Calcium carbonate v. calcium hydroxide for acid reduction

[z-bob]

Do both reduce acidity the same amount? I have a 20 year old bag of pickling lime that I should probably throw away because it most likely has absorbed CO2 from the air and turned to carbonate by now. But even if it has, I bet there is still some hydroxide in there. I want to deacidify some very tart grape juice to make some wine. If I assume this old lime is 100% carbonate and use it to do "double salt" deacidification, will the residual hydroxide make any difference? Seems to me both should absorb the same number of protons; the only 2 practical differences being; the CO2 which gets released by the carbonate, and the difference in mass between the 2 compounds. (but I will be measuring in 1/2 teaspoons, not grams; this is not all that precise)

I can't find anything online about using calcium hydroxide to remove acidity in grape must, other than one reference I saw that said it is an approved method someplace in Africa. South Africa, I think.

I also have a fresh bag of pickling lime, I could use that and it should have very little carbonate. But then I am in uncharted territory, and I miss out on an interesting thought experiment

 

[Silver_Is_Money]

0.441 grams of Ca(OH)2 should be the acidity neutralizing equivalent of 1 gram of NaHCO3 (Baking Soda).

0.596 grams of CaCO3 should be the acidity neutralizing equivalent of 1 gram of NaHCO3 (Baking Soda). (Provided that you know the means whereby to fully dissolve CaCO3 in water, else it may take perhaps as much as twice this amount)

1.351 grams of CaCO3 should be the acid neutralizing equivalent of 1 gram of Ca(OH)2. (Provided again that you know the means whereby to fully dissolve CaCO3 (Calcium Carbonate) in water)

NOTE: This above equivalence advice is for wine only, as for the case of beer the calcium component must also be accounted for during the mash, wherein the calcium has a pH reducing impact that also must be accounted for.

NOTE 2: Calcium Carbonate is highly insoluble in water.

NOTE 3: All of the above is predicated upon my having calculated correctly. As well as for Baking Soda fully dissociating in water (which some say will not happen, and others say will happen due to the evolution of CO2 as a gas).

NOTE 4: As you have stated, if packaged poorly, over time Ca(OH)2 will slowly turn into CaCO3 due to exposure to atmospheric CO2.

 

[mabrungard]

On an Equivalent by Equivalent basis, yes those salts will neutralize equally. In a solution with strong-enough acids, both salts can be used with equal effect. Do recognize that there aren't enough of the 'strong-enough' acids in a mash to react with the CaCO3.

 

[z-bob]

Tartaric and malic acids are strong enough, right? I'm not sure if tartaric acid is the stronger but (according to what I've read online) calcium carbonate neutralizes it preferentially over malic acid, although we would prefer it was the other way around.

Calcium carbonate is highly insoluble in water. Calcium hydroxide is moderately insoluble; perhaps that means it doesn't care and will attack both acids.

The procedure I've read is to titrate the must to calculate how much calcium or potassium carbonate to add. If calcium, add all of it to 20%-40% of the must and stir it well. Allow to settle, then decant the fully deacidified slowly into the remaining must. I think the point of that is to remove all of the malic acid from that first 20-40%. And E.C. Kraus says if you just wing it instead of doing the titration, use 1/2 tsp of chalk per gallon. Here's what I'm planning to do; stir 2 tsp of lime/chalk into a cup of water and add it to a gallon of Concord grape juice. Let it settle overnight, and add the cleared juice to 3 more gallons, and add however much sugar because Concord juice isn't sweet enough to hit 11% ABV. And it sounds like the residual calcium hydroxide in my stale bag of lime won't make a significant difference.

Someday I will try this again using fresh calcium hydroxide and see what difference it makes. I think it will just react much faster and not release CO2, but otherwise will be the same.

 

[z-bob]

I've been thinking about that procedure for using chalk to deacidify wine. If you only treat 20% or so at first and use excess chalk (or lime), all the tartaric acid will be removed (because calcium tartrate is insoluble) and the malic acid will all be converted to calcium malate, which is soluble so it stays in solution. And all the rest of the chalk will precipitate out. Decant the deacidified juice back to the rest of the juice and the calcium malate will react with tartaric acid and take out some of it, converting the malate back to malic acid. It's an equilibrium reaction, and since the tartrate is insoluble and precipitates out it should go almost to completion.

That's why the reaction favors removing tartaric acid and not the malic acid. In fact, you might have to add some tartaric acid back to the wine when it's finished fermenting.

I will give it a try tomorrow. I bet that first gallon of juice changes color.

 

[z-bob]

I finally got around to testing that old bag of lime. I put a spoonful in a small bowl and added a little vinegar. It bubbled but not as much as I expected. "That can't be right", so I added a few drops of hydrochloric acid and it fizzed like crazy. I bet it's pushing 100% carbonate.

I whisked 2 teaspoons (I did not weigh it) into a half cup of cold water, and added it to a half gallon of grape juice in a 4L jug and gently shook it. As the foam died down, I added most of another half gallon. I put it in a cool place and will continue topping it up as there's room in the jug. In a few days I'll add it (leaving the sediment behind) to 3 more gallons of juice, adjust the sugar (it's 16 Brix right now,) and pitch the yeast and nutrients.

 

[VikeMan]

I finally got around to testing that old bag of lime. I put a spoonful in a small bowl and added a little vinegar. It bubbled but not as much as I expected. "That can't be right", so I added a few drops of hydrochloric acid and it fizzed like crazy. I bet it's pushing 100% carbonate.

What do you mean by 100% carbonate?

ETA: nevermind, I re-read the thread.

 

[z-bob]

The calcium carbonate all dissolved into the gallon of juice, and not all that much of anything precipitated out. I added the treated juice to the untreated, added sugar and half the yeast nutrient, and pitched the yeast.

I think it will work just fine, but next time I'm going to experiment; I'll use calcium hydroxide and add it slowly to the first portion of juice until it changes color. (it should turn grayish blue) Refrigerate for a coupe of days, then decant into the untreated juice, etc.

 

[mabrungard]

Be careful with calcium hydroxide since it’s strong enough to hydrolyze organic compounds in the beverage. Chalk is a safer bet for that reason.

 

[z-bob]

Be careful with calcium hydroxide since it’s strong enough to hydrolyze organic compounds in the beverage. Chalk is a safer bet for that reason.

Thanks, Martin. I hadn't thought of that. I will dissolve/suspend it in water and add it *very* slowly instead of just slowly.