Ph levels?

Cellar Rats (ITB)
1

One thing I have been a bit unclear on is Ph in wine and what it means when it is referred to. As I always understood from chmistry classes Ph level was a scale for measuring acid/base levels of a substance. But it seems when people talk about Ph levels it is separate from the levels of acid. I’ve also been getting the idea that high Ph levels in wine seems to indicate that a wine will have that soft plush mouth feel but I am looking for to be educated on this point.

So when wine makers refer to Ph levels what exactly are you guys referring to? And what does it mean for the final product or even in process from juice to wine?

Thanks!

2

I’m no chemist. That said, pH refers to the strength of acidity. So two wines with the same amount of acid (g/L) can have a different pH. The pH shift upwards during ML fermentation occurs because stronger malic acid is degraded into weaker lactic acid. pH can also be affected by buffers like potassium. How, I don’t fully understand.

pH plays into the antimicrobial properties of SO2. The lower the pH, the more effective a given amount of SO2 will be in protecting the wine from spoilage bacteria. An issue with higher pH wines is that the necessary levels of SO2 for that protection, referred to as “molecular” SO2 levels, skyrockets. At pH 3.5, it doesn’t take much free (active) SO2 to achieve your molecular level. At 3.9, it takes a whole bunch, way more than typical sensory levels.

To get back to your post, typically higher pH wines (higher 3s, even into the 4s sometimes) will give a more plush sensation in the mouth.

I’m sure more knowledgable people can fill in more details, add to or correct what I’ve written.

3

very cool, Vincent. I did not previously know the distinction between amount and intensity of acid.


Another question: are humans only capable of tasting/sensing intensity of acid, or is there also a way to discern amount (g/L) of acid when tasting a wine?

4

And at some point, the level of SO2 required becomes so high as to be noticeable organoleptically. Further, a solution with a very high pH can grow some very toxic critters.
Best, Jim

5

I have had numerous conversations with Randy Dunn who intentionally keeps his Ph levels lower than many other winemakers. His wines age longer and are not as plush or up front as many would like and he is fine with that.
I wonder whether the classified growths in Bordeaux would also account for the need for ageing of their wines by utilizing the Ph balances of their winemaking.

6

PH is always a tough one for me as I am always looking for balance on the palette with my wines. I have had great balances with my Pinot at a ph of 3.84. Of course if you bottle at that ph without sterile filtration you are leaving yourself open to a bevy of microbial issues (Bret, lactobaccilus, etc.).

I have heard a ph of 3.70 is a threshold where above that microbial life has a much easier time working. I am not sure if that is said due to the relation to so2 or just the acidity making it difficult. If anybody can offer their thoughts on ph, so2 and wine stability I would love to hear them

7

John, et al,
You may be interested in this article:

Practical Winery Library | Search the archives of Practical Winery & Vineyard" onclick="window.open(this.href);return false;

Best, Jim

8

As some people here already know, the subject of pHat wines has long been one of my pet peeves.

[soap.gif]

Parker favors pHlush styles that are often unstable due to excessively high pH. I know of two particular wines that got very, very high scores that were 3.9 and 4.1. Sure enough, the wines did not age well at all, even for a few years.

I think it is very important for wine consumers to educate themselves about the importance of acidity and pH to the balance and longevity of a wine.

It’s very easy to do with a set of Accuvin tests–each kit costs less than a bottle of wine and is good for about 20 samples! Fits in a purse or wallet! Impress your friends on Cellartracker! Post pH and acidity numbers! Prove your chops in discussions on ‘balance’!

I have three sets–the acidity, pH and residual sugar kits, each kit is about $40. Ridiculously easy to use–a child can do it. I think ALL Berserkers should have them. And then when you post complete wine reviews on the ‘other board’ they’ll all be going, like “Whaaaa?”

[berserker.gif]

9

Jim, that’s what I meant with my comment about sensory levels (perceiving the free SO2). If I understood my instructor correctly, a way to try to get around things is to hit the wine hard with SO2 post ML to achieve the required molecular level, then be very careful not to introduce any new source of bacteria after that. Not failsafe by any means, but a strategy.

I’m assuming you’re using “toxic” pretty loosely here. Harmful to the wine, not people, right?

10

pH is the negative log of the concentration of H+ ions in solution. For a lot of things, it suffices to measure acidity. In wine, it doesn’t because you put it in your mouth. Wine contains a lot of acids at different levels and they vary in their strength (pH’s at which they release protons into solution - their pKa’s). Strong acids have a greater tendency to release protons into solution. When you take a static pH measurement of a wine, though, those protons may or may not be measured depending upon the pH level of the wine.

When you put wine in your mouth, the specific levels of these strong and weak acids as well as the specific buffering capacity of the wine come into play in affecting the perceived acidity, as some of these protons are released due to interactions with your saliva, tongue, etc. That is why we use a titration to measure how much base it takes to balance those acids to a certain pH (say, 8.2). In essence, a similar titration is occurring in your mouth. Evolutionarily speaking, probably to alert you and keep you from swallowing things that are going to f with the pH balance of your body’s systems. Draino probably doesn’t taste very good, for example.

TA’s and pH are usually pretty well related, but not exactly. There are plenty of cases of high[ish - this is relative and a matter of winemaker preference] TA’s and high[ish] pH. While I haven’t experienced any cases of low TA, low pH, given my career has been almost all in CA, I’m sure that can happen as well. I have worked with vineyards that are consistently showing strange things in this respect, the most extreme of which we couldn’t decipher whether it was a soil imbalance (most likely - high levels of K+ compared to Mg and Ca), rootstock or scion.

In general, pH is an important number for its effects on wine stability, the form pigments take (the main monomeric pigments in red wine are more “red” at lower pH’s) and its interaction with the form that SO2 takes (why higher SO2’s are needed for the same “killing power” at higher pH’s). It is true that high pH can take on a lusher mouthfeel that can become somewhat soapy in extreme cases, but only if the TA is low in my experience. The acid sensation seems to negate a lot of that in my experience when the TA is higher. TA is an important number in extrapolating how a wine will be perceived with respect to acidity. So both are important to us but for different reasons.

11

Mary, LOL. Your post should be in the Wine Berserkers hall of fame. That pretty much sums up what a wine berserker is to me. Wine geekery with a screw loose (in the best sense, of course).

12

I’ve seen folks use a variety of methods; some use small SO2 adds more often, some bigger ones less. I like the bigger ones less technique and try to keep my wines about 0.8 molecular.

I’m assuming you’re using “toxic” pretty loosely here. Harmful to the wine, not people, right?

Right.
Best, Jim

13

Thank you.

[bow.gif]

I’m hoping for some more participation in the Accuvin tasting in Wine Talk. Hopefully we can get a few more producers to participate too.

14

At the risk of lowering the level of conversation here, I have a few winemaking-for-dummies type questions:

  • as fruit become more ripe, acidity typically goes down, right? Does this mean lower TA or lower pH or both?

  • I’m still not clear on the relationship between TA and pH. Is there a typical relationship between the two? To restate, does the level of one usually dictate the range of the other?

  • As someone who like burgs and other ‘thin, acidic’ wines I gather it is the lower pH which I enjoy?

This is fascinating discussion. Thanks for your insights.

15

Normally, as sugars rise, TA falls and PH goes up.

16

  1. Sort of. In normal ripening, yes. Acids can be respirated. Once dessication kicks in, though, no. If you think about it, there is only so much sugar that the plant can transport to the berry and unload there via vasculature. At some point, increasing sugar concentration is due solely to loss of water. But, if you are losing water and sugar concentration is going up, the concentration of acids is increasing, too, right? So, TA would go up as would the concentration of H+ (meaning pH would decrease).

  2. When you look at them as precisely as we do, no. There is a very loose relationship. Just this year, in Cabernet alone, I would say I saw must TA’s vary by as much as 25% at the same must pH. All from the same estate.

  3. Maybe. Tough to say. You would have to tell us what sort of attributes of Burgs you like. Acidity to a taster would be more highly correlated with TA than pH. However, there might be a lot of things you like about Burgs that are correlated with pH moreso than TA. Not all Burgs are necessarily low pH, low alcohol, high TA, either. The world abounds with variation even within regions.