Bitter after taste

[maan]

Hi,

This is my 2nd batch of home made wine. I did Cab and Zinf back in 2021, which turned out pretty good.
Y'day I tasted my 2022 Merlot from one of the carboys, this is my 2nd tasting it. The first one was in early 2024. I feel like
it's turning bitter, especially the after taste. It tastes pretty good at the pallet in the beginning but the after taste is very bitter.

What could be going on ? Is there a way to fix it ?

Thanks in advance for the help.

-Maan

 

[sour_grapes]

I made a batch of Merlot a couple of years ago that was quite bitter. My suspicion (speculation?) was that I really pressed too hard and got lots of seed tannins.

I decided to just let it age and see if it softened up. You have inspired me to do more (ahem) "research" and open another bottle to see if it has improved. I will let you know the result, but not today.

But I wanted to mention that it was recommended to me to try using PVPP (Polyvinylpolypyrrolidone). This is commercially known as Polyclar (See it at Morewine: https://www.morebeer.com/products/p...L9cRUx_VwynPcjrmqmXQGqQrYrA-7INRpb3umoaxsL6Am )

I did not try this, as I decided to just try waiting.

 

[Rice_Guy]

* Yes, Seed tannins are bitter. AKA young, small chain polyphenols have bitter notes and as the plant matures these polymerize making astringent flavors and further polymerizing they drop out of solution. In crab apple I decide when to pick based on having passed through the bitter flavor notes. Tannins can also be pulled out with proteins like egg white or milk casein. One should be able to find a small protein that targets bitter or a large protein that would pick the larger astringent molecule.
* A second place where bitter shows up in flavor chemistry is that some wild lactic acid bacteria will metabolize glycerol producing bitter notes. I don’t think time can modify infection caused flavor, at least if I have an apple mixture with that it seems to stay. A wild organism which produces lactic acid should not grow if the pH is under 3.5 and is a high risk as you approach 4.0.
* another bitter goes along with reductive/ meaty/ sulfury flavor and aroma. This is low nutrient with H2S smell earlier.

Sugar is a masking agent which can balance out bitter flavor.
Flavors come in waves. Sweet for ten to fifteen seconds, Acid after that say to thirty seconds and tannins after that. You are doing good tasting to look at time, basically how fast saliva washes a compound off the taste buds.

 

[Hazelemere]

you can try treating it with egg white to strip some tannin.

 

[maan]

Thank you all for the replies and suggestions.
I did add some sugar before posting this thread. I did help but not enough. I plan to add some more in a week.
Do tannins increase the bitterness as they age ?

>you can try treating it with egg white to strip some tannin.

Any thread in this forum I can read to figure how to treat it with the egg white ?

Thanks

 

[sour_grapes]

Do tannins increase the bitterness as they age ?

No, the opposite. As tannins age, they polymerize into longer-chain molecules, until such time as they drop out of solution. Thus, the bitterness associated with the shorter-chainged tannins reduces.

 

[maan]

Then it's not making sense.
I don't recall such bitterness when I tasted it last year. It seems to have increased since then

 

[Hazelemere]

Thank you all for the replies and suggestions.
I did add some sugar before posting this thread. I did help but not enough. I plan to add some more in a week.
Do tannins increase the bitterness as they age ?

>you can try treating it with egg white to strip some tannin.

Any thread in this forum I can read to figure how to treat it with the egg white ?

Thanks

take one egg white, mix it with a tiny bit of water and a tiny bit of salt and whisk it until it has one consistency i.e. not 2 layers. Then shoot it into a 5 gallon carboy with a plastic syringe. Then stir what is in the carboy. You can also do it in a pail and rack it back into the carboy. Give it a couple of weeks to settle once it is back into the carboy. Then rack it off of the sediment with a bit of sulphite and top it up. Taste it before you add sulphite. If the bitterness drops which it should you win.

 

[Rice_Guy]

Then it's not making sense.
I don't recall such bitterness when I tasted it last year. It seems to have increased since then

There is a sequence which happens. The base monomer is flavorless (Gallic acid/ ellagic acid ), this starts to polymerize creating something which is bitter, when it gets longer it doesn’t fit into the taste buds si the bitter note goes away and a drying feeling / astringency happens, upon more polymerization it drops out of solution.

Seed tannins are bitter. This is possibly a protective strategy to keep animals from chewing them up. Skin tannins are astringent, which acts as an positive flavor giving length to acid flavor notes. And if excessive is called rough or harsh.

 

[winemaker81]

Then it's not making sense.
I don't recall such bitterness when I tasted it last year. It seems to have increased since then

Winemaking is biology, chemistry, and physics. You do not need a PhD in any to make wine, but after a few decades you might feel you qualify for a degree.

You'll continue to learn things as long as you make wine. I knew that bitterness of tannin would get worse before it gets better, but didn't know why. Now I know!

 

[winechef]

Could the bitterness be oxidation? if it's increasing over time your wine. might have been oxidized

 

[maan]

Thank you all for the feedback.
I have some experiments to try out. Will update this thread once I have the results.

 

[Rice_Guy]

Just a thought,
Bitter polyphenols should have the bitter flavor reduced / blocked off the taste buds with salt. Next time you sample this wine, have a salty food like chips to eat / see if the bitter is reduced.
Caffeine is the bitter flavor standard used in the taste lab. How does this flavor compare to sucking on no doze, faster? longer? quicker?

Bitter is a positive flavor in hoppy beer, bitter is considered OK in traditional hard ciders. If cut 50% as 10 ml water & 10 ml wine is it in a positive flavor range?
It would be useful to look at / taste 100 ml. , , , , making wine is cooking, who do you know who is a good cook?

If you feel oxidation was the cause run high oh metabisulphite right away. You may taste it at 100ppm, but it degrades with time.

 

[Snafflebit]

I have had a small battle with bitterness in my wines also. As you have pointed out in your wine, the bitterness of my wines also changed. I did not notice it in the beginning, then later the bitterness appeared. I considered using egg whites or PVPP but I was busy and did not get to it. The bitter taste (which I attribute to seed tanins) mostly dissapeared in wines in bottle. But, I can still detect bitter notes in my wine, perhaps some would call it a fault, I call it character. There are methods to remove this taste but they all require more work than I want to devote to my hobby

 

[winemaker81]

@maan, @Snafflebit -- do you use kieselsol and chitosan to clarify the wines?

I conducted a study a couple of years ago, which noticed that K&C introduce a small amount of bitterness in the wine. In our test sample (2 wines) the bitterness was noted in side-by-side comparison with untreated samples.

In the discussion it was noted that the K&C include in kits is a higher dose than vendor recommendation, and I suspect that the bitterness is produced by using the stronger dosage.

https://www.winemakingtalk.com/threads/bitter-after-taste.79690/#post-903322

 

[Snafflebit]

I used bentonite once to clarify, but I rarely need to do anything but wait. Interesting results you have.

 

[maan]

I also do not use anything in my wines for clarifying . I let it sit.
Rack 3-4 times.