the aroma of muscat of frontignan grapes: effect of the light environment of vine or bunch on...

Journal of the Science of Food and Agriculture J Sci Food Agric 80:2012±2020 (online: 2000)

The aroma of Muscat of Frontignan grapes:effect of the light environment of vine or bunchon volatiles and glycoconjugatesSylvie M Bureau, Alain J Razungles* and Raymond L BaumesInstitut Superieur de la Vigne et du Vin, IPV-ENSA-INRA, UFR de Technologie-Oenologie, Unite de Recherche Biopolymeres et Aromes,2 Place P Viala, F-34060 Montpellier Cedex 01, France

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* CoRechE-ma

# 2

Abstract: Effects of the modi®cation of whole vine or individual cluster light environment by shade

cloth from berry set to maturity were studied on the volatiles and glycoconjugates in Muscat (Muscat of

Frontignan; Vitis vinifera L) berries over 2 years. Whole vines were shaded with 50 and 70% shade

cloth, while bunches were shaded with 90% shade cloth. The sun-exposed berries were chosen as

control berries, and the berries naturally shaded under foliage were also studied. The natural shading

of bunches under foliage did not decrease the levels of free and bound compounds in Muscat berries

compared to sun-exposed berries. The arti®cially shaded bunches showed lower levels of

monoterpenols and C13 norisoprenoids than sun-exposed berries and berries from naturally shaded

bunches. Moreover, the effect of vine shading on the aroma composition of Muscat berries was lower

compared to arti®cial bunch shading. In 1996 the leaf area/fruit yield ratio was modi®ed by decreasing

the bunch number per vine. This change did not in¯uence the total amounts of glycosidically bound

compounds, except for monoterpenic glycoconjugates. However, the higher monoterpenic glycocon-

jugate levels in these berries were likely related to their early maturity. Under our experimental

conditions, berry aroma composition did not appear to be affected by foliage shade.

# 2000 Society of Chemical Industry

Keywords: Vitis vinifera; grape; shade; sun exposure; aroma; volatile; glycoconjugate

INTRODUCTIONMuscat of Frontignan, a white aromatic cultivar, is

well known for its high levels of terpenoid compounds

and its ¯oral or fruity ¯avour.1±6 Its aroma potential is

characterised by odorous volatiles and ¯avourless

glycoconjugates. The latter, present in large amounts

in grapes and wines, make up an important aroma

source which can be hydrolysed to release odorant

compounds.7,8

The effect of sun exposure on metabolic activities is

complex. Direct sunlight on grapes can cause stress

either by dehydration or by temperature increase.9

Sunlight increases photosynthesis and can modify the

level of photosynthetic pigments in green tissue of

higher plants.10±12 Carotenoids, the synthesis of which

is light induced, are considered to be precursors of

C13 norisoprenoids,13±15 which can have interesting

olfactive properties.16 The effects of shading treat-

ments by shade cloth on the carotenoid composition in

Muscat berries were previously reported.17 Light

appeared to increase carotenoid levels in green berries

and to decrease major carotenoid levels during

ripening. Climate, vineyard, location and bunch

microclimate were also shown to modify the free and

eived 2 May 2000; accepted 12 June 2000)

rrespondence to: Alain J Razungles, Institut Superieur de la Vigne eterche Biopolymeres et Aromes, 2 Place P Viala, F-34060 Montpellieril: [email protected]

000 Society of Chemical Industry. J Sci Food Agric 0022±5142/2

bound monoterpene levels in grapes and wines.18±22

Previous studies have not separated the respective

effects of vine and bunch shading on the levels of

volatiles and glycoconjugates in Muscat berries. That

is the aim of this work.

MATERIALS AND METHODSPlant materials and treatmentsThe two experiments (1995 and 1996) were located in

two different zones of the Languedoc region. The two

vineyards used for the experiment were chosen

according to their homogeneity of soil and vegetal

material (Muscat of Frontignan; rootstock 110 Rich-

ter, clonal selection), giving a good homogeneity of

shoot lengths and of crop level per vine. Both

vineyards were close to the Mediterranean Sea (less

than 5km). Thus the climate was typically mediterra-

nean: sunny, dry and hot during summer (Table 1).

The soils were issued from hard limestone weathered

into red soil mixed with broken stones. Vine roots were

generally in the 30±70cm depth zone. The two

vineyards were trained with a vase system, short

pruned (two buds). No canopy manipulation was

du Vin, IPV-ENSA-INRA, UFR de Technologie-Oenologie, Unite deCedex 01, France

000/$30.00 2012

Table 1. General climatic data: daily means in the two experimental areas of Pech Rouge (1995) and Frontignan (1996)

Pech Rouge (1995) Frontignan (1996)

May June July August September May June July August September

Daily radiation (Jcmÿ2) 1984 2233 2203 1934 1361 2260 2577 2373 2041 1633

Rainfall (mmmonthÿ1) 9.5 0.5 9.5 10.7 65.0 25.9 26.8 29.4 62.9 64.2

Average temperature (°C) 16.5 20.9 24.7 24.0 18.9 17.0 22.3 23.8 22.8 18.3

Minimal temperature (°C) 11.3 15.2 19.5 19.0 14.3 12.2 16.6 18.6 17.7 12.6

Maximal temperature (°C) 21.7 26.7 29.9 29.0 23.6 21.7 27.9 29.0 27.9 23.8

Aroma of Muscat of Frontignan grapes

performed. Shoots were in a vertical or semi-vertical

position.

Experiment in 1995Plant materials. The experiment was conducted in a

vineyard of the INRA experimental station, Domaine

de Pech Rouge (Aude), France. Vine spacing was

1.1m in WNW/ESE-oriented rows, with 2.5m be-

tween rows.

Grapevine treatments. The imposed shading treat-

ments, placed just after berry set (20 June) (berries

reached about 2mm in diameter), were as follows.

. Su: berries from external sides of the bunches

exposed to direct sunlight (Su for sunny). The Su

berries received between 60 and 100% of total

sunlight radiation: 100% when the photoelectric cell

was held in the direction of the sun (control) and

60% when it was held perpendicularly to the sun

direction and parallel to the soil.

. B90: bunches shaded arti®cially by 90% shade cloth

(10% sunlight transmission).

. V50: vines shaded arti®cially by 50% shade cloth

(50% sunlight transmission).

. V90: vines shaded arti®cially vines by 90% shade

cloth (10% sunlight transmission). This 90% vine

shading delayed dramatically both ripening and

Table 2. Effects of vine of bunch shading on weight and sugar level of Muscat berr

1995

Su

B90 V50

AC IC AC

Photosynthetically active radiationa

(mmolmÿ2sÿ1) 1956 184 51 1052 1

(% of direct sunlight value) 100 9.4 2.6 53.8

Temperaturea (°C) 34.4 35.2 29.1 28.3

Berry weightb (g per berry) 2.05 2.15 1.86

pH (at 20°C) 3.65 3.90 3.50

Sugar (g lÿ1) 226 207 218

Total acidity (meqlÿ1) 71 59 94

Maturity indexc 3.18 3.50 2.31

Su, control berries exposed to direct sunlight; Sh, berries of bunches shaded under f

70% shaded vines respectively; AC, sensor placed above canopy; IC, sensor placa Mean of six measurements performed in July and August, under clear skies, fromb Values corresponding to samples of 100 berries.c Maturity index: sugar (g lÿ1)/total acidity (meqlÿ1).

J Sci Food Agric 80:2012±2020 (online: 2000)

growth of the berries. It was not treated in this work

and was replaced with 70% vine shading in 1996.

. Su: 40 sun-exposed bunches were selected (one per

vine). Sampling: the berries of the sun-exposed face

were only kept for analysis.

. V50 and V90: shading was provided by black

polyethylene shade cloth of different mesh sizes

(Diatex SA, Lyon, France). Vines were shaded with

four V50 and four V90 shading cages each contain-

ing three adjacent vines. Shade cloth cages, com-

prising a parallelepiped (5m�1m�2m) wooden

frame, were suf®ciently high and wide to permit

normal development of the canopy without packing.

However, a few shoots touched the polyethylene

shade cloth. Shading cages V50 and V90 were

located alternately in close rows. Sampling: for the

two treatments, 40 bunches were picked at random

from the 12 shaded vines.

. B90: 20 bunches, selected at random (one per vine),

were put in 90% shading bags (tube-shaped,

25cm�15cm diameter) of the same black poly-

ethylene cloth. They were located inside the canopy.

Samples. Bunches or pieces of bunches (Su) were

picked 37 days after the beginning of veraison (1

September). The maturity was different for each

modality (see Table 2).

ies

1996

Su Sh

B90 V50 V70

IC AC IC AC IC AC IC

25 1923 125 179 46 1011 113 496 67

6.4 100 6.5 9.3 2.4 52.6 5.9 25.8 3.5

27.1 34.1 28.3 34.9 28.7 28.1 27.3 27.9 27.2

2.23 2.40 2.25 2.43 2.42

3.65 3.64 3.74 3.50 3.60

203 194 203 197 192

57 72 65 79 94

3.56 2.69 3.12 2.49 2.04

oliage; B90, berries of 90% shaded, bunches; V50 and V70, berries of 50 and

ed inside canopy.

11:00 to 12:00.

2013

SM Bureau, AJ Razungles, RL Baumes

Experiment in 1996Plant materials. The experiment was conducted in a

vineyard of Vitis vinifera L cv Muscat of Frontignan in

a Domaine in Frontignan (HeÂrault), France. Vine

spacing was 1.1m in NE/SW-oriented rows, with

2.2m between rows.

Grapevine treatments. The imposed shading treatments

were placed just after berry set (berries reached about

8mm in diameter) (21 June). Five treatments were

carried out.

. Su, V50 and B90: these three treatments were the

same as used in the 1995 experiment.

. V70: vines shaded arti®cially by 70% shade cloth

(30% sunlight transmission) replaced the V90

modality of the previous experiment (1995).

. Sh: this new treatment was addedÐbunches shaded

under foliage. The Sh bunches received about 15%

of total sunlight radiation. Forty naturally shaded

bunches were selected at random from 40 vines.

. V50 and V70: shading was provided by black

polyethylene shade cloth of different mesh sizes

(Diatex SA, Lyon, France). V50 vines (10 adjacent

vines) were shaded with a 50% shade cloth cage

comprising a parallelepiped (14m�1m�2m)

wooden frame. V70 vines (15 adjacent vines) were

shaded with a 70% shade cloth cage

(22m�1m�2m). Shading cages V50 and V70

were located in close rows. Sampling: for the two

treatments, 40 bunches were picked at random from

the shaded vines for each treatment.

Samples. In order to limit the effect of maturation,

grapes were harvested at different dates with about the

same maturity (see Table 2). Su and Sh grapes were

picked 45 days after the beginning of veraison (2

September); V50 and B90 grapes were picked 48 days

after the beginning of veraison (5 September); and

V70 grapes were picked 52 days after the beginning of

veraison (9 September).

Modification of bunch number per vine in 1996The leaf area/fruit yield ratio was modi®ed by

diminution of the bunch number. This experiment

was carried out in 1996 in the same area of the above-

mentioned vineyard (Frontignan).

Grapevine treatmentsThe treatments were applied from berry set (25 June).

For each treatment, ®ve vines were chosen at random.

. V2: vine with two bunches per shoot (16±18

bunches).

. V1: vine with one bunch per shoot (eight or nine

bunches).

. V1/2: vine with half a bunch per shoot (half of the

bunches were cut off).

Samples. All the bunches of each treatment were

2014

picked at the same date (2 September). The maturity

indices of the three treatments were different (see

Table 5).

Light absorption and temperature measurementsLight was measured with a photoelectric cell sensitive

to visible radiation (400±700nm). This cell was

connected to a quantum radiometer/photometer (LI-

COR 190 SA Quantum Sensor). Six light and

temperature measurements were performed under

clear skies (three sunny days in July and three sunny

days in August) from 11:00 to 12:00. For all measure-

ments the photoelectric cell was held in a position

50cm from the soil (grape zone). The sensor axis was

oriented in the direction of the sun. In all situations the

photoelectric cell was held 10cm from an organ (leaf,

shoot) or, in the case of shade cloth, 5cm from the

inside surface of the bags and 40cm from the inside

surface of the cages. Inside the cages the measure-

ments were performed outside the canopy (AC) or

inside the canopy (IC). For the measurements inside

the bags the photoelectric cell was held in the direction

of the sun, with the bag maintained outside the canopy

(AC) or inside the canopy (IC). The mean values of

photosynthetically active radiation (PAR) received by

the sun-exposed grapes were 1956mmolmÿ2sÿ1

(1995) and 1923mmolmÿ2sÿ1 (1996). Each year the

value of light passing through the shade cloth was

compared to this value of direct sunlight and expressed

as a percentage of light absorption (see Table 2).

The ambient temperature outside the canopy and

the temperature in the cages were measured with a

thermometer, sheltered in a box, placed at cluster

height, on the row side opposite to the sun. The

temperature of the sun-exposed grapes was measured

with the same thermometer directly exposed to the

sun. The temperature inside the bags was measured

with the thermometer held in the bag 4cm from the

cloth surface. The mean temperatures are reported in

Table 2.

Extraction and gas chromatography analysis of freeand bound compoundsPreparation of samplesImmediately after harvest, grapes were washed, dried,

frozen at ÿ20°C and stored prior to analysis. Two

hundred grams of berries, picked at random, were

deseeded and ground under liquid nitrogen using a

Dangoumau ball grinder.

The powder (50g) was suspended in 100ml of pure

water containing 0.5g of D-gluconic acid lactone

(Sigma, Saint Quentin Fallavier, France) to inhibit

grape b-D-glucosidase.23 Five microlitres of 4-nonanol

(3.2g lÿ1) was added as internal standard. After

stirring for 15min at 4°C, the mixture was centrifuged

(9000�g, 20min, 3°C). The supernatant was ®ltered

through glass wool. The process was performed in

triplicate.



Fractionation of free and bound fractions of aromaThe free and bound fractions were separated by

adsorption/desorption on Amberlite XAD-2 resin

according to the method of GuÈnata et al3 as modi®ed

by Voirin et al24 and Razungles et al. 25

The clear juice was passed through the XAD-2

column at a ¯ow rate of 1mlminÿ1. The column was

rinsed with 100ml of pure water to eliminate sugars,

acids and other low-molecular-weight polar com-

pounds.

The free fraction was eluted with 50ml of pentane/

dichloromethane (2:1 v/v). The extract was concen-

trated to a ®nal volume of 400ml using Dufton and

Vigreux columns at 35°C.

The bound fraction was eluted with 50ml of

methanol. The methanol extract was concentrated to

1ml under vacuum (Rotavapor) at 35°C. The extract

was then transferred into a small tube and concen-

trated to dryness at 50°C under a nitrogen stream.

Enzymatic hydrolysis of bound fractionThe dried glycosidic extract was dissolved in 100ml of

citrate±phosphate buffer (0.2M, pH 5). The mixture

was washed ®ve times with 200ml of pentane/dichlor-

omethane (2:1 v/v) to eliminate possible traces of free

volatiles. Two hundred microlitres of enzymatic solu-

tion of Pektolase 3PA (70mg) (Grinsted, Brabrand)

with glycosidase activities b-D-apiofuranosidase

18.8nkat, a-L-rhamnopyranosidase 2.3nkat, a-L-ara-

binofuranosidase 212.9nkat and b-D-glucopyranosi-

dase 83.4nkat in 1ml of citrate±phosphate buffer

(0.2M, pH 5) was added. After stirring, the tube was

sealed and placed in a water bath at 40°C for 16h. The

mixture was then extracted ®ve times with 200ml of

dichloromethane. After addition of 5ml of 4-nonanol

(3.2g lÿ1) as internal standard the extract was con-

centrated to a ®nal volume of 400ml using a Vigreux

column at 47°C.

Gas chromatography (GC) and gas chromatography±mass spectrometry (GC±MS) analysisGC analysis. A Varian 6500 gas chromatograph

equipped with a DB-WAX fused silica capillary

column (J&W Scienti®c; 30m�0.32mm id, 0.5mm

®lm thickness) and an FID detector was used.

Operating conditions were as follows. The injector

temperature programme was set from 20 to 245°C at

180°Cminÿ1, then isothermal for 80min. The oven

temperature programme was set from 60°C (3min

isothermal) to 245°C at 3°Cminÿ1, then isothermal

for 20min. The detector temperature was held at

250°C. The hydrogen carrier gas ¯ow rate was

1.2mlminÿ1. One microlitre was injected.

GC±MS analysis. A gas chromatograph (Hewlett-

Packard 5890 Series II) was ®tted with the above-

mentioned column. Temperature programmes of the

injector and oven were as described above. The helium

N60 carrier gas ¯ow rate was 1.3mlminÿ1. A Hewlett-

Packard 5889 A mass spectrometer equipped with a


quadrupole detector was used for electron impact (EI)

mode spectra. The transfer line from GC to MS was

heated to 250°C. The source temperature was kept at

250°C. EI was recorded at 70eV in the mass range m/z29±350 at 1s intervals. Identi®cations were carried out

by linear retention index, EI mass spectra with

published data or with data from authentic com-

pounds. One microlitre was injected.

The analyses of the free and bound compounds in

Muscat grapes were performed in triplicate with an

internal standard (50g of powder each from the same

200g of berry powder; see `Preparation of samples').

The means of three concentrations and the standard

deviations are reported in the tables. For each

compound an analysis of variance was performed

between the sun-exposed control berries and each

shading treatment: the italicised values were signi®-

cantly different from the control at p<0.05.

RESULTS AND DISCUSSIONEffects of bunch or vine shading on berry weightsand sugar levelAn increase in canopy development was visually

observed for the Muscat vines shaded by the 50 and

70% shading cages (V50 and V70). Shading treat-

ments applied from berry set to maturity affected the

Muscat berry growth in 1996 (Table 2). The berries of

naturally shaded bunches (Sh) and shaded vines (V50

and V70) were larger than the berries of arti®cially

shaded bunches (B90) and sun-exposed bunches (Su).

Shading treatments generally caused a delay in

ripening. The berries of shaded bunches (B90 and Sh)

and shaded vines (V50 and V70) had lower maturity

indices than sun-exposed berries (Su), except for the

B90 berries in 1995 (Table 2).

Effects of bunch shading on volatilesIn 1996 the total amounts of C6 compounds were

greater in the berries of shaded bunches (B90 and Sh)

than in the sun-exposed berries (Su) (Fig 1, Table 3).

This was due to the increased amounts of hexanal and

E-2-hexenal in the B90 and Sh berries. This difference

could be explained by the lower maturity of the shaded

berries, as the levels of C6 aldehydes decrease during

fruit ripening.26,27

Bunch shading did not modify the levels of non-

terpenic alcohols (Table 3), but the total amounts of

terpenols were lower in the berries of arti®cially shaded

bunches (B90) than in the sun-exposed berries (Su)

(Fig 1, Table 3). This was observed for most terpenols.

According to Belancic et al,22 80% arti®cially shaded

Muscat of Alexandria berries had total free terpene

contents lower than those of sun-exposed berries. The

effects of bunch shading on free terpenol contents in

this study were in accordance with the photostimula-

tion of some enzymes involved in monoterpene

biosynthesis.28,29

In contrast with arti®cial bunch shading, the total

amounts of terpenols were higher in the berries of

2015

Figure 1. Influence of bunch or vine shading on volatile contents of Muscatgrapes (amounts in mgkgÿ1 grapes): Su, control berries exposed to directsunlight; Sh, berries of bunches shaded under foliage; B90, berries of 90%shaded bunches; V50 and V70, berries of 50 and 70% shaded vinesrespectively. Values are the mean of three replications. The vertical barsrepresent the standard error of the replicates. Treatments marked with anasterisk were significantly different from the sun-exposed C control berries(Su) (p<0.05).


naturally shaded bunches (Sh) than in the sun-

exposed berries (Su), particularly for linalool, nerol,

geraniol and geranic acid. Arti®cial shading by bags

produced a higher ambient temperature (2°C up)

without modifying the red/far-red ratio (660/730nm),

whereas natural shading produced a lower ambient

temperature (5°C down) and decreased the red/far-

red ratio, compared to full sunlight.30,31 According to

Reynolds and Wardle,18 differences in cluster tem-

perature could explain our results. Modi®cation of the

red/far-red ratio could modify the activity of phyto-

chrome, which regulates the 3-hydroxy-3-methylglu-

taryl-CoA reductase (HMG-CoA reductase) involved

in the biosynthesis of monoterpenes.32

Effects of bunch shading on glycoconjugatesArti®cial (B90) and natural (Sh) bunch shading did

not modify the levels of bound C6 compounds and

alcohols (Fig 2, Table 4). Nevertheless, in 1996 the

levels of benzyl alcohol and 2-phenylethanol were

higher in the shaded berries (Sh) than in the sun-

exposed berries (Su).

The total amounts of bound terpenols were lower in

the arti®cially shaded berries (B90) than in the sun-

exposed berries (Su), particularly for glycosidically

bound geraniol and geranic acid (Table 4), in

accordance with Belancic et al. 22 However, they were

higher in the naturally shaded berries (Sh) than in the

sun-exposed berries (Su), as previously observed for

Table 3. Influence of bunch or vine shading on volatiles in Muscat grapes (amounts in mgkgÿ1 grapes)a

Compound LRI

1995 1996

Su B90 V50 Su Sh B90 V50 V70

C6 compounds

Hexanal 1090 205.2�23.1 297.1�12.4 281.1�12.9 884.4�36.7 1123.5�85.3 1682.5�25.5 1442.9�43.9 1611.3�18.3

E-2-Hexenal 1222 83.9�6.3 77.9�2.1 90.4�4.1 1321.0�51.9 1797.5�148.8 2176.5�42.3 2075.8�46.7 2237.2�15.8

1-Hexanol 1356 169.9�12.3 228.0�8.7 196.1�8.7 432.9�10.6 380.1�25.5 255.7�3.2 265.9�2.3 309.9�5.7

Z-3-Hexen-1-ol 1387 29.2�2.8 32.9�1.0 18.0�0.7 44.9�1.4 49.6�4.0 44.0�1.1 51.1�1.0 33.3�1.1

E-2-Hexen-1-ol 1409 223.2�13.9 125.4�6.6 207.1�7.8 453.0�9.7 354.1�24.2 171.0�5.6 223.4�3.9 200.8�6.9

Total 711.4�57.8 761.3�30.1 792.7�32.8 3136.3�108.4 3704.8�286.5 4329.7�73.9 4059.1�88.4 4392.4�20.9

Alcohols

2- and 3-Methylbutanol 1210 62.8�2.4 90.2�6.1 77.7�8.4 13.0�1.0 17.8�0.8 10.0�1.2 10.8�0.8 10.7�0.7

3-Methyl-3-buten-1-ol�pentanol 1252 26.0�1.6 34.2�3.3 36.7�1.7 13.4�0.5 16.3�1.2 12.9�1.2 14.3�0.6 12.0�1.2

Benzyl alcohol 1870 256.1�11.2 327.6�8.5 267.9�11.0 39.3�1.4 57.7�3.7 38.2�0.2 57.8�0.9 61.0�2.9

2-Phenylethanol 1906 150.2�4.2 178.3�7.9 188.5�11.5 40.4�4.3 63.1�2.2 32.2�1.3 45.9�1.6 42.4�1.4

Total 495.1�10.1 630.2�24.4 570.8�31.7 106.1�3.7 154.8�5.9 93.3�1.1 128.9�3.0 126.1�3.6

Terpenols

trans-Furan-linalool oxide 1446 NQ NQ NQ 21.1�1.3 19.7�0.5 10.3�0.6 11.4�1.0 5.4�0.1

Nerol oxide�cis-furan-linalool oxide 1472 16.5�1.4 20.0�0.5 12.4�0.8 41.6�1.4 41.0�1.7 19.5�0.3 19.7�0.7 7.9�0.2

Linalool 1551 212.3�9.1 178.5�5.3 186.9�9.2 864.1�19.0 1007.2�32.6 499.1�3.0 678.0�8.9 334.0�5.8

a-Terpineol 1700 NQ NQ NQ 18.1�0.7 19.8�2.3 10.0�0.8 11.5�1.0 7.2�0.1

trans-Pyran-linalool oxide 1740 213.4�7.1 156.4�3.3 128.4�9.5 286.5�11.7 296.3�10.7 158.3�2.1 193.0�0.8 88.8�3.1

Citronellol�cis-pyran-linalool oxide 1767 80.9�10.6 81.1�2.6 53.1�4.7 96.0�3.1 99.5�2.4 65.4�1.2 56.7�0.5 37.4�1.9

Nerol 1802 501.0�15.7 442.2�9.6 318.9�14.2 119.7�2.9 171.0�4.0 107.3�0.9 127.0�1.3 132.2�4.3

Geraniol 1850 650.4�15.8 593.8�15.9 400.6�20.0 193.6�2.6 301.9�7.0 169.8�3.4 250.1�2.7 255.7�12.5

3,7-Dimethyl-1,5-octadien-3,7-diol 1951 24.2�2.2 21.0�2.4 19.4�2.1 18.7�1.7 22.8�4.0 4.2�0.3 7.5�0.6 3.8�0.4


Geranic acid 2333 697.7�19.4 553.9�28.4 636.0�71.4 301.8�17.8 477.6�11.6 159.1�20.6 373.7�19.8 340.1�17.5

Total 2405.7�41.7 2060.3�60.4 1768.6�102.5 2018.2�50.2 2513.4�48.8 1211.2�18.4 1753.9�34.0 1223.1�42.6

LRI, linear retention index calculated on DB-WAX capillary column; Su, control berries exposed to direct sunlight; Sh, berries of bunches shaded under foliage;

B90, berries of 90% shaded bunches; V50 and V70, berries of 50 and 70% shaded vines respectively.a Mean of three replications; the italicised values were signi®cantly different from the sun-exposed control berries Su (p<0.05); NQ, not quanti®ed.

2016 J Sci Food Agric 80:2012±2020 (online: 2000)

Table 4. Influence of bunch or vine shading on glycoconjugates in Muscat grapes (amounts in mgkgÿ1 grapes)a

Compound LRI

1995 1996

Su B90 V50 Su Sh B90 V50 V70

C6 compounds

1-Hexanol 1356 53.0�8.2 65.3�1.9 65.8�0.5 82.8�0.8 79.9�2.5 50.4�2.4 61.6�2.2 74.1�0.6

Z-3-Hexen-1-ol 1386 15.3�0.6 10.2�0.5 7.5�0.2 14.4�0.4 14.9�0.4 9.4�0.8 17.5�0.7 17.9�0.2

E-2-Hexen-1-ol 1408 48.0�0.9 33.0�0.8 53.5�0.4 24.1�0.1 33.1�0.9 12.9�0.5 26.9�1.3 28.0�0.2

Total 116.3�8.5 108.5�3.0 126.8�0.8 121.3�1.1 127.8�3.8 72.8�3.7 106.0�4.2 120.0�0.8

Alcohols

2- and 3-Methylbutanol 1210 41.4�10.1 113.7�5.1 63.6�1.3 57.8�2.0 50.4�3.4 53.1�4.1 39.6�4.4 50.7�0.9

3-Methyl-3-buten-1-ol�pentanol 1250 55.6�12.6 53.5�1.9 65.3�1.9 106.9�3.5 99.8�5.8 87.5�5.9 95.8�9.5 111.4�1.7

2-Methyl-2-buten-1-ol 1322 52.3�9.6 56.6�2.0 62.9�1.7 88.1�2.2 85.6�2.9 84.8�5.8 87.0�6.6 99.7�0.7

Benzyl alcohol 1870 548.7�30.4 521.1�11.3 644.5�1.9 415.5�3.2 522.7�7.6 436.6�25.1 600.1�3.3 751.9�10.7

2-Phenylethanol 1905 208.9�8.6 170.3�3.8 199.3�0.6 284.9�2.4 384.0�6.8 292.6�12.0 340.5�6.9 359.5�8.3

Total 906.9�70.4 915.0�23.9 1035.6�5.5 953.2�9.5 1142.5�3.7 954.6�51.7 1163.1�13.9 1373.2�15.7

Terpenols

trans-Furan-linalool oxide 1446 78.8�3.7 82.1�6.9 69.6�2.7 111.6�6.2 135.1�1.9 100.0�4.6 113.8�8.5 86.5�1.9

Nerol oxide�cis-furan-linalool oxide 1471 61.8�3.6 52.0�1.7 63.6�1.3 56.6�1.4 77.5�2.1 59.8�3.7 69.9�0.1 69.6�0.2

Linalool 1549 138.7�4.4 146.0�1.1 90.8�1.0 923.6�6.3 1053.2�4.1 487.1�20.3 753.7�13.7 510.9�5.3

a-Terpineol 1700 36.3�1.6 34.3�0.1 31.6�0.3 103.7�1.0 99.0�1.9 54.0�1.7 61.8�0.8 46.5�0.8

trans-Pyran-linalool oxide 1739 142.7�2.3 121.9�0.6 145.0�5.1 151.7�1.5 183.4�5.1 151.8�8.1 152.2�5.7 132.0�4.1

Citronellol�cis-pyran-linalool oxide 1765 48.1�1.4 45.0�0.7 62.4�1.7 134.3�2.1 161.6�4.7 107.5�2.2 124.9�4.9 154.9�7.4

Nerol 1800 452.5�18.0 430.6�16.5 418.2�14.5 1867.4�26.8 1738.7�24.7 1385.9�46.8 1493.6�54.5 1686.9�73.3

Geraniol 1848 398.9�18.6 285.7�23.7 301.5�15.7 1409.1�28.0 1246.7�30.5 975.6�20.0 1416.1�62.8 1850.2�105.


7-Hydroxy-6,7-dihydrolinalool 1982 26.3�0.4 20.6�0.7 20.0�0.6 68.4�1.3 79.7�1.1 40.7�1.8 50.9�3.4 31.1�1.9


7-Hydroxy-6,7-dihydrocitronellol�8-hydroxy-6,7-dihydrolinalool

2209 267.3�11.6 271.4�4.9 412.9�2.9 301.8�13.4 341.2�2.6 296.2�17.5 333.9�21.8 372.3�9.9

7-Hydroxy-6,7-dihydronerol 2268 96.6�4.6 92.9�1.3 91.5�2.2 139.7�4.2 170.6�7.3 144.2�10.3 157.0�12.5 129.9�3.8

E-8-Hydroxylinalool 2272 463.2�17.3 529.2�20.7 555.8�4.9 879.0�32.5 1093.9�12.1 611.9�33.9 893.2�61.0 670.2�5.9

Geraniol hydrate�Z-8-hydroxylinalool 2312 1140.2�49.7 936.1�49.3 1109.0�22.7 825.4�30.5 1062.6�14.9 855.0�41.7 1228.7�83.0 1102.0�18.6

Geranic acid 2331 514.5�8.5 182.2�4.8 325.7�9.6 2530.3�113.5 2418.1�22.5 1403.4�34.9 2616.5�177.9 2513.2�45.4

p-1-Menthen-7,8-diol 2519 48.1�2.5 54.6�2.1 63.0�3.0 50.4�1.7 66.4�1.1 57.3�3.2 62.0�4.0 63.0�1.8

E-8-Hydroxygeraniol�3-oxo-a-ionol 2629 105.1�3.2 73.1�2.9 114.3�3.7 156.8�6.6 167.3�2.6 124.2�3.6 207.3�15.1 221.2�2.4

Terpenic acid (MW=168) 2826 340.0�11.1 273.8�17.3 304.6�4.8 324.4�10.9 356.8�7.8 376.7�28.5 398.5�32.7 377.1�12.6

Terpenic acid (MW=166) 3135 199.2�19.8 107.9�12.2 144.4�16.3 292.3�18.8 445.6�24.4 294.0�31.0 474.9�21.0 560.5�42.2

Terpenic acid (MW=166) 3167 261.3�21.1 146.8�6.1 156.6�7.5 423.4�23.7 634.5�35.7 400.8�39.9 641.7�45.2 721.8�48.6

Total 5097.7�135.2 4212.6�150.9 4702.8�45.7 11751.3�318.6 12818.1�43.8 8420.9�384.6 12297.9�660.5 11944.1�322

Phenols

Vanillin�unknown 2545 32.3�0.4 32.8�1.8 48.7�3.6 38.3�3.0 42.7�0.3 42.4�2.2 52.5�4.2 58.5�3.7

Methyl vanillate�unknown 2600 104.0�5.6 119.3�6.4 111.9�3.7 164.0�4.2 177.8�3.0 162.9�15.9 229.1�17.9 293.2�7.5

Acetovanillone 2620 52.0�3.5 50.6�1.4 58.4�1.3 24.3�1.2 21.1�0.5 15.8�0.6 27.6�2.1 34.0�1.1

Vanilloyl methyl ketone 2800 29.5�1.9 10.1�1.0 4.8�0.5 8.0�0.7 13.1�0.5 4.4�0.4 12.0�1.5 20.0�0.7

Methyl-4-hydroxybenzoate 2932 27.4�1.4 36.6�3.4 17.1�0.2 56.8�1.4 61.0�4.1 36.4�3.8 79.0�5.7 89.5�2.6

3-(4-Guaiacyl)propanol 2970 47.9�1.7 21.0�1.7 21.3�1.7 8.8�0.3 10.2�0.9 15.9�1.5 20.6�2.3 14.4�0.3

3,4,5-Trimethoxyphenol 3044 39.3�3.7 42.8�2.6 59.5�8.0 19.3�1.1 22.7�1.2 20.2�0.6 23.1�1.7 27.6�2.2

Total 332.3�8.2 313.3�2.0 321.7�10.9 319.4�4.0 348.6�7.3 298.0�21.8 444.0�31.1 537.2�12.2

C13 norisoprenoids

3-Hydroxy-b-damascone 2532 41.2�4.1 29.6�0.8 34.8�0.6 32.2�1.7 48.6�1.3 34.4�2.5 56.4�3.3 49.9�2.4

Unknown norisoprenoid (MW=212) 2573 43.7�1.4 32.2�1.5 33.1�1.1 57.1�3.6 71.6�1.8 60.8�1.8 47.7�3.8 36.7�1.4

3-Oxo-a-ionol�E-8-hydroxygeraniol 2629 105.1�3.2 73.1�2.9 114.3�3.7 156.8�6.6 167.3�2.6 124.2�3.6 207.3�15.1 221.2�2.4

Unknown norisoprenoid (MW=210) 2647 6.4�0.5 2.7�0.4 2.7�0.1 74.9�2.0 87.4�2.8 28.8�1.9 68.3�4.7 54.8�4.2

3-Hydroxy-7,8-dihydro-b-ionol 2661 39.2�1.5 32.2�3.0 43.5�2.7 110.8�4.3 91.5�2.6 30.9�3.0 64.8�5.0 33.4�1.5

3-Hydroxy-b-ionone�unknown 2675 23.6�0.9 11.0�0.8 13.3�1.4 37.6�1.7 33.9�1.7 16.8�1.2 26.6�1.6 22.8�1.8

3-Hydroxy-7,8-dehydro-b-ionol 2749 32.3�1.7 30.6�0.8 35.5�1.5 41.1�1.3 51.7�2.6 34.6�1.2 66.5�3.7 69.7�5.5

4,5-Dihydrovomifoliol 3064 27.0�0.4 24.8�2.5 20.5�1.2 32.3�0.8 47.6�3.3 45.3�4.4 37.5�2.0 23.8�1.9

Vomifoliol 3128 168.6�12.9 141.8�11.0 171.0�15.2 173.0�6.3 186.7�5.6 145.4�8.3 249.9�12.0 193.5�3.1

Total 487.0�12.1 378.1�7.0 468.8�12.2 715.7�14.9 786.2�13.8 521.0�18.5 824.9�40.4 705.8�18.1

LRI, linear retention index calculated on DB-WAX capillary column; Su, control berries exposed to direct sunlight; Sh, berries of bunches shaded under foliage;

B90, berries of 90% shaded bunches; V50 and V70, berries of 50 and 70% shaded vines respectively.a Mean of three replications; the italicised values were signi®cantly different from the sun-exposed control berries Su (p<0.05).


free terpenols, but in disagreement with the observa-

tions of Reynolds and Wardle.18

The levels of bound volatile phenols were not

modi®ed by the bunch shading treatments (B90 and

Sh) (Table 4).

The total amounts of C13 norisoprenoids were

lower in the arti®cially shaded berries (B90) than in the


sun-exposed berries (Su) (Fig 2), but natural bunch

shading (Sh) slightly increased the levels of many C13

norisoprenoids (Table 4). Previous work on grape

berries showed that the total content of carotenoids,

the C13 norisoprenoid precursors, decreased between

veraison and maturity,33 and this decrease was less

important in shaded berries (B90 and Sh) than in sun-

2017

Figure 2. Influence of bunch or vine shading on glycoconjugate contents ofMuscat grapes (amounts in mgkgÿ1 grapes): Su, control berries exposed todirect sunlight; Sh, berries of bunches shaded under foliage; B90, berries of90% shaded bunches; V50 and V70, berries of 50 and 70% shaded vinesrespectively. Values are the mean of three replications. The vertical barsrepresent the standard error of the replicates. Treatments marked with anasterisk were significantly different from the sun-exposed C control berries(Su) (p<0.05).


exposed berries (Su).17 This could explain the lower

C13 norisoprenoid accumulation in shaded berries,

but it was not observed for Sh berries (Table 4).

Effects of vine shading on volatilesAs already observed for bunch shading in 1996, the C6

aldehyde levels were higher in the berries of shaded

vines (V50 and V70) than in the sun-exposed berries

(Su) (Fig 1).

The total amounts of non-terpenic alcohols were

slightly higher in the berries of shaded vines (V50 and

V70) than in the sun-exposed berries (Su) (Table 3).

In contrast, vine shading (V50 and V70) decreased the

accumulation of free terpenols in berries (Table 3), as

observed for arti®cial bunch shading. Geraniol and

nerol levels were particularly low in 1995, while linalol

was reduced in 1996.

Effects of vine shading on glycoconjugatesVine shading (V50 and V70) did not affect the C6

compound levels in berries (Table 4). However,

among bound alcohols it increased the benzyl alcohol

levels in 1995 and 1996 and the 2-phenylethanol levels

2018

in 1996. The levels of the two last compounds were

increased by natural bunch shading too.

The total amounts of bound terpenols were not

affected by vine shading (Fig 2), as previously

observed for natural bunch shading. Indeed, the levels

of bound linalool, a-terpineol, nerol and geraniol and

the levels of bound linalool oxides were generally lower

in the berries of shaded vines (V50 and V70) than in

the sun-exposed berries (Su), while the behaviour of

the monoterpendiols and terpenic acid glycosides

depended on both the year and compound.

The total amounts of bound volatile phenols were

not modi®ed in 1995 (Fig 2), but in 1996 the levels of

all compounds were higher in the berries of shaded

vines (V50 and V70) than in the sun-exposed berries

(Su) (Table 4).

The total amounts of bound C13 norisoprenoids

were not modi®ed by vine shading (V50 and V70) in

Muscat berries (Fig 2, Table 4). The carotenoid

content decrease, which was less pronounced in the

berries of shaded vines (V50 and V70) than in the sun-

exposed berries (Su),17 should have resulted in a lower

C13 norisoprenoid accumulation in shaded berries.

Thus there was no evidence of the relationship

between carotenoid degradation and C13 norisopre-

noid accumulation in these Muscat berries.

Except for alcohols, bunch shading (90%) de-

creased the levels of volatiles and glycoconjugates in

Muscat berries (Figs 1 and 2). However, partial vine

shading (50 and 70%) did not affect their levels. Berry

composition seemed to be more affected by bunch

shading than vine shading. Thus, to study the effects of

foliage on the berry aroma composition, an experiment

was simultaneously carried out in 1996. It consisted in

modifying the leaf area/fruit yield ratio.

Effects of bunch number per vine on berryglycoconjugate contentsThe leaf area/fruit yield ratio was modi®ed by

decreasing the bunch number per vine. If there were

a migration of glycosylated compounds from leaves to

grape berries, the arti®cial decrease in fruit quantity

should increase the accumulation of these compounds

in berries.

The bunch number decrease did not affect berry

growth, but it accelerated berry ripening (Table 5), in

agreement with Iacono et al. 34

The total amounts of glycosidically bound C6

compounds, alcohols, volatile phenols and C13

norisoprenoids were not modi®ed by the bunch

number per vine (Table 5). On the contrary, bound

terpenol levels increased when the bunch number per

vine decreased (Table 5). This could be simply due to

the early maturity of the V1/2 and V1 berries (Table

5), insofar as bound terpenol levels increase during

berry ripening.4,6,35 In this experiment, berry compo-

sition in terms of glycosidically bound C6 compounds,

alcohols, volatile phenols and C13 norisoprenoids

appeared to be independent of foliage. This could

explain our previous observation that berry composi-


Table 5. Effects of bunch number per vine onweight, sugar level and glycoconjugate contents ofMuscat berries (1996 treatment) (amounts inmgkgÿ1 grapes)

V2 V1 V1/2

Berry weighta (g per berry) 2.38 2.38 2.39

pH (act 20°C) 3.38 3.59 3.74

Sugar (g lÿ1) 163 184 215

Total acidity (meqlÿ1) 72 69 55

Maturity indexb 2.26 2.66 3.90

Glycoconjugates c

C6 compounds

Total 107.9�1.3 129.4�4.3 116.4�4.6

Non-terpenic alcohols

Total 908.0�25.4 890.7�3.6 904.7�5.2

Terpenols

Total monoterpenols 3164.8�66.5 4137.6�22.7 4692.5�6.8

Total monoterpendiols 3298.3�101.8 3806.5�60.9 4356.2�113.7

Total terpenic acids 3145.7�89.0 3147.4�116.5 3117.0�118.4

Total linalool oxides 412.7�4.9 469.7�4.8 482.6�7.6

Volatile phenols

Total 278.5�8.5 250.5�10.4 280.2�7.0

C13 norisoprenoids

Total 829.4�26.2 767.0�24.5 809.8�19.4

V2, vine with two bunches per shoot; V1, vine with one bunch per shoot; V1/2, vine with half a bunch

per shoot.a Values corresponding to samples of 100 berries.b Maturity index: sugar (g lÿ1)/total acidity (meqlÿ1).c Mean of three replications; the italicised values were signi®cantly different from the control berries V2

(p<0.05).


tion was more heavily in¯uenced by bunch shading

than by vine shading.

CONCLUSIONSBunch shading modi®ed the Muscat berry composi-

tion. Arti®cial bunch shading decreased the levels of

free and bound terpenols, high levels of which are

characteristic of Muscat cultivars, while natural bunch

shading within the canopy increased their levels.

Factors such as temperature and red/far-red ratio

could explain the opposite effects of these two shading

modes. Moreover, natural bunch shading did not

decrease the levels of bound volatile phenols and C13

norisoprenoids.

Whole vine shading decreased the levels of free

terpenols, particularly those at the oxidation level of

linalool. Moreover, vine shading changed the relative

compositions of bound terpenols and C13 norisopre-

noids without affecting their total amounts. These

changes in¯uence the ¯avour of grapes and wines.

Finally, the effect of cluster environment (light and

temperature) would be greater on Muscat berry

composition than the effect of vine environment.

ACKNOWLEDGEMENTSThe authors gratefully thank FrancËois Champagnol

(INRA, Montpellier) for valuable discussions. The

authors are greatly indebted to Jean-Paul Lepoutre

and Daniele Mascre for their technical assistance.


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the aroma of muscat of frontignan grapes: effect of the light environment of vine or bunch on...

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