The sensory characterisation of old-vine Chenin blanc wine : an exploratory study of the dimensions of quality

Crouse, Renee (2016-12)

Thesis (MScAgric)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Recently, there has been a lot of mention of the term ‘old‐vine’ in the media, the quality of the grapes they produce and the type of sensory profile they exude. Chenin blanc in South Africa is, historically, one of the first wine grape varietals cultivated in South Africa and is not only the most widely planted variety, but many of these vineyards are far over 20 years old. The aim of this research was to characterise a representative set of old‐vine Chenin blanc wines and determine what could define it as a product style category, using descriptive sensory analysis (DA). There is no formally defined age for an old‐vine, therefore, for the purpose of this study all old‐vine wines evaluated were 40‐years and older. In this study the focus was shifted from mainly concentrating on the aroma characteristics of the wines, as had been the case in previous Chenin blanc research, to include other aspects that are also associated with the intrinsic quality of wine. These aspects were referred to as ‘in‐mouth sensations’ and were selected by a focus group of industry professionals and expert panellists. The in‐mouth sensations included body, heat, acidity, balance, complexity, concentration, integration and length. This was the first time the DA panel had to evaluate these concepts in wine, therefore, extensive panel training was needed and a framework was created to aid in the analysis of these concepts. Due to the difficulty of the analysis, and the limitations of DA, the wines were analysed in two smaller sets, with a maximum of 10 wines per set. In general, information on the vines and the production practices of the wines investigated in this study, is fragmented and scarce. Qualitative research was, therefore, used by means of a questionnaire to give context on how the vineyards of the wines investigated in this study are managed and the winemaking techniques used to produce these wines. The old‐vine Chenin blanc wines were not all characterised by distinctive aroma attributes, but elicited a subtle array of aromas. The aroma profile of these wines was, therefore, described as complex. The wines had prominent, but different in‐mouth properties within the set. The sensory data also showed that body, balance, concentration, complexity and integration were all positively correlated and that acidity was negatively correlated to those concepts. The correlation between the in‐mouth sensations and physicochemical parameters was investigated as a secondary objective. Body had a strong positive correlation to ethanol, dry extract and reducing sugars. The results showed that the physicochemical parameters correlated with body, were also positively correlated to balance, concentration, complexity and integration. Therefore, the physicochemical composition of the old‐vine Chenin blanc wines had a large impact on the perception of in‐mouth sensations. The results obtained on in‐mouth sensations with DA, for the second set which included 10 wines, were compared to a reference based rapid method, polarised sensory positioning (PSP). PSP allowed for the analysis of a larger sample set (15 wines) and the results were similar compared to that of DA. This was the first application of this rapid method to wine. Therefore, this study provided insight into the sensory profile of the old‐vines wines of South Africa’s most important cultivar, Chenin blanc, and developed a framework for analysing in‐mouth sensations in wines, that could be applied in future research. The study also proved that PSP could successfully be applied to wine, which would allow for the analysis of more comprehensive sample sets. Lastly, the qualitative information gathered helped to identify opportunities for prospective research. Overall, research on the old‐vine Chenin blanc wines helps aid in the awareness of the quality and importance of these vineyards.

AFRIKAANS OPSOMMING: Onlangs is daar baie melding gemaak van die term "ou‐wingerdstok" in die media, die gehalte van die druiwe wat dit produseer en die sensoriese profiel van die wyne wat van hierdie ou‐wingerde gemaak word. Chenin blanc in Suid‐Afrika is, histories, een van die eerste wyn kultivars wat in Suid‐Afrika verbou is en nie net die mees geplante kultivar nie, maar baie van hierdie wingerde is ver meer as 20 jaar oud. Die doel van hierdie navorsing was om 'n verteenwoordigende versameling van ouwingerdstok Chenin blanc‐wyne te karakteriseer en te bepaal wat hierdie wyne as 'n produk kategorie kan definieer, deur gebruik te maak van beskrywende sensoriese analise (DA). Daar is geen formeel gedefinieerde ouderdom vir 'n ou‐wingerdstok nie, daarom, vir die doel van hierdie studie was die oud‐wingerdstok wyne beoordeel almal van wingerde wat 40‐jaar en ouer is. In hierdie studie is die fokus verskuif van hoofsaaklik konsentreer op die aroma eienskappe van die wyne, soos die geval is in vorige Chenin Blanc navorsing, om ander aspekte wat ook verband hou met die intrinsieke gehalte van wyn, in te sluit. Hierdie aspekte is na verwys as ‘binne‐mondse sensasies’ in hierdie studie en is gekies deur 'n fokusgroep met gesiende persone in die industrie en kundige paneellede. Die binne‐mondse sensasies het volheid, hitte, suur, balans, kompleksiteit, konsentrasie, integrasie en lengte ingesluit. Dit was die eerste keer dat die DA paneel hierdie konsepte in wyn moes evalueer, dus, is breedvoerige paneel opleiding nodig gewees en 'n raamwerk is geskep om te help met die ontleding van hierdie konsepte. As gevolg van die moeilikheidsgraad van die ontleding van hierdie konsepte, en die beperkinge van DA, is die wyne ontleed in twee kleiner stelle, met 'n maksimum van 10 wyne per stel. Inligting oor die wingerde en die produksie praktyke van die wyne in hierdie studie ondersoek, is oor die algemeen gefragmenteerd en skaars. Kwalitatiewe navorsing is dus gebruik, deur middel van 'n vraelys, om konteks te gee oor hoe die wingerde van die wyne wat in hierdie studie ondersoek is, bestuur word en die wynmaaktegnieke wat gebruik is om hierdie wyne te produseer. Die ou‐wingerd Chenin blanc‐wyne is nie gekenmerk deur prominente aroma eienskappe nie, maar het 'n subtiele verskeidenheid van aromatiese geure ontlok. Die aroma profiel van hierdie wyne is dus beskryf as kompleks. Die wyne het prominente, maar verskillende binne‐mondse profiele gehad. Die sensoriese data het ook getoon dat die volheid, balans, konsentrasie, kompleksiteit en integrasie almal positief gekorreleerd is en dat suur negatief gekorreleer is met al die konsepte. Die korrelasie tussen die binne‐mondse sensasies en fisiese‐chemiese eienskappe is as 'n sekondêre doelwit ondersoek. Volheid is sterk gekorreleerd met etanol, droë ekstrak en reduserende suikers. Die resultate het getoon dat die fisiese‐chemiese eienskappe wat gekorreleerd is met volheid, ook sterk gekorreleerd is met balans, konsentrasie, kompleksiteit en integrasie. Daarom het die fisiese‐chemiese samestelling van die ou‐wingerdstok Chenin blanc‐wyne 'n groot impak op die persepsie van binne‐mondse sensasies. Die resultate verkry op binne‐mondse sensasies met DA vir die tweede stel wyne, is vergelyk met 'n verwysing gebaseerde vinnige metode, gepolariseerde sensoriese posisionering (PSP). PSP het toegelaat vir die ontleding van 'n groter monster stel en die resultate was soortgelyk in vergelyking met dié van DA. Dit was die eerste toepassing van hierdie vinnige metode op wyn. Hierdie studie verskaf insig tot die sensoriese profiel van die ou‐wingerde wyne van Suid‐Afrika se belangrikste kultivar, Chenin Blanc, en het 'n raamwerk ontwikkel vir die ontleding binne‐mondse sensasies in wyn, wat in toekomstige navorsing toegepas kan word. Die studie het ook bewys dat PSP suksesvol toegepas kan word op wyn, wat sal toelaat vir die ontleding van 'n meer omvattende monster stel. Laastens, die kwalitatiewe inligting wat versamel is het gehelp om geleenthede te identifiseer vir toekomstige navorsing. Navorsing oor die ou‐wingerdstok Chenin blanc‐wyne dra by tot die bewustheid van die gehalte en belangrikheid van hierdie wingerde.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100114
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