Marquette acid strategy

[RonObvious]

My 50 Marquette vines are in their 2nd year and will hopefully yield a crop next year. They seem to be doing well on our sunny, south facing hill side. The only major problem has been Japanese Beetles, which I took care of with a bit of Sevin.

Last year, while waiting for our vines to grow, we obtained some Marquette juice from the Finger Lakes. I have tasted other people's Marquettes and been very impressed, so I KNOW this grape can do great things. The juice we bought was pretty acidic (over 1.2 TA if memory serves) so I did the double-salt trick with calcium carbonate to try to get the acidity down. I only used about 2/3 of the recommended amount of calcium carbonate, however, because I have this chronic fear of overcorrecting. It went through MLF after fermentation. What I ended up with was a wine with both high TA AND high pH. Not where we want to be. Bottled it last week - very pleasant fruit flavor, powerful aromatics, beautiful color... but it tastes a bit sour. Not sour like it spoiled... just sour because the TA is still too high.

Observation #1 is that TA seems to contribute more to the perception of acidity than does pH. Maybe someone can confirm or deny this.

Observation #2 is that it probably started off with a LOT of malic acid. As I understand it, malic acid is stronger than tartaric or lactic, so when all that malic was chewed up by the MLF bacteria, it raised the pH. Yet lactic acid is still an acid, so it still contributes to the TA number. Which would explain the high pH AND high TA condition that resulted. Again, maybe someone can confirm or deny this too?

Anyway, I'm wondering what my strategy should be if it comes in with a really high TA again? 71B yeast? Or would it be pointless to use a yeast that consumes malic acid if one is planning on doing MLF anyway? How about cold stabilization? Double-salt again? Or just add CACO3 directly to the must and skip the double salt technique? And speaking of CACO3, would potassium bicarbonate be better? Or a blend of both? So many acid questions and only a couple weeks to figure it all out!

 

[ibglowin]

TA is a measure of the amount of acid(s) in the wine. pH is a measure of the strength of the acids. TA is the number to watch for tartness. pH is the number for microbial stability and sulfite needs.

Malic is not a stronger acid than Tartaric. You replaced Malic acid with Lactic acid durning MLF. Lactic is weaker acid than Malic so your pH should rise under normal MLF conditions.

The use of 71B is to consume as much Malic as possible during AF. See if the wine needs another round ofd treatment with MLB to fully get rid of all the Malic. It all depends on where your pH and TA levels are to start with as to how much you will need to play with it. Let your taste buds be your ultimate guide (always)

 

[RonObvious]

Thanks ibglowin. Any advice about neutralization (CACO3 or KHCO3)? I've never used KHCO3 before. I have used CACO3 with the double salt technique, but that was messy and frankly a pain in the rear. As I understand it, the point of the double salt technique is to preferentially get rid of more malic, while preserving more tartaric. Yet if the TA is really that high, then maybe I want to bring them BOTH down, which would mean simply dumping one (or a mix of both) of the neutralizers straight into the must, stirring, and racking a few hours later.

Another question - does 71B convert malic to lactic, similar to what MLF bacteria does? Or does it convert malic into something else... something not an acid? If it converts it to something non-acidic, then that would really help bring the overall TA load down. But if it just converts it to lactic, same as MLF, then why bother using it if you're going to do MLF later anyway?

Appreciate the info!

 

[RonObvious]

I may have found the answer to my 2nd question. From a conversation on a different board:

"No yeast can convert malic to lactic acid. That would be MLF, and only malolactic bacteria can do that. 71B-1122 and Lallemand SVG convert malic acid into ethanol and CO2. The net result is simply a lowering of acid levels. That's why they're recommended for "high acid" wines. There's a thread on the Google cider group where Claude Jolicoeur did experiments with 71B and reported a measurable drop in TA." -credit to Maylar on Homebrewtalk.

If that's the case, it sounds like a highly compelling reason to use 71B type yeasts for high TA must like Marquette. Then of course standard MLF after fermentation is done, to convert any remaining malic to lactic.

 

[ibglowin]

I have used Vintner's Acidex Super-K Acid Reduction Powder before and had no problems. I don't seem to have crazy high TA's with my grapes as we have plenty of heat and hang time with cool evenings and mornings all Summer long.

According to research papers done on wine yeast that convert/metabolize Malic acid, they can consume up to 50% of the available Malic acid. They metabolize it just like sugar during AF and convert it to EEOH and CO2.

 

[RonObvious]

Cool, thanks for confirming!