What does the start date of the harvest depend on?

The start of the harvest is generally based on subjective evaluations of the optimal composition of the grape, with a view to achieving an expected quality. Also, although the maturity of the grape at the time of harvest has an effect on the quality of the wine, there are other more specific indicators that must be kept in mind to start the harvest.

Let’s review below what we mean by vintage and some of the most important aspects when setting up your start.

What exactly is vintage?

Vintage is understood as the period that covers the harvest and collection of grapes, in general when it refers to the production of wine. It is usually celebrated in the countryside and in rural areas. It is rarely produced in urban areas, although there are of course exceptions and it will depend on where the vineyard in question is located.

It is an event so relevant at a historical level that there is a record that it was already carried out in Ancient Egypt, a region in which red wine had an important significance at a cultural level.

Beginning of the harvest in Chile

Today the tradition of this event remains intact in some countries. Chile is no exception, and it is common that in different regions of the Central Zone the well-known Harvest Festival is celebrated, in honor of the relative beginning of this period, instances in which the typical food and traditional games of the country abound, besides the best wine.

In general, the harvest in Chile takes place between the months of February and May, dates in which the grape composition indicators are usually at their optimum point to make the harvest decision.

Of course, these dates vary depending on the geographical location, affecting how far north or south the vineyard is at the start of the harvest. This is because the parameters that determine when to start harvesting are sensitive to weather conditions.

On what parameters does the harvest date of grapes depend?

This is the golden rule: the harvest begins when the grapes are ripe. Likewise, to determine when the grape is ripe for harvest, 3 main parameters are measured:

Sugar.

Phenolic maturity.

Acidity.

To measure each of these parameters, it is necessary to use the appropriate tools and take a representative sample of the grapes. Only in this way can an adequate quality control be carried out prior to the harvest.

Sugar

The accumulation of sugars in the grape will determine the alcoholic strength of the wine, which is why it is so important to know this parameter. One of the most widely used tools today is the field refractometer.

It works like this: a few drops of must must be obtained from the representative sample and dropped on the glass of the refractometer. From this we will be able to know the Probable Alcohol (AP) and the concentration of sugars in degrees Brix.

The degree Brix (Bx) is a unit of quantity used to measure the total dry matter dissolved in a liquid. It is one of the most relevant units of measurement not only in the wine industry, but also in the food industry in general.

Phenolic maturity

As the fruits approach ripening, it becomes necessary to collect samples to analyze the phenolic maturity. The latter will indicate the optimal state of phenolic compounds, especially tannins and anthocyanins, key to the wine’s aroma.

A very popular method is the Glories method, which consists of extracting the anthocyanins from the skins using two extremes: delicate conditions (pH similar to that of wine) and drastic conditions (high acidity). From these data we can obtain a cell fragility index, which will offer potentially valuable information for harvesting.

Acidity

Tartaric acid is one of the predominant acids in grapes, which is why it is commonly taken as a reference to measure the total acidity of the sample. Another commonly measured acid is malic acid. In both cases, by estimating the total reference acidity, the acid concentration can be obtained, a key indicator to determine the start of the harvest.

It is important to mention that the sugar/acidity ratio is also often used as a criterion to determine the harvest precocity of the varieties (above a minimum sugar level), although in biochemical terms the increase in sugar is not directly related to the decrease in acids.

In conclusion, the start date of the harvest and the length of this period will depend on 3 main variables, generally related to the expected level of maturity of the grape.

The challenge then is to find the exact moment when these three parameters are at their optimal points; this moment does not always coincide and the harvest date must be adjusted according to the oenological decision.