Chapter 2
Grape Varieties and Growing Regions
2.1 Wine grapes
The wine grape comes from the plants of the botanical genus Vitis, and mostly from one important commercial species, vinifera, of the vine plant. This genus belongs to the family, Vitaceae, characterized by a climbing habit, and includes other genera such as Parthenocissus quinquefolia, otherwise known as Virginia creeper. The genus Vitis includes also other species, for example V. labrusca, which has some interest for wine-making. The Concorde grape is thought to be a cross between V. lambrusca and V. vinifera, with its characteristic content of the ester, methyl methranilate that gives Concorde its specific flavour. Other species produce grapes more suitable for eating fresh.
Varieties (and cultivars) of V. vinifera selected for specific flavour and agronomic purposes abound. An obvious division is made between grapes with light green skins for making white wines, and those with black skins, generally for red wines, though not exclusively so. Some of the 10 000 known varieties are described as ‘noble’, largely grapes of French origin. The prevalence of French ‘noble’ grapes is, to an extent, due to tradition and to the history of France. ‘Noble’ grapes are those that give wines that are appreciated by wine connoisseurs and wine-drinkers in general for their sensory properties. Table 2.1 shows eight noble ‘whites’ and seven ‘reds’ – although this selection is not without some controversy. There are many other viniferous grapes of quality, which are largely of local rather than international significance, such as the Tempranillo grape of Spain and the Nebbiolo grape of Italy. These and possibly others may well become popular in the future, since wine-makers are ‘seeking’ to test their skills on new varieties, while consumers like to drink new wines.
The main controversy probably arises around two of these ‘noble’ grape varieties, Müller-Thurgau and Gamay. All these grapes and their vines originate in France and Germany (except Zinfandel); most have international repute, having been successfully transported to the newer wine-producing countries of the world, such as the USA, New Zealand, South Africa and Australia, and to other longer established European wine producing areas.
Table 2.1 ‘Noble’ varieties of the wine grape.
| Green-skinned grapes for white wine | Black-skinned grapes for red wine |
| Sauvignon Blanc | Cabernet Sauvignon |
| Sémillon | Pinot Noir |
| Pinot (Chardonnay) | Merlot |
| Chenin Blanc | Gamay |
| Muscat | Grenache |
| Sylvaner | Syrah (France)/Shiraz (Australia) |
| Mèller-Thurgau | Muscat |
| Riesling | Zinfandel (US) |
A differentiating characteristic between grape varieties is their ‘aromatic’ property, some grape varieties being quite ‘neutral’, others being quite ‘aromatic’. Most of the odour/flavour components in wine, as will be seen in Chapters 4 and 7, originate during fermentation and ageing, the so-called secondary and tertiary aromas. Some of the ‘noble’ varieties above have varying contents of terpenoid compounds, with the Muscat varieties having the highest. These compounds confer a ‘grapey’ or sometimes ‘floral’ flavour, which can give distinctive wines made from those varieties with sufficiently high terpene content, so that terpenes from the grapes constitute the main part of the so-called primary aroma in the wine. However, although many of these so-called ‘noble’ grape varieties tend to give wines with a recognizable sensory aroma, in most cases unique impact compounds have not (yet) been identified. The typical chemical composition of a grape variety supplies the ‘raw materials’ for fermentation and ageing processes (Chapter 7), and even grape varieties with not very distinctive varietal aromas give wines with recognizable flavour characteristics, which in wine appear highly dependent on the grape variety.
These noble ‘quality’ varieties do not constitute necessarily the largest acreage of vines cultivated in any given country. Some quality grapes are widely planted, but there are other varieties that also fill that position (Table 2.2), which produce viniferous grapes destined for lower quality denominations such as Vin-de-France quality or they are used in blending wines. Some wines are specifically produced to be distilled into brandy.
There are several other grape varieties with quality connotation, which are currently mostly of local significance (Table 2.3). The currently widely planted noble grapes were, to an extent, fairly haphazardly selected and in future we may well see other quality grapes gain in popularity with both the wine industry and the consumer. Viognier is an example of a grape traditionally grown in the Rhône region but now becoming more widely planted, and giving white wines with a distinctive varietal aroma.
Table 2.2 Grape varieties with the largest area of vine plantation.
| White wine | Red wine |
| Airén (Spain) (but low yield) | Grenache (world-wide) |
| Rkatsiteli (Russia) | Merlot (France, now world-wide) |
| Trebbiano (Italy) (known as Ugni Blanc in France) | Sangiovese (Italy) |
| Ugni Blanc (France) | Syrah (France)/Shiraz (Australia) |
| Carignan (France) |
Table 2.3 Some other grape varieties with quality connotation.
| For white wine | For red wine |
| Aligoté (France, Burgundy) | Barbera (Italy) |
| Marsanne (France, California, Australia) | Carignano (Italy) |
| Muscadelle (France) | Cariñena (Mazuelo) (Spain) |
| Pinot Gris (France); RulÏnder (Germany) | Cinsaut (France) |
| Pinot Grigio (Italy) | Malbec (SW France, Argentina) |
| Pinot Blanc (France); Pinot Bianco (Italy) | Mourvédre (France, Bandol) |
| Weisburgunder (Germany) | = Monastrell (SE Spain) |
| Scheurebe (Germany) | Nebbiolo (Italy, Piedmont) |
| Sylvaner (Alsace, France, Austria) | Petit Verdot (France) |
| Viognier (France) | Pinotage (South Africa) |
| Tempranillo (Spain) | |
| Zweigelt (Austria) |
Table 2.4 Some grape varieties with a poor quality connotation.
| White wine | Red wine |
| Airén (Spain) | Carignan (France) |
| Trebbiano (Italy) | |
| Ugni Blanc (France) |
There are also some grape varieties that have a poor quality connotation (Table 2.4), although they are widely planted (Table 2.2). Presumably their popularity is due to other factors, such as good yield. The quality connotation may not always be well deserved, for example, Carignan can give good wine, especially from old, low yielding bush vines.
2.2 Vine plant characteristics
The vine plant (Vitis vinifera) is indigenous to the Northern Hemisphere and grows in temperate regions, though with restrictions based upon soil and actual meso-climate (climate of the vineyard) generally. It is a shallow rooting plant, whilst the aerial parts have some particular botanical characteristics, apart from a climbing habit already noted, requiring training of cultivated species on poles. Information on botanical and genetic aspects can be found elsewhere. Very importantly, the cultivated plant is primarily a self-pollinating plant. The plant needs to reach some maturity before cropping fruit, since a young vine does not bear flowers until it is in its second or third season. The duration of full sunlight is important to achieve fruit bud development and flowering occurs within eight weeks of bud formation.
The fruits of the vine are, strictly speaking, berries. Maturity or ripeness of the grapes is expected to occur between 12 and 22 weeks after flowering, dependent on climatic conditions and grape variety.
After fruits set, the grapes develop, for 40 to 60 days, but remain approximately half their final size, hard, high in acid and green. Dependent on the climate, the next stage is veraison, the commencement of ripening period, taking between 30 days in hot regions and 70 days in cool regions. Some varieties are early maturing, others late maturing, needing less or more time to reach maturity when grown under the same circumstances. During veraison the grapes gain their red or yellow colour, gain sugar, lose acid, soften and increase in size. Other changes include the development of flavour (actual or precursor) compounds typical for the grape variety, often referred to as varietal aroma. Samples are normally taken throughout the growing season for chemical analysis of acidity, and sugar content, etc. and a tentative harvest date is set. However, in cool regions complete grape maturity at harvest may not be achieved, so that adjustments may have to be made at the vinification stage. Harvesting is usually accomplished in September or October in France and Germany. A special case is Beaujolais Nouveau, where vinification, bottling and distribution are accomplished by the official release date set on the third Thursday in November each year. In warmer vine growing regions, such as Southern Spain, the harvesting is carried out in August or September to avoid the grapes becoming over-mature.
The leaves of vine plants photosynthesize, so that carbon dioxide taken from the air is converted into carbohydrates and oxygen is expired. Photosynthesis takes place via the so-called Calvin biochemical pathway using UV light as an energy source. The leaves also absorb water as available. The roots also absorb water, but also take up many other essential nutrients, some in trace quantities. The roots absorb nitrogenous components, mainly the nitrate ion (NO3 2−), from the soil, regardless whether the soil is enhanced by organic manure or artificial fertilizers in aqueous solution. They also absorb phosphorus compounds (phosphate ions) and metallic cations, mainly potassium (K+) but also a wide range of other compounds, some in trace quantities. An adequate input of water through the roots is essential for the effective and healthy growth of the plant.
A recent review by Conde et al. (2007) states that wine quality largely depends on the vineyard and the wine grower. Sugars and acids are produced by the leaves, whilst acids and phenolics are produced in the berry. Some molecules related to aroma and taste, the so-called primary or varietal aromas, are formed during fruit development and are typical for the grape varieties used for wine-making. The characteristics of the grape when picked at commercial maturity for wine-making are crucial for the resulting wine quality.
2.3 Soil, climate and ripeness
2.3.1 Soil
The quality of the wine is thought to depend to a great extent on the vineyard and the skill of the viticulturalist being able to produce good quality grapes. Hence it is not surprising that the nature of the soil in which the vine is grown has always been a part of the mystique of desirable wine flavour and this is usually referred to as the effect of terroir. In the review of Conde et al. (2007) the definition is much broader defined, the term terroir is used by viticulturalists to define rather widely the geographical and environmental conditions of the vineyard in which the grapes were grown, with many factors contributing, such as composition of soil, climate, topography, even including strains of micro-organisms on the berry skin contributing the fermentation process. A terroir offering good growing conditions to a particular grape cultivar helps the plant to produce good quality grapes, forming a good start for a good vintage.
An important aspect of soil quality is water retention and drainage. This capacity of the soil is related to both chemical and physical characteristics. The vine plant does not like waterlogging, hence excessively ‘clayey’ soils are undesirable. Gravel (defined as mineral particles, >2 mm in diameter), in contrast to clay (particle size around 0.2 mm or less) is necessary for free water draining properties. However, clay has the advantage of attracting and holding humus, containing nitrogen and other nutrients. The vine plant is thought not to need an especially fertile soil; in any event, the plant will not pick up nutrients in excess of its need, even though they may be present. Suitable soils for growing quality grapes are not particularly fertile or deep (see Conde et al., 2007). A recent review on geology and wine suggests that the importance of geology in wine-making may have been over rated (Huggett, 2006). Most of the nourishment vines take from the top 0.6 m, although the plants can take up water from as far down as 2 m, even deeper in drought conditions. In most areas, even where the soil is thin, geological influences on vines will be minimal. The quality of the grapes is only influenced indirectly by factors such as soil composition, geomorphology and water retention. The direct effect of soil on resultant wine flavour is therefore questionable and no scientific proof currently exists. Indirect effects along with the meso-climate (conditions of the vineyard, as for example influenced by the slope and orientation towards the midday sun) will be important. Very light soil will reflect the sunlight, warming the area round the vine. Currently the Old World tends to emphasize the effect of terroir (generally the nature of the soil rather than the wider definition), while the New World tends to emphasize climate as having the greatest influence on wine quality and flavour. Further studies are needed to show the true relevance of these two factors. This difference is possibly also reflected in the aims of the wine-makers, Old World wines tend to be made reflecting the style typical for the area, whereas New World wines tend to be made to reflect the best the fruit can give.
2.3.2 Climate
Climate conditions above the soil have an important influence on growth of micro-organisms on grapes, which in some cases cause the grapes to rot. Botrytized grapes (resulting from Noble Rot) have a separate commercial importance, since they can be prized for the production of quality sweet wines, with a very distinctive flavour. Noble Rot is associated with particular grape varieties, the type of grape cluster and meso-climate (i.e. cyclical conditions of fluctuating humidity, humid mornings followed by dry afternoons). Heavy rains and protracted damp periods are more likely to lead to conventional rotting, such as bunch rot, which essentially makes the grapes unfit for wine-making.
Different varieties of grapes will have documented agronomic characteristics, which mean they are favoured for use in particular growing areas and the associated climates. Specific botanical factors can be also important, such as the type of cluster formation of the grapes on the vine, and resistance to various forms of fungal rot and diseases, which, to an extent, depend upon such factors as the thickness of grape skins. Pruning of vines involves removing growth, usually in winter, although lighter summer pruning can also be carried out. It ensures that the otherwise rampant vine is kept in a manageable shape, thus also avoiding so-called over-cropping. The excess production of grapes (over-cropping) of a vine leads to inferior quality grapes and wines, and it is thought to compromise the life span of the vine. Hence, controlling the yield is an important issue in vineyard management, although there does not seem to be firm scientific evidence to indicate the optimum yield for vines. There are a number of different pruning techniques which influence the character of the grape and the resulting wine, even within one varietal type. For example, insufficient pruning in cooler climates will give grapes that take too long to mature; hence a heavier pruning technique would be more appropriate to ensure a ripe grape crop. Summer pruning is often associated with canopy management and helps to ensure a desirable canopy micro-climate, for example, sufficient sunlight on the bunches of grapes.
A most important characteristic of the vine is the rate at which the grapes can reach maturity, i.e., whether the vine is early or later ripening. Late maturing varieties need a warmer climate with a sufficiently long warm autumn and they do not thrive in cool climates. As already mentioned, many grape varieties are currently only of local regional interest but a relatively small number of others, with well known names, are internationally grown and are suitable for vinification in widely different countries. However, often much research is carried out regarding climate, meso-climate and even micro-climate to be created around the vines, in addition to the suitability of the soil. All this ensures that, once the preferred variety is selected and planted, there will be healthy vines yielding healthy good quality grapes.
In Tables 2.5 and 2.6 the second column indicates some of these agronomic characteristics, which can be studied in greater detail in other texts. The third column indicates some botanical features of the grapes, including some general comments on the chemical composition of the grape must, in particular, relation to tannin content and acidity which are both modified during wine-making. Some grape varieties are used on their own in wine production, giving the so-called varietal wines, particularly popular in the New World. Many others are used for blending purposes, and despite the negative connotation of the word, it forms an essential part of good wine-making practice. For example, blending gives the opportunity to add complementary characteristics, adjust sweetness, enhance acidity, or reduce the ‘oaky’ character of a heavily oaked wine from ageing in barrels.
Chemical composition both of the must and of the resultant wine is the key to a full study of vinification practices and wine flavour, which is dealt with in subsequent chapters. Notably, internationally grown varieties such as Cabernet Sauvignon and Chardonnay can show some marked differences in wine flavour according to the region of vinification (e.g. France compared with Australia or California); these differences are explored in more detail later.
An important characterizing feature of chemical composition is the so-called terpene content of particular grapes, which is relatively unaffected by subsequent vinification. These terpenes are volatile compounds that confer a very distinctive grapey flavour, often referred to as ‘aromatic fruity’, in contrast to ‘ester fruity’ flavour aroma which can be generated during fermentation. As discussed in Chapter 4, terpene content varies with different varieties, and is highest in the Muscat variety, but it is also significant in certain ‘noble’ varieties, notably Riesling and Gewürztraminer, and hence in the wines produced by these grapes. Varieties with very low or zero concentrations of terpenes tend to be more neutral in character but often develop a more generally ‘fruity’ aroma. These distinctions are also reflected in comments in the third column of the tables. The whole subject is dealt with in later chapters. Terpene content can be used for distinguishing purposes between some varieties. During ageing, changes occur both in the type and amount of terpenes, which has a noticeable influence on the aroma bouquet of the wine (discussed in detail below).
Table 2.5 Some grape variety characteristics for red wines.
| Black grapes (red wines) | ||
| Variety (country of origin) | Agronomic | Botanical/composition/vinification |
| Cabernet Sauvignon (France) | Ripens late. Planted in warm climates. Susceptible to fungal disease. International variety (California and Australia, increasing in many wine regions). |
Small thick-skinned grapes. High ratio of solids, tannins, to juice, rich in colouring matter. Very suitable for ‘oaking’. |
| Merlot (France) | Early maturing/ripening. Can grow in cool climes, but can suffer frost damage. Likes ‘clayey’ soil. Susceptible to fungal disease. Most planted variety in Bordeaux. International variety (California, Argentina, South Africa and New Zealand). |
Thinner skins than above. Often blended with Cabernet Sauvignon. |
| Gamay (Gamay Noir à Jus Blanc) (France) | Ripens early. Sensitive to fungal disease, and frost damage. The ‘Beaujolais’ grape. |
Medium sized grapes with tough skins. Low tannin/high acidity. Usually processed by Maceration Carbonique. |
| Syrah (France) Shiraz (Australia) |
Unusual relationship of pruning technique with subsequent taste/flavour of wine. Northern Rhàne. |
Tannic wine with ageing potential, but loss of acidity past optimal ripening of grapes. |
| Cabernet Franc (France) | Vine similar in appearance to Cabernet Sauvignon. Ripens earlier. Useful in cooler regions. Internationally planted. |
Wines, fruity and less tannic than from Cabernet Sauvignon. |
| Pinot Noir (France) Spätburgunder (Germany) Pinot Nero (Italy) |
Ripens early, not very suitable for very warm regions. ‘Fussy’ about soil; sensitive to bunch rot; not easily transferable (except to Oregon and some other regions). The ‘Red Burgundy’ grape. |
Ancient French vine, very prone to mutation with slight varietal difference, and even variation between clones of the same cultivar. |
| Nebbiolo (Italy) | Late ripening. Susceptible to powdery mildew. Grown largely in Piedmont. |
Wine made is markedly high in tannin and acidity. Grapes need to be ripe (sugar content) to counterbalance. Requires long ageing. |
| Sangiovese (Italy) | Late ripening. Susceptible to bunch rot. Most planted type in Italy. The ‘Chianti’ grape. |
High acid. |
| Tempranillo (Spain) (Other Spanish regional names e.g. Cencibel) | Early ripening. Subject to both powdery and downy mildews. Important in Rioja and Navarra. Spain’s best quality grape. |
High in tannins and acidity. Mid-sized/thick skinned. Usually aged. Not necessarily high in alcohol content. |
| Zinfandel (USA) (= Primitivo of S Italy) | Uneven ripening. Needs warm climate and long growing season. Most planted variety in California. |
Gives red, white and rosé wine. |
| Grenache (France) (Garnacha (tinto) Spain) | Flourishes in barren soils. Needs careful pruning to keep down the yield. World’s most widely planted red wine grape. The ‘Southern grape’ (France). |
Thin skins. High alcohol producer. Generally used for blending purposes, e.g. S Rhône. |
| Malbec (France) | SW France grape. Fragile in cooler climates. Very popular in Argentina. |
Used in blending or as varietal wines (Argentina). |
| Petit Verdot (France) | Very late ripening limits possible growing regions. Small quantities in Bordeaux. Some interest for Chile, Australia and California. |
Acid. |
| Mourvédre (France) (= Monestrell) (Spain) | Needs very warm climate to ripen fully. Grape planted in SE France and SE Spain. Old fashioned grape coming into fashion again. |
Wines with high alcohol. |
| Pinotage (South Africa) | Early ripening. High yielding vine, hence requires pruning to maintain quality and yield. South Africa. |
South African variety by crossing of Pinot Noir and Cinsaut. |
Table 2.6 Some grape variety characteristics for white wines.
| Variety (country of origin) | Agronomic | Botanical/composition/vinification |
| Chardonnay (France) | Ripens early and useful in cool areas. Susceptible to powdery mildew and ‘bunch rot’. Famous white, internationally planted. The ‘Chablis’ grape. |
High alcohol, low acidity wine. Low terpene content. Fermentation and maturing in barrels possible. Wine flavour especially dependent upon area of production. Lends itself to different vinification techniques in individual wines. |
| Sauvignon Blanc (France) (Muscat-Silvaner, Germany) | Particularly sensitive to powdery mildew and black rot; with partial resistance to bunch rot and (downy) mildew. Bordeaux/Loire Valley white grape. Internationally planted. |
Small sized grapes. Popular variety for making crisp, dry, aromatic wines all over the world, and distinctive from Chardonnay. Moderate terpene content. |
| Sémillon (France) | Susceptible to bunch rot and frost, and to Noble Rot. Bordeaux grape, also international (e.g. Australia). |
Small clusters of medium sized fruit. Used in fine white wines and also for sweet wines. |
| Chenin Blanc (France) | Requires considerable sun to ripen. Susceptible to both downy and powdery mildews, bunch rot. Loire Valley, but international. |
Tough skinned, medium sized grapes. Used for sweet and dry table wines, sparkling wines. |
| Riesling (Germany) | Ripens slowly, moderate yield. Slate soil. They are sensitive to powdery mildew. Particularly suited to Germany. |
Small to medium sized grapes. Terpene content high. Characteristic flavour on ageing. Varietal wine not much blended. |
| Muscat Blanc (Muscat à Petit Grains, France) | Grown in Australia. Widely planted variety with many other names. Central and Eastern Europe. |
Small round grapes light skinned. High terpene content. Used for sweet and sparkling wines (Italy), but also dry. |
| Muscat of Alexandria (France) | Less distinguished variety than foregoing. Different names according to country. Used in hotter climates. |
High terpene content but most is in unavailable glycosidic form. |
| Muscat Ottonel (France) | Grown in cooler climates, e.g. Alsace. | Lower terpene content than foregoing. |
| Morio-Muscat (Germany) | Needs a good site for growing and rots easily. | German hybrid of Silvaner and Weissburgunder (Pinot Blanc) High terpene content. |
| Silvaner (Germany) = Sylvaner (France) | Ripens earlier than Riesling, but later than Müller-Thurgau. Central Europe planting. |
|
| Mèller-Thurgau (Germany) | Ripens early, and suitable for cool climates. Subject to both powdery/downy mildew and bunch rot. Grown in Germany and UK. |
Crossing, Riesling and Chasselas (1882). High yielding mid-sized grapes. Used in cheaper German wines (QbA). |
| Traminer (Germany), Savagnin Rose (France) | Planted in cooler regions. Subject to powdery mildew and bunch rot. N.B. Sauvignin grape of Vin Jeune (Jura). | Modest clusters of small grapes. Tough skins. Terpene content moderate. |
| Gewürztraminer (Germany) | Planted particularly in Alsace. | Higher terpene content than above. Produces wines of high alcohol content, but may be low acidity. |
| Aligoté (France) | Burgundy’s second wine grape; also grown in Romania and elsewhere. | Acid wine. |
| Muscadelle (France) | Planted in Bordeaux and SW France. | Largely used for sweet white wines. Related to Muscat. |
| Viognier (France) | Northern Rhàne, but also S France, Australia and California. Can be poor yielding in cool climates. | Fashionable variety. Wines best drunk young: good for blending. |
| Pinot Gris (France) (= Pinot Grigio, Italy) (= Ruländer, or Grauburgunder, Germany) NB. EU insists on name Tokay-Pinot Gris |
Quality grape in Alsace, also grown in Germany (Baden/Pfalz). | Colour mutation of Pinot Noir. Pink skinned. |
| Melon de Bourgogne (France) | Grown for Muscadet; and little known elsewhere. Pays Nontais area (R Loire). Withstands cold well. | Dry wine, neither very acid nor strongly flavoured. Often ‘Sur lie’. Alleged highly sulfured wines. |
| Scheurebe (Germany) | Grown in Germany (Pfalz etc.), also Austria. | Crossing (1915), Unknown variety* and Riesling. Good quality and wine flavour. |
| Viura (Spain) (= Macebeo) | Grown in Rioja, Spain. | Good acid, but poor ageing capacity. |
| Grèner Veltliner (Austria) | High yields. | Not very aromatic, ages well in-bottle. |
* http://www.vivc.de/datasheet/dataResult.php?data=10818 (last accessed 26.11.2010)
2.3.3 Ripeness
Harvesting the grapes at optimum ripeness is now thought even more important than in the past and research has focused on ensuring that grapes are picked at the level of maturity that gives the most desirable wine flavour characteristics. Traditional physiological ripeness is reached when grapes have accumulated sufficiently high sugar levels, without having lost too much acidity. However, compounds contributing to the flavour of the grape and the resulting wine also are taken into account. Studies on changes of grape composition, with particular interest on compounds thought to influence wine flavour, have been comprehensively reviewed by Conde et al. (2007). The development and production of compounds during grape maturation contributing to the sensory properties of the grape and wine are still not well understood. During ripening, the grapes become larger, sweeter and less acid, mostly due to malic acid being metabolized, resulting in a change of the frequently used acid/sugar balance. On a per berry basis tannins and aromatic compounds formed during the early part of berry development decline.
Concurrent there are also important changes in volatile compounds characteristic for the grape variety and contributing to the aroma and regional character of the wine, often referred to as forming part of the wine quality. Best studied are the monoterpenes, C13-norisoprenoids, methoxypyrazines and sulfur compounds. Conde et al. (2007) summarize the monoterpene concentrations in three categories: (1) up to 6 mg L−1 in intensely flavoured grapes (Muscat), (2) between 1 – 4 mg L−1 in some aromatic varieties (Tramines, Huxel and Riesling) and (3) very low concentrations, generally below perception threshold and thought to contribute only minimally to varietal flavour (Cabernet Sauvignon, Sauignon Blanc, Merlot, Shiraz and Chardonnay). The levels of methoxypyrazines, contributing to the herbaceous aroma of, for example, Cabernet Sauvignon, diminish during maturation. Carotenoids break down during ripening; the process is enhanced by sunlight. Excessive hydrocarbon smells, due to 1,1,6-trimethyl-1,2-dihydronaphtalene, can develop in Riesling wines and have been attributed to extremely high temperatures during grape maturation. This illustrates that although hot climates favour the accumulation of sugars in grapes, it may not always bring out the best in terms of flavour quality.
The increased attention given to the production of wines with the varietal characteristics in terms of optimized flavour has increased the level of ripeness at which the grapes are picked. This means the sugar contents are higher and the fermentation leads to wines with higher concentrations of ethanol (even up to 15% v/v) than in the past. There is research ongoing in selecting yeast strains less efficient in the conversion of sugar into ethanol, enabling the production of wines with lower ethanol concentrations from very sweet and ripe grapes.
2.4 Grape growing regions of the world
2.4.1 World wine production
The main wine producing countries are France, Italy and Spain, and they have well established industries. Quality denominations in these regions date back many years and are determined by area, discussed briefly in Section 2.6. Grapes for wine-making have been selected over centuries, driven by a desire to improve wines to satisfy knowledgeable consumers. Hence it is not surprising that many of the grapes now successfully established in new wine regions in the New World are exported mainly from France and, to a lesser extent, from Germany. Interestingly, not infrequently the grapes traditionally grown in the cooler wine regions of France thrive best in cooler regions elsewhere in the world, although the sensory properties of the wines can be quite different. An example is the successful Sauvignon Blanc wine production in New Zealand, a relatively cool wine region.
However, as can be seen from Table 2.7 the increases in wine production in 2006 since 1996–2000 in some of the New World countries, such as Australia, Chile and New Zealand, are enormous, as are their increases in exports. This no doubt reflects their successful application of research information and technology in both viticulture and wine-making techniques. These countries have no long established histories and traditions in their wine industry, hence they may feel free to experiment in their viticulture and wine-making. In particular Australia has moved traditional thinking about viticulture and wine-making forward. Although their wine industry is not large, their influence is probably world-wide. For example, the fact that grapes grown in hot, dry areas produce top quality white wines contradicts the traditional view on climatic requirements for viticulture and shows that irrigation can have a positive effect on wine quality.
Styles of wine produced have adapted with the changes in fashion, for example, heavily oaked, buttery Chardonnay wines from California have virtually disappeared and have been replaced by lighter, fruity Chardonnay wines. Market research and good marketing presumably helps to ensure the wine industry adapts their products to meet the consumer preferences and demands.
Table 2.7 Wine production and export data in 2006, with calculated increases in production and export since 1996–2000. Only countries with a significant export have been listed.
Data from OIV, 2006.
The United States is the fourth biggest producer, with many prestigious wineries in California, especially the Napa and Sonoma valleys. However, most of these wines are consumed within the USA and exports tend to come from the large Central Valley. Australia is at the leading edge of technology in wine-making and successfully implements know-how and new technology. The wine industry in South Africa dates from the mid seventeenth century and after the abolition of apartheid the export markets opened, giving impetus to the wine industry. Wines continue to improve and are good value. New Zealand is only a small producer, producing less than 1% of the world wine production. However, current popularity keeps the wine prices high. Detailed accounts on wine-making regions can be found in many popular wine books and websites.
2.4.2 Regions
Many books on wines are devoted to the grape growing and wine production regions of the world in greater or lesser detail, together with assessments of the wines produced in the numerous sub-areas, districts or groups of vineyards, e.g. Châteaux in Bordeaux, France.
Tables 2.8, 2.9, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21 and 2.22 which follow are primarily indicative, showing (1) region, (2) best known wine types, where only the quality wines are mentioned (i.e. AC in French wines), with a brief reference to some typical producers, and (3) main grape varieties used for the particular wine types.
Table 2.8 Wines in France: area/type Bordeaux.
| Region | Best known wine types/red wines a | Grape varieties used |
| Haut-Médoc (High quality clarets) |
Haut-Médoc, AC e.g. Château Cantemerle Pauillac, AC e.g. Château Lafite – Rothschild, Latour and Mouton-Rothschild (all 1st growth)a; Château Pichon-Longueville Lalande (2nd growth)a Listrac, AC e.g. Château Fourcas Holsten Cru Bourgeois) e.g. Château Margaux (1st growth)a St Julien, AC e.g. Château Léoville-Barton (2nd growth)a |
Cabernet Sauvignon Cabernet Sauvignon blended with Cabernet Franc and Merlot |
| Bourg and Blaye | Côtes de Bourg, AC | Merlot, also blended with Malbec |
| Graves | Graves, AC Pessac-Léogman, AC e.g. Château Haut-Brion (1st growth)a |
Cabernet Sauvignon and Merlot |
| St-Emilion, Pomerol, Fronsac | Pomerol, AC e.g. Château Pétrus St Emilion, AC e.g. Château Ausone Fronsac, AC Castillon Côtes de Bordeaux, AC |
Merlot dominant Merlot/Cabernet Franc/Malbec/Cabernet Sauvignon Cabernet Franc |
| White wines | ||
| Graves-Sauternes regions | Barsac, AC (sweet) Graves, AC Dry, aged Sauternes, AC e.g. Château Yquem |
Sauvignon Blanc/Sémillon Sémillon, blended with Sauvignon Blanc |
| Entre-Deux-Mers | Entre-Deux-Mers, AC Premiôres CÒtes de Bordeaux, AC (sweet) |
|
aGrowth = cru classé, 1855 classification.
Comments about the flavour of particular wines from wine writers and wine merchants are dealing often with wines made from blends of grapes and information about blends is not usually labelled. The flavour of the wines will depend upon the vintage year, which is being tasted, in addition to many other factors (age of wine, vinification method, maturation procedure, etc.).
Table 2.9 Wines in France: area/type Burgundy.
| Region | Best known wine types/red wines | Main grape varieties used |
| Côte de Beaune | Aloxe-Corton, AC Beaune, AC Premier Crua Chassagne-Montrachet Premier Crua Volnay AC Premier Crua |
Pinot Noir (most red Burgundy by law has 100% of this variety) Pinot Gris Pinot Liebault |
| Côte de Nuits | Chambertin, AC Grand Crua Gevrey Chambertin, AC Nuits-St-George Premier Crua |
Pinot Noir |
| Côte d’Or | Bourgogne Rouge AC | |
| Côte Chalonaise | Bourgogne Passe-Tout-Grains, AC | Gamay, 1/3 Pinot Noir |
| Beaujolais | Beaujolais AC Beaujolais-Villages AC |
Gamay Gamay |
| White wines | ||
| Côte de Beaune | Corton Charlemagne AC Grand Crua Le Montrachet, AC Grand Crua |
Chardonnay (a little Pinot Noir) Chardonnay |
| Côte de Nuits | Musigny, AC | Chardonnay |
| Côte Chalonnaise | Bouzeron AC | Aligoté |
| Maconnais | Pouilly-Fuissé, AC | Chardonnay |
| Chablis | Chablis AC Grand Cru AC and Premier Crua, AC |
Chardonnay (100% use) |
| Beaujolais | Beaujolais Blanc AC | Chardonnay |
aBurgundy classification.
The flavour characteristics of wines from single varieties are of the most interest to the scientist and chemist, since they can be related to the chemical composition of the grapes. Undoubtedly the grape variety has the greatest influence on wine flavour, but the conditions of vinification, including the type of yeast used, will also determine the wine flavour, especially by the formation and modification of the volatile components. Some important factors are agronomic, particularly the yield per vine. It will be evident that certain taste characteristics of the grapes, such as acidity and sweetness, will be determined by the level of maturity at which the grapes are harvested (see above), though the specification for vinification will nearly always be ‘ripe’ and ‘healthy’ grapes. Ripeness is usually defined in terms of concentrations of sugar and acid. As grapes ripen, they lose acid and gain sugar. The grapes are ideally picked when they have reached sufficient sugar to give about 11% alcohol (Chapter 3) while still having sufficient acidity to help to preserve the wine and to give an acid taste. Often sugar/acid ratios are used, but their use is probably very area specific. Little information is known about the flavour of the wine in relation to grape ripeness. The sugar and acid content of the grape at harvest will depend on grape variety and climate.
Table 2.10 Wines in France: area/type Champagne.
Table 2.11 Wines in France: area/type Loire.
| Region | Best known wine types (white) | Main grape varieties |
| Upper Loire |
Sancerre AC Pouilly-Fumé, AC |
Sauvignon Blanc Sauvignon Blanc |
| Middle Loire |
Anjou Blanc Sec, AC Touraine, AC |
Chenin Blanc + Chardonnay. Sauvignon Blanc |
| Muscadet | Muscadet AC | Melon de Bourgogne |
| Best known wine types (red) | ||
| Upper Loire |
Sancerre Rouge, AC | Pinot Noir |
| Middle Loire |
Touraine, AC Chinon, Saumur-Champigny, AC Saumur – Champigny AC |
Variety of grapes Cabernet Franc Cabernet Franc |
Table 2.12 Wines in France: area/type – south western.
| Region | Best known wine types (red) | Main grape varieties |
| Bordeaux fringe country (Bergerac) |
Bergerac, AC | Merlot, Cabernet |
| River Lot area | Cahors, AC | Malbec (70%), Merlot and Tannat |
| Armagnac region | Madiran, AC | Tannat, Cabernets, Fer |
| Best known wine types (white) | ||
| Bergerac | Bergerac Sec, AC Monbazillac AC |
Sémillon, Sauvignon Blanc, Sémillon, Sauvignon Blanc, Muscadelle |
| SW France | Gaillac, AC Pacherenc du Vic-Bilh AC |
Local varieties, Mauzac Local mixed varieties |
Chemical composition is considered broadly in the next section. In Chapters 3 and 4, the basic taste factors and volatile compounds are dealt with separately in much greater detail.
In Tables 2.8, 2.9, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15 and 2.16 France is recognized as historically the most important area in Europe for wine production, and still occupies a major position in the industry. Not all wine-producing countries have been included; other texts should be consulted for full descriptions of the world’s wine-growing regions. A comprehensive reference guide to the wines of the world is Sotheby’s World Wine Encyclopedia (Stevenson, 1997). Numerous wine writers have written books on wine regions, including listing of wines produced and their producer, some of which have been mentioned in the Bibliography of Chapter 1.
Table 2.13 Wines in France: area/type Rhône.
| Region | Best known wine types (red) | Main grape varieties |
| Northern Rhône | Côte-Rôtie, AC Crozes-Hermitage, AC Hermitage, AC |
Syrah/Viognier (white) Syrah |
| Best known wine types (white) | ||
| Condrieu, AC | Viognier | |
| Clairette de Die, AC (sparkling) | Clairette, Muscat | |
| Hermitage, AC | Marsanne, Roussanne | |
| Best known wine types (red) | ||
| Southern Rhône | Châteauneuf-du-Pape, AC | Some 13 different varieties allowed (mainly Grenache, Mourvèdre, Syrah) |
| Côtes du Rhône, AC | Grenache | |
| Lirac, AC | Grenache, Cinsau(l)t and others | |
| Tavel, AC (rosé wine) | Grenache | |
Table 2.14 Wines in France: area/type – south east.
| Region | Best known wine types (red) | Main grape varieties |
| South east (Provence) | Bandol, AC | Mourvèdre, with some Grenache, Syrah |
| (Island of Corsica) (Languedoc-Roussillon) |
Vin de Corse, AC Fitou, AC Corbières, AC |
Sciaccarellu, Niellucciu Carignan, Grenache Carignan, Cinsaut Grenache |
| Càtes de Roussillon, AC Banyuls AC (Vin Doux Naturel with added grape juice) |
Carignan, mainly 50% Grenache |
|
| Best known wine types (white) | ||
| South east | Bellet, AC | Rolle |
| (Provence) | Cassis, AC | Marsanne |
| (Languedoc-Roussillon) | Clairette de Bellegarde, AC | Clairette |
2.5 Chemical composition of grapes, must and finished wines
2.5.1 Grapes and must
Plants generally show marked differences in the chemical composition of the fruits of different species within a given genus (e.g. differences between Coffea arabica and Coffea canephora) but there are rather fewer differences between varieties of a given species (as in Coffea arabica, between Bourbon and Typica) grown under similar conditions. With wines, we are generally considering only one species of grape, Vitis vinifera, L., but there are a large number of varieties within that species, as already noted. Chemical composition differences between some grape varieties have been published, either in total or more likely with reference to particular groups of substances. There can also be differences, however, within a given variety, due to the location of vines (climate, soil, etc.), the different agronomic practices (pruning, yield, etc.) and degree of ripeness at harvest. Of more interest for observing changes in subsequent vinification and maturation is the chemical composition of the grape juice (must) immediately prior to fermentation, without any additions. The must for red wine will be very similar in percentage composition terms to that of the originating grapes, since it consists of the crushed grapes (see Vinification in Chapter 1). However, the clear juice for white wine production is free of skins, pips, etc. and during the clarification of the white juice most insoluble solids are removed. The soluble solids of the musts in either case are clearly important, as they ultimately affect the subsequent wine flavour obtained.
Table 2.15 Wines in France: area/type Alsace.
| Region | Best known wine types (white) | Main grape varieties |
| Alsace (white) | Types characterized by grape name | |
| Alsace AC | Muscat (Muscat Ottonel Muscat Blanc Group) Pinot Blanc Pinot Gris Riesling Sylvaner |
|
| Alsace Grand Cru Ac (50 vineyards, in 1992 classification) |
Riesling Muscat Gewürztraminer |
|
| Alsace Vendanges Tardives (VT) | Late picked grapes. Riesling, Gewürztraminer, Pinot Gris, Muscat |
Table 2.16 Wines in France: area/type Jura and Savoy.
| Region | Best known wine types | Main grape varieties |
| Jura (red) (white) |
Arbois AC L’Etoile, AC Arbois, AC |
Trousseau Savagnin/Chardonnay |
| Vin Jaune | Also Chateau Chalon, AC | Savagnin |
| Savoy (white) | Rousette de Savoie, AC | Altesse/Chardonnay (Roussette) |
| Seyssel, AC | (Roussette) | |
| (red) | Vin de Savoie, AC | Pinot Noir |
Table 2.17 German wines.
Water, of course, is the main component of the grape, amounting to some 70–80% by total weight, though in a clear must, the water content is even higher at around 83%. Fresh grapes weigh about 200–225 g per 100 berries. Grapes will contain 15–25% w/w ‘sugar’, constituting the reducing sugars, glucose and fructose. Glucose is often referred to as ‘grape sugar’. Partially dried grapes contain a higher percentage of sugars, say 40%. When fermented, these sugars provide the ethyl alcohol of wine, but they are also the precursors of many of the flavour/aroma compounds as will be seen later. There are very small quantities of other sugar types, but these are non-fermentable (like arabinose) and hence these sugars remain in the wine. There is a small proportion of nitrogenous matter (e.g. protein and free amino acids) at 0.3–1.0% and these are of particular importance in wine-making, for example as flavour precursors. However, protein can also give a haze in wines, leaving the wine unacceptable for consumption. The pigments of the grape are mostly located in the epidermal cells of the skin, and are part of the phenolic and anthocyanin compounds, which will be discussed in more detail later. The skin also contains some of the volatile compounds that contribute to the wine aroma, especially the terpenes responsible for so-called ‘aromatic fruity – grapey’ flavour.
Table 2.18 Italian wines.
Table 2.19 Spanish wines.
| Region | Best known wine types (red) | Main grape varieties |
| Central to North Spain |
||
| Rioja | Rioja, DOC | Tempranillo, |
| Rioja Alta | Styles | Garnacha, Some |
| Alavesa | Joven, to be drunk young | Graciano and Mazuelo |
| Baja | Aged – American oak (Crianza, Reserva, Gran Reserva) |
(Cariñena) |
| NW Spain | ||
| Ribera de Duero | Ribera del Duero, DO | Tempranillo also Cabernet/Merlot/Malbec |
| Central to Southern Spain |
Valdepeñas, DO | Cenibel (Tempranillo) |
| NE Spain | ||
| Navarra | Navarra, DO | Tempranillo, also Garnacha also Cabernet Sauvignon |
| Penedés (Catalonia) |
Penedés, DO | Cabernet Sauvignon |
| Canary Islands | Tacorante – Acentejo, DO | Listan Negro (red) and others |
| Listan Blanco (white) and others | ||
| Best known wine types (white) | ||
| Central Spain | ||
| La Mancha | La Mancha, DO | Airén |
| Rioja | Rioja, DO (oak aged) |
Viura |
| NE Spain | ||
| Penedés | Penedés DO | Chardonnay (only) |
| Cava, DO | Champagne – type (Viura = Macebeo) |
|
| Catalonia | Cava, DO | Champagne – type |
| Rueda | Rueda DO | Verdejo |
Table 2.20 Wines from the USA.
Table 2.21 Wines from Australia and New Zealand.
Table 2.22 Wines from South Africa, Chile and Argentina.
There is even a small quantity present of phospholipids and glycolipids (vegetable oils linked with phosphor group or sugars respectively) based on the unsaturated fatty acids, linoleic and linolenic acids. On breakdown, these are flavour and aroma precursors. The skins also contain carotenoids. Pectins are present in grape juice and can be a source of problems during vinification, since pectins can make wines difficult to filter. Of the non-volatile acids, tartaric acid is almost unique to the grape and it is in part responsible for the special properties of wines; grapes also contain malic acid (the apple acid) and citric acid (characteristic of oranges/lemons). There are also inorganic constituents of the grape, metal cations such as K+, which will be evident on ashing grapes in a furnace.
The most complicated chemical group of substances present is the phenol-based group, which includes the so-called flavanoids and non-flavanoids. These are discussed fully in Chapter 3, since they are responsible for the basic taste characteristics such as bitterness and astringency in the finished wine. One group of phenols, the anthocyanins, are the red pigment responsible for the grape, must and wine colour, of red wine. The term tannin, though somewhat loose, is often used to describe many of these compounds, which also include some volatile phenolic compounds, that contribute to wine aroma. Grapes also contain a surprising quantity of volatile compounds, e.g. terpenes, some of which, as already noted, will appear in the finished wine, though it is important to emphasize that many new volatile compounds, are generated in the vinification processes in great amounts.
The chemical composition of must or grape juice (and also of the wine) is conveniently expressed in grams per litre, (g L−1, clear juice) of each known non-volatile constituent or group of constituents. The volatile substances will only be present in parts per million or less, and therefore their content is expressed as mg, μg L−1, or even ng L−1. The most important non-volatile substances will be the sugars, which should be present in white wine must, generally above the level of 215 g L−1 of solution (see Chapter 3). Similarly, for red wine the sugar concentration determined in clarified must needs to be similar as for white wine must, since this sugar content is reflected directly in the eventual ethyl alcohol content after fermentation. This content of sugar can be measured in a number of different ways, mostly simply by the use of a refractometer reading on the degrees BRIX scale (strictly speaking, for sucrose sugar content) together with conversion tables, which actually give the concentration of sugar (calculated as sucrose) present in g sugar/100 g solution (i.e. % w/w).
Non-volatile acids in must will amount to about 5 g L−1 tartaric acid, 5 g L−1 malic (1–2 g L−1 in southerly regions) acid and 0.3 g L−1 citric acid, giving rise to a pH of 3.3–3.4 (Ribéreau Gayon et al., 2006). These amounts will greatly depend on the ripeness of the grapes.
Data on the volatile compounds of must is somewhat rare, but Vernin et al. (1993) have investigated the must from Mourvèdre grapes and reported about 100 different compounds, not all identified, including terpenes, importantly the C6 aldehydes and alcohols but very few esters (aliphatic or benzenoid) that typically characterize finished wines.
Bourzeix (1983), quoted by Jackson (2008), has provided some interesting quantitative data on the total phenolics content and total anthocyanin content separately, on some 14 different types of grapes. The highest in both categories was found in the Colombard variety, at 10 and 9.9 g kg−1 respectively fresh weight, whilst the variety Grenache showed 3.6 and 1.2 g kg−1 respectively.
Immediately before vinification, sugar (sucrose) may be added to the must to ensure 10–12% v/v ethyl alcohol content after the fermentation process, by pre-testing the sugar concentration as described above and further in Section 2.6.5. Acidity may also be adjusted at this stage by adding tartaric or malic acid to decrease a high pH, or by adding calcium carbonate to increase a low pH. Sulfur dioxide is usually added at the must stage at around 50 ppm or less (see Chapter 1) to inhibit oxidizing enzymes and encourage a clean fermentation. All such additions are under legal control in most wine-producing countries (e.g. in the EU, see Section 2.6). Undesirable oxidizing enzymes, which cause browning, specifically very undesirable in white wines, appear to be associated with particulate matter. Pectin-hydrolyzing enzymes may therefore be added to reduce this particulate matter. Various clarifying agents used before or after fermentation will be largely removed by filtration and fining procedures before the wine is bottled.
In the must from ‘botrytized’ grapes (Noble Rot), certain chemical composition differences from ‘normal’ must will be noted, as discussed in Chapter 7.
2.5.2 Finished wine
Quality control procedures mentioned in Sections 2.5 and 2.6 encompass a number of factors regarding composition, though not all. A typical content range of actual composition of the more significant constituents is shown in Table 2.23.
The substances present in finished wine will include those from in-cask ageing if practiced, though not necessarily from in-bottle ageing unless specifically mentioned. They are divisible into the non-volatile compounds, responsible for the basic tastes of the wine, i.e. bitterness, sweetness, acidity and the mouthfeel of wine, often referred to as astringency (discussed in detail in Chapter 3), the stimulant compounds and the volatile compounds responsible for the aroma components of the total flavour (discussed in detail in Chapter 4). A number of the compounds, often included in the tannins group (Table 2.23) are responsible for the colour of wines and they are discussed separately.
In respect of the flavour of the wine, the sweetness (due to residual glucose and fructose but also the glycerol and possibly even the terpenes), the acidity (due to the non-volatile tartaric, malic and citric acids but also the volatile acetic acid) and the bitterness/astringency (due to the ‘tannin’ substances listed in Table 2.23) all significantly contribute to wine character. Especially important, however, is the volatile compound content, or the so-called aroma, which is divisible into three groups of flavour significance: (1) primary, originating in the grape, mainly terpenes as in Muscat grapes; (2) secondary, generated during fermentation, by the particular enzymes present in the yeasts, essentially for the production of ethyl alcohol; and (3) tertiary, which arise in the maturing stages of the wine, especially when the wine is kept in oak barrels.
2.6 Quality control and classification of wines
An important aspect of wine production is in Classification, Quality Control and Appraisal systems, together with detailed analytical procedures. Such systems exist in all wine-producing countries and originated in France. Quality control and chemical analytical procedures are particularly prominent in the USA (California). Australia has introduced a system ensuring grapes come from a certain area. Classification systems in France, Germany, Italy and Spain primarily focus on the concept of origin (or terroir).
Table 2.23 Typical range of substance content in wines.
Data adapted from Peynaud (1986), Ribéreau-Gayon et al. (2006), Amerine & Ough (1974).
aEU definition of ‘dry’, <9 g L−1 sugar.
2.6.1 France
In France, the top level of classification enabling appropriate bottle labelling for both white and red wines is the Appellation d’Origine Contrôlée (or AC preceded by the name of the particular region or wine-producing area applicable). This system is controlled by the ‘Institut National de l’Origine et de la Qualité’, as initially organized in 1936. It is based upon a number of factors, for which particular rules apply regulating wine production, as follows:
(1) Geographical. Local factors of soil and climate for grape production are specified.
(2) Grape variety. Each appellation for a given area will have one or more grape varieties permitted, according to proven and historic practice, e.g. only Pinot Noir is allowed in most red Burgundies, like Beaune, AC, though Châteauneuf-du-Pape AC may use 13 different red and white grape varieties.
(3) Alcoholic content. There is usually a minimum alcohol content, dependent upon the district but generally 10–12% v/v is required. It can be achieved by sugar addition to the must before fermentation in the more northerly regions, where in cool years ripeness of the grapes may not be achieved.
(4) Yield of wine. This is usually expressed per area of vineyard used for grape growing. All appellations have maximum allowable yields, usually 45–50 hL of wine per hectare of vineyard, although in some AC areas the permitted yield is higher, though it can be as low as 25 hL ha−1. Dispensations can be granted from time to time. (NB 50 hectolitres = 66 666 bottles (at 750 ml), and 1 hectare = 2.4 acres.)
(5) Vineyard practice. Control of number of vines per hectare, method of pruning and even the method of picking. In southern regions, irrigation is also regulated.
(6) Methods of wine-making. In particular, monitoring methods of controlling acidity are laid down and certain methods, like ion exchange, may not be allowed.
(7) Analysis. An official taste panel that may reject faulty or untypical wines for the particular AC. Chemical analytical methods are discussed in Section 2.6.5.
In addition, there are two lower levels of wine classification: firstly, Vin Délimité de Qualité Supérieure (VDQS) and secondly, Vin de Pays introduced in 1973. The VDQS category, historically used for wines aspiring to AC status, is being phased out. Vin de Pays has a regional definition but the rules are more flexible, although quantity, alcoholic strength, area, etc., are defined. Wines also have to be assessed by a taste panel. Vin de Pays comes in three categories; regional, departmental and locally specific - the smallest areas. All others are Vin de France.
A much earlier system of classification first devised in 1855 and still applicable virtually in the same form and content, is used for some of the finest red and white wines in Bordeaux. This system applies to particular designated vineyards or rather châteaux, which are classed according to their cru (literally translated into English as ‘growth’) in five groups (premier to 5 ème) for reds, and three groups for white wines (Sauternes). AC appellations still apply but this classification is meant for an extra dimension of quality appraisal. The same châteaux may, however, also set aside part of their production, which is not of ‘cru’ standard; these become so-called second wines, with slightly different châteaux names. Certain other châteaux may be classed as Cru Bourgeois, a classification outside the classed growths, though they may in the opinion of some wine experts be classed with them.
The wines in Burgundy, apart from AC, etc., are classified in somewhat different manner. The Burgundy vineyards have an AC ranking, such as grand Cru, Premier Cru, Commune, etc. Differences in classification are to a large extent historical, since large holdings like the châteaux in Bordeaux were not broken up during the French Revolution of 1789. In contrast, the Burgundy vineyards are owned by numerous different growers.
2.6.2 Germany
Labels on German wines are generally regarded as being rather confusing. Essentially the German wine law introduced in 1971 uses a quality classification based on ripeness (sugar content) of the grapes. This is not surprising, since in this cool climate the conditions need to be just right to attain ripe grapes. A vineyard classification of the top sites, Erste Lage and Grosses Gewächs, was published in 2002. There are two Quality Law levels, one defining the size of the area, the other the level of grape maturity.
These are the two Quality Levels: QbA and Prädikatswein:
(1) QbA (Qualitätswein Bestimmter Anbaugebiete)
This is by far the most dominant quality category and includes all Liebfraumilch and basic Grosslage wine blends. It means ‘quality wine from designated regions’, i.e. one of the following specified regions:
(a) Ahr (Northerly region near Bonn)
(b) Mittelrhein (between Bonn and Koblenz)
(c) Mosel – Saar – Ruwer
(d) Rheingau (around Mainz, near Wiesbaden)
(e) Nahe (along River Nahe, tributary of the Rhine)
(f) Rheinhessen (biggest, fairly central region)
(g) Pfalz (West of River Necker)
(h) Hessische Bergstrasse (above Heidelberg)
(i) Franken (between Frankfurt and Würzburg)
(j) Württemberg (above Stuttgart)
(k) Baden (most southerly region, close to Alsace)
(l) Sachsen (Former E Germany)
(m) Saale-Untrue (Former E Germany)
Inside these 13 regions, there are three groupings:
(i) Einzellage. (Single location, about 3000 names.) Refers to production from a single vineyard, and therefore expected to have the highest quality.
(ii) Grosslage. This name refers to a group of vineyards of similar type, based on one or more villages. Grosslage names (smaller number than above) can refer to a very large area and can refer to poorer quality wines.
(iii) Bereich (district). An amorphous term refers to a collection of villages, though often using a single village name and vineyard name, e.g. Bernkasteler Schlossberg, Schlossberg (Berg – Castle) is a vineyard in the Bernkastel district. Bernkastel is the whole of the Mittel-Mosel. Similarily, Nierstein (Rheinhessen) and Johannisberg (Rheingau) are the names of both villages and districts. Hochheim (Rheingau) is a wine town with several vineyards. Deidesheim (Pfalz) is also a wine village with several vineyards.
(2) Prädikatswein
This is a higher quality designation, translating as ‘quality wine with special attributes’ (or predicates). This part of German wine law is especially concerned with minimum grape ripeness levels and therefore ‘sweetness’. Prädikatswein wines are not allowed to be chaptalized. Su“ssreserve may be used for Kabinett and Spätlese. The following wine categories are classified in ascending order of sweetness:
(a) Kabinett. Least ripe, made from ordinary ripe grapes from a normal harvest.
(b) Spätlese (late harvest). From late picked and therefore riper grapes. Can provide either dry to medium dry wine.
(c) Auslese (selected choice). From selected, particularly ripe, late picked grapes, and may be affected by Noble Rot. Usually a medium-sweet wine.
(d) Beerenauslese (BA) (berry selected). Also made from specially selected very ripe grapes, and usually affected by Noble Rot-dependent upon variety. Very sweet wine sold at high price.
(e) Trockenbeerenauslese (TBA) (dried grapes, which were late picked). Made from even riper grapes than BA, affected by Noble Rot, which causes shrivelling. To qualify, there must be 150 Oeschle degrees of sugar content (the German potential alcohol system), equivalent to 21.5% v/v potential alcohol, but not actual. The finished wine will be very sweet and also expensive.
(f) Eiswein. A wine from grapes picked at dawn in winter, so that the grapes are frozen pellets of ice and which may only be made from BA and TBA quality grapes. Removal of ice prior to vinification gives a very sweet, concentrated wine.
Two other qualities should be mentioned:
(1) Landwein. A ‘Vin de Pays’ is from one of 20 designated areas, and must be Trocken (dry) or Halbtrocken (semi-dry).
(2) Deutscher Tafelwein. No specific vineyard origin. Usually sugared must has been used.
2.6.3 Italy
The DOC Laws are not unlike the French system. However, some of the growers disagree with the restrictions imposed by these laws, and therefore some very good quality wines are in the lowest quality denomination.
Only 10–12% of the Italian wine harvest is strictly regulated, and most is designated as Vino de Tavola, outside the strict regulation. The regulated wines are:
(1) Vino de Tavola. This is applied to table wines which have some reference to place, colour and maybe grape variety but they do not qualify for DOC status. However, some quality wines can be included. Table wines with Indicazione Geografica Tipica are allowed to use area of production, grape variety and production year on the label.
(2) Denominazione di Origine Controllata (DOC). This is designated for specified wine varieties, grown in delimited zones. Wines are vinified by prescribed methods and aged by prescribed methods to certain standards.
(3) Denominazione di Origine Controllata e Garantita (DOCG). This is a top tier introduced in (1982), with more stringent restrictions on grape types, yields and chemical and sensory analysis than DOC wines.
There are two other specified terms:
(1) Classico – meaning the best parts of the original region.
(2) Superiore – reference to ripeness.
Other label terms are used such as Riserva (generally denoting prolonged ageing), Spumante (sparkling) and Frizzante (highly sparkling).
2.6.4 Spain
Spain has the largest acreage of vineyards in the world but only a small number of demarcated regions, which are called Denominación de Origen (DO). DO is akin to the French system and based on suitable terrain, permitted grape varieties, restricted yields and approved methods of vinification.
It also has an equivalent of Vin de Pays, i.e. ‘Vino de la Tierra’, which are wines with a local character, ‘Vino de Mesa’ is Table wine (as opposed to both foregoing); this is the basic category, many wines being blends.
Some other label descriptions are of significance, especially those related to ageing:
- Joven (or sin crianza). Young wine, with minimal ageing.
- Crianza. A wine that has undergone a legal minimum period of ageing in-barrel and vat/bottle.
- Reserva. Wines with a longer legal minimum period of ageing in-barrel and bottle.
- Gran Reserva. Top of range, wines aged for longer than a Reserva.
2.6.5 Australia
Blending is an acceptable practice, in order to get the required fruit characteristics in a wine, blends of wine from different vineyards or even regions are quite common. The appellation control laws introduced are perfectly adapted to encompass blending. In 1993 Australia introduced the term Geographical Indication (GI), and these are classified into:
- South East Australia, the states.
- Zones (which form part of the states).
- Regions (which form part of the zones).
- Sub-regions (which form part of the regions).
The GI claimed on the bottle depends on the origin of the grapes. It is not uncommon in Australia to move the cooled grapes a considerable distance from the vineyard to the winery and grapes from a large area can be used for any particular wine. Hence the claim to be used depends on the area from which the grapes came: if all are sourced from a sub-region that is the claim to be made. Once a GI claim is made on the label, only 85% of the fruit needs to come from the GI area, although more than one area can be claimed on the label, specifying proportions of grapes in the blend.
Some of the zones are large, such as South Eastern Australia, hence grapes could be sourced from any of the vineyards in New South Wales, Victoria, Tasmania, even parts of Queensland and South Australia. A region is much smaller, but must contain at least five independently owned vineyards, and there are criteria on the production, such as size and grape attributes, while a sub-region within the region has more stringent criteria.
The GI system is not dissimilar to the European Appellation systems in use, although it is less restrictive regarding both viticultural practice and wine-making. Both systems aim to protect the use of the regional name, much as many European regional names are protected for wine, for example the on sparkling wines not from the Champagne region in France, the words ‘traditional method’ have to be used rather than ‘Champagne method’ to indicate that fermentation took place in the bottle. Currently Australia has about 60 wine regions, with 103 Geographical Indications for wine areas, covering zones, regions and sub-regions.
2.6.6 USA
The USA has introduced the Appellations of Origin, and this can be the name of a:
- state;
- county or counties;
- American Viticultural Area (AVA).
If a name of a state is claimed as the appellation of origin, 100% of the grapes must have been sourced within the state. A county appellation of origin needs to have sourced 75% of the grapes from the claimed county. Up to three counties can be used on the label and the percentage of grapes sourced from each needs to be stated on the label. For an AVA 85% needs to come from the claimed area.
The system of AVAs is regulated by the government, however, it does only approve the area as being distinct from other areas but it does not signify any quality differences between the grapes or wines. Distinguishing features of an area can be geographical, such as soil, climate, elevation, but can also be the result of historical information. There are currently 157 AVAs throughout the USA, most of them (94) are in California.
2.6.7 Quality control systems in the European Union
Reference should be made to Thompson (1987) where he discusses the European system and the system used in the USA in detail. The 1954 International Convention for the Unification of the Methods of Analysis and Appraisal of Wines published in the Recueil des Méthodes Internationale d’Analyse de Vins (1962–1973) provided the original compendium of procedures that formed the basis of most of the methods, now used throughout Western Europe. Many of these methods were included in the Annex to EEC Commission Regulation 2676/90 published in the Official Journal of the European Communities, 1990, L272, last amended by Commission Regulation No 1293/2005 (OJ No L205, 6.8.2005). This is a detailed document with precise descriptions of basic wine analyses to be used throughout the EU. They are the required methods when it is necessary to verify particulars given on documents relating to wines, for all commercial transactions and QC procedures. The reader should refer to the latest EU publications. All the wine regulations currently enforced in the EC are listed in Statutory Instruments (2009), No 386, Agriculture, England.
Methods are given to determine density and specific gravity at 20°C, alcohol content by volume (also at 20°C), total dry extract (expressed in terms of sucrose), reducing sugars, sucrose, ash, total and volatile acidity, tartaric and citric acids, free and combined sulfur dioxide, sorbic and ascorbic acid, together with the cations sodium, iron, copper and potassium. A method is also included for carbon dioxide content, based on the filtration of an alkaline sample in the presence of carbonic anhydrose from pH 8.6 to 4.0. Test kits for rapid methods for some of these factors have also been developed. Many of these factors feature in the Appellation Contrôlée and other systems already mentioned.
Sulfur dioxide addition is an important aspect of vinification. Thompson (1987) reports that it has been recommended that, after pressing, the juice be analysed for total and free SO2, pH and titratable acidity, so that the SO2 can be adjusted according to pH, so that less SO2 is used at lower pH values. When pectin-hydrolyzing enzymes are added to must, followed by clarification, the free SO2 is again checked and adjusted as necessary. Sufficient free sulfite must be present to restrict oxidation during processing (compounds formed in fermentation can bind to SO2 and render it ineffective) and inhibit the development of infecting micro-organisms. Nevertheless, the tendency is to minimize the use of SO2, for example, malo-lactic fermentation is encouraged in red wines, thus improving biological stability. Just before bottling, the level of SO2 may be again adjusted, to about 30 ppm free SO2, but the relevant national legal limit for total SO2 must not be exceeded. These national upper limits vary widely; the current EU permitted levels are: 150 mg −1 for red wines (160 mg L−1 for wines harvested before 2009) and 200 mg L−1 for dry whites (210 mg L−1 for wines harvested before 2009). Sorbic acid can be used up to 2000 ppm, but it is not very satisfactory in terms of anti-bacterial activity and can give an off-flavour in wine. The relatively low pH of wine inhibits the growth of most micro-organisms but it does not inhibit acetic and lactic acid bacteria. Some of the constituents of wine, notably ethyl alcohol, are also inhibitors of micro-organisms but the modern trend is to keep wine in sound condition by ensuring plant hygiene throughout fermentation and maturation, controlling the temperature during the entire process, together with sterile bottling and filtration.
Quality control is directed to the flavour of the finished wine, the judgement of which primarily resides in the mouths and noses of expert tasters. Modern QC techniques for volatile compound determination are, however, increasingly playing a role, together with multivariate statistical analysis of data to identify features which are desirable or undesirable, or differences between wines. However, it is not yet possible to include such techniques as a major part of quality control management, since these chemical analyses can ‘only’ identify compounds, including their concentration, up to now they cannot give much information regarding the flavour of wines but see also Chapter 5.
Bibliography
General texts
Clarke, O. (1989, 1998 and 2001) Wine Guide. Webster/Mitchell Beazley, London.
Clarke, O. & Rand, M. (2001) Grapes and Wines. Webster, London.
Galet, P. (1998) Grape Varieties and Rootstock Varieties. Oenoplurimédia, Chaintré.
Grainger, K. & Tattersall, H. (2005) Wine Production Vine to Bottle. Blackwell Publishing Ltd., Oxford.
Jackson, R.S. (2008) Wine Science, Principles, Practice, Perception. 3rd edn. Academic Press, San Diego.
Johnson, H. & Robinson, J. (2001) World Atlas of Wine. 5th edn. Mitchell Beazley, London.
Peynaud, E. (1986) The Taste of Wine. Macdonald, Orbis, London.
Ribéreau-Gayon, P., Glories, Y., Maujean, A. & Dubourdieu, D. (2006) Handbook of Enology, Volume II, The Chemistry of Wine, Stabilization and Treatments. John Wiley & Sons, Ltd, Chichester.
Robinson, J. (1993, 1995) Jancis Robinson’s Wine Course. BBC Books, London.
Web general information
L’Alliance des Crus Bourgeois du Médoc (2009) Crus Bourgeois du Médoc. http://www.crus-bourgeois.com/documents/selection_officielle_2008.pdf (accessed 4 May 2011).Vitis International Variety Catalogue (2011) http://www.vivc.de/index.php (accessed 4 May 2011).
References
Bourzeix, M., Heredia, N. & Kovač, V. (1983) Richesse de different cépages en composés phenolique totaux et en anthocyanines, Prog. Agric. Vitic., 100, 421–428 (1983), quoted by Jackson, R.S. (2008) loc. citation, p. 285.
Conde, C., Silva, P., Fontes, N., Dias, A.C.P., Tavares, R.M., Sousa, M.J., Agasse, A., Delrot, S. & Geros, H. (2007) Biochemical changes during grape berry development and fruit wine quality. Food, 1, 1–22. Global Science Books.
Huggett, J.M. (2006) Geology and wine: a review. Proceedings of the Geologists’ Association, 117, 239–247.
Stevenson, T. (1997) Sotheby’s World Wine Encyclopedia. Dorling Kindersley, London.
Thompson, C.C. (1987) Alcoholic beverages and vinegars. In: Quality Control in the Food Industry, Vol. 4 (ed. S.M. Herschdoefer), Section 5 ‘Wine’, pp. 57–64. Academic Press, London.
Vernin, G., Pascal-Mousselard, H., Metzger, J. & Parkanyi, C. (1993) Aromas of Mourvèdre wines. In: Shelf-Life Studies of Foods and Beverages (ed. G. Charalambous), Developments in Food Science No. 33, pp. 945–974. Elsevier, Amsterdam.