long-term plan for raisin wine astringency. ideas?

[reynardthefox]

greetings from the heart of Iran, the magical city of Shiraz (yes, they did steal our grapes )

so I made raisin wine. quick recipe: 5 kg seedless raisins, 2 kg sugar, topped up to 21 L with filtered water. after two weeks, took it off the raisins, another two weeks racked off the lees. fermentation is over.
now, it smells fine, it gives quite a buzz but it is astringent as hell. from what I've gathered aging and back-sweetening may solve it. I did add some sugar and tested a sip and it tasted better. I've got 9 months till the Persian new year, so I'm gonna age and see the result. my question is if I wait long enough is sorbate enough before back-sweetening. can I avoid sulfites?
or maybe, should I back-sweeten now and then age?
I would appreciate any ideas u might have.

 

[bernardsmith]

To backsweeten you need to stabilize the wine and to stabilize the wine you really do need to add both sorbates and K-meta (the sulfites). Sorbates prevent cells still in solution from reproducing but they do not in fact do anything to prevent those fully formed from continuing to ferment. The K-meta has a limited ability to kill cells but if the colony is large and is viable (could be dormant but not active) K-meta also has limitations. Back sweetening much closer to the time when you intend to bottle will allow you opportunities to rack and racking will help remove more and more of the colony so that when you stabilize you are dealing with a relatively small population of yeast.
On a different tack: do you have any way to measure the TA of your wine? (not the pH which is the strength of the acids, but the TA which measures the amount of acidity in g/l ). Wines need to be about .6 g/l otherwise they tend to be too tart. I would not think aging reduces the acidity but there may be other ways to reduce this - some chemically (adding a chemical base to the wine (K-carbonate, for example) or by blending your wine with another wine that is far less acidic. There may be other methods but I cannot imagine any off the top of my head.

 

[jgmillr1]

Mmmm... shiraz. At least they stole some of the best grapes!

I suggest you add sulfites now to protect the wine from oxidation & spoilage but do not add sorbate yet. Let the wine age and the yeast to settle so you can really taste what the wine is like. This will probably resolve some of the astringent mouthfeel you are experiencing now. Rack it a time or two over the next 6 months to get it off the lees. Be sure to add some sulfites (~20ppm) when you rack each time.

About two months before you bottle, taste the wine and judge whether it still seems to astringent or acidic. Astringent will taste bitter while acidic will taste sharp and make your mouth water. You can manage the astringency by adding gelatin and letting it settle.

If the wine is too tart for your taste, you can either back sweeten or lower the acidity (or both). Note that you can measure the acidity (TA). If you back sweeten, you need to add sorbate. If you lower the acidity, you will want to watch the pH to make sure it doesn't get too high (keep below 3.7). Dry wines run 5-7g/L for TA while sweet wines can run up to 11g/L. These values are "tartaric acid" equivalent.

For perceived sweetness, a good rule of thumb is to consider the ratio of g/L of sugar to g/L of acid. A value of 1 is dry, 3 is semi-sweet, and 5 is sweet. So, if your TA is 8g/L and you want a semi-sweet (ratio of 3), you would add 24 g/L of sugar to back-sweeten.

 

[reynardthefox]

Mmmm... shiraz. At least they stole some of the best grapes!

I suggest you add sulfites now to protect the wine from oxidation & spoilage but do not add sorbate yet. Let the wine age and the yeast to settle so you can really taste what the wine is like. This will probably resolve some of the astringent mouthfeel you are experiencing now. Rack it a time or two over the next 6 months to get it off the lees. Be sure to add some sulfites (~20ppm) when you rack each time.

About two months before you bottle, taste the wine and judge whether it still seems to astringent or acidic. Astringent will taste bitter while acidic will taste sharp and make your mouth water. You can manage the astringency by adding gelatin and letting it settle.

If the wine is too tart for your taste, you can either back sweeten or lower the acidity (or both). Note that you can measure the acidity (TA). If you back sweeten, you need to add sorbate. If you lower the acidity, you will want to watch the pH to make sure it doesn't get too high (keep below 3.7). Dry wines run 5-7g/L for TA while sweet wines can run up to 11g/L. These values are "tartaric acid" equivalent.

For perceived sweetness, a good rule of thumb is to consider the ratio of g/L of sugar to g/L of acid. A value of 1 is dry, 3 is semi-sweet, and 5 is sweet. So, if your TA is 8g/L and you want a semi-sweet (ratio of 3), you would add 24 g/L of sugar to back-sweeten.

thank you for taking the time to answer my question, I learned a lot and I will apply ur suggestions.

p.s. what you don't hear about the wine of Shiraz is that it has roots in the former Persian empire and it was made by the followers of Zarathustra (still made in secret) hundreds of years ago which is immortalized by ancient Persian poets such as Hafez and Khayyam.