The use of different oak products during the fermentation and ageing of Chenin Blanc : sensory properties, perceived quality, and consumer preference

Botha, Anri (2015-12)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: Wooden barrels have been the preferred method for oak maturation for wines, but the use of alternative oak products have increased options of oak maturation for winemakers, since new barrels are expensive and have a limited lifetime. The main aim of this study was to investigate the effect of different oak products used during fermentation and ageing on the sensory profile, degree of liking and perceived quality of Chenin blanc wine. The different wine treatments included an unoaked tank control wine, wines matured in 5th fill barrels, wines matured in new barrels from three different cooperages, and wines matured in 5th fill barrels with stave inserts from two different cooperages. All of the treatments, except for the unoaked tank control, were performed in triplicate, rendering a total of 19 experimental wines. Sensory descriptive data were obtained with Pick-K attributes, using a trained and expert panel at three different intervals of wine maturation. These intervals included 4 months oak maturation, 9 months oak maturation, and 9 months oak maturation with an additional 6 months bottle ageing. At the third maturation interval, an untargeted consumer study was also conducted using CATA questions to obtain descriptive and hedonic data. At this interval the perceived quality of the wines were also investigated using an expert panel. The expert panel received no formal training prior to any of the testing intervals. The trained panel were trained to recognise aromas from a list of 89 descriptors used by sensory scientists and industry experts to describe Chenin blanc wines. The results obtained from the different panels at the different ageing intervals were compared. The biological repeatability of the different treatments were satisfactory from a cooperage point of view. There were clear differences between the sensory profiles of the different wine treatments. Differences between the oak products from the different cooperages used within treatments were less pronounced. There were significant differences in the degree of liking and perceived quality of the different products, but the degree of liking and perceived quality for different products were comparable. The degree of liking and perceived quality of the 5th fill barrels and new barrels were higher than the degree of liking and perceived quality of the stave treatments. The mean degree of liking for the 5th fill barrels and new barrels were higher than for the stave treatments. There were no significant difference between the degree of liking for the unoaked tank wine and the oaked treatments. The sensory descriptive data obtained from the trained, expert and consumer panel were comparable in terms of panel consensus and configurational congruence. This validates the suitability of CATA and its variant, Pick-K attributes, as rapid methods to elicit qualitative information for the sensory profiling of wine. The results from this research made significant contributions towards method validation for CATA as rapid sensory method, and the descriptive and hedonic sensory results from this research can be used by winemakers to both inform and justify the usage of specific oak products.

AFRIKAANSE OPSOMMING: Houtvate word uit ‘n tradisionele oogpunt verkies vir wynveroudering, maar die gebruik van alternatiewe houtprodukte het meer opsies vir wynmakers beskikbaar gestel, aangesien nuwe vate duur is en oor ‘n beperkte leeftyd beskik. Die doel van hierdie studie was om die invloed van verskillende hout produkte op die sensoriese profiel, mate van goedkeuring en kwaliteitspersepsie van Chenin blanc wyne wat in kontak daarmee gefermenteer en verouder is te ondersoek. Die verskillende wynbehandelings het bestaan uit ‘n ongehoute tenkwyn, wyne verouder in vyfde vul vate, wyne verouder in nuwe vate van drie verskillende kuipers, en wyne verouder in vyfde vul vate met stawe van twee verskillende kuipers. Behalwe vir die tenkwyn, was al die behandelings in triplikaat uitgevoer, en in totaal was daar 19 eksperimentele wyne. Beskrywende sensoriese data is verkry deur die “Pick-K attributes” metode met die gebruik van ‘n deskundige- en opgeleide paneel by drie verskillende intervalle van veroudering. Hierdie intervalle sluit in 4 maande houtveroudering, 9 maande houtveroudering, en 9 maande houtveroudering met ‘n bykomende 6 maande bottelveroudering. Tydens die derde verouderingsinterval is ‘n ongeteikende verbruikerstudie ook uitgevoer deur gebruik te maak van die CATA metode om beskrywende en hedoniese data te verkry. Die kwaliteit van die wyne is ook tydens hierdie interval ondersoek deur ‘n deskundige paneel. Die opgeleide paneel was opgelei om Chenin blanc spesifieke aromas te herken vanaf ‘n lys van 89 beskrywers wat saamgestel is deur industrie deskundiges en sensoriese wetenskaplikes. Die resultate wat verkry is van die verskillende panele by die verskillende verouderingsintervalle is vergelyk. Die biologiese herhaalbaarheid van die verskillende behandelings was bevredigend vanaf ‘n kuiper perspektief. Daar was duidelike verskille tussen die sensoriese profiele van die verskillende wynbehandelings. Verskille tussen die houtprodukte van die kuipers wat binne spesifieke behandelings gebruik is was minder duidelik. Daar was beduidende verskille in die mate van goedkeuring en kwaliteitspersepsie van die verskillende produkte, maar die tendens van kwaliteitspersepsie en mate van goedkeuring was soortgelyk. Die mate van goedkeuring en kwaliteitspepsie van die vyfde vul vate en die nuwe vate was hoër as dié van die vyfde vul vate met die stawe. Daar was geen beduidende verskil in die mate van goedkeuring en kwaliteitspersepsie tussen die ongehoute tenkwyn en die gehoute behandelings nie. Die beskrywende sensoriese data wat verkry is van die opgeleide-, deskundige- en verbruikerspaneel was vergelykbaar in terme van paneelkonsensus en konfigurasionele kongruensie. Dit bekragtig die geskiktheid van CATA en sy variant “Pick-K attributes” as vinnige metodes om kwalitatiewe inligting vir sensoriese profilering te verkry. Die resultate van hierdie navorsing het ‘n groot bydrae gelewer om CATA as vinnige sensoriese metode te valideer. Verdermeer kan die beskrywende en hedoniese resultate wynmakers bemagtig om ingeligte en geregverdigde keuses te neem rakende die gebruik van spesifieke houtprodukte.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98006
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