WSET® 2 Reading, Chapter 3: Factors Affecting Wine Style, Quality, and Price (Class Notes)

The main factors that determine how a wine will taste are:

  • The grape variety used;
  • The environment in which it is grown (climate and weather, soil and slope);
  • The care with which the grapes are grown and harvested;
  • How the wine is made; and
  • How it is matured (including bottle-age).

These factors have a cost effect and will influence the final selling price of a bottle of wine.


Just as there are different kinds of apples and potatoes, there are different varieties of grapes. Over centuries, particular vines have been chosen that have desirable characteristics (pleasant flavour, high yields, and resistance to disease and so on). These chosen vines include those that are most well known to us, such as Chardonnay and Cabernet Sauvignon, as well as many hundreds of others. The type of grape used determines a large part of the character of the wine: as well as affecting the flavours and colour of the wine, different grape varieties have different levels of sugar (for alcohol), acidity and tannins.


In order to grow and produce a crop of ripe, healthy grapes, a vine needs carbon dioxide (CO2), sunlight, water, warmth, and nutrients. The first of these is found in the air (much of it is breathed out by animals), but the availability of the other four is affected by the vine’s environment. In particular, climate and weather affect sunlight, heat and water, and the soil affects warmth and water, as well as the availability of nutrients.  


Climate describes what weather conditions (temperatures, rainfall, sunshine) we may expect in a typical year. Climates suitable for wine production can be divided into three categories; hot, moderate, and cool. Broadly speaking, the climate of a wine region is determined by latitude or, in other words, how close it is to the Equator. The closer a region is to the Equator, the hotter it is. For example, South Africa has a hotter climate than Germany. However, there are two other important factors to consider: altitude and the oceans. A region that is at a high altitude will have a cooler climate than a region closer to sea level, even if they share the same latitude. The influence the ocean has on a wine region depends on the temperature of the water. There is a warm ocean current that ensures that Western Europe is not as cold as regions with a similar latitude in North America. Conversely, many of the wine regions of California, Chile, and South Africa are cooled by cold ocean currents.

The climate type can have a dramatic effect on the flavour of ripe grapes. Some grape varieties (such as Cabernet Sauvignon) need a lot of heat to ripen fully. If the grapes have not fully ripened, wines from these varieties will taste excessively sour, astringent, bitter and lacking in fruit flavours. Other grapes (such as Sauvignon Blanc and Pinot Noir) need a moderate or cool climate otherwise they over-ripen and lose their refreshing fruit character and acidity. Unpleasant jammy or raisiny cooked flavours may then dominate the wine, or it may simply taste bland. A few grapes (such as Chardonnay) can make interesting wines in hot, moderate and cool climates.

The flavours in the wine gives clues as to the climate. In general, we may say that:

  • Hot climate: more alcohol, fuller body, more tannin, less acidity
  • Cool climate: less alcohol, lighter body, less tannin, more acidity


As weather conditions vary from one year to the next, the weather of each particular year affects the style and quality of wines from that year. The most important time is the growing season, particularly when the grapes are ripening. Extreme weather conditions such as hail, high winds, floods, and late frosts can cause problems with the size and quality of the crop. Hail in particular can cause a great deal of damage to ripening grapes and to vines. Once the skins of grapes have been damaged, they are very susceptible to rot. Unusually cool or hot weather can affect the style and quality of the wines produced in a given year (vintage). Vintages are most important in regions such as Bordeaux and Champagne, where the weather varies greatly from one year to the next. Modern grape growing and winemaking techniques mean that even in these regions, differences between vintages are becoming less pronounced, and there are fewer bad years. Blending of varieties, or between different sites, villages, or even regions, is a useful way to keep style and quality consistent from one year to the next. This is especially important for branded wines.


Sunlight is the source of the energy that allows the grape to combine carbon dioxide and water into sugar. From a winemaking perspective, these sugars are the most important part of a grape for it is these that are fermented to become alcohol. Quite simply, without sunlight, carbon dioxide and water, there would be no grape sugars; and without grape sugars there would be no wine. In regions far away from the Equator, vines can receive more sunlight by being planted on slopes that angle them towards the sun, or above rivers that reflect sunlight. In sunny regions, this is unnecessary.


Water can come from rain, or from the ground, or from irrigation. Too much water can cause grapes to become bloated. This may result in bigger crops, but the flavours and sugars will be diluted, and the wine will have less alcohol, body, and flavour. In areas where rainfall is high, such as much of Europe, the best vineyards are on slopes or soils, such as gravel or chalk, which drain water away quickly. In regions where there is insufficient rainfall, such as many parts of the New World, irrigation is essential if the vine is to survive. For the highest quality wines, just enough water is provided to sustain sugar production. For cheaper wines, irrigation can be used to increase the size of the crop. Although a supply of water is essential for wine production, too much rain can cause problems, with wet conditions encouraging the growth of rot. Rain and hail can damage vines and grapes.


Warmth is needed for the production of sugars—but not too little or too much. If the weather is too cool or too hot, sugar production slows and can stop. This is one of the reasons why most of the world’s vineyards are found in a temperate zone between 30° and 50° from the Equator. A vine can keep itself cool by evaporating water through its leaves. This process occurs more rapidly in hot, dry conditions. In extreme cases, the vine may shut down its leaves to prevent the plant drying out, so, although there is warmth and heat, no sugars are produced. The main factors affecting warmth are climate and weather. In addition, soils vary in their ability to absorb or reflect warmth. Dry, stony soils are generally warmer than wet clay soils, for example.


The sugars produced by the leaves do not just provide sweetness in the grapes, they are also the building blocks for the whole vine. In a sense, almost the entire plant is built out of the material provided by the carbon dioxide in the air, and the water obtained via its roots. However, the plant also needs tiny amounts of nutrients, in the right balance. These are provided by the soil. Grapevines are very tolerant, and will grow in a wide range of soils. In general, provided there are sufficient nutrients, poorer soils result in better quality grapes.


Over the course of the vineyard year, the two main factors that affect the quality and style of the raw grape material are the degree of care that is taken in the vineyard, and the control of the yields.

There are many vineyard activities that can help all the grapes to ripen fully, at the same time. These include careful pruning, controlling the number of bunches of grapes on each vine, and the careful positioning of the leaves to increase or lower the temperature of the grape bunches, or their degree of exposure to sunlight. These techniques all use expensive labour, which increases the cost as well as the quality. The other options are minimal pruning and maximum mechanisation, which is only appropriate in regions with suitably large, flat vineyards.

Yields also have an effect on quality. Lower yields generally result in riper grapes with more concentrated flavours, but controlling yields by limiting the number of grape bunches takes time. Also, because the crop is smaller, each kilogram costs more to grow and will have to sell for a higher price if the effort is to be worthwhile. The other option is to maximise yields using irrigation to fill the grapes with water, with the result that flavours and sugars are diluted. The resulting wine will be cheap, but probably not very interesting. Most wines lie somewhere between these two extremes.

In addition to the effects of soil, slope, climate, weather, and care in the vineyard, some pests and diseases are bad for the production of healthy grapes:

  • Animal pests (including birds and insects) can damage shoots, buds, leaves, and may eat the grapes.
  • Attacks of fungal diseases such as mildew or rot can damage green parts of the vine as well as leading to spoiled grapes.
  • Long-term diseases caused by fungi, bacteria or viruses can affect the health of the vine, reducing yields and inhibiting ripening. Some eventually lead to the death of the vine.

The harvest occurs once the grapes have ripened. In larger vineyards on flatter sites, harvesting will generally be done by machines which shake the grapes off their stems. Where whole bunches of grapes are needed, the grapes must be hand-harvested. Steep sites with difficult access must also be hand-harvested, and regions where labour is cheap may hand-harvest, even where machines could be used. Top-quality wines can be made from both machine-harvested and hand-harvested grapes.


The most important part of this process is fermentation. When yeasts feed on sugars in the grape juice, they produce alcohol, carbon dioxide, and heat, changing the flavours of the grape juice into those of wine.

The flesh of almost all wine grape varieties is white. The colour of red and rosé wines is obtained by soaking the coloured skins in the fermenting juice. If the skins are removed at an early stage, there is little or no colour. This is how rosé wines are made from black grapes. White wine can be made from black or white grapes. Red wine can only be made from black grapes.

White Wines

For white wines, the grapes are usually crushed to break the skins before they are pressed to separate out the juice. Yeast is added. This will usually be a commercially obtained yeast culture, which gives predictable results. Some winemakers choose not to use commercial yeasts, believing that the ‘natural’ yeasts that dwell in the vineyard and winery give more interesting results.

The must is transferred to a fermentation vessel (usually a stainless steel tank, but some winemakers use oak barrels or open-topped concrete or wooden fermenters). White wines are then fermented at low temperatures (typically 12° C—22° C), to preserve the delicate fruit aromas. This takes between two and four weeks.

Sweetness in white wines is caused by unfermented sugar.

Red Wines

Black grapes for red wines are crushed to release the juice, then the juice and skins are put in the fermenting vessel together. Fermentation takes place at a higher temperature for red than for white wine (20°C—32°C). Alcohol helps the extraction of colour, tannins, and flavours from the skins. In order to keep the juice in contact with the skin, the juice may be pumped over the floating skins or the skins may be ‘punched down’ into the juice. The amount of colour and tannin in the finished wine depends on how long the wine is kept in contact with the skins. This may be for over two weeks for richly flavoured Bordeaux, or as little as five days for light wines such as Beaujolais. It also depends on how much tannin, colour, and flavour is in the skins—some black grape varieties are naturally light in colour and tannins. Hot climates encourage higher colour and tannin levels in the grapes.

When enough colour and tannin have been extracted the free run wine is drawn off. The skins are then pressed yielding a further quantity of wine, known as the ‘press wine’. Press wines contain higher levels of tannin, and may be blended with free run wine to produce the style required.

Rosé Wines

Like red wines, rosé wines must be made from black grapes. The method of production is similar to that for red wines, but they are fermented at a lower temperature (12° C—22° C). They must also have a much shorter period of grape skin contact (12 to 36 hours). Pink wines labeled as ‘white’ Zinfandel are made this way.

Oak Flavours

Many wines receive some oak contact, often in the form of staves (small planks) or chips (large splinters) added to a vat. Extra money pays for better quality staves or chips. The very cheapest method of adding oak flavours is to use oak essence. In the finest wines all oak contact must be achieved by fermenting or ageing in oak barrels. If a wine is fermented or aged in oak, a large premium has to be paid, particularly if the oak is new, because oak is expensive. French or European oak is more expensive than American oak, but tends to give more subtle, toast and nutty flavours and smoother tannins, whereas the American oak gives sweet coconut and vanilla but harsher tannins. A further premium is also to be paid where the highest-quality air-dried staves and expert cooperage is sought. Looking after a wine in oak barrels, and ensuring it is always topped up to avoid air in the cask spoiling the wine, is labour-intensive and therefore expensive.

Fermentation, as well as ageing, in oak barrels is common for premium Chardonnay wines, including many of those made in Burgundy. It is impractical to ferment red wines in oak barrels, but many premium red wines are aged in oak.


Maturation can take place in barrels or large neutral wooden or stainless steel vats. It also takes place in the bottle after bottling. The most important changes that occur are the slow chemical reactions that can allow complex flavours to develop.

Maturation with Oxygen

We have already seen that new oak directly adds oaky flavours to the wine. Old oak vats do not directly add any flavours. However, in both cases, the vessel is porous and allows small amounts of oxygen to dissolve in the wine. This softens the tannins in red wines, making the wine taste smoother, and can cause flavours such as toffee, fig, nut (hazelnut, almond, walnut) and coffee to develop.

Maturation without Oxygen

Bottles, cement, and stainless steel vats are airtight and do not add any flavours, and the chemical reactions that occur are different to those in oak. In large stainless steel vats, the wine flavours stay almost unchanged for months. Changes occur faster in bottles because they are smaller. In bottles, in the absence of oxygen, the fresh fruit aromas of young wines change into cooked fruit, vegetal and animal notes (wet leaves, mushroom, leather).

Few wines improve in the bottle. It is common for the attractive fruit flavours simply to fade away, and nothing else to appear in their place. Often the animal and vegetal notes that develop will be unpleasant. For a few special wines, the fruit character remains while the other complex flavours develop around it. These wines are not easy to make, and are usually expensive to buy, but the flavours they offer are among the most rewarding of all wines.


It is useful to summarise here some of the factors that affect the cost of producing a bottle of wine.

In the Vineyard

  • Cost of vineyard land: sites with the greatest potential for quality can be vastly more expensive than ordinary locations.
  • The degree to which the vineyard work is mechanised (almost impossible for very steep sites).
  • The cost and availability of labour and/or equipment.
  • Yield size and the degree of selection of grape material: discarding underripe or rotten grapes can be enormously labour intensive and, like yield control, must be justified in the final selling price.

In the Winery

  • Winery equipment, and how efficiently this is used.
  • Cost of barrels or other forms of oak flavouring.
  • Ageing, which requires expensive storage facilities and ties up capital.

Packaging, Distribution and Sale

  • Exchange rates can affect the final selling price for exported bottles.
  • Packaging (bottles, etc.) and cartons for distribution. Unusual bottles cost extra.
  • Transport costs (these are a surprisingly small part of the selling price of most wines: shipping long distances by sea is relatively inexpensive).
  • The efficiency of the distributer and retailer, and the profit margins they expect. Low-volume, high-service distribution costs more.
  • Taxes and levies are also absorbed in the final retail price of a bottle of wine.

The ultimate factor that determines the selling price of a bottle of wine is how much the consumer is willing to pay. A bottle may be very expensive to produce, but if the quality does not match the price it will not sell. Marketing and the reputations of the producers, regions or brands can help sustain high prices, but if the quality fails to match the consumers’ expectations, then they move on to other wines. The reason that some regions continue to sell their wines at extremely high prices  is that there are people who are prepared to pay high prices for those levels of quality. If the market disappeared, then the prices of these wines would fall or they would no longer be made.


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