Wednesday, January 30, 2008

From Plant to Bottle: The Grapes – To Pick or not To Pick

This is part 3 of the From Plant to Bottle series.  If you are just joining me, you may want to start from the beginning of this series. 

As we approach harvest, this is where the winemaker gets more involved.  Periodically, a visit to the vineyard is needed to taste and test the grapes with a refractometer, which is a portable device that looks a little like half of a pair of binoculars.  Tasting is very important and has various facets.  First, you taste the juice, which should taste like any good grape juice, sweet and balanced and ready to drink. Then chew the skin to see if it tastes ripe or sharp and acidic like a lemon.  Next you look at the seeds.  They need to be very brown and hard.  If they are green or even somewhat green and/or soft, they are not ripe.  A few drops of juice are squeezed from individual grapes onto the glass surface of the refractometer, at the far end, under a little flap of plastic.  The flap is then laid down on the juice, sandwiching it between the two, and the user looks through the end, as one does with binoculars.  The light refracts through the juice and gives a reading inside that tells the user what the sugar level is in the grape.  Random samples are taken all over the vineyard to get an idea of average sugar level. 

When it appears that the grapes are reaching maturity, a 100 to 200 berry sample is taken (one grape at a time off of different bunches) from all over the section of a specific variety and brought into the lab. This wide sampling provides a much more accurate picture of the overall ripeness of the grapes.  The grapes are hand crushed and the juice strained for testing including sugar content, total acidity, and pH, which are the major factors evaluated (in addition to taste, of course) in making the decision to harvest.  Sugar is measured with an apparatus called a hydrometer.  This consists of a tube, usually 100 milliliters or larger, into which the juice is poured and a glass item that looks a bit like a thermometer (this is the actual hydrometer), which is then floated in the juice.  There are specific markings on the hydrometer and the sugar content is indicated by where the juice level ends on the hydrometer.  Total acidity and pH are measured with a pH meter, the former with the addition of various chemicals.

Vinifera grapes are generally harvested at anywhere between 18 and 28 brix (with a few exceptions noted later).  Brix is the measurement of sugar in the juice.  If a solution is 22 brix, this means that it is 22% sugar and 78% water or other components.  The sugar content is very important because yeast feeds on the sugar and turns it into alcohol.  So, besides the fact that low sugar grapes may not be ripe and have other flavor profile problems, you may end up with a wine that does not have enough alcohol to be of good keeping quality.  In addition, alcohol creates viscosity, which helps with the mouth-feel and body of the wine.  Incidentally, I have heard people pronounce the word “brix” as “bree” as though it were French, but it is actually pronounced exactly as it looks, as in “hit by a ton of…”.

21-22 brix will generally give you 11% to 12% alcohol in a wine if the fermentation goes to completion.  What happens here is that the yeast that creates fermentation feeds on the sugar and creates alcohol.  There are various reasons for the stretch between 18 and 28 brix mentioned above.  In certain parts of the United States, e.g. New York and Ohio, Riesling is often harvested between 18 and 20 brix.  The reason for this is that they have found through experience that higher sugars in Riesling tend to lower the nice crisp acidity needed for that wine and therefore, yield what they call a “flabby” wine with less character.  In other words, a wine that is not very interesting or distinct.

At the other end of the spectrum, Zinfandel grapes in California are harvested at higher brix levels, such as 27-28 or even higher.  This calls for leaving the grapes hanging on the vine for a long time to reach such high sugar levels, something that cannot generally be done in other areas of the country due to climate.  These wines end up with high alcohol content such as 15% or more.  This has been a stylistic characteristic of Zinfandel for many years.  In recent years, there is a new trend in California where winemakers are having the grape growers do the same with other grapes such as Cabernet Sauvignon, Merlot, Syrah and other reds to create intense, big fruit, high alcohol wines.  The wine writers describe them as “fruit bombs”.  It is my opinion that this is not a good trend and makes these wines unfriendly to food, which, after all, most of us are consuming with our wine.

Next Week: Just Pick ‘em Already


  1. Great blog. This really helped my brewing and winemaking techniques.


    Brewson Davis

  2. So glad this is helping you out. That is my aim and my goal.


  3. I really like this blog good job.