Berry tannin structure and phenolics evolution in cv. Cabernet Sauvignon (Vitis vinifera L.) : effect of light and temperature

Blancquaert, Erna (2015-12)

Thesis (PhD)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: This study investigated grape flavonoid (proanthocyandins, flavonols and anthocyanins) accumulation and composition in grape seeds and skins from Cabernet Sauvignon (Vitis vinifera L.) under altered light intensities and temperatures, within the bunch zone in the Stellenbosch Wine of Origin District. Furthermore, the study examined the link between wine sensory properties and the harvest date. This study was conducted in 2010/2011 and 2011/2012 and comprised of two main treatments with altered bunch microclimates in both seasons: no lateral shoot or leaf removal in the bunch zone (STD) and leaf removal in the bunch zone (LRW). The leaves were removed just after flowering on the western side of the canopy at the fruiting zone level (±35–40 cm above the cordon). Furthermore, to study the effect of change in light quality and quantity on fruit growth and composition, supplementary treatments were applied. In 2010/2011, a UV-B reducing sheet was added on the western side of the canopy to the STD (STD-UV-B) and LRW (LRW-UV-B) treatments. During the 2011/2012 season two types of UV-B reducing sheets were installed on both sides of the canopy to exclude the effect that the row direction can have on grape development. The latter resulted in the following treatments: LR (-UV-B, 2xOp50) and LR (-UV-B, 2xUHI). The accumulated thermal time varied between the treatments and within a season. The 2010/2011 season had a higher accumulated thermal time than the 2011/2012 season. There was a significant difference in the photosynthetic active radiation (PAR) (p≤0.001) among the treatments indicating that the applied treatment were successful in creating variation in the amount of sunlight intercepted in the bunch zone. There were no significant differences in berry weights in 2010/2011, but a significant difference were observed in 2011/2012 (p≤0.001). Light and temperature had little effect on grape seed flavan-3-ol monomer and dimer concentration and content. Seed development after flowering potentially influenced light quality and quantity which impacted the seed number and affected flavan-3-ol concentration and content. Grape skin flavan-3-ol concentration and content differed significantly among the treatments in 2010/2011, but not in 2011/2012. Generally, the seasonal impact was larger than those of the different treatments on flavonoid concentration and content during ripening resulting in significant differences among the treatments at harvest in the 2010/2011 season. However, treatment did not have a significant effect on either concentration or composition of a compound. Grape seed and skin (terminal and extension subunit) composition were influenced by the seasonal impact, rather than the treatment in both seasons. Moreover, the structural characteristics such as the percentage galloylation (%G), percentage prodelphinidins (%P), mean degree of polymerization (mDP) and average molecular mass (avMM) were influenced by seasonal variation. The accumulation of flavonols was higher in the exposed treatments and low in treatments with UV-B reducing sheets. This indicates that flavonol synthesis is highly dependent on UV-B radiation. The accumulation of anthocyanins commenced at véraison and had two distinct patterns of accumulation in the respective seasons. The 2010/2011 season was characterised by a higher anthocyanin concentration and content compared to the cooler 2011/2012 season. Grapes were harvested sequentially based on the sugar loading model at the fresh fruit stage (four treatments) and pre-mature (control treatment only) in 2010/2011. In the 2011/2012 season four treatments were harvested at the mature fruit stage. Identified aromas in the respective wines corresponded to the sugar loading model profile. Wine tannin, anthocyanin and flavonol concentrations were the highest in the LRW treatment in 2011/2012. Mouthfeel properties (adhesiveness, coarse, puckery – in and after expectoration) were rated higher in the treatments which were exposed to high light intensities in both seasons. This research denotes the complex nature of flavonoid biosynthesis and composition. Therefore further research is needed to elucidate impact of the functioning of individual genes in the phenylproanoid and flavonoid pathways which have an influence on the final concentration, content and composition of flavonoids at harvest.

AFRIKAANSE OPSOMMING: Hierdie studie ondersoek druifflavonoïde (proantosianidiene, flavonole en antosianiene) se akkumulasie en samestelling in druifsaad en -doppe van Cabernet Sauvignon (Vitis vinifera L.) onder veranderde ligintensiteite en temperature binne die trossone in die Stellenbosch Wyn van Oorsprong Distrik. Verder het die studie die verband tussen wynsensoriese eienskappe en die oesdatum ondersoek. Die studie is gedurende die 2010/2011- en 2011/2012-groeiseisoen uitgevoer en bestaan uit twee hoofbehandelings met veranderde mikroklimate in beide seisoene: geen laterale loot- of blaarverwydering in die trossone (STD) nie en blaarverwydering in die trossone (LRW). Die blare is verwyder net tot (±35–40 cm bo die kordon). Om die effek van ligkwaliteit en -kwantiteitverandering op die vrugontwikkeling en – samestelling verder te bestudeer, is aanvullende behandelings toegepas. In 2010/2011 is 'n UV-Bverminderingsplaat aan die westekant van die lower van die STD (STD-UV-B) en LRW (LRW-UV-B) - behandelings bygevoeg. Gedurende die 2011/2012- seisoen is twee tipes UV-B-verminderingsplate op beide kante van die lower geïnstalleer om die uitwerking wat die ryrigting op druifontwikkeling kan hê, uit te sluit. Laasgenoemde het tot die volgende behandelings, LR (-UV-B, 2xOp50) en LR (-UV-B, 2xUHI), gelei. Die geakkumuleerde termiese tyd het tussen die behandelings en binne 'n seisoen gewissel. Die 2010/2011- seisoen het 'n hoër geakkumuleerd termiese tyd as die 2011/2012- seisoen. Daar was 'n beduidende verskil in die fotosintetiese aktiewe bestraling (PAR) (p≤0.001) onder die behandelings, wat aandui dat die toegepaste behandeling suksesvol was om variasie te skep in die hoeveelheid sonlig wat in die trossone onderskep is. Daar was geen betekenisvolle verskille in korrelgewigte in 2010/2011 nie, maar 'n beduidende verskil is waargeneem in 2011/2012 (p≤0.001). Lig en temperatuur het ‘n geringe uitwerking op druifsaad se flavan-3-ol-monomeer en dimeerkonsentrasie en -inhoud. Saadontwikkeling na die blomperiode beïnvloed potensieel die ligkwaliteit en –kwantiteit, ingesluit die saad getal, en beïnvloed ook die flavan-3-olkonsentrasie en -inhoud. Die druifdop flavan-3-ol-konsentrasie en -inhoud het beduidend verskil tussen die behandelings in die 2010/2011-seisoen, maar nie in die 2011/2012-seisoen nie. Oor die algemeen was die seisoenale impak groter as dié van die verskillende behandelings op flavonoïd konsentrasie en -inhoud tydens rypwording, wat aanleiding gegee het tot aansienlike verskille tussen die behandelings by die oes in die 2010/2011-seisoen. Die behandeling het egter nie 'n beduidende uitwerking op die konsentrasie of samestelling van 'n verbinding gehad nie. Die druifsaad- en dop-(terminale en ekstensiesubeenheid) samestelling is beïnvloed deur die seisoen, eerder as die behandeling in beide seisoene. Verder is die strukturele eienskappe, soos die persentasie galloilasie (% G), persentasie prodelphinidiene (% P), gemiddelde graad van polimerisasie (mDP) en gemiddelde molekulêre massa (avMM) deur seisoenale variasie beïnvloed. Die akkumulasie van flavonole was hoër in die blootgestelde behandelings en laag in behandelings met UVB- verminderingsplate. Dit dui daarop dat flavonolsintese hoogs afhanklik is van UV-B-bestraling. Die akkumulasie van antosianiene begin by deurslaan en het twee afsonderlike patrone van die akkumulasie in die onderskeie seisoene getoon. Die 2010/2011-seisoen is gekenmerk deur 'n hoër konsentrasie antosianien en inhoud in vergelyking met die koeler 2011/2012-seisoen. Druiwe is opeenvolgende geoes, gebaseer op die suikerakkumulasiemodel by die varsvrugte- (vier behandelings) en voor-volwasse-stadia (kontrole behandeling alleen) in die 2010/2011-seisoen. In die 2011/2012-seisoen is vier behandelings op die volwassevrugtestadium geoes. Die wynaromas wat in die onderskeie wyne geïdentifiseer is, stem ooreen met die suikerakkumulasiemodelprofiel. Wyntannien-, antosianien- en flavonolkonsentrasies was die hoogste in die LRW-behandeling in die 2011/2012-seisoen. Mondgevoeleienskappe (klewerigheid, grofheid, sametrekkend - in en na ekspektorasie) is hoër in die behandelings wat blootgestel was aan hoë ligintensiteit in beide seisoene. Hierdie navorsing dui op die komplekse aard van flavonoïdbiosintese en -samestelling. Verdere navorsing is dus nodig op die impak van die funksionering van individuele gene in die fenielpropanoïd- en flavonoïd paaie, wat 'n invloed op die finale konsentrasie, inhoud en samestelling van flavonoïede by oes het.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98095
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