Re: value of ph meter

I don't agree with that. I've found that low acid juices tend to taste flat/too sweet, and high acid juice tastes too sour. IOW, it's possible, given experience, to tell if the juice is balanced reasonably well just by tasting it.

Estimating by taste whether the Brix is right is a bit more difficult, but I have a refractometer for that.

Tom S

In the example of reference (earlier in the thread), the pH was 4.2, and the TA was 6.5, indicating the wine was quite high in potassium. You said there were 2000 ppm K+ vs. a more normal 1000 ppm. I'm almost certain I would be able to taste that. Potassium has a very distinct flavour.

Earlier in the thread, Tom S wrote "The solution is to hit the wine with tartaric and follow with chilling to precipitate the excess potassium. Of course this is best done _before_fermentation."

You are correct. In an earlier post you said "there's little need to measure it analytically, unless your taste tells you that you need to modify it." Somehow I missed the last part of the sentence.

Tom: I quit measuring TA many years ago, but Brix and pH measurements are *essential*.

Negodki: May I ask how you adjust the acidity without also measuring the TA?

Tom: Dump in tartaric until the pH is where you want it to be.

Perhaps you misunderstood the question. If I know the TA, and I know the desired TA ("where I want it to be"), adjustments are fairly simple with a bit of arithmetic: 4.7 grams per gallon of typical acid blend will raise the TA by .15. (The precise amount is usually provided by the manufacturer on the label.)

Lowering the acid is a bit more complicated. Ideally one would blend the (finished) wine with a low-acid wine of the same varietal to achieve the target TA. I suppose this could (and should) be done by taste testing, but the TA measurement gives one a good starting point.

When blending isn't an option, one gallon of water to 5 gallons of must reduces acidity by about 10%, and 2.5 grams CaCO3 or 3.8 grams K2CO3 per gallon will reduce the acidity by roughly .1%.

Less predictable via analytical methods: malolactic and carbonic fermentation will lower the malic acid component. Cold stabilization and cold fermenting will precipitate some of the potassium bitartrate.

If one only has the pH measurement available, is there a computational method of determining the amount of acid (or water, CaCO3, or K2CO3) to add? Or must one "guestimate" the addition conservatively, and then test the results, and repeat this procedure until the desired pH is achieved?

Additionally, how often do you need to replace the probes and recalibrate the ph meter with buffer solutions?

Thanks.

Hi,

As I mentioned in a previous post, all the acid adjustments I do, both up and down, are done on bench-scale first, then on the whole volume. I had thought that this practice was absolutely routine, not just for acid adjustments, but for ANY change to wine. I can't seriously imagine making asjustments to wine any other way.

But heck, I also can't imagine diluting my wine or must by 20% with water, either. :-)

So anyway, I adjust the acid up or down in 0.5 g steps, doing 5 or 6 trials, and then taste them. I gauge how much Bentonite, skim milk, egg whites, drifine, sugar etc. to use in exactly the same way (except I don't actually *taste* the bentonite trials). Do you do your trials in another way, or do you not do them?

I calibrate my pH meter every day that I use it. A probe will normally last me 3 or 4 years.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

That assumes that you know what target TA you need to make the wine _taste_ right. How do you know that in advance?

I find that pH is a more reliable standard to work with, taste-wise. I like white wines to be ~3.4-3.5, and reds a bit higher (depending on varietal). A simple titration with tartaric acid to that pH tells me all I need to know.

Here again, pH works better. Titrate the wine with potassium carbonate, degas and measure the pH. Repeat if necessary, and cold stabilize to drop out the extra K.

I won't even bother commenting on _that_ approach. :^P

No guessing is necessary. You simply titrate with tartaric acid until you reach the target pH. You can _see_ it on the readout as you add the acid! Of course you have to keep track of how much acid you added, but you can do that by weight difference.

Probes don't need to be replaced too often, and I understand that contact lens enzyme cleaner works well to rejuvenate them. When they go bad, the response time becomes very slow.

Calibration is not necessary very frequently unless you're into splitting hundredths of a pH unit.

Tom S

Nor -would- I, although I did dilute some (very tart) Thompson juice by 11.8 %. I read that NY wineries routinely add up to 30% water to their Concord grapes to bring down the acidity. The water is usually brought up to a brix of 24-25 by sugar additions before being mixed in.

Remember, I did say blending was preferable. The point of mentioning the dilution and CO3 procedures was to illustrate what I meant by adjusting TA with a formula.

I do my chapitalization (when necessary) by measuring the SG. If the sugar needs adjustment, I determine the liquid volume of the must, and use a formula to determine the amount of sugar to be added.

I do my pre-fermentation acid adjustments (as described earlier) by measuring the TA, determining the liquid volume, and using a formula to determine the amount of acid to be added. I try to handle reductions by cold-stabilization and blending, rather than dilution of CO3 additions.

All post-fermentation adjustments and blending are done by tasting.

I don't use bentonite, skim milk, or drifine. I rarely use egg-whites, but when I do, I use a particular amount per gallon.

This seems to work --- for me. Keep in mind, that I'm dealing with batches that are somewhere between 1-15 gallons. If I did "bench trials", I wouldn't have anything left to bottle.

me 3 or 4 years.

I asked this because you and Tom have pretty much convinced me to go out and purchase a pH meter, and use it. But when I read through the calibration procedure in the faq, and read somewhere else that probes last less, it didn't seem to practical for this home winemaker.

Although I make wine from apples, table grapes, and juice throughout the year, when the vinafera are ripe I get up at 4 am, drive for an hour to the vineyard, spend the entire morning hand-picking my grapes, return home, spend the rest of the day destemming (by-hand) and crushing, and the next couple of hours measuring and adjusting sugar and acid. I'm lucky to pitch yeast by 10pm. And I'm to exhausted to do much of anything the next couple of days.

Spending another hour or so calibrating a pH meter might kill me. :)

Yeah, that's a real issue. But for most of these trials, you can add the wine back later.

me 3 or 4 years.

:-) The procedure reads as WAY more cumbersome than it is. A two-point calibration (all that's necessary) takes me maybe two minutes. It's really very fast to do, but long-winded to describe.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

The same way you know that you want your white wines to be ~3.4-3.5 pH: wine lore, rumor, and experience.

Pre-fermentation, I want my reds to be be around .65% TA, and my apple wines to be around .7%. If I made whites, I would shoot for .75%. Post-fermentation, I go by taste, and use the formula to effect a .01 to .05% adjustment, and then re-taste.

You've pretty much got me convinced. :)

Sounds simple enough.

Which approach, the dilution or the CaCO3? I assume you don't object to the K2CO3, since it is essentially the same procedure you mention

--- the difference being I am measuring TA and you are measuring pH. I agree that test trials are needed, since you can't predict how much will actually precipitate.

Aha! So the procedure is essentially the same as the titration I do to determine the TA, except I would be using a more relevant measurement (pH)! Keeping track of acid added should be no more difficult than keeping track of NaOH used. I'm beginning to like this method. :)

Now, does anyone have an opinion of the Hanna pHEP 5 digital pH meter? Or do I need to spend a lot more for a reliable meter?

Speaking of which, I bought a non-ATC model today. With as little use as the thing will get, and what with as easy as it is to compensate, do you think I'll be happy with the thing? Iow, if it's going to see little use, is ATC really needed? Thanks. Ken A.

I am not arguing with anyone and I find the gist of what is covered by this thread extremely interesting. I have been using a pH meter now for about a year and find it very useful for most of the reasons sited. I will say that when I have tried to adjust TA to a pre defined value after the fact, I usually do not like the results.

But adding water to make adjustments! Several have really poo-poo this idea and I think they have overstated the negative. Water is THE major component in wine and of all things we could do to wine, adding water is about the gentlest and will change the chemistry the least. Yes it will effect the flavor but if we were not trying to effect the flavor we would not be adjusting the wine. There is nothing wrong with adding water if it is done intelligently and with care. This is where taste is extremely important. We add water to many fruit wines right up front to adjust them. And if we do not get them right up front, I see nothing wrong with further adjustment at the end.

I made some peach wine where I used more peaches than normal. I made it with 14-15% alcohol. I may well dilute it by 10-15%. I may not. Taste will guide me. If I will do it with fruit wine, I will also do it with grape wine under the right circumstances.

I avoid using water to top up with because it will change the wine. I avoid using "similar" wines to top up with for the same reason. But in adjusting a wine, water is just another component that can be used.

Now if adding water just totally goes against your religion ... then maybe you should not add water! ;o)

Ray

Near as I can tell, ATC is utterly useless for winemaking. While ATC can compensate for the different interactions of H+ ions and probe at various temperatures, it CANNOT account for the tendency of weak organic acids (which is all you have in wine) to dissociate less at colder temperatures, and more at higher temperatures.

ATC can lull you into a false sense of complacency and some real pH errors.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

Which is another great advantage of using the pH meter! When I do an acid titration, I'm always terrified that I will accidentally pour the sample (which now has phenothalen and NaOH in it) back into the primary --- especially when it's 10pm and I've been up since 3am. If I understand correctly, with the pH meter technique, all I've added to the sample(s) is a bit of acid or carbonate, which I need to add to the must anyway.

I'm beginning to realize that. I (just now) read the calibration procedure for the meter I'm considering purchasing at

and discovered it to be embarrasingly simple. It's easier than testing the strength of the NaOH solution before acid titration. Rather than taking more time, and being more complicated, as I had thought, it will probably save me time, and be far simpler.

Thank you. I've learned a geat deal from this thread.

I don't think predicting post fermentation TA values are all that easy. The above technique may be OK for fruit wines but it doesn't work very well for grape wines.

Potassium bitartrate is precipitated during fermentation and the TA drops by

0.5 to 1.5 grams per liter (tartaric). During fermentation, the yeast produces from 0.5 to 2 grams per litter of succinic acid, so the TA increases. See Margalit, "Concepts in Wine Chemistry," page 17, 19, 291.

Sometimes, the decrease in TA due to tartrate precipitation just about equals the increase due to succinic acid production and the post fermentation TA is about equal to the pre fermentation TA. But, the post fermentation TA can be lower or higher by more than a gram per litter depending on the fermentation parameters.

Or, am I confused again? lum

That's not really true. Adding tartaric acid effects the chemistry of a must/wine far less than adding water. Adding tartaric will change the TA, pH, and balance of different acids in the wine. Adding water will change the TA, pH, colour, aroma, flavour, tannin content, SO2 content, etc etc. That's pretty drastic compared to just adding an acid.

we would not be adjusting the wine.

Usually winemakers DON'T want to adjust flavour (in fact, usually they want to increase it, not decrease it). Dilution with water is usually done to reduce acidity without any desire to adjust anything else. The other adjustments that occur are consequences, and many would regard them as negative consequences.

I'm not saying that you should never dilute your must, but it is not a preferrable option and is generally avoided if there are reasonable alternatives.

Ben

HEY! Watch your attributions, there. *I* didn't write that. :-)

I'm with you--I don't believe that post-fermentation TA's can be accurately guessed at, and I'd go a step further to say that it wouldn't matter if you could or not. There is no "right" value for any given wine, except that one that achieves balance (without screwing up the pH).

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com

I agree that one can't (easily) predict post-fermentation TA, but one must start somewhere. I start at .65 for reds, .7 for apples, .75 for whites. Post-fermentation I may make another adjustment. [Also, I'm under the impression that if the TA is too low or too high, it may retard or prevent fermentation.]

Similarly, one can't (easily) predict post-fermentation pH (or can they?) So, those using a pH meter start at .32-.36 (depending on the type of wine), and make a second adustment (if needed) after fermentation.

The methods are not that dissimilar. The primary difference is whether TA or pH is adjusted prior to fermentation, not whether our "predictions" are accurate.

I agree that one can't (easily) predict post-fermentation TA, but one must start somewhere. I start at .65 for reds, .7 for apples, .75 for whites. Post-fermentation I may make another adjustment. [Also, I'm under the impression that if the TA is too low or too high, it may retard or prevent fermentation.]

Similarly, one can't (easily) predict post-fermentation pH (or can they?) So, those using a pH meter start at .32-.36 (depending on the type of wine), and make a second adustment (if needed) after fermentation.

The methods are not that dissimilar. The primary difference is whether TA or pH is adjusted prior to fermentation, not whether our "predictions" are accurate.

Dave, can you please elaborate on this. Are you suggesting that we should use a meter _without_ ATC, and do the temperature adjustment calculations manually? Or that the adjustment is irrelevant, and should not be done?

How do we avoid the "real pH errors" you mention?

So far as I know, the only way to get accurate pH measurements on wine samples is to get the wine to a standard temperature (60-70 F for me).

There may be some way to manually calculate pH errors vs. temperature for weak organic acids, but you'd have to do it for all of the different acids in wine (i.e., understand the relationship between pKa and temperature for all those acids). It's easier to adjust sample temps.

And yeah, I'm happier not having ATC, though if you get all your samples totemperature anyway, it doesn't matter if it's there or not.

Dave

**************************************************************************** Dave Breeden snipped-for-privacy@lightlink.com