Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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tbl0001 Table 1 World regional statistics for vineyard coverage and total grape, wine, table grape, and raisin production in 1998

RegionVineyardarea%

(10

ha)

Total grape production

(10

kg)

% Wine production

(10

% Table grapes

(10

kg)

%Raisins

(10

kg)

Africa 314 4.0 2 873 4.7 931 3.6 1 398 10.6 27 2.8

Americas 859 11.0 10 391 17.2 4 421 17.1 1 871 14.3 302 31.4

Asia 1 478 19.0 11 891 19.6 612 2.4 6 833 52.1 499 51.9

Europe 5 041 64.6 30 633 50.6 19 112 73.8 2 951 22.5 95 6.8

Oceania 107 1.4 1 176 1.9 802 3.1 66 0.5 38 3.9

Total 7 799 60 585 25 878 13 119 961

Data from Dutruc-Rosset G (2000) The state of vitiviniculture in the world and the statistical information in 1998. Bulletin de l’Office International de la Vigne

et du Vin 73: 1–94.

Percentage of world production.

tbl0002 Table 2 Top ten countries in vineyard coverage, total grape, wine, table grape, and raisin production in 1998

Country Vineyard area

(10

ha)%

Country Total grape

production

(10

kg) %

Country Wine production

(10

% Country Table grapes

(10

kg) %

Country Raisins

(10

kg) %

Spain 1180 15.1 Italy 9208 16.1 Italy 5418 20.9 Turkey 1833 14.0 Turkey 350 36.4

France 914 11.7 France 6877 12.1 France 5267 20.4 China 1792 13.7 USA 255 26.5

Italy 889 11.4 USA 5355 9.4 Spain 3032 11.7 Iran 1724 13.1 Iran 90 9.4

Turkey 602 7.7 Spain 4884 8.6 USA 2045 7.9 Italy 1294 9.9 Greece 87 9.1

USA 364 4.7 Turkey 3650 6.4 Argentina 1267 4.9 Egypt 858 6.5 Australia 38 4.0

Iran 270 3.5 China 2358 4.1 Germany 1083 4.2 India 630 4.8 Chile 35 3.6

Portugal 260 3.3 Iran 2315 4.1 South Africa 816 3.2 Chile 599 4.6 Afghanistan 28 2.9

Romania 253 3.2 Argentina 2002 3.5 Australia 742 2.9 USA 569 4.3 South Africa 25 2.6

Argentina 210 2.7 Germany 1408 2.5 Chile 548 2.1 Syria 413 3.2 Syria 16 1.7

China 194 2.5 South Africa 1300 2.3 Romania 500 1.9 Brazil 398 3.0 Argentina 9 0.9

Data from Dutruc-Rosset G (2000) The state of vitiviniculture in the world and the statistical information in 1998. Bulletin de l’Office International de la Vigne

et du Vin 73: 1–94.

Percentage of world production.

10 ⬚C

20 ⬚C

Equator

fig0001 Figure 1 Association between the major grape-producing regions of the globe, with the 10 and 20



C annual isotherms. Major grape-

producing regions are shaded black. Drawing courtesy of H. Casteleyn, reproduced by permission.

2958 GRAPES

located in regions characterized by a Mediterranean

climate. Cultivation in cooler, warmer, or more moist

regions is commercially feasible only when local

climatic conditions or cultural practice compensate

for less than ideal conditions.

0004 Approximately 65% of the world’s vineyards occur

in Mediterranean Europe. Of this proportion, about

60% are located in Spain, Italy, and France. Although

the coverage has declined by some 16% since the mid-

1980s, grape production has actually increased by

about 10%.

Grape Species and Cultivars

0005 Grapes are produced by members of the genus Vitis

(family Vitaceae). All members are viny and develop

swollen or jointed nodes from which leaves, tendrils, or

flower clusters form. Each cluster produces many,

miniature, nonshowy, bi- or unisexual flowers. These

develop into fleshy berries containing up to four seeds.

The fruit is normally dark blue–purple owing to the

production of anthocyanin pigments. Green to yellow-

colored varieties do not produce these pigments.

0006 The genus is divided into two sections or subgenera.

The subgenus Vitis (bunch grapes) is the larger, con-

taining all species (about 65) except V. rotundifolia and

V. popenoei. These two are placed in the subgenus

Muscadinia (muscadine grapes). Muscadine grapes

are native only to coastal southeastern North America.

0007 The origin of the genus probably involved several

interspecies crosses, associated with subsequent

chromosome doubling. Modern species are derived

from very ancient hexaploids (plants possessing sets

of chromosomes from three different species). Bunch

grapes (subgenus Vitis) possess 38 chromosomes,

whereas muscadine grapes (subgenus Muscadinia)

have 40 chromosomes.

0008 Domestication of Vitis vinifera probably started in

northeastern Iran and northern Turkey some 4000

years ago. In contrast, the earliest evidence of wine

production predates domestication by about two mil-

lennia. Archeologic evidence of grapevine domestica-

tion appears as changes in seed shape (length relative

to width) and an increase in bisexuality (reduction in

the presence of infertile pollen from female vines).

0009 Most present-day grape varieties appear to have

developed locally, possibly from the crossing of indi-

genous vines and introduced domesticated varieties.

One view of the diffusion routes of the introduction

of grape culture to Europe is given in Figure 2.

0010 There are more than 5000 named grapevine culti-

vars. Most are of local interest only, with few having

achieved world-wide distribution. Examples are ‘Cab-

ernet Sauvignon,’‘Syrah,’‘Pinot noir,’‘Tempranillo’

and ‘Sangiovese’ (red), and ‘Chardonnay,’‘Riesling,’

and ‘Sauvignon blanc’ (white). Their productivity is

usually lower, and their cultivation typically more

demanding. Their reputation comes from their

yielding fine, varietally distinctive wines with long-

aging potential. In favorable locations, their

excellent wine-making properties compensate for

reduced yield and increased production costs. Modern

cultivars are often crosses between North American

Vitis species and V. vinifera varieties. Examples are

‘Concord,’‘Chambourcin,’ and ‘Cayuga’. Crossing

with North American and European grapes has also

been crucial in the production of rootstocks that pro-

vide resistance or tolerance to many important grape-

vine pest, diseases, and complicating soil conditions.

Vine Cycle and Vineyard Activity

0011The end of one growth cycle and the beginning of

another typically coincide with the onset of winter.

The absence of foliage facilitates the removal of

unessential shoot growth and the selection of growth

from which to generate the subsequent year’s crop.

0012The first indicator of renewed grapevine activity in

the spring is the flow of sap from the ends of pruned

shoots. When the average temperature rises above a

critical value, buds begin to burst. Once initiated, de-

velopment and enlargement of the embryonic leaves,

tendrils, and flower clusters occur quickly (Figure 3).

Disease, pest, and weed control measures begin early.

0013Flower development progresses from the outer-

most flower parts inward. Maturation of the anthers

and anthesis (pollen release) coincides with separ-

ation of the fused cap of petals (calyptra) (Figure 4).

The separation shakes pollen on to the stigma, thus

initiating self-fertilization. Flower induction for the

subsequent season occurs at this time in newly de-

veloping buds. Following fertilization, fruit develop-

ment begins. Except for seedless varieties, one seed is

required for berry development.

0014Once the shoots have elongated, they are typically

tied to a trellis for support. Irrigation, if required,

usually ceases at ve

raison (the beginning of mature

fruit coloration). This restricts additional vegetative

growth. Removing excessive leaf or shoot growth

may be conducted to limit shading and a nutrient

drain that can retard fruit ripening. Irrigation may

be reinitiated after harvest to avoid stressing the

vine and permit optimal shoot maturation.

0015As the grapes near maturity, vineyard activity shifts

toward preparing for harvest. Based on chemical an-

alysis of the fruit, environmental conditions, and the

desires of the winemaker, a harvest date is set. In cool

climates, frost protection measures are set in place.

0016Once harvest is complete, vineyard activity turns to

preparing the vines for winter. In cold climates, this

GRAPES 2959

Major Diffusion Routes

of Viticulture

in Southwest Asia and

Europe

40⬚

50⬚

30⬚

20⬚

40⬚

20⬚

Miles

500

800

Kilometers

0⬚

Britain

RHINE

SOVIET UNION

Alsace

GAUL

BERIA

Marseille

Italy

Balearic

Sicily

Greece

ANATOLIA

Mesopotamia

Asia

Crete

EGYPT

Black sea

Caspian

Sea

50⬚

30⬚

0⬚

ALGERIA

Ancient routes

Greek dispersal

Roman diffusion

Later expansion

fig0002 Figure 2 Major diffusion routes of grape growing in southwest Asia and Europe. From de Blij HJ (1983) Wine. A Geographic

Appreciation. Rowman and Allanheld, Totowa, NJ, reproduced by permission.

3.0

150

2.6

130

2.2

110

1.8

1.4

1.0

0.6

0.2

Rate of berry growth (g day

−1

100 berries

−1

)

0 20 40 60 80 100 120 140 160 180 200 220

Days from budbreak

Shoot elongation rate (cm day

−1

)

Actively growing root tips

(Number, m

−2

)

Rate of change

in trunk radius (mm x 10

−1

week

−2

)

Budbreak

Shoots

Anthesis

Roots

Veraison

Harvest

Berries

Trunk

fig0003 Figure 3 Growth rate of various organs of ‘Colombar’ grapevines grown in South Africa throughout the season. After van Zyl (1984),

from Williams LE and Matthews MA (1990) Grapevine. In: Stewart BA and Nielsen DR (eds), Irrigation of Agronomic Crops, Agronomy

Monograph # 30, pp. 1019–1055. Madison, WI: American Society of Agronomy, Crop Science Society of America and Soil Science

Society of America, with permission.

2960 GRAPES

may vary from mounding soil up around the shoot–

rootstock union to removing the whole shoot system

from its support system and burial with soil.

Grape Structure and Development

0017 Fruit growth typically shows an S-shaped curve

(Figure 5). In the initial phase, lasting 6–8 weeks,

cells divide rapidly, followed by enlargement. In the

second phase, lasting 1–6 weeks, berry growth slows,

and the seeds develop. At the end of this period,

the skin begins to lose its green color (ve

raison –

Figure 4). In the final phase, the fruit enlarges to its

mature size, tissues soften, acidity falls, sugars accu-

mulate, anthocyanin pigments form (in blue-skinned

varieties), and aroma compounds are synthesized.

(a) (b) (c)

(d) (e) (f)

fig0004 Figure 4 (see color plate 79) Stages in the flowering and fruit development of grapes: A, flowers with the fused petals (calyptra)

about to be shed; B, calyptra in last stage of separation and anthers about to shed pollen; C, very young grape still showing filaments of

anthers; D, young cluster of green grapes; E, maturing grapes beginning to change color (ve

raison), the bloom on the berry surface is

evident; F, fully mature grapes of ‘Cabernet Sauvignon.’ From Flaherty DL, Christensen LP, Lanini WT et al. (1992) Grape Pest Man-

agement, Publication No. 3343, 2nd edn. Oakland, CA: University of California, with permission.

GRAPES 2961

The final stage lasts 5–8 weeks. The duration of each

phase is cultivar- and climate-controlled.

0018 Mature grapes possess two morphologic regions –

the skin and the flesh (Figure 6). The thin skin layer

consists of an outer, single-layered epidermis and

an inner hypodermis (four to 20 cells thick). The

hazy coating (bloom) seen on ripe grapes comes

from waxy plates and ridges of the cuticle that

cover the epidermis (not yeast cells as commonly

believed). Anthocyanins produced in the outer layers

of the hypodermis generate the blue–purple color

typical of most grapes. White grapes derive their

yellowish coloration from the carotenoids and

flavonoid pigments in the hypodermis. The hypoder-

mis is also the production site for most aroma

compounds.

0019 During ripening, the cell wall of the hypodermis

thickens as a result of hydration, loosening bonding

between the cells. In ‘slip-skin’ varieties, however,

a layer of cells between the flesh and hypodermis

become thinner and lose much of their pectinaceous

cell-wall material. This produces a zone of weakness,

allowing the skin to separate readily from the flesh.

0020 The internal fleshy tissues of the grape are subdiv-

ided into two ill-defined regions – one between the

hypodermis and the peripheral vascular strands, and

the innermost, being delimited by the peripheral and

axial vascular strands (Figure 6).

0021 Grape size is largely dependent on enlargement of

the central vacuole of flesh cells. The vacuole is also

the primary site for sugar and acid accumulation

during ripening.

Chemical composition (see Table 3)

Sugars

0022Grape chemistry changes most significantly during

the later phases of ripening, beginning with ve

raison.

This is particularly marked as sugars, translocated

from adjacent leaves, accumulate. A simultaneous

reduction in vegetative growth, and a metabolic shift

to malic acid respiration, also favor sugar deposition.

0023On reaching the berry, sucrose is hydrolyzed and

stored as fructose and glucose. Depending on the culti-

var and prevailing conditions, the sugar content may

reach 12–28%. For wine-making, the desired sugar con-

tent generally ranges from about 21 to 25%. Lower

sugar contents are preferred for table grapes. Small,

but largely insignificant, amounts of other sugars accrue

in ripe grapes – notably raffinose, stachyose, melibiose,

maltose, galactose, arabinose, and xylose.

Acids

0024After sugar, the most marked chemical modification

during ripening involves a reduction in acidity.

Phase I Phase IIIPhase II

Bloom

Fresh weight (g)

Veraison

⬘

Maturity

fig0005 Figure 5 Diagrammatic representation of the growth phases of

grapes.

Exocarp (skin)

Pericarp

Cuticle

Stylar remnant

Locule

Septum

Mesocarp

(flesh)

Peripheral

bundle

network

Brush

Pedicel

Receptacle

Cap trace

Stele

1 mm

Seed

Ovular

Axial

Vascular

bundles

Peripheral

Endosperm

Testa (outer

integument)

Embryo

BGC

fig0006Figure 6 Diagrammatic representation of a grape berry. After

Coombe BG (1987) Distribution of solutes within the developing

grape berry in relation to its morphology. American Journal of En-

ology and Viticulture 38: 120–128, published by the American Soci-

ety for Enology and Viticulture, with permission.

2962 GRAPES

Tartaric and malic acids account for about 70–90%

of the berry acid content. The remainder consists of

variable amounts of organic acids (citric and succinic

acids), phenolic acids (e.g., quinic and shikimic acids),

amino acids, and fatty acids.

0025 The tartaric acid content of grapes generally remains

stable during ripening. Its perceived acidity declines,

though, as the proportion of free acid (not associated

with potassium and calcium ions) decreases. In con-

trast, the malic acid content decreases during ripening.

This trend is particularly marked in hot climates. Shoot

vigor is another factor influencing fruit acidity, par-

tially by increasing fruit shading and cooling.

Phenolics

0026 Phenolics constitute the third most significant group

of organic compounds found in grapes. Phenolics not

only donate the color to red wines, but also give them

their characteristic taste and aging properties. During

ripening, the anthocyanin content of red grapes both

increases and changes in composition. Because the

final distribution can significantly influence the hue,

intensity, and color stability of a wine, these changes

are of great importance to wine quality. White grapes

have a lower total phenolic content and do not syn-

thesize anthocyanins. Aside from seed phenolics, both

red and white grapes synthesize most of their phenolic

constituents in the skin.

0027 In addition to anthocyanins and tannins, red-skinned

cultivars contain flavonols, various benzoic acid and

cinnamic acid derivatives, and hydroxycinnamic acid

esters of tartaric acid. They are commonly glycosidically

linked to glucose, rhamnose, or glucuronic acid.

0028A small group of phenolic compounds, the stilbene

phytoalexins, has attracted considerable attention

recently. The major phytoalexin in grapes – resvera-

trol – is credited with many of the health benefits of

moderate wine consumption.

Pectins

0029Pectins function as the primary glue holding grape

cells together. Their retention at the end of ripening

provides table grapes with their traditional texture. In

contrast, pectin hydrolysis is critical to the softening

of wine grapes. Softening facilitates juice and flavor

release during grape crushing and minimizes the

likelihood of haze production in wines.

Lipids

0030The lipid component of grapes consists primarily of

the surface waxes (mostly oleanolic acid) and cutin

fatty acids, membrane phospho- and glycolipids, and

seed oils. Of these, the most significant are the long-

chain fatty acids on the surface of the skin. These

frequently act as important sources of unsaturated

fatty acids during wine fermentation. Although they

occur in minute amounts, oxidized carotenoid deriva-

tives from grapes generate important aromatic com-

pounds. Examples are damascenone, b-ionone, as

well as several norisoprenoids.

Nitrogen-containing Compounds

0031The concentration of nitrogen-containing com-

pounds in grapes is relatively low and has little direct

effect on taste or flavor. Nevertheless, one of the most

common amino acids in grapes (proline) may play a

significant role in limiting the cytoplasmic damage

caused by the rapid drop in osmotic potential associ-

ated with the storage of sugar during ripening. Also

important, but to wine quality, is the most common

peptide in ripe grapes, glutathione, which functions

as an important antioxidant early in wine fermen-

tation.

Aromatic Compounds

0032Compounds that give particular grape varieties their

distinctive aroma usually occur in trace amounts,

occasionally existing as a few parts per billion.

Typically, they accumulate as the grapes ripen. As

they collect, an increasing fraction may become

bound in nonvolatile complexes, such as glycosides,

polymers, or oxidized derivatives. This is particularly

noticeable with flavorants such as monoterpenes,

norisoprenoids, and nonflavonoid phenolics. In

tbl0003 Table 3 Major chemical constituents in grapes (% fresh

weight)

Constituent Range

Water 70–85

Carbohydrates 15–25

Glucose 8–13

Fructose 7–12

Pentoses 0.01–0.05

Pectins 0.01–0.1

Organic acids 0.3–1.5

Tartaric 0.2–1.0

Malic 0.1–0.8

Citric 0.01–0.05

Acetic 0.00–0.02

Phenolics 0.01–0.15

Anthocyanins 0.00–0.05

Tannins 0.01–0.1

Nitrogenous compounds 0.03–0.17

Amino acids 0.01–0.08

Ammonia 0.001–0.012

Minerals 0.3–0.5

Data from Amerine MA, Berg HW, Kunkee RE et al. (1980) TheTechnology

of Wine Making, 4th edn. Westport, CT: AVI.

GRAPES 2963

contrast, the concentration of a few impact com-

pounds declines near maturity (Figure 7).

0033 Most modern research confirms the belief that

most flavorants collect in the skin. Nonetheless, im-

portant aroma compounds such as linalool and TDN

(1,1,6-trimethyl-1,2-dihydronaphthalene) are stored

in the flesh.

0034 For several grape varieties, varietal distinctiveness

depends on the synthesis of one or a few related com-

pounds. Examples are the Cabernet group of varieties

that produce methoxypyrazines and Muscat cultivars

that produce monoterpenes. In other cultivars, though,

varietal distinctiveness seems to come from the unique

combination of many standard grape aromatics.

Examples are ‘Chardonnay’ and ‘Pinot noir.’

Cultivation

Training and Pruning

0035 Vineyard practice aims at obtaining the maximum

yield of fully ripened fruit, consistent with long-term

vine health. One of the major means of achieving this

goal involves training and pruning. Training usually

involves a support (trellis). The specific form chosen

depends on factors such as the prevailing climate,

harvesting practices, and the fruiting characteristics

of the cultivar. Associated with training is the pos-

itioning of fruit-bearing shoots in a microclimate op-

timal for grape quality, inflorescence initiation, and

shoot maturation. Pruning may involve the selective

removal of growing shoots, mature wood, leaves, or

excess numbers of flower or fruit clusters. However,

pruning typically refers to the removal of excess shoot

growth of the previous season during the winter or

early spring.

0036Central to effective grape culture is maintaining

just sufficient leaf area (for photosynthesis) to ad-

equately ripen the crop. This leaf area/fruit (LA/F)

relationship is related to the more familiar concept

of yield per hectare. It is more direct, though, by

focusing attention on the fundamental relationship

between the supply and demand for photosynthetic

energy. However, because of the complex, adaptive

nature of the grapevine, excess leaf area is often as

detrimental to grape quality as is insufficient foliage.

Excessive leaf area tends to promote extended shoot

growth, causing undesirable fruit shading and

directing nutrients away from the maturing grapes.

Thus, it is essential to neither over- nor underprune

grapevines. The appropriate level tends to be in the

range of 10 cm

of leaf surface per gram of fruit.

However, the value can vary considerably, depending

not only on the cultivar (Figure 8), but also on the

training system, soil nutrients, water supply, and

climatic conditions. The target is to establish the

optimal foliage canopy and placement to nourish

the crop to its ideal state of ripeness.

0037On relatively nutrient-poor, dry soils, the vine’s

inherent vigor must be restrained. This can be

achieved by dense vine planting (about 4000 vines

1

) and severe pruning (removal of > 90% of the

200

180

160

140

120

100

0 5 10 15 20 25 30 35 40

Grape colour (P.T.A units)

Leaf area/Fruit weight (cm

/g)

Pinot noir

Shiraz

fig0008Figure 8 Relationship between grape color and leaf area/fruit

weight ratio for ‘Shiraz’ and ‘Pinot noir.’ From Hand PG, Gawel R,

Coombe BG, and Henschke PM (1993) Viticultural parameters for

sustaining wine style. In: Stockley CS, Sas AN, Johnson RS,

Leske PA and Lee TH (eds), Proceedings of the 8th Australian

Wine Industry and Technology Conference, Adelaide, 16^19 July 1996,

pp. 167–169. Adelaide: Winetitles, with permission.

2468

Time (weeks) from 1st January

Methoxypyrazine concentration (ng/L)

Cabernet-Sauvignon

Sauvignon blanc

Veraison

fig0007 Figure 7 Decline in the concentration of grape methoxypyra-

zine with ripening. From Allen MS, Lacey MJ and Boyd SJ (1996)

Methoxypyrazines of grapes and wines. Differences of origin and

behaviour. In: Stockley CS, Sas AN, Johnson RS and Lee TH

(eds), Proceedings of the 9th Australian Wine Industry and Technol-

ogy Conference, Adelaide, 16^19 July 1996, pp. 83–86. Adelaide:

Winetitles, with permission.

2964 GRAPES

yearly shoot growth). However, on rich moist loamy

soils, wide spacing of the vines (about 1500 vines

1

) with limited pruning is preferable. Under such

conditions, the improved growth potential of the vine

must be directed into increased yield, not undesirable

vegetative growth. When an appropriate LA/F ratio is

developed, both fruit yield and grape quality increase.

Examples of training systems ideal for rich soils are

the Scott Henry trellis, the Smart-Dyson trellis, and

the Lyre. These systems not only achieve a desirable

LA/F ratio, but also provide better exposure of the

grapes to light and air. These features promote ideal

berry coloration, flavor development, fruit health,

and flower-cluster initiation.

0038 When considering pruning, many features need to

be considered, notably the prevailing climate, genetic

characteristics of the rootstock and bearing cultivars,

soil fertility, and training system. Of the forms avail-

able, most pruning systems can be categorized as

either spur or cane pruning.

0039 Spur pruning refers to the retention of only a short

shoot segment containing about two buds. It is easier

to perform, being effectively conducted by machine.

In addition, spur pruning restricts fruit production to

predetermined locations, making it particularly ap-

plicable to mechanical harvesting. The tendency of

spur pruning to limit productivity can be either

beneficial or detrimental, depending on the vigor

and bearing capacity of the vine. Berry size is gener-

ally reduced with spur pruning. This has the advan-

tage of increasing the grape surface area/volume ratio

and, thus, potentially enhancing a wine’s flavor and

color.

0040 Cane pruning involves retaining fewer but longer

shoots. These may contain upward of 20 or more

buds. Cane pruning is generally more popular in

cooler, more moist climates and with cultivars bear-

ing small fruit clusters. However, it must be con-

ducted by skilled workers and demands more shoot

support than is typical with spur pruning.

0041 Commonly accepted norms for the number of

shoots per meter of vine canopy fall in the range of

about 15 shoots per meter (positioned more or less

equidistantly along the vine). This assumes an

average of about 12–18 buds per shoot.

Grafting

0042 Most grapevines in commercial culture are grafted to

a rootstock. In much of the world, grafting is essential

to obtain resistance from a particularly devastating

root-infecting pest, the phylloxera root louse. In the

late 1800s, it decimated European grape culture until

grafting was introduced. In other areas, rootstocks

are required to achieve adequate protection against

nematodes, viruses, or saline soil conditions. Certain

rootstocks can also limit grapevine vigor in highly

fertile, moist soils.

Irrigation and Soil Fertilization

0043Irrigation is outlawed in most European countries, on

the mistaken belief that it is inherently detrimental to

grape quality. However, when used wisely, irrigation

not only permits grape growing in semiarid to arid

regions, but also enhances grape quality. In a process

called partial rootzone drying, selectively limited

water availability limits vegetative growth and favors

optimal fruit ripening. Irrigation can also be used to

simultaneously apply fertilizer and pest-control

chemicals to vines.

0044In comparison with other crops, grapevines have rela-

tively limited nutrient demands. This, combined with

the accumulation of nutrients in the woody parts of the

plant, makes assessing grapevine response to fertilizer

application particularly difficult. The primary method

of nutrient analysis is based on sampling plant tissue.

Optimal fertilizer addition is roughly equivalent to vine

requirements minus the amount already available in the

soil. Excessive application seldom enhances vine growth

or fruit quality, and can be detrimental to both the vine

and the environment.

0045Of inorganic nutrients, only nitrogen is often in

marginally short supply. The other two major inor-

ganic nutrients, potassium and phosphorus, are

seldom limiting. Vineyard soils are rarely deficient

in required micronutrients.

0046Organic fertilizers, such as compost or manure,

have many advantages over inorganic chemical fertil-

izers. These include improved soil texture and a more

even nutrient supply. However, the higher cost and

limited availability of organic fertilizers restrict their

more extensive use in commercial grape growing.

Improving Table Grape Quality

0047Grape quality is primarily achieved by the application

of the best cultural techniques, under climatic and soil

conditions ideally suited to the particular cultivar.

However, table grape production requires several prac-

tices unique to their cultivation. These include training

systems that permit the grapes to hang free, facilitate

manual picking, and protect against sunburn, as well as

the use of girdling and the application of growth regu-

lators. Of these, the most unique to table grapes are

girdling and the use of growth regulators.

0048Girdling typically involves the removal of a complete

strip of bark from trunks or bearing canes below the

clusters. This increases the supply of sugars to the fruit

by stopping their translocation below the cut. With

varieties that set poorly or are seedless, girdling shortly

GRAPES 2965

after pollination increases the number of grapes that

develop. Girdling also increases fruit size in seedless

cultivars. With table grapes, girdling at ve

raison can

improve fruit color and hasten maturation.

0049 Some of the advantages achieved by girdling can be

enhanced or replaced by the application of specific

growth regulators. Gibberellin is of particular use

in seedless cultivars, where it increases grape size. In

addition, gibberellin lengthens the stalks of fruit clus-

ters, improving spacing between the grapes. Im-

proved pigmentation can be achieved in colored

varieties by the application of ethephon.

Harvesting

0050 Choosing the harvest date is probably the single most

important viticultural decision taken yearly by the

grower. It sets a limit on the qualities of the grapes.

Timing usually is based on one or more chemical

analyses of the fruit. In cool climates, sugar content

is the primary indicator of maturity, whereas in

warmer temperate climates, the sugar/acid ratio is

often preferred. In either case, the accumulation of

sugar often correlates well with anthocyanin and fla-

vorant build-up in the fruit. Where the correlation

is poor, direct measurement of the anthocyanin or

flavorant content may be a better indicator of de-

sirable maturity (Figure 8). A new indicator of ma-

turity under investigation measures the glycosyl

glucose content. Because most grape flavors are gly-

cosidically bound, assessment of the glycosyl glucose

content may provide a direct indicator of flavor

potential.

0051 In addition to chemical indicators of maturity,

environmental factors that can reduce quality must

also be considered in choosing a harvest date. The

detrimental effects of early frosts and protracted

rainy periods on fruit quality are well known.

0052Until the development of mechanical harvesters in

the late 1960s, all grapes were harvested manually.

Except for table grapes and premium wine grapes,

labor shortages and market forces have combined

to favor machine harvesting. Mechanical harvesters

not only reduce harvesting costs (by up to 75%), but

also permit rapid harvesting. In comparative tests,

no clear sensory difference has been detected be-

tween wines produced from hand- and machine-

harvested grapes. The main mechanisms used by

mechanical harvesters in removing grapes are illus-

trated in Figure 9.

Packaging and Storage of Table Grapes

0053Because of the importance of appearance, table

grapes are trimmed of unsightly or diseased fruit

either in the field or in storage sheds before packing.

Packing must be done with due care to avoid

damaging the fruit. After packing, the containers

are placed in cool storage.

0054Cooling is particularly critical when the grapes are

shipped long distances. Cooling not only increases

fruit shelf-life (by suppressing respiration), but also

limits microbial activity. Cool temperatures also

retard water loss, browning, and separation of the

fruit from the cluster. If harvesting has occurred

under hot conditions, the fruit is usually precooled

to 10



C, before being placed in storage at near 0



Frequent fumigation of the storage area with sulfur

dioxide further helps limit decay organisms, fruit

browning, and fruit separation.

(a) (b)

fig0009 Figure 9 Two main methods of grape removal used by mechanical harvesters: (a) Pivotal strikers that strike the vine. (b) Pulsator

rods that shake the vine trunk. From Hamilton RP and Coombe BG (1992) Harvesting of Winegrapes. In: Coombe BG and Dry PR (eds),

Viticulture,Vol. 2, Practices, pp. 302–327. Adelaide: Winetitles, with permission.

2966 GRAPES

Raisin Production

0055 Table grapes, even with optimal storage, are a perish-

able crop. Our ancestors solved this problem by

processing grapes into either wine or raisins. Raisins

have a moisture content of between 10 and 15%,

the remainder being almost exclusively sugar. The

low moisture content and high osmolarity of the

sugar content effectively stop all microbial spoilage

activity.

0056 Most grapes used for raisin production are seed-

less, eliminating the need to remove the seeds. The

large-fruited ‘Sultana’ (‘Thompson Seedless’) is the

most widely grown raisin grape. The small-fruited

‘Black Corinth’ (‘Zante’) grape is used for currant

production.

0057 Natural drying, either in the sun or under shade,

produces the common dark purple–brown raisin of

commerce. The browning results from the enzymatic

oxidation of phenols released from cell vacuoles

during drying. Sun exposure also favors the produc-

tion of caramelized flavors. Submerging the grapes in

a mixture of potassium carbonate and a specially

formulated dipping oil disrupts the waxy fruit

covering, speeding up drying and producing a

golden-brown raisin. Yellow–gold raisins are primar-

ily produced by a hot bleach dip (about 4 s in a boiling

solution of dilute sodium hydroxide and sodium

sulfate). This is followed by rapid dehydration. Sulfur

dioxide in the bleach solution prevents the browning

that typically occurs during drying.

See also: Flavor (Flavour) Compounds: Structures and

Characteristics; Production Methods; Pectin: Properties

and Determination; Food Use; Phenolic Compounds;

Sensory Evaluation: Aroma; Taste; Wines: Types of

Table Wine; Production of Table Wines; Production of

Sparkling Wines; Dietary Importance