The effect of grape temperature on the phenolic extraction and sensory perception of Méthode Cap Classique wines

Mafata, Mpho (2017-03)

Thesis (MSc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The first sparkling wine in South Africa was released in 1971. The South African Cap Classique Producers Association (CCPA), formed for the appreciation of Méthode Cap Classique (MCC) traditional style sparkling wines (TSW), was established in 1992 and has since contributed to the growth of these wines on a competitive footing with the international market. Generally, studies on TSW have focused primarily on the foam capability, volatile composition and autolytic character of the wines and very little on phenolic content of the wines. Phenolic compounds are important quality indicators of wine. Their composition in wine is determined by various factors including grape variety, terroir, viticultural practice, and oenological practices. In this project, MCC wines were made by the traditional method using Chardonnay and Pinot noir grapes harvested from two regions (Robertson and Darling) and stored at 0, 10, 25 and 30ºC, over two vintages (2014 and 2015). The phenolic concentration of the wine samples throughout the winemaking process was analysed by spectrophotometer and the aroma and taste of the final 9 month old sparkling wines performed. The study was aimed at investigating the effect of the grape storage temperature on the phenolic content and the sensory properties of MCCs through a quantitative phenolic analysis. The study found that MCCs made from grapes stored at lower temperatures (0 and 10ºC) had lower total phenolic content, colour intensity and total hydroxycinnamates than wines made from grapes stored at higher temperatures (25 and 30ºC) showing that there was greater phenolic extraction from grapes stored at 25 and 30ºC. The total phenolics, as measured by spectrophotometer, was below the range cited in literature for Champagne made from the same cultivars. The sensory evaluation of the MCCs comprised a sorting analysis similar to that used for beers. Separating the aroma and taste sorting of the MCCs, the study showed a grouping of the MCCs according to temperature treatments for both vintages. There were, however, clear vintage differences in terms of the attributes cited and the frequency of citations. Based on frequency of citation, 2014 MCCs made from grapes stored at 0 and 10°C were described by judges as being fruity, fresh and crisp whilst those made from grapes stored at 25 and 30°C were described as having oxidised fruit, volatile acidity and solvent-like aromas. The judges perceived less oxidation and VA (in terms of the frequency of citation) in the aroma of 2015 MCCs, although higher temperature treatments were still associated with less desirable attributes compared to lower temperature treatments. Judges were better able to separate the Darling wines according to treatments compared to the Robertson wines. This study has shown that the grape storage temperature has an effect on the phenolic extraction and the sensory perception of MCCs aged 9-months with no changes in the phenolic content observed throughout winemaking.

AFRIKAANSE OPSOMMING: Die eerste vonkelwyn was vrygestel in 1971 in Suid-Afrika. Die “South African Cap Classique Producers Association” (CCPA) was gestig in 1992 vir die waardering van Méthode Cap Classique (MCC) tradisionele styl vonkelwyne (TSW), en het sedertdien bygedra tot die groei van hierdie wyne op 'n kompeteerende steunpunt met die internasionale mark. In die algemeen fokus studies wat gedoen is met TSW hoofsaaklik op die skuim vermoë, vlugtige samestelling en outoliese karakter van wyne en baie min op die fenoliese inhoud daarvan. Fenoliese verbindings is betekenisvol gehalte aanwysers van wyn. Die samestelling daarvan in wyn word bepaal deur ‘n verskeidenheid van faktore, insluitend druif variëteit, terroir, wingerdbou en wyn-kundige praktyke. In hierdie projek word MCC wyne gemaak volgens die tradisionele metode en strek oor twee oes jare (2014 en 2015). Chardonnay en Pinot Noir geoesde druiwe vanaf twee streke (Robertson en Darling) word gebruik en onderskeidelik gestoor by 0, 10, 25 en 30ºC. Die fenoliese konsentrasie van die wyn monsters deurgaans die hele wynmaak proses was geanaliseer met ‘n spektrofotometer en die aroma en smaak van die finale 9- maand oud vonkelwyne was uitgevoer. Die studie se hoof doelwit is om die uitwerking van die druif stoor temperatuur op die fenoliese inhoud en die sensoriese eienskappe van MCC te ondersoek met behulp van kwantitatiewe fenoliese analise. Die studie het bevind dat MCCs wat gemaak is van druiwe wat teen laer temperature (0 en 10ºC) gestoor was, het laer totale fenoliese inhoud, kleur intensiteit en totale hydroxycinnamates as die wyn van druiwe wat gestoor is by hoër temperature (25 en 30ºC). Dit toon dat daar beter fenoliese ekstraksie vanuit druiwe wat gestoor word by 25 en 30ºC verkry word. Die totale fenole, soos gemeet deur ‘n spektrofotometer, was benede die reeks aangehaal in literatuur vir Champagne wat gemaak is van dieselfde kultivars. Die sensoriese evaluering van die MCCs bestaan uit die ontleding van sortering, soortgelyk aan dié wat gebruik word vir bier. Die studie toon groepeering van die MCC’s volgens die temperatuur behandelinge vir beide oesjare met die skeiding van die aroma en smaak sortering van die MCCs. Daar was egter duidelik verskille in oesjaar in terme van die aangehaalde eienskappe en die aanhalings se herhalendheid. Op grond van die aanhaling se herhaling, die 2014 MCCs gemaak van druiwe wat gestoor is by 0 en 10ºC word beskryf deur die beoordeelaars as vrugtige, vars en fris, terwyl MCCs gemaak van druiwe gestoor by 25 en 30ºC beskryf word as geoksideerde vrugte, vlugtige suur (VA) en oplosmiddel-agtige geure. Die beoordelaars het minder oksidasie en VA (in terme van die herhaling van aanhaling) in die aroma van 2015 MCCs waargeneem, hoewel hoër temperatuur behandelings verbonde is met minder gewensde eienskappe in vergelyking met 'n laer temperatuur behandelings. Beoordeelaars was beter in staat om die Darling-wyne te skei volgens behandelings as met die Robertson-wyne. Hierdie studie toon dat die stoor temperatuur van druiwe 'n uitwerking het op die fenoliese ekstraksie en die sensoriese persepsie van 9-maand oud MCCs en geen verandering in die fenoliese inhoud was waargeneem deurgaans die hele wynmaak proses nie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101234
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