- Publish Date
- Friday, 21 April 2017, 12:36PM
- By Julie Harrison
The start of autumn is the arguably the most exciting time of the year in any winery as it means the start of the wine harvest, otherwise known as vintage. Traditionally the decision on when to start picking the grapes has been based on the sugar level, which determines the potential alcohol level of the wine, alongside perfect acidity and pH. Sugar level is measured in either degrees Brix or degrees Baume depending on what country you are in. Baume loosely relates to the final alcohol level, so grapes that are 13 Baume will make wine that is around 13% alcohol if fermented to dryness. Wines are most often between 22 and 25 degrees Brix when harvested and again winemakers can predict final potential alcohol levels using this scale. Different varieties ripen at different times with Chardonnay and Pinot Noir ripening relatively early in contrast to Cabernet Sauvignon.
In warmer climates obtaining high enough sugar levels happens easily but in cooler regions it can take longer to get to the required sweetness. Generally speaking warmer climates will product more alcoholic and less acidic wines with cooler regions producing wines lower in alcohol and higher in acidity. More recently there has been a trend to assess what is called physiological ripeness, which relates to the ripeness of the tannins and other phenolic compounds as well as flavour components. Because grapes take longer to ripen in cooler regions physiological ripeness is more likely to coincide with the sugar/acid ripening, however in warmer climates grapes can very quickly become “sugar ripe” but haven’t had time to ripen physiologically. Assessing the physiological ripeness is all about tasting the grapes and observing changes in the colour of seeds and stems. One of the problems is that if you leave fruit on the vine to gain physiological ripeness you can get very ripe fruit with low acidity resulting in a flabby overly alcoholic wine. In other words deciding when to pick can be a tricky business.
Agonising about when to pick goes out the window if weather or some other outside force intervenes. Lots of rain or extreme heat at the wrong time can have a devastating effect on crop quality and under these circumstances getting the fruit in before the weather event is critical, even if the grapes should ideally be on the vine for a bit longer. Once the decision to pick has been made it is all about logistics. Harvesters or picking crews need to be booked as well as trucks to take the fruit to the winery where it also needs to be slotted in to be crushed. Harvesting can be by machine or by hand. Whilst you often see a back label describing how the grapes have been lovingly hand picked, machine harvesting has a number of advantages. From a practical point of view it is a lot cheaper than hiring a picking crew and this saving has made the production of high volumes of good value wine possible. The speed of it means the crop can be picked quickly at optimal ripeness, which is especially important if poor weather is on the way. Picking is done at night meaning the fruit is cooler which lowers the rate of oxidation and it is much more pleasant than hand picking grapes in 40 degree heat in South Australia. For physiological reasons some grape varieties are not so suited to machine picking a good example being thin-skinned Semillon whose skins break easily if machine picked. If you are producing a delicate Riesling you would probably go for handpicking as you want to minimise the extraction of phenolics from skin and seeds which occurs more when grapes are machine picked. Botrytis infected sweet wines obviously need to be hand picked and you probably don’t want to be operating a machine harvester on steep terrain. Whatever the way the grapes are picked once they are safely at the winery the next stage is converting them into wine.
Julie and soon to be husband, Frenchman, Richard Guerra own Frog in a Barrel Wine Shop and Thirsty Frog Wine Bar in Milford. After developing an interest in wine at Massey University, Julie completed a Post Graduate Diploma in Wine Making and Viticulture at the University of Adelaide and following this worked in Australia for a number of years at Penfold Wines and Andrew Garrett Wines.
Travelling in Europe Julie developed an interest in European wines and now Richard and Julie import wine from France to sell in their shop and bar. Julie is looking forward to sharing her knowledge of local and imported wines.
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