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Under-ripe red grapes are low in sugar, low in flavor, low in color and high
in acid. Wines made from under-ripe grapes can be overly tart because of the
excess amounts of acid, and these wines often have a herbaceous taste. Excess
acidity can be removed either biologically or chemically. But, any acid
adjustments should be done before fermentation is started and leaving the
right amount of acid can be tricky. For none commercial wines, sugar
deficiencies can be easily corrected by adding sucrose. In addition to acid
and sugar problems, wines made from under-ripe grapes are also overly
herbaceous, have poor color, low flavor intensity and lack varietal
character. Mitigating flavor problems in wines made from under-ripe grapes is
difficult.
Ripe red grapes have the correct amount of sugar, acid, color, and good
varietal character and flavor intensity. Depending on variety, ripe red
grapes may have some herbaceous taste but they also show some "red
fruit" flavors.
Overripe red grapes have high sugar levels, low acid, high color and
excessive "red fruit" flavors. Wine made from overripe grapes are
high in alcohol, and they can taste "flat" or bland because they
are too low in acidity. Acid deficiencies can be corrected by adding tartaric
acid to the must prior to fermentation. But, wines produced from overripe
grapes often have "cooked fruit" or prune flavors.
Sugar can be measured easily, so Brix has been a
historic way of specifying grape ripeness. Unfortunately, grapes from one
vineyard may be ripe at 23 Brix, while the same
variety of grapes in a nearby vineyard may not be ripe until they reach 25 Brix. So, contentious winemakers/winegrowers take into
account Brix plus several other parameters when
making harvest decisions.
When to pick is such an important decision that most winegrowers start
checking their grapes well before harvest time. As harvest day approaches,
the winegrower goes to the vineyard every few days to inspect the fruit. He
looks at the condition of the vineyard to see if the vines are strong enough
to continue ripening the grapes. Then the winegrower walks up and down the
rows of vines. He picks grapes one by one and carefully examines each berry.
In the later stages of ripening, the berries become softer. So, the
winegrower checks the berries by gently squeezing them between his thumb and
forefinger to see if they have started to soften.
Under-ripe grapes often have a heavy herbaceous smell and taste. Ripe grapes
have less herbaceous character and more plum and cherry character. So, the
winegrower tastes and smells the grapes to see if the herbaceous character
has diminished and if the red fruit character has started to develop.
The color of grape seeds changes from green to brown as the berries ripen.
So, the winegrower spits the seeds in his hand and looks to see if the seeds
have changed color. Some winegrowers will NOT pick red grapes until 80 to 90
percent of the seeds are brown.
The winegrower then collects a "sugar sample" of a hundred or more
berries. Back at the winery, the Brix, TA and pH of
the sample grapes are measured and these data, together with the vineyard
observations, are used to help the winegrower decide when the grapes should
be picked.
High quality wine can only be made from high quality, properly ripened
grapes, so this walking up and down the vineyard picking, squeezing, tasting
and spitting seeds is an annual, pre harvest ritual.
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