Understanding Whole-Bunch Fermentation

ask the

Understanding whole-bunch fermentation What sensory changes should I expect over time, and by only making a small from using whole bunches? amount of whole-bunch fermented wine, The major sensory differences between which can then be blended into other whole-bunch fermented and conventional wines to the point where the desired wines made from de-stemmed fruit sensory effects are achieved. relate to the phenolic profiles and the With which varieties is the technique aroma. During the period that intact most commonly used, and how many berries remain attached to the stems, it is whole bunches should I use? possible that similar enzymatic reactions occur as with carbonic maceration, The technique is most commonly and thus the wines may contain some applied to Pinot Noir and Shiraz, with of the same ‘fruity’ or ‘spicy’ aromas. the proportion of whole bunches used The inclusion of stems can result in in Pinot Noir being as high as 100%, but higher concentrations of compounds with 15 to 20% being more common, which confer ‘cut-grass’ and ‘herbal’ especially with Shiraz. Use of the aromas, as well as potentially ‘fruity’ technique is uncommon with Cabernet and ‘floral’ aromas, and there is some Sauvignon and related varieties, During the 2016 and 2017 vintages, the evidence that it can also result in higher because of the high methoxypyrazine AWRI made small-lot Pinot Noir and pH and decreased acidity. There is also concentration in the grape stems, which Shiraz wines from single batches of fruit, strong evidence of increased tannin can result in ‘cut grass’ and ‘herbal’ demonstrating the effects of changing concentrations, which if overdone, characters in the wine. one winemaking variable at a time. can lead to excess astringency and a During tastings of those wines presented Is whole bunch fermentation becoming perception of ‘greenness’ in the wines. more popular, and if so, why? across Australia, many winemakers The effect on wine colour is unclear, with asked why there are such large sensory the consensus of winemaker observations The popularity of whole bunch differences between wines made with being that colour is generally reduced, fermentation is growing in Australia 100% pure carbonic maceration and but data in some publications indicating according to a range of anecdotal those made with the more common an increase in colour density. sources. As a possible explanation of this whole-bunch fermentation treatment. trend, Jamie Goode (2012, re-published What are the risks associated with using A previous ‘Ask the AWRI’ discussed 2016), says that “……. very few young whole bunches in my fermentation? carbonic maceration, and this one winemakers worldwide are looking to examines whole-bunch fermentation. The biggest risk associated with the use produce bigger wines – certainly not What is whole-bunch fermentation and how of whole bunches is the potential for at the high end. They tend to prize is it different from carbonic maceration? ‘green’, ‘grassy’ and ‘herbal’ aromas and elegance, freshness and definition above flavours, and overly astringent tannins all else”, and maintains that whole- As the name suggests, whole-bunch in the wine. The best results are achieved bunch fermentation can result in wines fermentation describes a red winemaking when bunches with a high degree of displaying those characteristics. He technique where intact bunches of grapes lignification are selected (i.e. stems that notes that “People in the past used stems are placed in the fermenter, rather than are ‘woody’ rather than green), and the by default, and the results weren’t always grapes that have been removed from most well-lignified bunches are likely to good. Now the choice to use stems is the stems. Destemmed and/or crushed be found in relatively low-vigour sections an active one, so the people doing it are berries are then generally placed on top of of the vineyard. Lignification is likely doing a better job of it”. them, and as the fermentation progresses, to be lower in cool climates, and in the intact bunches are often partially cooler years, and is known to commence For further information about whole- or wholly crushed by plunging, or at the cessation of shoot growth. bunch fermentation or other technical traditionally by foot-treading. Carbonic Consequently, lignification tends to questions, contact the AWRI helpdesk on maceration, on the other hand, involves be lower in wet years, especially when (08) 8313 6600 or [email protected] placing 100% intact whole bunches of there is mid to late-season rainfall which Reference grapes, with absolutely no free grape stimulates vine growth, and in high- juice, in a closed fermentation vessel vigour vineyards. It is advisable to take a Goode, J. 2012 and 2016. Stemming the filled with carbon dioxide, for around cautious approach when trialling whole- tide. World of Fine Wine. 37: 90–97 and a week, prior to destemming, crushing bunch fermentation, by only using a http://www.worldoffinewine.com/news/ and fermenting with yeast under normal small percentage of whole bunches at stemming-the-tide-4869650 winemaking conditions. first (10 to 15%), and assessing the results

May 2018 – Issue 652 www.winetitles.com.au Grapegrower & Winemaker 63