Research NoteSpraying ethanol (5 % v/v in water) onto grape clusters at mid-veraison led to a 30 % drop in the malic acid concentration at harvest. As a consequence, titratable acidity also dropped by 10 %. The concentration of tartaric acid did not change significantly. The mode of action of ethanol on malic acid metabolism is discussed.

Chervin, C.

Dedieu, F.

El-Kereamy, A.

Garcia, M.

Ibrahim, H.

Ollat, N.

Romieu, C.

Roustan, J. P.

English

JKI Open Journal Systems (Julius Kühn-Institut)

Vitis 41 (3), 155156 (2002)Research NoteEthanol application at veraisondecreases acidity in CabernetSauvignon grapesC. CHERVIN1), A. EL-KEREAMY1), H. IBRAHIM1), M. GARCIA1),F. DEDIEU2), C. ROMIEU3), N. OLLAT4) and J. P. ROUSTAN1)1) Ecole Nationale Supérieure Agronomique de Toulouse,Castanet, France2) Faculté de Pharmacie, Université Paul Sabatier-Toulouse III,Toulouse, France3) UMR Sciences pour lOenologie, INRA/ENSAM, Mont-pellier, France4) INRA, Centre de Bordeaux, Villenave dOrnon, FranceSummary: Spraying ethanol (5 % v/v in water) ontogrape clusters at mid-veraison led to a 30 % drop in themalic acid concentration at harvest. As a consequence,titratable acidity also dropped by 10 %. The concentrationof tartaric acid did not change significantly. The mode ofaction of ethanol on malic acid metabolism is discussed.K e y   w o r d s :  Vitis vinifera, ripening, malate, tartrate,ethanol, acidity.Introduction: As shown previously, spraying aqueoussolutions of ethanol onto Cabernet Sauvignon clusters atmid-veraison increased the ethylene concentration in ber-ries in comparison to controls sprayed with water (CHERVINet al. 2001). This is similar to results obtained after sprayingethanol solutions onto tomatoes (BEAULIEU and SALTVEIT1997). Since ethylene is known to increase plant cell respira-tion (ABELES et al. 1992) which is known to catabolise someof the malate pool in grapes (RUFFNER 1982), we studied theinfluence of ethanol sprays on grape acidity.Material and Methods: The experiments were conductedover three consecutive years (1999-2001) in a vineyard closeto Toulouse, southwestern France. Cabernet Sauvignonvines (Vitis vinifera L.) grafted to 110 Richter rootstocks(Vitis Berlandieri x V. rupestris) were used. Bunches weresprayed with an aqueous solution of ethanol (5 % v/v) us-ing a back-pack spray unit (200 l·ha-1). Controls were sprayedwith water. This was done when approximately 50 % of theberries had started to change colour, 8 to 9 weeks after fullbloom. Observations by HALE et al. (1970) suggest thatgrapes respond to ethylene only after veraison is initiated.At harvest, 8 weeks later, batches of 60 berries were pickedfrom a block of 5 vines. Three blocks were used per treat-ment. The experimental blocks were set up on different vineseach year. For analyses, berries were weighed and thenblended for 2 min in a Seb blender, 15 ml of this slurry werethen centrifuged for 3 min at 2,000 g at room temperature.Brix values were obtained with a hand-held refractometer(Atago, Japan) using 200 µl of clear supernatant. Titratableacidity was assessed using 5 ml of supernatant with0.1 NaOH (to a pH of 7.0). The concentrations of malic andtartaric acids were assessed by capillary electrophoresis onaliquots of the remaining supernatant as described byARELLANO et al. (1997).Results and Discussion: Compared to controls titratableacidity of grape juice at harvest was reduced by 11 % due toethanol sprayed at veraison (Table). This reduction was sig-nificant at the 0.05 % level, even though calculation wasbased on sets of data from three consecutive seasons withdifferent weather conditions and different sites in the vine-yard with individual effects on vigour and ripening (datanot shown). Detailed analyses of the two major grape acidsshowed that the decrease in acidity was due to a significantdecrease (33 %) in the malic acid content in ethanol-treatedgrapes, compared to the controls (Table). Tartaric acid con-centration was not significantly altered and there was nosignificant change in the pH of the must.The decrease in titratable acidity can be explained bythe change in malic acid content. Calculations showed thatcation contents were unaffected (Table). This may indicatethat there was no change in the rate of phloem loading be-tween ethanol-treated and control plants. Potassium accu-mulation was shown to be a continuous process in ripeningberries (POSSNER and KLIEWER 1985).Correspondence to: Dr. C. CHERVIN, Ecole Nationale Supérieure Agronomique de Toulouse, Institut National Polytechnique, Avenue del'Agrobiopole, BP 107, 31326 Castanet-Tolosan Cedex, France. Fax: +33-5-6219-3901. E-mail: chervin@ensat.frT a b l eBerry juice acidity and calculated cations at harvest, as a function of spraying Cabernet Sauvignon clusters at veraisonwith an aqueous ethanol solution (5 %); n=9 (over three seasons, 1999 to 2001)Malate Tartrate Titratable acidity pH Calculated cations(meq/l) (meq/l)         (meq/l)        (meq/l)Control 33.72 ± 10.28 46.54 ± 10.08 66.94 ± 5.75 3.38 ± 0.09 13.3Ethanol-treated 22.40 ± 5.85 50.90 ± 9.23 59.48 ± 7.13 3.34 ± 0.15 13.8t-test (P value) 0.016 0.380 0.035 0.530156 C. CHERVIN et al.The mean Brix values of the batches were not signifi-cantly different (19.2 ± 0.9 for controls and 20.0 ± 1.0 fortreated grapes; means ± SE with n = 9 over three seasons;t-test P = 0.114). Thus the differences in acidity induced byethanol cannot be explained by a global increase in maturity.They cannot be explained by a difference in berry weighteither (1.30 ± 0.21 g for controls and 1.29 ± 0.19 g for treatedgrapes; means ± SE with n = 9 as above; t-test P = 0.904).In a recent study, we reported that ethanol treatmentenhanced colour of red wines and suggested that ethanolaffects anthocyanin accumulation through an increased eth-ylene production (CHERVIN et al. 2001). The decrease in themalic acid content, observed here, agrees herewith, sincethe malate is a substrate of both respiration and gluconeo-genesis. The rates of both of these pathways happen to beincreased by ethylene (BEAUDRY et al. 1989; ABELES et al.1992). However, ethanol may also act independently of eth-ylene. It is well known that malate respiration begins simul-taneously with sugar accumulation in berries, just beforecolour changes (RUFFNER 1982; COOMBE 1992). The onset ofsugar storage is accompanied by a compartmentation break-down of the apoplast, phloem unloading strongly increas-ing as a result of xylem rupture (LANG and DÜRING 1991;COOMBE 1992; DREIER et al. 1998). Regarding the effects ofethanol on phloem unloading we got no clear indicationabout changes in water, sugars and potassium (berry weight,Brix and calculated cations). Malate respiration may resultfrom increased permeability of the vacuolar membrane (TER-RIER et al. 2001). Ethanol and its oxidation product, acetalde-hyde may conceivably increase malate decompartmentationand respiration (TERRIER and ROMIEU 1998).Whether the treatment could have commercial applica-tions or not will depend on further research on and develop-ment of commercial sprayers. Indeed the optimal ethanolconcentration will vary according to the spraying equipment.The authors are grateful to Dr. R. VAN HEESWIJCK (Adelaide,University, Australia) for fruitful discussions, to F. ATTIA for tech-nical help and to Dr. C. DAVIES (CSIRO, Adelaide) and anonymousreferees for valuable comments on the manuscript. They also thankthe French Embassy in Australia for supporting this study withvisiting fellowship grants.ABELES, F. B.; MORGAN, P. W.; SALTVEIT, M. E.; 1992: Ethylene in PlantBiology. Acad. Press, New York.ARELLANO, M.; ANDRIANARY, J.; DEDIEU, F.; COUDERC, F.; PUIG, P.; 1997:Method development and validation for the simultaneous deter-mination of organic and inorganic acids by capillary zone elec-trophoresis. J. Chromatogr. 765, 321-328.BEAUDRY, R. M.; SEVERSON, R. F.; BLACK, C. C.; KAYS, S. J.; 1989: Bananaripening: Implications of changes in glycolytic intermediateconcentrations, glycolytic and gluconeogenic carbon flux, andfructose 2,6-bisphosphate concentration. Plant Physiol. 91,1436-1444.BEAULIEU, J. C.; SALTVEIT, M. E.; 1997: Inhibition or promotion oftomato fruit ripening by acetaldehyde and ethanol is concentra-tion dependent and varies with initial fruit maturity. J. Amer.Soc. Hort. Sci. 122, 392-398.CHERVIN, C.; EL-KEREAMY, A.; ROUSTAN, J. P.; FARAGHER, J. D.; LATCHE, A.;PECH, J. C.; BOUZAYEN, M.; 2001: An ethanol spray at veraisonenhances colour in red wines. Aust. J. Grape Wine Res. 7, 144-145.COOMBE, B. G.; 1992: Research on development and ripening of thegrape berry. Amer. J. Enol. Viticult. 43, 101-110.DREIER, L. P.; HUNTER, J. J.; RUFFNER, H. P.; 1998: Invertase activity,grape berry development and cell compartmentation. PlantPhysiol. Biochem. 36, 865-872.HALE, C. R.; COOMBE, B. G. ; HAWKER, J. S.; 1970: Effects of ethyleneand 2-chloroethylphosphonic acid on the ripening of grapes.Plant Physiol. 45, 620-623.LANG, A.; DÜRING, H.; 1991: Partitioning control by water potentialgradient: Evidence for compartmentation breakdown in grapeberries. J. Exp. Bot. 42, 1117-1122.POSSNER, D. R. E.; KLIEWER, W. M.; 1985: The localisation of acids,sugars, potassium and calcium in developing grape berries. Vitis24, 229-240.RUFFNER, H. P.; 1982: Metabolism of tartaric and malic acids in Vitis: Areview  Part B. Vitis 21, 346-358.TERRIER, N.; ROMIEU, C.; 1998: Inhibition of vacuolar proton pumps byethanol impairs grape berry compartmentation. Aust. J. GrapeWine Res. 4, 39-45TERRIER, N.; SAUVAGE, F. X.; AGEORGES, A.; ROMIEU, C.; 2001: Changes inacidity and in proton transport at the tonoplast of grape berriesduring development. Planta 213, 20-28.

Ethanol application at veraison decreases acidity in Cabernet Sauvignon grapes

https://ojs.openagrar.de/index.php/VITIS/article/download/4470/4404

Ethanol application at veraison decreases acidity in Cabernet Sauvignon grapes

Abstract

Similar works

Full text

Available Versions

JKI Open Journal Systems (Julius Kühn-Institut)