What is whole bunch fermentation?

Whole-bunch fermentation is gaining popularity as a winemaking technique to add more complexity to the resulting wine. Yes, it’s a geeky wine term, but it simply means the process of not de-stemming the grapes when they are harvested and letting the grapes go directly into the vats, stems and all when fermentation begins. It’s a process that we use at Holm Oak for some of our small parcel releases, giving added characters to the resulting wines.

The alternative method, and the one often more common is to remove the stems prior, either in the vineyard, on a sorting table or with a crusher de-stemmer.

Whole bunch fermentation is a technique that Bec has been using at Holm Oak for 11 years. As you may have seen on our Facebook page, we often get our children to gently foot-tread the grapes once they come into the winery, especially for the 100% whole bunch pinot noir. Alternatively, we’ll do a plunge to start to crush the grapes and commence the process of fermentation (when the grapes start to convert to alcohol). It’s an age-old process which has been used for centuries, but with winemakers looking to slightly differentiate their styles and add more complexity it’s definitely coming back into vogue.

How is the flavour profile in the wines different?

The stalks can add a little more fragrance and perfume to the flavour and complexity to the wine when the bunches are left intact. It’s also reputed to help to create silkier tannins. The decision often is dictated by the clone of grape used along with the vineyard site and age of the grapes. Some winemakers will add 100% whole bunches into the ferment, others will experiment with different percentages depending on the end flavour profile they are looking for.

It’s also thought that this technique can give a slightly different structure for the aromas of the wines when the bunches are left intact. As the AWRI noted in their research, the inclusion of stems can result in higher concentrations of compounds which confer cut grass and herbal aromas as well as potentially fruity and floral aromas.

It’s a delicate balance though, as when not used correctly it can dull the fruit adding different characters.