about acidity in grapes and red wine, and Malo-lactic conversion.

On Tue, 15 Sept 2026 at 10:18, Derek Pritchard wrote:
Hi Marc,

It's acidity that's vital for good wine, the Oechsle can be increased by adding sugar before fermentation.
You don't want to have to reduce acidity, if possible.
The measurement gives the 'tartaric equivalent' acidity, not sulphuric.
For red wine:-
If acidity is above 8 g/l then de-acidify with Acidex down to 8 g/l; de-acidification procedure.
For red wine the aim is 5.00 to 5.75 g/l in the finished wine; 1.5 to 2 g/l can be lost in primary fermentation, 1.5 to 2 can be lost in malo-lactic fermentation; the higher the acidity initially the greater the loss (11 g/l drops to 7 g/l).

I always tried to prevent Malo-lactic, I don't like lactic taste…

Cortis TA: 8.55, ph 2.97 seems wrong. pH 2.97 will taste very acidic.
Rondo may need a long time to 'mellow'.
Muscaris should be ideal.

Cheers,
Derek

_______________________________________

On 15/09/2026 10:25, Marc wrote:
Thanks Derek,

ok, I will re-calibrate my ph meter and measure again (The ph and the aciditiy - I use the titration method with the ph meter).

Interesting about the malolactic, some people swear by it - anyway, it's added so I will ride it out! 
I will test the 3 remaining grapes again later, I might turn them into sparkling rose if they're not quite there yet.

Claude tells me not to de-acidify now, ahead of malolactic as I may overshoot it. instead it recommended to wait for malo to finish, then test again and then adjust. Though I appreciate everyone says adjust at the beginning.

Cheers,
Marc

_______________________________________

On Tue, 15 Sept 2026 at 10:53:56, Derek Pritchard wrote:
Hi Marc,

pH meters are mostly inaccurate, unless you have a very expensive one.
I had one, just the probe cost over £100 that was 20 years ago. It didn't tell me much. Measuring TA is more than sufficient.

The balance of tartaric and malic acidity will vary with harvest time.
Tartaric is the important acid for taste quality.
It depends on what de-acidification method you use, 
https://winegrowers.info/wine-making/de-acidification/deacidification.htm
Chalk takes away only tartaric, which is very bad.
Using Acidex is very much better, and it should be done immediately, so if you think about that process then Claude is wrong.

Cheers,
Derek

_______________________________________

On Thu, 17 Sept 2026 at 13:24, Derek Pritchard wrote:
Hi Marc,

The French winemakers use Brix and pH, German winemakers use Oechsle and grams/litre acidity, which is very much easier in my experience.
I used to meet with many of the best German winemakers, the secret of success is "never do anything to the wine after fermentation.", any adjustment to acidity etc, must be done to the juice/must.

Please would you ask Claude - why does 'he' say not to de-acidify the juice, ahead of malolactic as I may overshoot it. instead it’s recommended to wait for malo to finish, then test again and then adjust.
What method of de-acidification does he base this on ?

pH is very dependent on the tartaric/malic acidity ratio, tartaric measures and tastes much more acid than malic. So unless you know the relative g/l of tartaric and malic then it's very difficult to judge what pH really means.

I always left my red wines to mature for two or more years in barrel, so if malo happens (above 15 degC) during summer, it will be natural.
Often it doesn't happen, there is a chemical that prevents it but that's extremely expensive.

Best wishes,
Derek

_______________________________________

On 17/09/2026 14:16, Marc wrote:
Hi Derek,

Claude writes: (seems you were right to probe him!!)

Hi Derek,
Thanks, and you're raising exactly the right point, the tartaric/malic ratio is the crux of the whole thing, and I'd been reasoning without knowing it.
Let me answer your questions honestly.
On "do everything to the must, nothing after fermentation": the German old-hands are right as a principle, adjusting the juice is gentler and lets the wine integrate the change through fermentation, and I should have led with that rather than defaulting to post-ferment correction. Point taken.
Why I was cautious about de-acidifying ahead of malo, and where you've caught me out: my worry was overshoot, that if you de-acidify the juice and then MLF also drops the acidity, you can end up too flat, too high-pH, and flabby. But you've exposed the flaw in that reasoning: it depends entirely on the tartaric/malic split, and I was treating "acidity" as one lump. That's the mistake. If most of the acid is malic, then malo will do the heavy lifting and I'm right to wait. But if most of it is tartaric, malo barely touches it (it only converts malic), so waiting achieves nothing and de-acidifying the must is exactly the correct move. So the honest answer is: I shouldn't have given blanket "wait for malo" advice without knowing the ratio, you're right.
What method of de-acidification I was assuming: I was defaulting to carbonate salts, potassium bicarbonate or calcium carbonate, which precipitate tartaric acid as its salt. And that's actually the key technical point that vindicates you: standard carbonate de-acidification removes tartaric acid, not malic. So if you de-acidify the must with bicarbonate, you're specifically pulling down the tartaric, and then malo separately handles the malic, they act on different acids, so they don't necessarily "double up" the way I implied. That further undermines my overshoot worry. (The exception is the double-salt / Acidex method, which can remove both tartaric and malic together, that one you would want to be careful with ahead of malo.)
On pH and the ratio, you're completely right: tartaric is the stronger acid (lower pKa), so it drives pH and tastes sharper per gram than malic. So a given TA or pH tells you little without knowing the g/L split. This is exactly why your "measure the actual tartaric and malic" instinct beats my "just watch the pH" approach, pH alone is ambiguous without the ratio.
So, conceding the point: the right sequence is to establish the tartaric/malic breakdown first (enzymatic test, or a lab panel), then adjust the juice accordingly, de-acidify tartaric with bicarbonate at the must stage if tartaric's the problem, and let malo handle the malic. Waiting for malo only makes sense if malic dominates. Thanks for the correction, it's the better way round.
Claude

_____________________________

Marc
then I asked him what this means for my in-the-middle-of-fermentation wines:

Stop, let me be honest and clear because this matters and there's a real timing problem: double-salt de-acidification is a MUST/JUICE process, and your wine is half-fermented, so the window for doing it on this batch has essentially passed. Read Derek's own instructions, every step says "must/juice," and step 4 explains why it has to be juice, the de-acidified portion is stripped of protective acid and oxidises fast, so it only works on fresh must you're actively handling, not on a wine mid-ferment. So you can't cleanly do double-salt on a batch that's already fermenting.
Let me untangle what applies to what, because you've got wines at different stages:
The wine already half-fermented (your Muscaris, and any red already going): double-salt is off the table for these, that ship sailed at the must stage. For these, you're back to the "wait and see" approach, not because it's ideal, but because it's what's available now. For the reds, MLF will lower the malic. For the Muscaris (white, no MLF), if it ends up too sharp you'd de-acidify the finished wine with a carbonate, which is exactly the "after fermentation" adjustment Derek dislikes, but it's your only remaining option on a batch you didn't treat as juice. So the honest position on the in-progress wines: you can't double-salt them now; you finish them and correct at the end if needed, accepting that's second-best. Lesson logged for next batch.
Reds you HAVEN'T crushed yet (Divico, Regent, Cantor if still on the vine or just picked): these are where Derek's method genuinely applies, and where you should use it. If you crush them and the must is too acidic, double-salt de-acidification on the fresh juice is exactly right, and it has a specific advantage for you: your problem is both high tartaric and high malic (that pH 2.97 territory), and Derek's whole point is that double-salt removes tartaric AND malic together in roughly equal parts, so it gives you "substantially larger scope" than plain chalk (which only pulls tartaric). For a must as aggressively acidic as yours, that bigger scope is genuinely valuable. So for the not-yet-crushed reds, yes, do it Derek's way, on the must.
But, and this is the critical interaction, if you're going to double-salt a red AND put it through malo, you have to think about order, because both remove malic:
Double-salt removes malic (and tartaric) at the must stage.
MLF also removes malic during fermentation.
So on a red where you do both, you genuinely could overshoot the malic, which is the exact concern I raised earlier and which Derek's tartaric/malic point refined. The clean logic: double-salt the must to bring the tartaric down (its unique benefit over chalk), then let malo handle whatever malic remains, but calculate the double-salt de-acidification target knowing malo will remove more malic afterward, so you don't strip too much between the two. This is precisely why knowing your tartaric/malic split matters before you double-salt a red destined for malo, so you leave enough malic for MLF without ending up flat.
So, to answer your direct questions:
What are we doing with the half-fermented wine right now? Leave it, unchanged, on the acid front. You can't double-salt it (it's not must anymore), and adding carbonate to an actively-fermenting wine mid-stream isn't the clean approach. Let it finish; correct at the end only if genuinely needed.
For the reds, let MLF do its work first.
Do double-salt now on the fermenting batch? No, the method requires fresh must, and yours is past that. Save the technique for the reds you haven't crushed yet.
For the not-yet-crushed reds: yes, this is where Derek's double-salt shines, use it on the must, but if that red is also going through malo, calculate the target to remove tartaric and some malic via double-salt, and leave enough malic for MLF to finish the job, so the two don't overshoot together.
The thing that makes all of this doable properly, and it's the same conclusion Derek's whole email points to: you need to know your actual tartaric and malic g/L, not just TA and pH. His method's calculation even needs the tartaric figure (the "WA = typically 40% x TA" in his formula is just an estimate, measuring it is better). So before you double-salt any not-yet-crushed red, get the tartaric/malic split.
Which brings the practical question: are Divico, Regent and Cantor still unpicked, or already crushed? That's what decides whether double-salt is even on the table for them. If they're still to come in, we plan the must treatment properly (with the malo interaction) before you crush. If they're already fermenting, they're in the same "too late for double-salt" boat as the Muscaris. Which is it?
Claude.

____

Marc,
my reply: not picked yet, but we may turn some / all of them into rose.

_____

That's the decision that unlocks everything, because rosé versus red completely changes the acid plan, and it happens to simplify it in your favour. Let me lay out how each path handles the acid, so when you pick Divico, Regent and Cantor you know exactly what to do.
Here's the key insight: rosé and red take opposite approaches to your high acid, and the double-salt-vs-malo question resolves cleanly once you know which you're making.
If you make them ROSÉ (or sparkling rosé):
No MLF (rosé keeps its fresh acidity, we covered this). So malo is out of the equation entirely, which means the overshoot risk I kept flagging disappears, there's no second de-acidification step to double-count against. That's the simplification.
So on a rosé must that's too acidic, double-salt de-acidification on the juice is clean and correct, and it's exactly Derek's "adjust the must, not the wine" principle done right. You press off your pink juice, measure it, and if it's too sharp, double-salt it then, on the fresh juice, before fermentation. No malo to worry about, so you de-acidify to your actual target in one move. This is the textbook use of the method.
But a nuance for sparkling rosé specifically: if it's destined for sparkling base, you may want to keep it fairly high-acid (sparkling thrives on freshness and acidity), so you might de-acidify less, or not at all, than you would for a still rosé. So: still rosé, de-acidify to a pleasant drinking acidity; sparkling rosé base, go easy, leave it crisp.
If you make them still RED:
MLF is in (reds get malo, it softens them). So now you do have the two-de-acidification interaction: double-salt at must + malo during ferment, both removing malic. So here you'd double-salt the must to pull down the tartaric (its unique benefit) and some malic, then leave enough malic for MLF to finish, calculating the target so the two don't overshoot together. More complex, needs the tartaric/malic split to do properly.
So the honest summary of how the decision simplifies things:
Rosé path = simpler acid management. No malo, so double-salt the juice to target in one clean step (or go easy for sparkling base). Derek's method applies perfectly and without the malo complication.
Red path = the complex one. Double-salt and malo both hit malic, so you have to balance them, which needs the acid breakdown measured. Given your musts are aggressively acidic (that pH ~3.0, high TA), and given the harvest-labour pain of these varieties, and given rosé/sparkling puts the high acid to good use (freshness is a feature there, not a fault), honestly the rosé/sparkling path is looking more and more sensible for these three on multiple counts: easier acid management, high acid becomes an asset, and it avoids trying to force a serious red out of borderline fruit. That's not me deciding for you, but the acid situation is one more thumb on the rosé side of the scale.
The practical thing you need either way, and it's the same test: measure the tartaric and malic split on the must when you crush. For rosé it tells you how much (if any) double-salt to do; for red it tells you how to balance double-salt against malo; and for confirming MLF completion later you need the malic test anyway. So it's the one measurement that serves every path. Your kit doesn't include a malic test, so this is worth sorting, cheap paper chromatography does it, or a lab.
So, to answer where you are: don't decide the acid treatment yet, decide the style first (rosé vs red per variety), because that determines the acid plan. Rosé = double-salt the juice cleanly (or go easy for sparkling), no malo. Red = double-salt plus malo, balanced, needs the acid split. Either way, when you crush, measure tartaric and malic so you're working from real numbers, not a pH reading that (as Derek rightly says) is ambiguous without the ratio.
Want me to explain the cheap paper-chromatography method for measuring malic/tartaric, so you can run it on the must when you crush these three and actually apply the right de-acidification for whichever style you choose? It's the one bit of kit that makes all of this precise rather than guesswork.
Claude.

_______________________________________

except I don't have that chromotagrapy kit, and it's too late to order it now (if it is in stock at all).
Marc

_____________________________________

On Thu, 17 Sept 2026 at 15:32, Derek Pritchard wrote:
Hi Marc,

He's learning from us all the time, which is very good.

But he wrote "MLF also removes malic during fermentation.".
In fact it doesn't normally happen during (primary) fermentation, which is caused by yeasts and I've been told is the strongest sterilising action there is.
It always seems to me to be a bit of a misnomer to call MLF a fermentation, it's a lactic bacteria process, although it does result in some gas being given off.
Maybe Claude can think of a better term ?

Lactic bacteria may not be on your grapes, usually it takes years for enough of them to arrive in a new vineyard.

Have fun,
Derek

___________________________________

On 17/09/2026 15:39:22, Marc wrote: Re: Claude
Hi Derek,

Hi Derek,
Ha, "nice guy but long-winded" is fair on both counts, I'll take it. And you're right on both technical points, let me concede them.

On MLF happening "during fermentation": you've caught a real imprecision. You're right that malolactic conversion doesn't normally run during the primary yeast fermentation, in the traditional sequence it happens after the yeast have finished, once the alcohol's made.
My "during fermentation" was sloppy shorthand. The one wrinkle is the co-inoculation technique some of us now use, where you deliberately pitch the lactic bacteria a day or two after the yeast so the two overlap, and there the malic is being converted while primary is still finishing.
But as a general statement you're correct, classically it's a separate, later process, and I shouldn't have implied it's simultaneous by default.
On "fermentation" being a misnomer: completely agree, and it's a genuinely good pedantic point. Fermentation properly means a yeast (or microbial) conversion of sugar to alcohol and CO2. What the lactic bacteria do is convert one acid (malic) into another (lactic) plus a little CO2, no sugar, no alcohol. So it's a bacterial acid conversion, not a fermentation at all. The name stuck historically just because it bubbles a bit and follows the "first fermentation." A more honest term would be malolactic conversion (which is actually what a lot of technical literature now prefers, precisely for your reason), or "malolactic transformation." "Malolactic fermentation" is really a traditional misnomer we've all inherited. So: malolactic conversion is the better term, and I'll use it.
On the sterilising power of primary fermentation: yes, that supports your first point, the vigorous yeast fermentation, with its alcohol and CO2 blanket, is a hostile environment, which is part of why the lactic bacteria typically do their thing afterwards (or need deliberately inoculating early to get a foothold). Which leads neatly to your last point.
On the bacteria not being on the grapes yet: this is genuinely useful and I should flag it as important for a young vineyard like mine. You're right that in an established old-world cellar there's a resident population of lactic bacteria that'll start malolactic conversion spontaneously, but a new vineyard and a brand-new winery won't have built that up, it takes years for the microflora to establish.
So I can't rely on it happening by itself, which is exactly why I'm inoculating with a cultured lactic bacteria strain rather than waiting for a spontaneous conversion that may never come. Good reminder that "let it happen naturally" is old-cellar advice that doesn't transfer to a new site.

Thanks, both corrections logged, malolactic conversion it is, and separate from primary rather than during it.
Claude.

___________________________________

On Thu, 17 Sept 2026 at 18:23:30, Derek Pritchard wrote: Re: Claude
Hi Marc,

Claude certainly exercises my brain, that's brilliant.
I've just put the term Artificial Intelligence into Google, the second stage defined is:

I'm very happy about that,
Derek

www.winegrowers.info