Saturday, August 15, 2009

Good Chemistry

Chemical analysis can help you make a better decision about the optimum time to pick your grapes. Good chemistry is important to good winemaking. It's also helpful in a lab partner. I haven't had this much fun since Kendal P., bless her heart, was my lab partner in 8th grade science and I received my worst grade ever as she was a serious distraction. This time I kept all hands on deck and my eyes on the pipettes and the beakers and the LCD display and came away with some useful information.

I took a 100-plus random sample of berries from different parts of the clusters from each row of the Tempranillo block yesterday evening, hand crushed them in a baggie and measured the sugar: 22 brix. I purchased a Milwaukee pH meter and an acid measuring kit and not sure how to use them Coyote Karen volunteered to show me how so I went to her kitchen lab with my specimen. The reason she is called "Coyote" Karen is her vineyard is host to the crafty critters and they and men alike howl at her beauty. She is something of a scientist and I watched intently as she she showed me how to calibrate the pH meter then measure my sample. The reading came in at 3.63.

Next, she showed me how to test the acid. You do this by seeing how many cc's of indicator solution you drip into 50 cc of distilled water combined with 10 cc of grape must and 3 or 4 drops (we used 4 drops) of another solution until you reach 8.2 on the pH meter (or until the liquid becomes dark). Because it's not exactly certain when the liquid becomes dark, use of the pH meter is a bit more scientific. Being a scientist Coyote Karen has all kinds of beakers and pipettes and measuring devices and a machine that vibrates when you put a beaker on it and you put a little magnet at the bottom of the beaker and the magnet spins around creating a whirlpool to keep the mixture mixed and she puts her mouth over the pipette and pulls the poisonous indicator fluid (10 cc's) up the pipette and she doesn't waste a drop and I'm thinking if anyone in the neighborhood goes to their car and finds the gas siphoned then she's the #1 suspect. She tests some finished wine that has way too much acid in it and the wine doesn't taste good but it's not a total waste because she'll hang on to it and some time in the future she may blend it with a wine that is way too low in acid.

Being a good teacher she then insists I try (there is no better way to learn than by doing) and my butterfinger hands pick up the glass pipette and I start sucking up the poisonous liquid and as it rises up the pipette my saliva starts going down the tube and resting on top of the liquid and she starts laughing and making fun of me and I swear I wasn't drooling over her although the chemistry is good. She tells me to multiply the 10.5 cc of solution I dropped into the beaker to raise the pH to 8.2 by a factor of .15 and the resulting acid level of 1.57 doesn't sound good to me at all and I read the directions and the directions say to use a correction factor of .075 and she says that's because I used 10 cc of grape juice instead of 5 cc and despite the fact I would have ruined my wine based on the information she gave me the chemistry is good. The acid recalculation is .785, which, I am told, is a good level.

In summary: The brix are 22; the pH is 3.63 and the acid is .787 and she says those are good numbers. So, here's the decision to be made. Should I cut the water and try to get the brix up to 24 next Sunday in which case the acid is likely to drop a little and I'll have good numbers for making a good wine?

Or, should I water the vines a little tomorrow and plan on harvest in 2 weeks? Two weeks from now I could get the brix up to about 25 (keeping it from reaching 26 or 27 by adding a little water) and the grapes will be full of sugar and riper and the seeds will be darker brown and crunchy but the acid will drop maybe a little too much. You can always do a little acid adjustment (most winemakers do by adding tartaric acid) and if the brix get too high you can always add water to the must (many winemakers do). If the brix get too high then the wine may have too much alcohol and it may "burn". Waiting two weeks would allow me to make a "bigger wine". On the other hand if I wait two more weeks the birds may get more of the grapes and I'll be left with less, and, I'm dealing with younger vines (only their 3rd leaf) so perhaps I shouldn't get my hopes up about making a big red wine.

To pick or not to pick? Experienced winemakers, vineyardistos and vineyardistas, what should I do?


Vinogirl said...

Craig...major brownie points with your comment on my blog...I'm still blushing!!!
I seem to be missing what varietal you are planning on harvesting. Chemistry is all well and good, but stylistic/winemaking considerations with particular varietals are important here. Also indicators out in the vineyard, lignification of peduncles and slip-skin of the grapes to name but two. Let me know.

Vinogirl said...

I need to let that acid come down to about at least 6.5 and look for that little pucker of the skins. Harvest too early and you'll end up with those nasty green tannins.

Douglas Henning said...

Vinogirl Thank you for thee infomation and the book reference. I have ordered it. It may get to me in Mexico before next Spring. Craig. Keep the good posts coming.

Pete Anderson said...

What has the ripening process been up to now - weekly brix increase/acid decrease?? We have had some warm weather up to now, but, seem to have more average temps now. If we get some warm/hot temps the sugars could rise quite fast - in that case I would put on the water to keep the maturation process working on an even keel.
If the temps remain normal I would continue to manage the vines as you have been - give them water only if they need it. Let the process work itself.
Don't forget the maturation is not only based on numbers. If you pick unripe berries there is no way you will be able to remove the green bean, veggie flavor in your wine. This is more important for younger vines.
Don't let the acid concern you - you can always add tartaric acid at fermentation.
You might already have the picking guidlines I had obtained from Seghesio, but, I will attach a copy anyway.
I have also attached a paper on Climate and Ripenng - I find this to be one of the best guides for making a decision on harvest.


Lum Eisenman said...

Hi Craig,
As you say, "it all depends."
Tempranillo can make a very nice red wine. But, the grapes need to be ripe at 24 Brix or higher in order to make a decent wine.
So, I would not pick and I would not water. I would keep an eye on those bad birds. We sure enjoyed the sushi very much. That was very kind of Kazuko so please
give her our thanks again.

Shermigirl said...

I vote for two weeks....Just ran across an article in WineMaker that talked about refractometers and hydrometers and how they can be off.. it gave ways to make know solutions to check accuracy of scales.

Jim Larsh said...

Water and wait. Bigger is Better!

Craig Justice said...

We waited, and we watered, a bit. As of Aug 26th we're at 24 brix, with acids coming down nicely and ripening progressing. Depending on the weather -- and this heat wave which has come up -- harvest is about a week away. Wondering if we can hold out until Labor Day Weekend?