What causes my wine to be bitter?

[Snafflebit]

I am starting to get organized for bottling 2020 Cab and Merlot and did a sampling of carboys with friends. I noticed a bitterness on the back end of my wines that I did not seem to notice before. I guess that bitterness comes from seed tanins. I am fermenting on the skins to 1.004 SG, so almost to dry. I have recently learned that some winemakers press as high as 10 Brix. So, that is a technique I am considering for future vintages. But also I have 3 ounces of French oak cubes per carboy. I also use enological tannins. Do those create bitterness?

 

[Rice_Guy]

I will be interested in the answers/ solutions others have come up with:

* Tannin is made up of catechins which polymerize, as the size of the polymers grow it changes from flavorless to astringent and bitter. (last years black raspberry was bad on astringent notes at 2 years age, ,, I tried fining but gave up). Your OP notes steeping so polyphenols chemistry may be the origin.
If you are judging/ tasting I would expect tannin chemistry to have long lasting (bind in the mouth) flavor notes. I would expect chasing the flavor by eating a protein as sandwich meat would clear it out of the mouth.
* I have observed bitter notes on whites and am guessing it is also related to low YAN and mercaptan generation.
*If you have residual CO2 it will give a bitter flavor.
* On food systems contrasting flavors as sugar are used to mask bitter.
* Acid is synergistic with tannin flavors so high acid will increase that sensation.

 

[salcoco]

try a fining with clear gelatin found in the grocery store follow package directions

 

[mainshipfred]

I'm having/had the same problem with a Zin from 2020 and possibly a PS that I'm blending with. I took a sample to a commercial guy and his first thought was seed tannins and possibly a hot ferment. I don't record everyday but I never seem to have a temp higher than the low 80s. As far as seeds go the majority of them are always on the bottom of the fermenter and do not get pressed. After letting him know this he then asked if I keep up with my sulfites. I have to admit they were neglected a little and when I checked them prior to the last racking they were down to 8 ppm and never seen a barrel or oak as far as that goes.

His remedy was to try finishing tannins primarily those derived from French oak. He recommended Tannin Riche (not Riche Extra). I couldn't find it so I went with Laffort Quertanin Sweet which is a comparable. I bench tested using 100, 200 and 300 ppm which were all too much but the bitterness was gone. I ended up using 75 ppm. Even at this the tannins were a little pronounced but bearable, it just may have to lay down for a while.

 

[Snafflebit]

(last years black raspberry was bad on astringent notes at 2 years age, ,, I tried fining but gave up). Your OP notes steeping so polyphenols chemistry may be the origin.

What did you use as a fining agent? I have some bentonite, but I like the suggestion by @salcoco to try gelatin. I have a few bottles of 2016 Merlot that taste bitter. I see a very small controlled gelatin fining experiment in my future. I assume the gelatin form a lee that I try to avoid bottling?

I have also noted bitterness in whites like Chardonnay. I have never received a good explanation for its source. It could not be seed tanins

 

[Snafflebit]

I'm having/had the same problem with a Zin from 2020 and possibly a PS that I'm blending with. I took a sample to a commercial guy and his first thought was seed tannins and possibly a hot ferment. I don't record everyday but I never seem to have a temp higher than the low 80s. As far as seeds go the majority of them are always on the bottom of the fermenter and do not get pressed. After letting him know this he then asked if I keep up with my sulfites. I have to admit they were neglected a little and when I checked them prior to the last racking they were down to 8 ppm and never seen a barrel or oak as far as that goes.

His remedy was to try finishing tannins primarily those derived from French oak. He recommended Tannin Riche (not Riche Extra). I couldn't find it so I went with Laffort Quertanin Sweet which is a comparable. I bench tested using 100, 200 and 300 ppm which were all too much but the bitterness was gone. I ended up using 75 ppm. Even at this the tannins were a little pronounced but bearable, it just may have to lay down for a while.

The commercial guy may have pointed out every one of my winemaking problems. I try to keep my ferments in the mid 70's with ice jugs, but that never works perfectly. I need to ensure that in the future seeds stay in the fermenter and don't get dumped into the press. But I assume the alcohol is stripping seed tanins which then are integrated into the wine and pressing seeds will not change that.

Also, I do not add SO2 to the carboys if the carboys are just sitting in the cellar with airlocks. Maybe I need to be more rigorous with my sulfites. I do sulfite before bottling. I guess that the idea is that SO2 is binding the tannins before they polymerize?

 

[mainshipfred]

The commercial guy may have pointed out every one of my winemaking problems. I try to keep my ferments in the mid 70's with ice jugs, but that never works perfectly. I need to ensure that in the future seeds stay in the fermenter and don't get dumped into the press. But I assume the alcohol is stripping seed tanins which then are integrated into the wine and pressing seeds will not change that.

Also, I do not add SO2 to the carboys if the carboys are just sitting in the cellar with airlocks. Maybe I need to be more rigorous with my sulfites. I do sulfite before bottling. I guess that the idea is that SO2 is binding the tannins before they polymerize?

Your point of the alcohol and seeds is well taken. Maybe I'll try delestage on a wine but it is a lot of extra work.

 

[Snafflebit]

The mid 70's reminded me of this picture

 

[Rice_Guy]

I tested egg white and did gelatin on the whole batch. The size of the protein needs to be proportional to the size of tannin. i didn’t get the astringent to pull out with either egg or gelatin. Milk/ caseine is another choice.
Tannin will not complex bentonite. Bentonite can pull residual clumps of protein out, ,,, and I have meant to try that yet.

What did you use as a fining agent? I have some bentonite, but I like the suggestion by @salcoco to try gelatin. I have a few bottles of 2016 Merlot that taste bitter. I see a very small controlled gelatin fining experiment in my future. I assume the gelatin form a lee that I try to avoid bottling?

I have also noted bitterness in whites like Chardonnay. I have never received a good explanation for its source. It could not be seed tanins

 

[Snafflebit]

I am searching for fixes to bitterness. Here is information regarding tannins. I found a video from Gusmer regarding their StellarTan products. I think this includes some great info for the winemaker.

Polyphenolics StellarTan Part 1: Let's Talk Tannins!
Polyphenolics StellarTan Part 2: Tannin Preception & Management
Polyphenolics StellarTan Part 3: Tannin Management In The Winery
Polyphenolics StellarTan Part 4: Why Add Tannins?

The presenter mentions biting into a green versus ripe banana. The green banana is very astringent but the ripe banana is not. However there are exactly the same tannins in both, the sweetness masks the flavor. Actually it is more complicated, involving saliva protein being pulled away by tannin. He also mentions bitter tannin flavor will diminish as the tannins polymerize and become astringent.

I considered trying some wine conditioner to bump up the glycerol and sweetness of the wine in order to mask the bitter. But then I am concerned about affecting the aging potential.

Adding cellaring tannin seems to be another technique as mentioned prior by @mainshipfred. For the record, StellarTan HP was suggested by the video for reducing bitterness and astringency.

 

[Snafflebit]

My first instinct was to remove or fine the bitter tannins, but maybe that is fighting the battle wrong. The research is leading me to think that masking the bitterness is the right approach.

Here is a second video that more or less coroborates the other video's findings: "Adding tannins can reduce astringency. I know it sounds crazy but it works" Bucher-Vaslin Vinitan Advance

The Use of Tannins In Winemaking

 

[mainshipfred]

I am searching for fixes to bitterness. Here is information regarding tannins. I found a video from Gusmer regarding their StellarTan products. I think this includes some great info for the winemaker.

Polyphenolics StellarTan Part 1: Let's Talk Tannins!
Polyphenolics StellarTan Part 2: Tannin Preception & Management
Polyphenolics StellarTan Part 3: Tannin Management In The Winery
Polyphenolics StellarTan Part 4: Why Add Tannins?

The presenter mentions biting into a green versus ripe banana. The green banana is very astringent but the ripe banana is not. However there are exactly the same tannins in both, the sweetness masks the flavor. Actually it is more complicated, involving saliva protein being pulled away by tannin. He also mentions bitter tannin flavor will diminish as the tannins polymerize and become astringent.

I considered trying some wine conditioner to bump up the glycerol and sweetness of the wine in order to mask the bitter. But then I am concerned about affecting the aging potential.

Adding cellaring tannin seems to be another technique as mentioned prior by @mainshipfred. For the record, StellarTan HP was suggested by the video for reducing bitterness and astringency.

View attachment 86237

I was considering sweetening the wine after the tannin addition but it went through MLF. Wine conditioner has sorbate added so I'm afraid to add it. Glycerin might be considered though in my experience it takes quite a bit. I may try some bench trials using it.

 

[Rice_Guy]

flavor? ,,, last harvest I did several pickings of crab apple, *early september would be harsh/ very aggressive, *normal apple picking in October was smoother and still bitter, *collecting after frost the flavor was weak basically useless.
Banana skin has excellent astringent notes when green. Without chemistry numbers as Gusman it feels similar to the apple case where the molecules are evolving as the season progresses, ,, grape harvesting stories also use terms as harsh for early harvest tannin.

good videos, will have to think how to translate to fruit wines.

. . . mentions biting into a green versus ripe banana. The green banana is very astringent but the ripe banana is not. However there are exactly the same tannins in both, the sweetness masks the flavor. Actually it is more complicated, involving saliva protein being pulled away by tannin. He also mentions bitter tannin flavor will diminish as the tannins polymerize and become astringent.

I considered trying some wine conditioner to bump up the glycerol and sweetness of the wine in order to mask the bitter.

I have tried glycerine. In bench tests it seemed to work, but in the real world where I added two 4oz bottles and then went to the store for more and now have the quart size it turns out as not really practical.

 

[Mekpdue]

I just wanted to say this is an interesting string. I placed a WE Super Tuscan (Private Reserve-w/skins) in carboys on November 4th, '21 for aging and just sampled it. I was disappointed. Now, I have read that most red 'pasteurized' wine kits have an 'off-flavor' that can be strongly detected by some, and that by aging for 6-12 months (or longer) and bottling for another 4-6 months usually brings out the wine characteristics and leaves most of the bitterness behind. But having this wine still be 'extremely bitter' after 4 months, and especially a WE Luna Rosa bottled as per directions (still nowhere near good) in August 21, I'm beginning to wonder if adding some cellaring tannin or bottling tannin on these kits a month before bottling will help.

For what it's worth, the red FWK kits that I have crafted don't seem to have the issue. I believe someone else on here echoed this earlier on a separate thread.

And lastly, I did add some Vintner Wine Tannin to an Italian Nebbiolo juice last fall. It's coming along nicely, but truly just needs more age.

 

[balatonwine]

I will be interested in the answers/ solutions others have come up with:

Well.... Since you asked... I think it complicated. See below....

* I have observed bitter notes on whites and am guessing it is also related to low YAN and mercaptan generation.

I can only comment on white wines, since that is what I make (well... I do make Amber wine but that is another topic). And to fully clarify my position I really dislike the American ideal of wine.... Way too sweet. The total concept of back sweetening a wine. Eww. Common in the USA, but pretty much only in the USA.

So, knowing where I stand, to that, what someone in the USA calls "bitter" may not be "bitter" to another wine drinker in another country. Thus this is the first issue to consider. I for one like a bit of astringency in my wine. And rather dislike sweet wines oh too popular in the USA. Tastes differ as to what is "bitter". And, no, for reference, I thus do not like Tokaji wine.

As for YAN and mercaptans, when I have had mercaptans in my wine, the wine was flabby and dull. Not bitter or acidic or astringent. I have never measured my YAN (in fact, I do not adjust my wine or my vineyards), but I do measure my yearly environmental factors. And different years, with different weather, do create different wine, with different amounts amounts of bitter, sweetness, etc. etc. etc. That is a lot has to do with that year's environment in which the grapes are grown. That is... the age old idea of a "vintage". Some years will be different than others.

One has two options (or more --- I do not want to create a false dichotomy, but these two are the ones to most consider):

1) Spend a lot of time and effort to try to correct the wine in the cellar to make it want you want it to be.
2) Let the wine be what is it, and enjoy it for what it is. A vintage.

 

[mainshipfred]

Well.... Since you asked... I think it complicated. See below....




I can only comment on white wines, since that is what I make (well... I do make Amber wine but that is another topic). And to fully clarify my position I really dislike the American ideal of wine.... Way too sweet. The total concept of back sweetening a wine. Eww. Common in the USA, but pretty much only in the USA.

So, knowing where I stand, to that, what someone in the USA calls "bitter" may not be "bitter" to another wine drinker in another country. Thus this is the first issue to consider. I for one like a bit of astringency in my wine. And rather dislike sweet wines oh too popular in the USA. Tastes differ as to what is "bitter". And, no, for reference, I thus do not like Tokaji wine.

As for YAN and mercaptans, when I have had mercaptans in my wine, the wine was flabby and dull. Not bitter or acidic or astringent. I have never measured my YAN (in fact, I do not adjust my wine or my vineyards), but I do measure my yearly environmental factors. And different years, with different weather, do create different wine, with different amounts amounts of bitter, sweetness, etc. etc. etc. That is a lot has to do with that year's environment in which the grapes are grown. That is... the age old idea of a "vintage". Some years will be different than others.

One has two options (or more --- I do not want to create a false dichotomy, but these two are the ones to most consider):

1) Spend a lot of time and effort to try to correct the wine in the cellar to make it want you want it to be.
2) Let the wine be what is it, and enjoy it for what it is. A vintage.

All your points are well taken and in my opinion to be very true. In my case though the bitterness is way above the threshold of acceptable, almost to the point I might consider it a fault and the first time I've ever experienced it. Prior to adding the tannins the fruity level was almost non existent though tannins did bring it back a little. I have some Norton that is a real fruit bomb I'm going to blend with it and pretty sure this will be the fix, blending is a wonderful thing.

 

[balatonwine]

All your points are well taken and in my opinion to be very true. In my case though the bitterness is way above the threshold of acceptable, almost to the point I might consider it a fault and the first time I've ever experienced it. Prior to adding the tannins the fruity level was almost non existent though tannins did bring it back a little. I have some Norton that is a real fruit bomb I'm going to blend with it and pretty sure this will be the fix, blending is a wonderful thing.

Appreciate your comment. Very kind.

Of course, I can only comment on the vines I grow and the wine type I make. My experience may not be appropriate for others. For all vines and wine types. None of which be correct in all cases. Ergo -- Back to as I often say: It is complicated. We can but default to the collective mind here, and hope to improve our individual art of wine making based on maybe imperfect information, but information that will evolve over time with experience...

 

[heatherd]

Well.... Since you asked... I think it complicated. See below....




I can only comment on white wines, since that is what I make (well... I do make Amber wine but that is another topic). And to fully clarify my position I really dislike the American ideal of wine.... Way too sweet. The total concept of back sweetening a wine. Eww. Common in the USA, but pretty much only in the USA.

So, knowing where I stand, to that, what someone in the USA calls "bitter" may not be "bitter" to another wine drinker in another country. Thus this is the first issue to consider. I for one like a bit of astringency in my wine. And rather dislike sweet wines oh too popular in the USA. Tastes differ as to what is "bitter". And, no, for reference, I thus do not like Tokaji wine.

As for YAN and mercaptans, when I have had mercaptans in my wine, the wine was flabby and dull. Not bitter or acidic or astringent. I have never measured my YAN (in fact, I do not adjust my wine or my vineyards), but I do measure my yearly environmental factors. And different years, with different weather, do create different wine, with different amounts amounts of bitter, sweetness, etc. etc. etc. That is a lot has to do with that year's environment in which the grapes are grown. That is... the age old idea of a "vintage". Some years will be different than others.

One has two options (or more --- I do not want to create a false dichotomy, but these two are the ones to most consider):

1) Spend a lot of time and effort to try to correct the wine in the cellar to make it want you want it to be.
2) Let the wine be what is it, and enjoy it for what it is. A vintage.

I appreciate your points very much. On the idea of letting the wine be what it is, I talked to a US-based, small-scale winemaker (Kevin at Harford Vineyards here in MD) a couple years ago who said he doesn't adjust the grapes and let's the wine be as it is and representative of all the factors of that year. Several folks on this forum and I bought fresh grapes and juice from him for a few years.

 

[Snafflebit]

I am certainly not a wine expert, but because I make wine my American friends ask for my wine recommendations. I get to experience what my wine drinking friends say they like in a wine and how their reactions differ after their choice. Most of the time people cannot really explain the style of wine they like. A sommelier's job must be very stressful. What I have noticed in less experienced wine drinkers is a preference for fruitier, bolder wines, with a touch of sweetness which seems to signal that the wine is good value for the money. I have selected lighter Bordeaux or Brunello di Montalcino and everyone drinking them thinks they taste fine, but I can tell that they are wondering what the fuss and high price are all about. Bitter tasting wine is a very high hurdle to cross for most people, and because I make the wine for other people I have to be aware that most people will not be able or willing to explain why they don't like my product.

 

[Ohio Bob]

I was considering sweetening the wine after the tannin addition but it went through MLF. Wine conditioner has sorbate added so I'm afraid to add it. Glycerin might be considered though in my experience it takes quite a bit. I may try some bench trials using it.

If MLF is complete then it’s ok to add sorbate and Kmeta. If MLF is not complete the Kmeta will produce a geranium flavor.