Causes of High PH / High TA?

I was looking at a small vineyard recently (southwest of Sebastopol, not one I currently buy from). The vineyard owner had numbers on past wines…and they pretty much all had High PH and High TA (ph above 3.8, TA above 7). My question here is what are the various causes of this? Soil? Viticulture? Climate? Winemaking? All of the above? And what are the various possible solutions to this?

Primer on PH vs TA for folks unfamiliar with this and are curious (trying to stay at the broad stroke level here): PH is a measure of the number of free/unbound electrons from the acid molecules in solution. TA (titratable acidity) is, roughly speaking, a measure of the number of acid molecules in solution. Generally speaking, the higher the TA (the more acid molecules you have in solution) the more free electrons you’ll have and hence the lower the PH. There are two things that can alter that: First, strong acids vs weak acids. Strong acids (hydrochloric acid for example) create many more free electrons for a given amount of acid molecules than weak acids do (tartaric or malic acids are examples of weak acids, and are the main acid component of wine). Second, buffer capacity. A buffer is a compound that can neutralize an acid, preventing it from having a free electron. If you add an acid to a solution that contains a buffer, the PH won’t change (despite the acid addition, because a buffer molecule interacts with the added acid molecule). If you keep adding acid, eventually you will ‘use up’ all the buffer molecules and the PH will begin dropping with each added acid molecule.
Perception (i.e. the taste) of acidity: With strong acids, the perception is due mainly/completely to the PH of the solution. With weak acids, the perception is due mainly to the TA of the solution.

I think the big one is the Potassium level in the grapes.

Shaded canopies, irrigation levels and fertilization all affect the amount of Potassium along with rootstock and variety.

-Bryan

itb

Bryan is right. I’ll bet the canopies at said vineyard were quite large and thick. I’ve seen the same situation in a couple of vineyards around here, and usually either the rootstock was not devigorating enough or the trellis system choice was not adequate to accommodate the vine vigor.

So, as long as we are on the subject of ph, why would, for instance, a wine with a 3.9 ph and 67 ppm molecular SO2 have a free of 33 ppm while another wine with a 3.7 ph and a 107 total, have a free of 27. This goes against basic priciples, or not??? Va doesn’t have any bearing on unbound S02 does it?

You said the first wine has a 3.9ph, 67ppm molecular so2 and 33ppm free…did you mean 67ppm total so2 (in my comments below, I assume that’s what you meant)? A 3.9ph and 33ppm free would have a molecular so2 of 0.26ppm, I believe (you’d need a 3.5ph to get a molecular so2 of 0.67ppm from a free of 33).

I don’t believe there’s any fixed relationship between bound so2 and free…other than when something comes along that a free so2 can bind to…it will.

SO2 binds mainly to Acetaldehyde (so2 binds to what else? I’m forgetting). Just out of curiousity…how much so2 did you add at the crusher for the 107 total vs 67 total? Acetaldehyde gets generated during fermentation on its way to becoming Ethanol, terpines or esters…but any free so2 in the fermenting must would bind to that first. So adding more so2 at the crusher for one lot than another would give you a higher level of bound and total so2.

But…do high levels of bound so2 matter? I’ve read that high levels of bound so2 can (in theory) cause problems with ML…basically that the Oenococcus can cause bound so2 to become unbound, and the free so2 molecules then kills the Oenococcus. Talk about curiosity killing the Oenococcus. I’ve also heard that high levels of bound so2 can affect the flavors (or texture, not sure which)…tho I have no idea why or if that’s really true.

Eric,
That particular lot of Zin did, in fact have a bit of rot in it and we did add 40ppm instead of the normal 0-25ppm. I had the wines analyzed after ML and there was “no sulfites detected”. The total was added (in small increments, over the first year in barrel, 5 to 10 parts at a time) in order to achieve a +/- 25 free, which is in the range I have been shooting for. Most of the rest of the totals are in the 60- 80 range, with FS02 in the 24-30 range. We are bottling these 07’s next week. Exciting!

What are typical F/T SO2 levels at bottling for you all?

Hey…thanks for the thoughts Bryan and John. Potassium level in the grapes from canopy issues, and possibly soil issues, makes perfect sense.

How can irrigation levels affect potassium in the grapes? From too little irrigation stressing the vine too much? Or too much irrigation? Or both?

Seems like the canopy management is contributing to the problem. They use a kind of Lyre trellis. From the following picture, they are using option B, i.e. a single cordon lateral on each wire (i.e. cordons from each adjacent vine overlapping each other on the parallel wires):

http://www.agric.wa.gov.au/objtwr/imported_images/fig5.jpg" onclick="window.open(this.href);return false;

The thing is tho, the wires and split cordons are very close to each other…maybe 1.5 feet apart or so. The owner said they hedged multiple times (not sure if it was hedged twice, or more than that, but at least twice) to keep the canopy open. But that’s going to eliminate a lot of new leaves…and young leaves are the real engine for the vine right? So I’m assuming too much hedging will cause vine balance problems and contribute to this?

Also, from his soil analysis, the soil has very high levels of Mg. Really high levels of Mg can block the vines uptake of nutrients right? Tho I thought it blocked the vines taking up potassium. I was surprised by the high Mg…this is sebastopol loam (according to the soil maps, and is my interest in the vineyard), which should have a nicely balanced soil chemistry. Petiole analysis would be interesting here.

Anyways…thanks

My free and total so2 levels are in the same range. Good luck with the bottling…can’t wait to try them out.

Sorry for the previous thread drift.

If they have to hedge mutiple times, on a quadrilateral trellis, it sounds like; a) they are watering/fertilizing too much(leading to thicker canopies/higher K levels in the grapes), b) chose a roostock that was too vigorous for the site, c) have a relatively high water table that the vines are tapping into. If they are indeed watering/fertilizing, It sounds like they could cut back a bit at certain times to control excessive growth.
Hedging can cause new side shoot growth, producing lots of new young leaves(which really are an engine for ripening the fruit). We did the same in our Old Mill vineyard(Humboldt and Aria’s Syrah) where there is also quad trellis and extreme vigor(do to silty soil with high organic matter(>5%)), but pull all of the side shoots below the first set of catch wires to open up the fruit zone. This hedging deffinately requires more tucking in order to keep the middle open.
Magnesium and Calcium are on a teeter totter scale and need to be balanced with one another for greater availabilty of nutrients. Oyster shell flour is a great source of calcium, and minerals, which are very important and often overlooked by many farmers.

As you get towards the end the vines start storing nutrients from the leaves. The roots and the clusters are the main sinks. Large vines with small roots are one cause, ie in heavy soils that are closed or anaerobic at relatively shallow levels. Not enough root to store into. Make sure to remove basal leaves near the clusters, those are the first to export K into the cluster.

The other thing which is counterintuitive and which basically disproves the generally accepted interpretation of terroir is that vines in nutrient deficits can create excesses, especially of K because they start to hoard it. The gene regulating the expression of the protein embedded in the root hair cell wall membrane increases the uptake of what is less available and decreases what is more available. In low k sites, vines can have high juice pH from K contrary to intuition, especially as the vine starts looking for a sink approaching harvest.

Balance in all aspects of nutrition is key.

Crop size also affects the pH because a larger crop is a larger sink to store K. Big canopy small crop you will see a faster pH shift upward at harvest than a larger crop with same size canopy. The vine is looking for sinks. Just like the fruit is a sink for carbohydrate and crop size influences sugar accumulation in relation to the other compounds that are ripening on disparate trajectories from sugar.