Rapid Induction of Ageing Character in Brandy Products. Ageing and General Overview

Ageing is one of the most important and most costly factors determining the quality of distilled beverages.As part of a broader study that investigated techniques for the rapid induction of a desirable ageing characterin brandy products, the effect of maturation for eight months at room temperature and below 0°C inglass bottles, and the relationship/correlation between treatment, chemical composition or wood-derivedcongener concentrations and pot-still brandy sensory quality, are reported on. Extracts representing differentoak types (American or French), levels of toasting, suppliers (i.e. cooper or commercial), types ofmedium (ethanol or water), concentration types (open or reduced pressure) and concentration levels (by45, 65 or 85%) were added to pot-still spirit and stored for eight months in glass containers. Matured andunmatured (control) pot-still brandy samples were analysed for wood-derived compounds by means ofHPLC and GC. The different treatments brought about chemical changes with a noticeable impact on theacceptability of oak extracts and the overall quality of pot-still brandies. Through application and selectionof the correct oak type and treatment combinations, it therefore was possible to rapidly produce goodquality brandies without the use of expensive oak barrels. Maturation in glass bottles had a lesser impacton further improvement of the final product, not the same as the reported improvement from ageing inwooden barrels. The production of good quality brandies and the rapid induction of the ageing characterthrough certain treatment combinations, with little need for further maturation, therefore was achieved inglass. The complexity of brandies aged in glass rather than wooden barrels might be different, since ageingin wooden barrels brings about all the characteristics, complexities and flavours that characteristicallyevolve over time under the more oxidative conditions in wooden barrels. Future research should focus ona combination of both technologies, using certain oak treatment combinations together with traditionalbarrel maturation for the improvement and rapid induction of the ageing character in brandy products

Rapid Induction of Ageing Character in Brandy Products – Part II. Influence of Type of Oak

As part of a broader study that investigated techniques for the rapid induction of the needed ageing character in brandyproducts, the effect of oak type on quality and chemical composition of oak wood extracts and matured and unmatured potstillbrandy, is reported on. Extracts, prepared from American and French oak chips supplied by a South African cooper,and from commercially obtained oak, and representing different levels of toasting, were added to 70% (v/v) unmaturedpot-still brandy and stored for eight months in glass containers (Schott bottles) at room temperature, or in the case ofcontrols, below 0°C. Matured and unmatured (control) pot-still brandy samples were analysed for wood-derived congenersby means of HPLC and GC. Although French oak initially yielded better quality products, these effects lost prominenceand, after eight months maturation, yielded similar sensory quality to American oak. French oak samples had higherconcentrations of wood-derived congeners (including eugenol, the furan derivatives and aromatic aldehydes). However,the American oak generally contained higher concentrations of oak lactones than their French counterparts, with higherproportions of the more sensorially potent cis-form of lactone than its trans-isomer

Rapid Induction of Ageing Character in Brandy Products – Part III. Influence of Toasting

As part of a broader study that investigated techniques for the rapid induction of the needed ageing character inbrandy products, the effect of oak wood toasting on quality and chemical composition of oak wood extracts andmatured and unmatured pot-still brandy, is reported on. Extracts, prepared from oak chips supplied by a SouthAfrican cooper, and from commercially obtained oak, and representing different oak types and levels of toasting(i.e. untoasted, light, medium and heavy), were added to 70% (v/v) unmatured pot-still brandy and stored for eightmonths in glass containers (Schott bottles) at room temperature, or in the case of controls, below 0°C. Matured andunmatured (control) pot-still brandy samples were analysed for wood-derived congeners by means of HPLC andGC. Toasted, as opposed to untoasted oak, gave acceptable extracts, the best overall quality pot-still brandies andgenerally higher concentrations of volatile (GC-determined) and less volatile (HPLC-determined) wood-derivedcongeners. Toasting provoked an important separation as indicated by discriminant analysis

Attempted Identification of Causal Constituents of Pink Discolouration in White Wines

The pinking phenomenon has been known in the wine world for the past 50 years. The phenomenonoccurs when a white wine turns pink under certain conditions. Since then, a Portuguese study foundmalvidin-3-O-glucoside in Siria grapes making a connection to anthocyanin as the causing agent. Control(K), naturally pinked (NP) and pink induced (PI) Sauvignon blanc wine samples were analysed by LCMSand WineScanTM (Fourier Transform Infrared – FTIR) after Solid Phase Extraction. The monomericanthocyanins were analysed by a pH differential method, and CieLab was used to differentiate colourdifferences between the control and pinked samples. It was found that malvidin-3-O-glucoside was belowthe threshold values to facilitate pinking in Sauvignon blanc wines. Petunidin-3-O-glucoside showed aslight peak in the LC-MS analysis, and together with the malvidin-3-O-glucoside, the potential to pinkthe white wines increased. FTIR results showed that phenols and anthocyanins absorption could not bedistinguished and that there were possibly other compounds involved in the pinking of white wines. Analysisby CieLab expressed the PI wines as a darker pink colour than the control wine and the absorbency valueat 500 nm was at least three times higher for PI than the control, showing the aggressive oxidative natureof H2O2 on wine

Rapid Induction of Ageing Character in Brandy Products – Part I. Effects of Extraction Media and Preparation Conditions

The purpose of this study was to investigate the use of different wood types and treatments, and extraction mediato induce rapid ageing of brandy. Extracts were prepared from American and French oak, specially preparedand supplied by a cooper, and from commercially obtained oak; both representative of different toasting levels,including untoasted, light, medium and heavy toasted. To extract the wood components, wood chips in either 55%(v/v) neutral wine spirits or water media were boiled under reflux. Distillation was followed by either open (higherboiling temperature) or closed (vacuum or reduced pressure – lower boiling temperature) concentration of thedecanted solvent by 45, 65 and 85% (v/v). The concentrated extracts were fortified. Screened extracts were addedto unmatured pot-still brandy and aged for eight months at room temperature in glass containers. Controls werestored below 0°C. Matured and unmatured (control) pot-still brandy samples were analyzed for wood-derivedcongeners by means of HPLC and GC. This article focuses on the effects of the extraction media, and on level andmethod of concentration (open and reduced pressure) on sensory quality and chemical composition. The treatmentsthat gave acceptable extracts, and the best overall quality pot-still brandy were those that entailed (1) using ethanolinstead of water as extraction medium, and (2) levels of concentration above 45% (v/v). Open and reduced-pressureconcentrations showed little difference in the quality of the products yielded. Treatments yielding the most acceptableextracts and best overall quality pot-still brandy generally also contained higher concentrations of volatile andless volatile wood-derived congeners. Multivariate data analysis was conducted on the pot-still brandy samplesrepresenting the different treatments. Discriminate analysis provided better separation of samples than principalcomponent analysis

Effect of Juice Turbidity and Yeast Lees Content on Brandy Base Wine and Unmatured Pot-still Brandy Quality

The aims of this project were to identify a suitable grape juice clarification technique for the attainment of the optimal brandy base wine turbidity, to determine the importance of chemical components (volatile components and long-chain fatty acids) in brandy base wine and unmatured pot-still brandy quality, and to study the effect of yeast lees content on quality. Although common industry practice is to use the grape cultivars Colombar(d) and Chenin blanc for the production of brandy base wine, the optimal conditions for Chenin blanc have been defined in this study. The juice clarification treatments applied included no settling, cold settling, whisk, large- and small-scale centrifugation and bentonite. Yeast strain 228 was compared with VIN13, large-scale (L) distillation was compared with small-scale (s) distillation, and the use of no enzyme was compared with the use of pectolytic enzyme. The data for four vintages were compiled and evaluated. Settling with or without pectolytic enzyme, bentonite, small-scale centrifugation and whisk treatments gave clearer Chenin blanc juice, higher concentrations of certain volatile components and long-chain fatty acids, and higher quality brandy base wine and unmatured pot-still brandy. No settling and large-scale centrifugation yielded the most turbid and lowest quality products. There is a definite relationship between treatments, turbidity, concentrations of esters, higher alcohols and acids, and overall brandy base wine and unmatured pot-still brandy quality. The use of yeast strain VIN13 (as opposed to strain 228), in conjunction with an increased yeast lees content of 1.5x that is normally found in brandy base wine, yielded the best quality unmatured pot-still brandy. Based on the results of this study, it is possible to recommend the best juice clarification method(s) for optimal turbidity as well as optimal levels of yeast lees addition, and to identify chemical compounds that positively relate to quality

The Effect of Grape Temperature on the Sensory Perception of Méthode Cap Classique Wines

The production process of South African bottle-fermented sparkling wine, the Méthode Cap Classique (MCC), follows the traditional French method (méthode champenoise), although each cellar has its own unique additions to the method. South African winemakers use different techniques and blends to achieve their award-winning MCCs, but there have not been many scientific investigations of the science behind these wines. This project is one of the first scientific studies on MCC. MCC wines were made using Chardonnay and Pinot Noir grapes harvested over two vintages (2014 and 2015) from two regions (Robertson and Darling) and stored at 0°C, 10°C, 25°C and 30°C before processing. The study was aimed at investigating the effect of grape storage temperature on the sensory characteristics of MCCs. The aroma and taste of the final nine-month old MCCs were evaluated, with each region analysed separately. The study showed a grouping of the MCCs according to temperature treatments for both vintages. There werevintage differences in terms of the attributes cited and the frequency of citations. Based on the frequency of citation, the MCCs made 2014 from grapes stored at 0°C and 10°C were described by the judges as having a fruity, fresh and crisp aroma, whilst those made from grapes stored at 25°C and 30°C were described as having oxidised fruit, volatile acidity and solvent-like aromas. The judges perceived less oxidation and volatile acidity (VA) (in terms of the frequency of citation) in the aroma of the 2015 MCCs, although treatments at higher temperatures were still associated with less desirable attributes compared to treatments at lower temperature. This study shown that the temperature of the grape at the time ofprocessing has a significant effect on the aroma of MCCs aged nine months, and not so much of an effect on the taste