Adjust pH?

[schlapppy]

So i pulled the trigger and bought a pH meter. Seemingly just in time. I just picked up these buckets grape juice today..

reisling
sg 1.095
ph 4.14

merlot
sg 1.089
ph 4.22

pinot grigo
s.g 1.093
ph 3.99

I know ideal pH is withing 3.4-3.6.. these juices are obviously not in that range. How much of what kind of acid should i add to each? Is there a calculator or good guide somewhere out there on the net? Each bucket is 6 gallons. I'll be using D47 yeast for all of these

 

[AToE]

I would add none probably - the yeast will lower the pH on their own. Generally speaking if your pH is a little high it's not a worry (unless it's really high after fermentation because that can allow spoilage organisms to have an easier time), almost all the pH problems you'll encounter will be with the pH dropping too low.

 

[schlapppy]

Thanks for the reply AToE.

How much does the pH typically drop during fermentation?
If I did want to correct it.. are there any known good calculators (or equations)?

Are there any advantages of NOT fixing the pH?

 

[AToE]

Thanks for the reply AToE.

How much does the pH typically drop during fermentation?
If I did want to correct it.. are there any known good calculators (or equations)?

Are there any advantages of NOT fixing the pH?

I don't know if there's a "typical" drop in pH, it depends on a lot of factors including the buffering capacity of the liquid - a traditional mead has no buffering, so I'm sure the yeast could drop the pH down below 3 all the way from 7 if given the opportunity, but with fruit juice there's lots of buffering - given that those are fruit juices (and take with salt, I'm no expert on wine fermentation as opposed to mead) I'd say your starting pH is perfect based on what I know - the yeast will drop it a little but probably not too much thanks to the buffering.

 

[Medsen Fey]

With pure grape juice, the buffering capacity is usually good, and the pH will not shift dramatically with fermentation. If your grapes juice has been frozen, you may get a reading that is somewhat higher than it actually because of tartrate precipitation. When the juice warms up, the pH drops and the TA rises as the tartrate dissolves back into solution.

The other key question is what is the TA. To get this, you need an acid test kit. The usual instructions for such a kit will involve adding an indicator like phenolphthalein and titrating with sodium hydroxide until you get color change. For reds this is difficult, and it is easier to titrate to a pH of 8.2. With your TA number and your pH, you can decide how to go.

If you pH is high, and your TA is high, you can try adding gypsum to precipitate tartrate will lowering the pH.

If you pH is high and your TA is low, you can add acid (preferably tartaric).

Most wine makers advocate making the adjustments before fermentation, but I don't think that is necessary, and several wine texts also suggest that the acid adjustments can be done post fermentation.

I hope that helps.

Medsen

 

[schlapppy]

I hope that helps.

Indeed it does. Thank you.

If your grapes juice has been frozen, you may get a reading that is somewhat higher than it actually because of tartrate precipitation. When the juice warms up, the pH drops and the TA rises as the tartrate dissolves back into solution.

This is an excellent tip. I did not know this. I imagine that most grape juice buckets imported from Italy come frozen. O never actually did an initial tempature reading... oops. I'll check in in the AM tomorrow. Along with the pH.

The other key question is what is the TA. To get this, you need an acid test kit.

Shucks. The good news is I looked these, and they are inexpensive. Is it terribly risky to balance the pH without knowing the TA?

 

[schlapppy]

I decided that I'd let these ferment for a day or two, and see if the pH drops naturally at all. None of them are in the 4.x pH range anymore.. and one of them came all the way down to 3.7 pH. I'm thinking about waiting until about the 2/3 sugar break before making any adjustments.. if i even need to make any at all. Each day they have been dropping about .1 - 0.5 pH.

I do now have a pound of tartaric acid, and 2 oz of mallic acid. Maybe just purchasing the acids, and dipping in the pH meter scared them straight.

 

[Medsen Fey]

Is it terribly risky to balance the pH without knowing the TA?

If you want to make consistently good wines, it pays to measure and manage the TA. Can you adjust acids by taste alone? Absolutely. You just may not get the same degree of control and consistency.

 

[schlapppy]

If you want to make consistently good wines, it pays to measure and manage the TA. Can you adjust acids by taste alone? Absolutely. You just may not get the same degree of control and consistency.

Good to know. I'll pick one up. Any recommendations?

 

[Medsen Fey]

I find the VinoFerm kit easy to use, and if you get the iodic solution you can also test for Free SO2.

 

[Chevette Girl]

I do now have a pound of tartaric acid, and 2 oz of mallic acid. Maybe just purchasing the acids, and dipping in the pH meter scared them straight.

Wouldn't surprise me... Them yeasties KNOW things...