So you get some grapes from a grower you are interested in the "numbers".
Measurments of the sugar level {Brix}, Acid level {PH} , and Total Acidity {TA} are typical measurements that home wine makers are interested in.
Brix and PH should be easy to measure with a hypdometer and a PH meter. TA is not so easy.
I always measure brix since this will determine if I can just start fermentation or if I have to adjust the sugar level before fermentation starts. Sugar level adjustments will get a separate blog entry.
I'm not so concerned with meauring PH and TA, though perhaps I should be..?? Mostly I am relying on getting good grapes {proper numbers} from a good source.
For me, acid level adjustments are done by taste and usally late in the wine making year when the wine is more of less finished with whatever changes it will go through.. The key question for me is; does it taste the way I want it to? e.g. is the acid level too high or too low?
A reason I rely more on taste than a PH measurement is that I have seen widely different numbers from different sources on the same grapes! What if the PH number is not accuate!
Note: a low PH wine tastes like it has high acid taste-wise. e.g. the lower the PH number, the higher the acid level to the taste... can be confusing no?...
If the acid level is too high, I can lower the level through blending in a lower acid wine.
If the acid level is too low, I usually add tartaric acid to bring the acid level up....I'm talking about small levels of acid adjustments like 1/2 teaspoon per 5 gallons of wine. I can always add more if needed....
Though I don't usually measure the PH, I probably should since it is a quantifable number to tell me where the wine is, and how I have changed it during adjustments.
What is "normal" PH for wine? Does that make a difference? --> Yes! for stability. See the article link below!
What is most important is what tastes good to you! This is your wine, make it for your taste! But it should not be out of a normal acid range due to spoilage and stability.
Here's a good general description of PH levels and how it impacts wine and the making process:
http://www.eutechinst.com/techtips/tech-tips42.htm
Wine Characteristic
Low pH Range(3.0 - 3.4) --> more stable, less Bacterial Growth, tastes more acidic...
High pH Range(3.6 - 4.0) --> less stabled, more Bacterial Growth, tastes bland, flat...
The Sauvignon Blanc numbers were: 24.5; TA = 4.7 & pH = 3.7
A PH of 3.7 is on the high side {lower in acid} and would indicate that something should be done to get a more stable wine. I think both Joe and Mike added acid to lower the PH. Perhaps they could comment on this...
There are formulas for computing how much acid to add to change a PH of x to y for z gallons of wine, so it is a fairly straightforward process, just don't add too much!
My thinking about the Sauvignon Blanc is that I have two other wines that I think are high in acid, the Malvasia Blanc and Pinot Grigio, and that blending for these wines with the Sauvignon Blanc is definitely in the plans.
Here's another link that points up the value of tasting the wine when adding acid...
http://www.winemakermag.com/stories/article/indices/6-acid/344-high-ph-low-ta-bottles-wine-wizard
But now that I say that the Malvasia and Pinot Grigio are high in acid {low PH}; I'm thinking that a PH number would be good to have.... Think I'll get a new PH meter....
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George and I have different perspectives on when to correct the acid level in a wine. Based on the pH and TA of juice or must (I have a pH meter if I didn't get the numbers from the grower), I adjust the acid before I begin the fermentation. My primary reasoning is that the tartaric acid is better incorporated into the wine by going through the fermentation process. I like my reds to have a pH of around 3.5 and my whites to be at 3.2 when I start the fermentation. As George noted, there are equations for how much acid to add to juice or must to adjust the acid (the TA will increase 0.1 with the addition of 3.9 grams of tartaric to a gallon of wine). I always add a little extra, because the wine will drop acid if you are going a cold fermentation, a malolactic fermentation and/or cold stabilizing your wine.
ReplyDeleteThe other advantage of adding acid at the beginning is that you can still make that small adjustment at the end, if necessary. I want to avoid have to make a large adjustment at the end.
Joe
Mike here. I tend to add tartaric acid prior to fermentation if the pH is low and the acid tastes low. In terms of how much I add, I guess I'm somewhere between Joe and George. George is right in that the pH readings can be off (when we got the SB, the grower got two very different readings from two different labs). First thing is to taste the juice and allow your instinct to play a role in the decision-making process. Acid will drop during primary fermentation and malolactic fermentation, but if your mouth tells you the acid level isn't that off, go easy on how much you add. You can always add more acid before bottling but you can't take it out.
ReplyDeleteAs for the SB, I only added enough to lower the pH to 3.5. That's still on the higher side, but the wine didn't taste that low in acid. Now that the wine has gone through primary fermentation, I like how it tastes (I don't put my whites through malo, so I won't lose acid there). Joe may like his SB a little more acidic, George may like it less, that's why your own taste is the unknown variable.