Wine Science

Principles and Applications

Ronald S. Jackson

• Éditeur: Academic Press
• Année: 2008
• ISBN:
  9780080568744
• Édition: 3
• Sujet: Technology & Engineering
• Sous-sujet: Agriculture

Wine Science, Third Edition, covers the three pillars of wine science – grape culture, wine production, and sensory evaluation. It takes readers on a scientific tour into the world of wine by detailing the latest discoveries in this exciting industry.

From grape anatomy to wine and health, this book includes coverage of material not found in other enology or viticulture texts including details on cork and oak, specialized wine making procedures, and historical origins of procedures. Author Ronald Jackson uniquely breaks down sophisticated techniques, allowing the reader to easily understand wine science processes.

This updated edition covers the chemistry of red wine color, origin of grape varietyies, wine language, significance of color and other biasing factors to wine perception, various meanings and significance of wine oxidation. It includes significant additional coverage on brandy and ice wine production as well as new illustrations and color photos.

This book is recommended for grape growers, fermentation technologists; students of enology and viticulture, enologists, and viticulturalists.

NEW to this edition: * Extensive revision and additions on: chemistry of red wine color, origin of grape varietyies, wine language, significance of color and other biasing factors to wine perception, various meanings and significance of wine oxidation
* Significant additional coverage on brandy and ice wine production
* New illustrations and color photos

1 Introduction

Grapevine and Wine Origin

Wine has an archeological record dating back more than 7.5 thousand years. The earliest suspected wine residues come from the early to mid-fifth millennium b.c. – Hajji Firuz Tepe, in the northern Zagros Mountains of Iran (McGovern et al., 1996). Evidence from Neolithic pottery from Georgia suggests that contemporaneous wine production was dispersed throughout the region (McGovern, in preparation). Older examples of fermented beverages have been discovered (McGovern et al., 2004), but they appear to have been produced from rice, honey, and fruit (hawthorn and/or grape). Such beverages were being produced in China as early as 7000 b.c. The presence of wine residues is usually identified by the presence of tartaric acid residues, although additional procedures for identifying grape tannin residues are in development (Garnier et al., 2003).

Other than the technical problems associated with identifying wine residues, there is the thorny issue of what constitutes wine – does spontaneously fermented grape juice qualify as wine, or should the term be restricted to juice fermented and stored in a manner to retain its wine-like properties?

The first unequivocal evidence of intentional winemaking appears in the representations of wine presses from the reign of Udimu (Egypt), some 5000 years ago (Petrie, 1923). Wine residues also have been found in clearly identified wine amphoras in many ancient Egyptian tombs, beginning at least with King Semerkhet – 1st Dynasty, 2920–2770 b.c. (Guasch-Jané et al., 2004). They have also discovered evidence for both white and red wine in amphorae found in King Tutankhamun’s tomb (1325 b.c.). Identification of red wine was made by the presence of syringic acid, an alkaline breakdown product of malvidin-3-glycoside. The same technique was used to establish the red grape origin of the ancient Egyptian drink – Shedeh (Guasch-Jané et al., 2006).

Most researchers believe that winemaking was discovered, or at least evolved, in southern Caucasia. This area includes parts of present-day northwestern Turkey, northern Iraq, Azerbaijan, and Georgia. It is also generally thought that the domestication of the wine grape (Vitis vinifera) ensued in the same area. Remains of what appear to be domesticated grapes have been found in a Neolithic village in the Transcaucasian region of Georgia (Ramishvili, 1983). It is in this region that the natural distribution of V. vinifera most closely approaches the probable origins of Western agriculture – along the Tigris and Euphrates Rivers (Zohary and Hopf, 2000). Grapevine domestication also may have occurred independently in Spain (Núñez and Walker, 1989).

Although grapes readily ferment, due to the prevalence of fermentable sugars, the wine yeast (Saccharomyces cerevisiae) is not a major, indigenous member of the grape flora. The natural habitat of the ancestral strains of S. cerevisiae appears to be the bark and sap exudate of oak trees (Phaff, 1986). If so, the habit of grapevines climbing trees, such as oak, and the joint harvesting of grapes and acorns, may have encouraged the inoculation of grapes and grape juice with S. cerevisiae. The fortuitous overlap in the distribution of the progenitors of both S. cerevisiae and V. vinifera with the northern spread of agriculture into Anatolia may have fostered the discovery of winemaking, as well as its subsequent development and spread. It may not be pure coincidence that most major yeast-fermented beverages and foods (wine, beer, mead, and bread) have their origins in the Near East.

The earliest evidence of the connection between wine and Saccharomyces cerevisiae comes from an amphora found in the tomb of Narmer, the Scorpion King (ca. 3150 b.c.). S. cerevisiae was confirmed by the extraction of DNA from one of the amphoras. The DNA showed more similarity with modern strains of S. cerevisiae than closely related species, S. bayanus and S. paradoxus (Cavalieri et al., 2003). The latter is considered to be the progenitor of S. cerevisiae. Specific words referring to yeast action (ferment) begin to appear about 2000 b.c. (Forbes, 1965).

Other yeasts indigenous to grapes, such as Kloeckera apiculata and various Candida spp., can readily initiate fermentation. However, they seldom complete fermentation. Their sensitivity to the accumulating alcohol content and limited fermentative metabolism curtails their activity. In contrast, beer with its lower alcohol content may have initially been fermented by yeasts other than S. cerevisiae.

The Near Eastern origin and spread of winemaking are supported by the remarkable similarity between the words meaning wine in most Indo-European languages (Table 2.1). The spread of agriculture into Europe appears to be associated with the dispersion of Proto-Indo-European-speaking Caucasians (or their language and culture) (Renfrew, 1989). In addition, most eastern Mediterranean myths locate the origin of winemaking in northeastern Asia Minor (Stanislawski, 1975).

Unlike the major cereal crops of the Near East (wheat and barley), cultivated grapes develop an extensive yeast population by maturity, although rarely including the wine yeast (Saccharomyces cerevisiae). Piled unattended for several days, grape cells begin to self-ferment as oxygen becomes limiting. When the berries rupture, juice from the fruit is rapidly colonized by the yeast flora. These continue the conversion of fruit sugars into alcohol (ethanol). Unless S. cerevisiae is present to continue the fermentation, fermentation usually ceases before all the sugars are converted to alcohol. Unlike the native yeast population, S. cerevisiae can completely metabolize fermentable sugars.

The fermentation of grape juice into wine is greatly facilitated if the fruit is first crushed. Crushing releases and mixes the juice with yeasts on the grape skins (and associated equipment). Although yeast fermentation is more rapid in contact with slight amounts of oxygen, continued exposure to air favors the growth of a wide range of yeasts and bacteria. The latter can quickly turn the nascent wine into vinegar. Although unacceptable as a beverage, the vinegar so produced was probably valuable in its own right. As a source of acetic acid, vinegar expedited pottery production and the preservation (pickling) of perishable foods.

Of the many fruits gathered by ancient man, only grapes store carbohydrates predominantly in the form of soluble sugars. Thus, the major caloric source in grapes is in a form readily metabolized by wine yeasts. Most other fleshy fruits store carbohydrates as starch and pectins, nutrients not fermentable by wine yeasts. The rapid and extensive production of ethanol by S. cerevisiae quickly limits the growth of most bacteria and other yeasts in grape juice. Consequently, wine yeasts generate conditions that rapidly give them almost exclusive access to grape nutrients. Subsequent yeast growth is possible after the sugars are metabolized, if oxygen becomes available. An example is the respiration of ethanol by flor yeasts (see Chapter 9).

Another unique property of grapes concerns the acids they contain. The major acid found in mature grapes is tartaric acid. This acid occurs in small quantities in the vegetative parts of some other plants (Stafford, 1959), but rarely in fruit. Because tartaric acid is metabolized by few microbes, wine remains sufficiently acidic to limit the growth of most bacteria and fungi. In addition, the acidity gives wine much of its fresh taste. The combined action of grape acidity and the accumulation of ethanol suppresses the growth and metabolism of most potential wine-spoilage organisms. This property is enhanced in the absence of air (oxygen). For ...