Introduction

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-fi fth millen- nium b.c. – Hajji Firuz Tepe, in the northern Zagros Mountains of Iran (McGovern et al., 1996). Evidence from Neolithic pottery from Georgia suggests that con- temporaneous wine production was dispersed through- out 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 identifi ed 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 1 CCH01-P373646.inddH01-P373646.indd 1 22/8/08/8/08 111:35:531:35:53 AAMM 2 1. Introduction restricted to juice fermented and stored in a manner to S. paradoxus (Cavalieri et al., 2003). The latter is con- retain its wine-like properties? sidered to be the progenitor of S. cerevisiae. Specifi c words The fi rst unequivocal evidence of intentional win- referring to yeast action (ferment) begin to appear emaking appears in the representations of wine presses about 2000 b.c. (Forbes, 1965). from the reign of Udimu (Egypt), some 5000 years ago Other yeasts indigenous to grapes, such as Kloeckera (Petrie, 1923). Wine residues also have been found in apiculata and various Candida spp., can readily initiate clearly identifi ed wine amphoras in many ancient fermentation. However, they seldom complete fermen- Egyptian tombs, beginning at least with King Semerkhet – tation. Their sensitivity to the accumulating alcohol 1st Dynasty, 2920–2770 b.c. (Guasch-Jané et al., 2004). content and limited fermentative metabolism curtails They have also discovered evidence for both white and their activity. In contrast, beer with its lower alcohol red wine in amphorae found in King Tutankhamun’s content may have initially been fermented by yeasts tomb (1325 b.c.). Identifi cation of red wine was made other than S. cerevisiae. by the presence of syringic acid, an alkaline breakdown The Near Eastern origin and spread of winemaking product of malvidin-3-glycoside. The same technique are supported by the remarkable similarity between the was used to establish the red grape origin of the ancient words meaning wine in most Indo-European languages Egyptian drink – Shedeh (Guasch-Jané et al., 2006). (Table 2.1). The spread of agriculture into Europe Most researchers believe that winemaking was dis- appears to be associated with the dispersion of Proto- covered, or at least evolved, in southern Caucasia. This Indo-European-speaking Caucasians (or their language area includes parts of present-day northwestern Turkey, and culture) (Renfrew, 1989). In addition, most eastern northern Iraq, Azerbaijan, and Georgia. It is also gen- Mediterranean myths locate the origin of winemaking erally thought that the domestication of the wine grape in northeastern Asia Minor (Stanislawski, 1975). (Vitis vinifera) ensued in the same area. Remains of what Unlike the major cereal crops of the Near East appear to be domesticated grapes have been found (wheat and barley), cultivated grapes develop an exten- in a Neolithic village in the Transcaucasian region of sive yeast population by maturity, although rarely Georgia (Ramishvili, 1983). It is in this region that the including the wine yeast (Saccharomyces cerevisiae). natural distribution of V. vinifera most closely approaches Piled unattended for several days, grape cells begin to the probable origins of Western agriculture – along the self-ferment as oxygen becomes limiting. When the ber- Tigris and Euphrates Rivers (Zohary and Hopf, 2000). ries rupture, juice from the fruit is rapidly colonized Grapevine domestication also may have occurred inde- by the yeast fl ora. These continue the conversion of pendently in Spain (Núñez and Walker, 1989). fruit sugars into alcohol (ethanol). Unless S. cerevisiae Although grapes readily ferment, due to the prevalence is present to continue the fermentation, fermentation of fermentable sugars, the wine yeast (Saccharomyces usually ceases before all the sugars are converted to cerevisiae) is not a major, indigenous member of the alcohol. Unlike the native yeast population, S. cerevisiae grape fl ora. The natural habitat of the ancestral strains can completely metabolize fermentable sugars. of S. cerevisiae appears to be the bark and sap exudate The fermentation of grape juice into wine is greatly of oak trees (Phaff, 1986). If so, the habit of grapevines facilitated if the fruit is fi rst crushed. Crushing releases climbing trees, such as oak, and the joint harvesting of and mixes the juice with yeasts on the grape skins (and grapes and acorns, may have encouraged the inocula- associated equipment). Although yeast fermentation is tion of grapes and grape juice with S. cerevisiae. The more rapid in contact with slight amounts of oxygen, fortuitous overlap in the distribution of the progenitors continued exposure to air favors the growth of a wide of both S. cerevisiae and V. vinifera with the northern range of yeasts and bacteria. The latter can quickly spread of agriculture into Anatolia may have fostered turn the nascent wine into vinegar. Although unaccept- the discovery of winemaking, as well as its subsequent able as a beverage, the vinegar so produced was proba- development and spread. It may not be pure coinci- bly valuable in its own right. As a source of acetic acid, dence that most major yeast-fermented beverages and vinegar expedited pottery production and the preserva- foods (wine, beer, mead, and bread) have their origins tion (pickling) of perishable foods. in the Near East. Of the many fruits gathered by ancient man, only The earliest evidence of the connection between wine grapes store carbohydrates predominantly in the form and Saccharomyces cerevisiae comes from an amphora of soluble sugars. Thus, the major caloric source in found in the tomb of Narmer, the Scorpion King grapes is in a form readily metabolized by wine yeasts. (ca. 3150 b.c.). S. cerevisiae was confi rmed by the Most other fl eshy fruits store carbohydrates as starch extraction of DNA from one of the amphoras. The and pectins, nutrients not fermentable by wine yeasts. DNA showed more similarity with modern strains of The rapid and extensive production of ethanol by S. cerevisiae than closely related species, S. bayanus and S. cerevisiae quickly limits the growth of most bacteria CCH01-P373646.inddH01-P373646.indd 2 22/8/08/8/08 111:35:561:35:56 AAMM Grapevine and Wine Origin 3 and other yeasts in grape juice. Consequently, wine of grapes to the local inhabitants. Although most of yeasts generate conditions that rapidly give them these seed remains indicate charring, seed escaping the almost exclusive access to grape nutrients. Subsequent heating process could have found conditions ideal for yeast growth is possible after the sugars are metabo- growth among the ashes. Were any of these progeny lized, if oxygen becomes available. An example is the rare bisexual (self-fertile) vines, they could have pro- respiration of ethanol by fl or yeasts (see Chapter 9). duced a crop, despite being isolated from feral vines. Another unique property of grapes concerns the acids More likely, functional bisexual vines were unintention- they contain. The major acid found in mature grapes is ally selected when feral vines were planted adjacent to tartaric acid. This acid occurs in small quantities in the settlements, and away from wild populations. Self-fertile vegetative parts of some other plants (Stafford, 1959), vines would have become conspicuous by their fruit- but rarely in fruit. Because tartaric acid is metabolized fulness, especially if unfruitful (male) vines were rogued. by few microbes, wine remains suffi ciently acidic to Cuttings from such vines could have provided plants limit the growth of most bacteria and fungi. In addi- appropriate for the initiation of nascent viticulture. tion, the acidity gives wine much of its fresh taste. The Although other modifi cations may characterize dom- combined action of grape acidity and the accumulation esticated strains, changes in seed and leaf shape are not of of ethanol suppresses the growth and metabolism of viticultural value. The lower acidity and higher sugar most potential wine-spoilage organisms. This property content that characterize cultivated varieties are not the is enhanced in the absence of air (oxygen). For ancient exclusive attributes of domesticated vines. These proper- man, the result of grape fermentation was the transfor- ties may refl ect more cultural conditions than genetic mation of a perishable, periodically available fruit, into modifi cations. a relatively stable beverage with novel and potentially Because canes lying on the ground root easily when intoxicating properties. covered by soil, layering probably developed as the Unlike many crop plants, the grapevine has required fi rst method of vegetative propagation. Success with little genetic modifi cation to adapt it to cultivation. Its layering would have ultimately led to propagation by mineral and water requirements are low, permitting it to cuttings. Early viticulturalists, if they did not already fl ourish on soils and hillsides unsuitable for other food know from other perennial crops, would have come to crops. Its ability to grow up trees and other supports realize that to retain desirable traits, vegetative propa- meant it could be grown with little tending in associa- gation was preferable to sowing seed. Vegetative prop- tion with other crops. In addition, its immense regener- agation retains desirable combinations of genetic traits ative potential has allowed it to permit intense pruning.

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