When are grapes harvested in texas

The berries have all turned into a nice deep purple color, the irrigation is keeping them alive, sprays have been applied to keep the bugs out, so now what?

Now we wait! The ideal time to pick grapes is not easily determined. Grapes look and taste very good as soon as they start turning colors and ripening up. So (at least for me) it is not a very easy decision trying to determine when to harvest. Fortunately, technology comes to the rescue. As you may (or may not) be aware, as the grapes are ripening, the sugar and pH content is steadily going up while the acid levels are going down. Since these grapes are destined to transform into a nice glass of wine someday, there are a few things that really matter to use as a winemaker. The most important of these, is the sugar level. This will determine the potential for alcohol. In red/blue grapes, we are looking for a final alcohol content of around 13-14%. Since sugar is converted into alcohol, we want to have our grapes around 24-26% sugar (Brix). Right now, the Shiraz grapes here are at 14 Brix, so they still have a little ways to go. I will be checking them next week, and will determine how fast it is rising. As it gets closer to the harvest date, the pH value will start to change radically. Ideally I would like a pH of around 3.5. Its not easy to describe exactly what pH is or does, but all you really need to know it is greatly effected by how ripe the grapes are. When the pH gets near/above 4.0 the grapes will start to rot on the vines and turn to mush. We do not want that. At or near 3.5 is usually the best time to harvest (for me at least). This gives the grapes a beautiful deep claret color. The final value is acid. This is really just a balancing issue on how the wine will taste. It can be corrected over time with chemicals, so it is not as important as the other two. However, for red wines, we would like to have a acid value of around .6-.8. That way we can make very minor corrections, and it will not be noticed.

The calculation I like to use is: pH *pH * Brix and getting as close as I can to 260 (for red wine grapes 200 for white).  The number will only go up, and once it gets to a pH of 3.5 it will go up pretty fast to 4.0, so as you approach a pH of 3.5 start checking the grapes daily. There is another way you can use Brix and Acid levels and try to reach a ratio of 30:1. This is often good during the bad years where your vines are not producing the numbers that you want.

Next, you can look at the seeds inside the grapes. Are they still green? Or have they matured and turned brown?

Finally, how do the grapes taste? Does it still taste acidic or bitter? Or do they taste sweet and delicious? Bottom line, if they taste bad, the wine will too. Any off flavors in the taste at this point will be compounded in the finished wine.

All of these things help the winemaker determine when to harvest.

To get your readings, it is best to sample grapes from all over the vineyard and from all parts of the cluster. I like to take one from the top and bottom, and two from the middle. This gives me a good balance of what the cluster will be like. Then I go around the vineyard and select around 20 clusters to test. Some near the edge of the vine, some near the middle. Taking this sample gives my vineyard around a 5% deviation. Which is close enough for me.

Some other factors the can effect your decision on when to harvest, is the weather also. If you are expecting a big rain, it is better to harvest before rather than after a rain. What happens just after a rain, is the grape swell up with excess water. This lowers the sugar concentration and the flavor of your juice. This is not a good thing. I have harvested after a rain, but had to wait an additional 2 weeks for the berries to drop back down to their normal size and sugar readings. What happened, is the pH continued to rise during that time, and the grapes were more susceptible to contamination during the wine making process, and hence a lot more meta had to be added to compensate. As I do not like to add any more chemicals that is absolutely necessary, I always harvest before a rain now.


So for now, we wait, until the grapes are ready to harvest.

Currently as of June 25, 2011

Viognier – 16 Brix

Shiraz – 14 Brix

As of July 1, 2011

Viognier – 18 Brix

Shiraz – 17 Brix

As you can see in one weeks time, the grapes have moved about 3 Brix. This is a pretty rapid improvement, and I will be checking the grapes every other day now until harvest time. The pH values are really close to 3.5 pH. Which means that the grapes are getting about as ripe as they are going to get before they start turning to mush. I am gonig to measure the TA (Titratable Acidity tomorrow) and will let you know what I found out, and how it will effect my decision on when to harvest.

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