Microclimate and grape ripeness effects on the phenolic composition of grapes and wine (Vitis vinifera L. cv. Shiraz/101-14 Mgt)

Minnaar, Phillipus Petrus (2018-12)

Thesis (PhD)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The study was aimed at the impact of canopy microclimate by means of grapevine row orientation (GVRO) and grape ripeness levels (GRL) on individual phenolics of Vitis vinifera L. cv. Syrah/101-14 Mgt grapes and wine. Grapes were harvested over four consecutive vintages at ca. 22°Brix, 24°Brix and 26°Brix GRL and representative of NS, EW, NE-SW and NW-SE GVRO. Wines were made from harvested grapes. Phenolics were quantified in lyophilised grape skin and wine samples. Treatment affects were distinguishable by HPLC and sensory analyses and confirmed by ANOVA, PCA and MFA. Grapes from NE-SW GVRO were highest in anthocyanins, flavonols and flavan-3-ols at ca. 22°Brix, whereas those from NW-SE GVRO were highest in anthocyanins, flavonols, flavan-3-ols, and phenolic acids at ca. 24°Brix. At a GRL of ca. 26°Brix, grapes from NW-SE GVRO were highest in flavonols and phenolic acids, whereas anthocyanins were highest from NS GVRO and flavan-3-ols highest from NS and NE-SW GVRO. Lowest anthocyanins and phenolic acids were in grapes from NW-SE GVRO at ca. 22°Brix GRL. Grapes at ca. 24°Brix and 26°Brix GRL from NS GVRO were lowest in flavonols. Flavan-3-ols seemed lowest in grapes from NS and NW-SE GVRO at ca. 24°Brix and 26°Brix GRL, respectively. At GRL of ca. 24°Brix and 26°Brix, lowest anthocyanins and phenolic acids were found for NE-SW GVRO. Wines from NW-SE GVRO had highest anthocyanins at ca. 22°Brix and 24°Brix GRL, but wines at ca. 26°Brix from EW GVRO had highest anthocyanins. Flavonols, flavan-3-ols and phenolic acids were highest in wines from NE-SW GVRO at ca. 22°Brix GRL. At a GRL of ca. 24°Brix and 26°Brix, wines from NS and NW-SE GVRO, respectively, were highest in flavonols, flavan-3-ols and phenolic acids. Lowest anthocyanins, flavonols, flavan-3-ols and phenolic acids were found in wines from EW GVRO at ca. 22°Brix GRL. Phenolic acids were also lowest in wines from EW GVRO at ca. 24°Brix GRL. At ca. 24°Brix GRL, lowest anthocyanins were found in wines from NS GVRO, lowest flavonols from NE-SW GVRO and lowest flavan-3-ols from NW-SE GVRO. At ca. 26°Brix GRL, lowest anthocyanins, flavonols and flavan-3-ols occurred in wines from NS GVRO and lowest phenolic acids from NE-SW GVRO. Phenolics, sensory attributes, GVRO and GRL were associated with each other. Sensory attribute scores of wines differed among GVRO. Wine quality was associated with NE-SW and NW-SE GVRO. Despite the complexity of impacting factors and different phenolics, results showed the likelihood that a chosen GVRO and GRL may affect wine style. Grapevine row orientation enables a “natural” change in canopy microclimate, leading to grape quality improvements. In practice, a desirable GVRO may not necessarily be applicable to all environments. Management of the fruiting zone remains an option for increasing or decreasing grape exposure, irrespective of GVRO. Further research is needed to understand the relationships of vine phenology, light intensity, temperature and GVRO with grape and wine phenolic profiles and wine quality. Phenolic concentration differences in wines in this study and association thereof with GVRO is important in oenology, because phenolics can be affected by vineyard practices, which may further lead to a desired wine style. However, phenolics of grapes and ultimately of wine, are affected by multiple factors, e.g. climate, grape cultivar, viticultural practices, GRL and berry size, all of which must be considered when a specific wine style is intended.

AFRIKAANSE OPSOMMING: Die studie was gemik op die invloed van lowermikroklimaat d.m.v. wingerdryrigtings (WR) en druifrypheidsgraad (DRG) op fenole van Vitis vinifera L. cv. Syrah/101-14 Mgt druiwe en wyn. Die druiwe was oor vier opeenvolgende seisoene by drie DRG, naamlik ca. 22°Brix, 24°Brix en. 26°Brix, geoes en wyn was gemaak. Die druiwe het NS, OW, NO-SW en NW-SO, WR verteenwoordig. Wingerryrigting verskille was onderskeibaar deur HPLC en sensoriese analises en bevestig deur ANOVA, PCA en MFA. Druiwe van NO-SW WR was die hoogste in antosianiene, flavonole en flavan-3-ole by ca. 22°Brix, terwyl dié van NW-SO WR die hoogste in antosianiene, flavonole, flavan-3-ole en fenoliese sure by ca. 24°Brix was. By ’n DRG van ca. 26°Brix, was druiwe van NW-SO WR die hoogste in flavonole en fenoliese sure, terwyl antosianiene die hoogste was in NS WR en flavan-3-ole die hoogste in NS en NO-SW. WR. Laagste antosianiene en fenoliese sure was in druiwe van NW-SO WR by ca. 22°Brix gevind. Druiwe van NS WR, by ca. 24°Brix en 26°Brix, was laagste in flavonole. Flavan-3-ole was oënskynlik laagste in druiwe van NS en NW-SO WR by onderskeidelik ca. 24°Brix en 26°Brix. By DRG van ca. 24°Brix en 26°Brix was die laagste antosianiene en fenoliese sure in NO-SW WR gevind. Wyne van NW-SO WR het die hoogste antosianiene by DRG van ca. 22°Brix en 24°Brix gehad, maar by ca. 26°Brix, het OW WR die hoogste getoon. Flavonole, flavan-3-ole en fenoliese sure was die hoogste in wyne van NO-SW WR by ’n DRG van ca. 22°Brix. By DRG van ca. 24°Brix en 26°Brix was wyne van onderskeidelik NS en NW-SO WR, hoogste in flavonole, flavan-3-ole en fenoliese sure. Laagste antosianiene, flavonole, flavan-3-ole en fenoliese sure het in wyne van die OW WR by ’n DRG van ca. 22°Brix voorgekom. Fenoliese sure was ook laagste in wyne van OW WR by ’n DRG van ca. 24°Brix. By laasgenoemde DRG was die laagste antosianiene in wyne van NS WR, terwyl laagste flavonole in dié van NO-SW WR en laagste flavan-3-ole in dié van NW-SO WR gevind. By ca. 26°Brix DRG het die laagste antosianiene, flavonole en flavan-3-ole in wyne van NS WR en die laagste fenoliese sure in NO-SW WR voorgekom. Fenole, sensoriese eienskappe, WRen DRG was met mekaar geassosieerd. Sensoriese eienskap punte van wyne het tussen WR verskil. Wyngehalte was met NO-SW en NW-SO WR geassosieerd. Ten spyte van die kompleksiteit van impakfaktore en verskillende fenole, het die resultate die waarskynlikheid getoon dat ’n gekose WR en DRG wynstyl kan beïnvloed. Wingerdryrigting bring ’n “natuurlike” verandering in lowermikroklimaat teweeg, wat lei tot druifgehalte verbeterings. In praktyk is ’n gewenste WR nie noodwendig vir alle omgewings toepaslik nie. Bestuur van drasone bly ’n opsie vir verhoging of vermindering van druifblootstelling, ongeag die WR. Verdere navorsing is nodig om die verband tussen wingerdfenologie, ligintensiteit, temperatuur en WR en druif- en wyn fenool profiele en wyngehalte te verstaan. Fenoliese verskille in wyne van hierdie studie en assosiasie daarvan met WR is belangrik in wynkunde omdat fenole deur wingerdpraktyke beïnvloed kan word en verder tot ’n gewenste wynstyl kan lei. Die fenoolinhoud van druiwe en uiteindelik die van wyn word egter ook deur faktore soos, klimaat, druifkultivar, wingerdpraktyke, DRG en korrelgrootte beinvloed, wat oorweeg moet word wanneer ’n spesifieke wynstyl beoog word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/104947
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