Doctoral Degrees (Viticulture and Oenology)

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Browsing Doctoral Degrees (Viticulture and Oenology) by Author "Bougas, Nina Valleska"

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    Factors influencing the style of brandy
    (Stellenbosch : Stellenbosch University, 2014-04) Bougas, Nina Valleska; Van Rensburg, Pierre; Lambrechts, Marius; Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology.
    ENGLISH ABSTRACT: Brandy producers in South Africa can produce three categories of brandy, and within those categories, varies styles in order to cater for diverse consumer needs. Thus they have divergent opinions as to what comprises a good base wine and distillate for their individual end-product style in mind. Due to the fact that brandy is the largest locally produced spirit in South Africa, it is crucial to investigate the factors that influence the production of brandy as better understanding and control of these processes leads to the production of a brandy that is more consistent in quality and in style. The factors known to influence the quality of brandy are the grape cultivar, vinification techniques, distillation and the oak maturation process; however limited research has been done on the factors contributing to the style of brandies. Understanding and identifying the factors that contribute to the style of brandy, will allow for better control and manipulation of the process to ultimately produce a spirit product with a desired style classification. In order to do so, one must distinguish as to what differentiates (chemical and sensory analyses) the two most divergent styles of brandy (in this study referred to as class one and class five three-year barrel matured brandy). Over 104 three-year old barrel matured brandy samples were collected and analysed using GC-FID and HPLC analysis over a three year period. Of these samples, only 7 were classified as a class one three-year barrel matured brandy and 23 were found to be classified as class five three-year barrel matured brandy. The results obtained showed that the class one samples were found to contain a higher concentration of total higher alcohols, higher ratio of higher alcohols vs. esters, higher alcohols vs. acids and aldehydes vs. esters, but a lower level of total esters and acids. The class five samples contained a higher concentration of total esters, furans, lactones and acids, but a lower level of total higher alcohols and ratio of higher alcohols vs. esters. The factors investigated that possibly influence the style of brandy were: the base wine prior to distillation, yeast strain, fermentation temperature, condenser water temperature and barrel age. Results of the base wine analysed prior to distillation show that those samples that scored a sensory score of one could produce a class one three-year barrel matured brandy, and base wines that scored a sensory score of five would yield a class five three-year barrel matured brandy. Alchemy 1 yeast was found to produce elevated levels of total esters and could by default result in a class five three-year barrel matured brandy. Similarly if the wine was fermented at 24⁰C it would result in the increased production of higher alcohols and total acids and in-turn could yield a class one three-year barrel matured brandy. The results obtained show that the different condenser water temperatures do not necessarily influence the concentration of esters and higher alcohols. However, if a lower condenser water temperature (8⁰C) was employed, it could yield a class one barrel matured brandy sample. These distillates are associated with a higher concentration of total higher alcohols and even though they may be positively associated with higher levels of esters, the esters could be removed during the head fraction in the distillation process. The results also show that during the maturation process that the use of 18 year old barrels for the maturation of three-year barrel matured brandy samples could possibly produce a class one three-year barrel matured brandy and the use of new barrels could yield a class five three-year barrel matured brandy sample. It is recommended that analysing the base wine prior to distillation using GC-FID to identify the chemical composition is the most important step in determining the outcome of the style of brandy.