A close eye is kept on the weather for frosts, heatwaves and hail in particular, which can decimate a vineyard in minutes. During the growing period, grapes are checked carefully throughout the days until ideal levels of acidity and sugar ripeness are reached for the desired style of wine. The amount of natural sugar in the grape is responsible for the final alcohol level as well as how dry or sweet the wine is going to be. The “phenolic” or physiological ripeness of the grape is also key; this refers to the color of the skin, pips, stems and how the tannins taste in the mouth. Grapes for sparkling wines are picked a little earlier than for still wines, as they need a higher level of acidity and less sugar. It’s worth noting that many wine regions with designated rules, such as AOC or IGP, will issue strict rules to adhere to for all of the above.
Making wine is a long, slow process. It can take a full three years to get from the initial planting of a brand-new grapevine through the first harvest, and the first vintage might not be bottled for another two years after that. But when terroir and winemaking skill combine, the finished product is worth the wait.
Wine has been likened to “poetry in a bottle.” Just like any creative process, winemaking requires knowledge, commitment, and time. In this article, we’ll take a look at the grape-growing process, as well as explore more of the winemaking process once the grapes have been harvested. From the first planting to harvesting to turning it into wine, this is the complete life cycle of a wine grape.
Veraison is the magical moment when those hard, green grapes transform into plump, juicy clusters. Veraison is especially noticeable in red grapes as the fruit turns from green to purple. In white grapes, like Sauvignon Blanc and Chardonnay, the clusters turn from bright green to a more mellow golden green.
At last, the time has come to harvest those beautiful grapes! But how do growers know when to pick? It’s certainly not an exact science, although winemakers and vineyard managers will measure the sugar levels in the grapes (called Brix).
A series of warm days can speed up harvest because ripening happens fast in hot weather. Cooler temperatures, on the other hand, can delay harvest. But ultimately, it’s the flavor profile of the grape that determines pick date.
After 12 months of caring for a vineyard, it becomes time to harvest. This usually happens from the beginning or mid-January, depending on the cultivar. A crop forecast is essential to determine the expected volume of grapes per vineyard and the total yield of the farm in order to determine the number of workers needed to bring in the harvest. It will also help to plan the cost of the harvest and possible income. In addition, the crop forecast helps the winemaker to plan his wine-making and marketing of the wines. The best way to determine a crop forecast is to count the number of grape bunches per vine.
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Wine grapes are harvested at a predetermined sugar:acid ratio, depending on the end product and wine style required. The sugar:acid ratio is the amount of sugar and acid in grapes and an indication of ripeness. Other ripeness indicators are: Sugar level, acidity, colour, flavour development and pH
Sugar Level
The sugar level in grapes is measured with a refractometer or ballingmeter and expressed as degree balling (°B) - equal to 1.0 gm/100 gm juice dilution. Colombar for white wine can be harvested at ± 20°B while red grapes are normally harvested at between 23 and 25°B. Sugar level increases 1°B every four days but can increase by up to 1°B every two days depending on the climate. The sugar level can decrease after rain or irrigation while warm weather increases the tempo of sugar accumulation.
Acidity
Acidity in grapes decreases as sugar levels increase. All wines should have a level of acidity. If not, the wine will be ‘flat' and without character. The two most important wine acids are tartaric acid and malic acid.
Tartaric acid is the main acid in grapes and contributes to taste and the preservation of the wine while malic acid is a naturally occurring acid found in grapes. Malic acid can be digested by malolactic bacteria to form lactic acid and carbon dioxide. Acidity levels are determined in a laboratory and are indicated as gram/litre.
pH
The pH of a wine is an indication of the concentration of the acids in the grapes. The lower the pH, the higher is the wine's acidity. The taste, freshness and complexity (of red wines specifically), are affected negatively by a pH higher than 3,5-3,6. These could be described as ‘flabby' wines. Wine made from grapes with a high pH do not age well and develop "off" flavours more easily. Measuring of the pH is extremely important as it can determine the taste, stability and colour of a red wine. Both the acidity and the pH has an important effect on how long a wine can keep.
Colour
Colour development in red wine grapes starts as early as December/January. Colour compounds are formed – just like flavour compounds – in the cell layers just beneath the grape skin. In the majority of red wine cultivars, it is only the skin that is coloured, the flesh stays white. The colour of a wine comes from the skin and not the juice - the juice in most red grapes is clear (transparent).
When the grape juice ferments with the red skins, the colour pigments are transferred to the juice to create a ‘red' wine. Colour can be determined in a laboratory but can be seen in the vineyard by crushing a berry and rubbing the skin to see if the colour is released. White grape cultivars are yellow or light green in colour.
Flavours
Two groups of flavours are found in wine grapes: natural grape flavours and aromas imparted by the yeast during fermentation. Natural grape flavours are formed by the grape such as the muscat flavour of the Hanepoot and Muscadel grapes. Flavours formed during the fermentation process cannot be tasted in the grape but is formed when special yeast is added to the juice to ferment the sugar in the grapes.
