Identification of the major drivers of 'phenolic' taste in ... - GWRDC

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AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines 8 Sensory Characteristics of Different Phenolic Composition Brought About by Variations in Winemaking 8.1 Introduction We aimed to produce a set of white wines that varied enough in phenolic composition to elicit measurable differences in both taste and texture. A mix of both conventional and less practiced white wine making techniques were used over two vintages. Hyperoxidation and skin contact were two processes conducted pre-fermentation. Wines were also made from musts that were high in solids, consisted of light and heavy press fractions, or included a small proportion of whole berries. Most winemaking treatments were repeated over two years (2010 and 2011) using the same varieties, and in the case of Riesling and Chardonnay the fruit was sourced from the same vineyards. Therefore, in addition to providing wines of varying phenolic profile that could be used to identify those responsible for ‘phenolic taste’, the work had the potential to provide preliminary data on the effect of maceration and other aspects of juice handling on the phenolic profile and tastes/textures in white wine. However, it should be noted that while fermentations were conducted in duplicate to ensure an adequate set of sound wines with similar basic analysis, the winemaking treatments were not replicated within each vintage. 8.2 Methods 8.2.1 Winemaking Treatments Musts were vinified over two vintages (2010 and 2011) from both low and high phenolic varieties to create a set of wines with divergent phenolic composition. The treatments applied are given in Table 8-1. Grape Sources The Riesling and Chardonnay grapes were sourced from the Orlando St Helga vineyard (Eden Valley, South Australia) and the Jacob’s Creek Lyndoch vineyard (Barossa Valley, South Australia) respectively. Viognier grapes destined for commercial production were sourced from the Adelaide Hills in 2010 and the Barossa Valley in 2011. All fruit was handpicked in order to avoid uncontrolled maceration prior to winemaking, and chilled overnight. 64
AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines Juice Preparation 65 Table 8-1: Summary of vinification treatments over two vintages Treatment Code 2010 2011 Whole bunch pressed WBP Free run FR Hyperoxidised free run HOX-FR Free run with high solids SOL Free run with 10% skin ferment SKI Light pressings LP Hyperoxidised light+heavy pressings HOX-LHP Heavy pressings HP Hyperoxidised heavy pressings HOX-HP Macerated and pressed MAC Grape processing was carried out in the HRWSL using a destemmer-crusher (Diemme 4 tonne/ hr), crusher-destemmer (Demoisy 7EP) and membrane press (Willmes “Merlin”, 1 t whole bunch and 2.5 t crushed capacity). Figure 8-1 and Figure 8-2 provide a schematic of the treatments. Specifically, the winemaking treatments were (in italics): Whole-bunch pressing (WBP): the press was loaded with 500 kg of whole bunches and pressed from 1.0 to 2 bar. Juice yield was typically 450 L/ tonne. The press was loaded with 1750 kg of destemmed and crushed fruit and dry ice was added to the press and the receival tray. The must was pressed using a manual press cycle to yield three fractions: Free run (FR), press pressure < 0.5 bar pressure Light pressing (LP), 0.5 – 1.0 bar pressure Heavy pressing (HP), 1.0–2.0 bar pressure
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