(Another) Year in the Vineyard,
Week #26: September 3-9, 2010
The Winery is Ready, The Grapes are Not!
Welcome, once again to another episode of ‘Year in the Vineyard’. Well, we’re counting down to the madness that is harvest and crush, but for now we’re a bit relaxed—stuck between the business of bottling and the beginning of harvest.
The barrels and tanks are all clean and empty in the winery, and we’re spending some time in the vineyard dropping thjose last few green or pink clusters on the ground sol that the fruit remaining is perfectly and consistently ripe. We also are testing the fruit a few times a week for sugar and pH content. This gives us a good indication of the style, alcohol content and structure of the wine that would result from any given moment if we pulled the trigger and started harvesting grapes.
I also spent a day this week (Tuesday) with a winery tech in the winery going over all of our winery equipment with a fine toothed comb and a food-grade grease machine. All parts of our press and crusher/destemmer have been checked and tested, so we are ready to start making wine today! Our vineyard crew has scrubbed and cleaned our picking bins and our fermenters, and all the barrels have been delivered and tucked into corners at the winery. Pre-season is over and we’re ready to rock.
Next week I plan to do a video on fruit testing so you can see how it’s done—a little video in the field and a little video from our lab: aka the intern’s kitchen.
Until then, everything I wanted you to know about this week is in a 4 minute HiDef video that I took in the field this morning. I’ll keep it short this week, as my 10th wedding anniversary is tomorrow, and I have a lot of celebrating to do. Help us celebrate love by opening a great bottle of wine tonight, and every night, to celebrate the miracle of this life and those that we care about.
Have an awesome week, and I’ll see you all next week for another installment of ‘Year in the Vineyard’!
Weekly Bonus article: (GEEK WARNING!) Preview of upcoming article in WineMaker Magazine: Questions and Answers from readers. I answered a question today in my regular WineMaker Column, Backyard Vines, about harvest chemistry, and to explain the decision making process I had to describe the difference between titratable acidity and pH. While this won’t appeal to all readers, those that have reached the level of bonafide wine geek will probably salivate all over this stuff. With that caveat, read on intrepid wine nerds, cork dorks, lab rats.
I am hoping you can help me with a problem I am having.
Our Cynthiana grapes we make both into a port and a bold red. We usually
harvest at 26 brix (its sunny and hot here in Texas).
But my question, is when to judge harvest time from a pH / TA stand point.
All things being equal, is it better to harvest at pH 4.0 and have the TA at .65 or harvest 2 weeks early and have the pH at 3.4 and the TA at 1.1.From what I have read, it is better to harvest at the lower pH and adjust the acidity/blend as needed., But most of the wineries around here actually harvest at pH 4.0 and TA at .65.Can you offer any advice?
Jeff: Texas viticulture is really taking off, and I appreciate your pioneer spirit in making wine in a relatively new winegrowing region. I recently attended a tasting of some commercial Texan wines and was very impressed with the whites, and although all of the reds had a unique perfumey aroma, they were balanced and quite well made. The bottom line is that Texas represents a legitimate option for winegrape growers and winemakers, although any new region will have its challenges to overcome.
You may find the challenge of balancing TA (titratable or Total acidity, usually measured in grams/liter) and pH (which is a measure of the hydrogen ion activity in a solution) a harsh mistress in such a warm clime. I suggest that the warm, humid Texan nights are partly to blame. Areas where there are larger diurnal temperature shifts (warm days and cold nights) generally produce wines with a more balanced level of sugar and acidity—allowing winemakers to allow the wines to be processed with minimal intervention, and resulting in wines that have a natural balance between sugar (potential alcohol) and structure (tannin and acidity).
But of course winemakers have every right to intervene to make their wines better with chemistry when nature doesn’t provide the perfect base ingredients. Let’s first take a broad view of the difference between TA and pH, and then we’ll try to solve your problem specifically.
TA is the actual weight of the acid (mostly malic and tartaric) in your grapes. Bruno D’alfonso, a local Santa Barbara winemaker and controversial character, explains TA and pH with a fabulous analogy that I’ve never forgotten. Imagine your juice or wine like a fishbowl. TA would be the weight of the fish in the bowl, regardless of activity. Imagine those poor little fish with tiny balls and chains around their fins, so they were locked in place and couldn’t move. Say there are 8 goldfish in the bowl and each goldfish weighs 25 grams. Your total goldfish weight is 200 grams in a ten liter fishbowl. This is perfectly analogous to TA. TA measures the weight of acidity (goldfish) in your juice or wine (aquarium), regardless of how active the hydrogen ions (fish) are. So 200 grams of goldfish (acid) in a 10 liter bowl (wine sample) would be 200g/10l, or 20g/l. That’s titratable, or total acidity. T&A, so to speak.
The measure of pH is a little more complicated. Because pH has no interest in the weight of the acid in solution, the disparity between pH and TA can seem confusing, and in Texas (and even in the Santa Rita Hills, CA) the numbers can get a little whacky. The measurement of pH is roughly equivalent to how fast those goldfish are swimming in that ten liter tank. Now this is where it gets interesting. Freed from their little balls and chains, the goldfish swim frantically in swift ellipses as if someone dumped a little espresso into the water. So pH measures how fast those little hydrogen ions are whipping around in solution. Your tongue is actually a very good receptor/gauge for hydrogen ion activity, so pH is known to have more of an impact on mouth feel. (I can usually judge pH in a wine or juice to .1 margin of error using only my mouth.)
It’s easy to fool a palate with TA, but almost impossible to hide the pH of a wine as it’s tasted. Working at Babcock Vineyards in 1996, Bryan Babcock showed me an amazing experiment you can try at home with a pH meter. Take a sample of juice around 3.0 pH and measure it with the pH meter. Let’s assume that the TA of said juice is 10g/l, which would be about correct for Santa Barbara pinot at 20 Brix. Leaving the electrode in the juice, double the sample size by adding deionized water. You have now halved the TA in the juice from 10 g/l to 5 g/l by virtue of the amount of liquid. But what happens to the pH? In our experiment it nudged from 3.0 to only 3.2. But how is that possible? Staying with Bruno’s analogy of the fishbowl, you have increased the size of the aquarium, giving the spastic little fish more room to zip around. The hydrogen ions aren’t going to relax just because the sample size increases. The reduction in concentration of the hydrogen ions causes a small rise in pH , but not nearly as much as one would imagine. OK, that was a long introduction to a simple question, but now we thoroughly understand the difference between pH and TA. (I hope.)
I can’t see a red wine being all that pleasant to drink with 11 g/l TA at 3.4 pH. I would imagine that the tannins would be green and the acid would tear up your mouth. I like my reds and ports a bit softer than that! I like my white wines to have around 7-8 g/l TA with a pH range of 3.1-3.3 and my reds to have 5-7 g/l TA at a pH of 3.4-3.7. I like a lot of acidity in my wines, so keep that in mind. Your hot days and warm nights are allowing the acid to respire from the grapes around the clock, while cold nights would retain more acidity through the growing season. We have the opposite problem in cold years here at Clos Pepe—one of my producers saw numbers in his pinot noir fermenters that were nearly impossible: 27.1 Brix, 3.17 pH and 7.5 g/l TA. Now that’s brisk! (And sweet!)
My final answer may seem simplistic after all of this scientific hee-haw. Trust your mouth, as it will be the same mouth that drinks most of your wine. Taste the juice when you sample it and go with your gut when the proper moment for harvest comes. If it was me, I’d try to pick it under 4.0 pH—maybe split the difference around 3.8 pH and 7.5 g/l TA. And remember to sulfite your juice and wine just to the edge of where it can still ferment and go through ML (if you want it to), because high pH wine is a perfect breeding ground for spoilage microbes. But again, experiment, take notes, try an earlier harvest one year and a later harvest the next and taste the wines side by side. Science makes a fascinating discussion, but I find the final wine tastes much, much better than a textbook or a Bunsen burner. Have fun and keep me appraised of your progress with Texas Cynthiana. I think you chose a good varietal for your location.