels. The exceptions are probably darker 'grape-like' berries. Adding standard doses of nutrients, without knowing YAN, seems relatively safe, especially with organic nitrogen (Fermaid O). If you really wanted to play it safe, then it would be prudent to select a low H2S producing yeast as well to avoid potential problems.

* Back to the test, the formal titration is based on having excess formaldehyde to react with the nitrogen. If I had a juice with 1000ppm YAN I would need to increase the quantity of formaldehyde. When I first started running I miss read the instructions and didn’t add prescribed formaldehyde, ,, with my low YAN juices the number was the same when I reran the test correctly. ,,, The Vinmetrica instructions specify any pH meter accurate to 0.02 units. ,,,, Formaldehyde forms a white solid at 5C, DO NOT REFRIGERATE THE CHEMICALS. ,,, I haven't run enough duplicates yet but am guessing the test is accurate to ten ppm (+/- 5 ppm). ,,, I may have thirty juice varieties/ buckets to run in fall. I weigh samples example if gravity is 1.089 the sample will be 10.89 grams. ,,, With my pH probe I use a glass vial that fits a #7 cork to adjust the pH of the formaldehyde. ,,,, The test is as easy as running any titration (TA) one just needs to be careful/ run slowly to accurately reach the pH end point.
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