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Flavours in wine - where do they come from

Flavours in wine come from three very distinct sources, the grapes, the winemaker and ageing the wine. In this section we explore these three key ingrediants to the flavour of your wine.

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Wine Flavours from the Grape

What causes the flavour in grapes?

The flavours in grapes are driven by a number factors, primarily the grape variety, then secondarily, the climate (and the picking time) and finally, and most controversially, the soil.

As grapes ripen the flavours develop from a green flavour through to a range of flavours such as ripe berry fruits, citrus aromas and even floral notes are common, but which ones depend upon the grape variety. Typically fruity aromas in the wine come from the grapes.

It is important to remember that the climate is relative. Wines made in hot climates often produce jammy ripe flavours, while cool climates can produce fruits with more defined flavours. But this is relative, as some vines that are adapted for hot climates may taste much leaner when grown in more moderate climates, while similarly grapes designed for cool climates may become over ripe in moderate or even hot regions.

But how do the grapes change?

To answer this we need to ask, what set of flavour profiles does your average grape go through on the way to maturity, and secondly how fast do they change between say minimum sugar and maximum sugar that is acceptable for wine making?

The development of flavours for different grapes varieties change by different amounts, some Sauvignon Blanc grapes grown in Marlborough can change quite a bit while other varieties change very little. For example Sauvignon Blanc goes through a range of flavours:

grassy-> gooseberries-> grapefruit-> black current bud-> tropical fruit.

But what is driving the flavour changes? Tim Finn, winemaker at Neudorf vineyard in Nelson, New Zealand believes that changing the amount of UV a vine has changes the ratio of sugar and acids in the vine and creates different flavour profile for a given picking sugar level.

Another example of the effect of UV light on the flavours of wine is Cabernet Sauvignon. In regions where green unripe flavours can dominate, viticulturists can assist flavour development in grapes by exposing bunches to light early in the season. Also research carried out by Catena Zapata in Argentina show that wines that are higher in altitude develop thicker skins and more polyphenols (flavours and tannins).

Green flavours can also come from hot climates. In South Africa and Lebanon some wines show a green character, even though the grapes are grown in hot climates. This is from stressed vines shutting down and not ripening flavours. The stress may be because of disease, the temperature or lack of water.

Occasionally stress on the vine can produce enjoyable flavours in grapes, this could be because the soil lacks a chemical the plant needs, this missing molecule means the vine adapts, and perhaps the adaptation results in a change in either the size or flavour of the grapes.

Flavours from the Winemakers

While fruit flavours can generally be associated with grapes, there is a number of different sources of flavours that can be introduced into the wine by the winemaking process - key ingredients include oak barrels and chips, yeast, malolatic fermentation as well as carbonic maceration and temperature control.

Ageing a wine in an oak barrel can introduce vanilla, coconut, cloves, butterscotch, smokey aromas. For more information on flavours from oak barrels click here.

Yeasts can introduce a range of flavours including fruity, floral and perfumed aromas

Malolactic fermentation is a bacterial fermentation that changes malo acid to lactic miik acid and in doing so can produce buttery flavours in the wine, often associated with oaky, buttery chardonnays.

Carbonic maceration is a winemaking technique where whole grapes are left to ferment into wine inside a vat, resulting in softer, bubble gum, banana, and occasionally cinnamon and vanilla aromas.

By controlling the temperature during fermentation winemakers can control some of the flavours, for example many whites are fermented at a cool temperature to preserve fruit flavours, while reds are fermented warmer to help extract flavours from the grape skins. But too cold a temperature and the wine can develop pear drop aromas, and too high the wine may develop jammy, caramel, burnt or cooked characters.

Wine Flavours from Ageing

At many a wine tasting the host will disappear and return moments later with a bottle of wine that they have been keeping for years asking when they should drink it. I often answer, today! It is not that I want to drink the wine there and then - more often the wine in question should have been opened 5 or 10 years before to be enjoyed at its best. Ageing of wine is confusing to most people. A few understand that tannins and acidity all decrease as the wine ages, these along with sugar all act as a preservative, so different concentrations will change the speed that the wine will develop. But perhpas the least understood is why flavours in wine change.

The final wine that goes into the bottle is made up of flavours from the fruit (Primary flavours or aroma), the winemaking process and any exposure to oak. At the time of bottling these flavours are not stable, in fact wine is like any vegetable product slowly decaying. Alcohol, acidity, tannins and sugar all help to preserve the wine, but ultimately the wine will break down to a more stable state.

It is not a surprise that fresh fruit flavours fade and earthy, animal savoury flavours develop - this is the referred to as the "bouquet" of aged wines as opposed to the "aroma" of young wines. Many white wines will develop a honeyed note as they age, Bordeaux reds can create a tobacco, cedar and pencil shavings bouquet.

But how does wine change over time? At a basic level, a flavour in wine is caused by a molecule called a phenol, in most wines phenols come from the skins, the grape juice does contain some phenolic compounds but not as many as the skin.

Phenols over time can react with other components in the wine. These new molecules can then interact in new ways with other molecules, slowly changing through a number of states before becoming stable. As the molecule changes the aroma may change or even completley vanish, this is often the case in a wine that is said to be closed. Confusingly what can appear to be a dead or closed wine can spring back into life as the phenols responsible for the flavour, change again into a phenol with a bouquet.

The development of these flavour molecules is known as a pathway, and is governed not only by the starting point but the conditions in the bottle as it ages. There are hundreds, if not thousands, of different pathways occuring and interacting in a single bottle of wine, this is why it can be very difficult to tell how a wine will evolve in a bottle.