You might think that you can tell if a grape is ripe just by taste. To some extent that is true. For the winemaker, though, there is more to it than just taste. There are seed characteristics and chemistry stuff like Brix and pH to measure. It is a good thing John was a chemist in his former life and knows what he is doing - at least he acts like he does! ;)
As grapes reach maturity, the seeds change color from green to dark brown and become crunchy instead of chewy. The pulp of the grape no longer clings to the seeds and the two are easily separated.
To test for the Brix, which is the percentage of sugar in the grapes, and the pH, samples must be picked. To do this each person takes a row and walks down picking at predetermined plants. Alternating between left, right, top and bottom, clusters are picked. The goal is to have a random sample to get an accurate representation of the level of ripeness. No matter how hard you try, if you do not pick in a predetermined way, you will subconsciously pick the riper clusters.
Once the samples are picked, they are brought back to the house. The picture above are the samples picked from the Montepulciano and Aglianico.
John then weighs the clusters and crushes the grapes to release the juice. He uses the weight of the clusters in determining how many tons of fruit per acre are on the vines. It is important for the wineries to know how much fruit to expect. (We found the crusher he is using at a yard sale and it works great for jelly too!)
As you can see, when he is finished we have a lot of grape juice.
Using a hydrometer, he measures the Brix and a pH meter tells him the pH. Winemakers want the pH under 4.0.
With harvest so close, samples are taken twice a week. You might wonder what we do with all the juice - we drink it! It is amazing how much sugar is in the grapes, in fact, they get so sweet that I must dilute it with water before the children will drink it!