Award winning Adelaide Hills sparkling winemaker, Kate Laurie, takes a closer look at the silent work of yeasts in creating the magical combination of aromas and textures in champagne wines.
Champagne’s ‘something special’ is unparalleled, in my mind, by any other drink; so much so that the bottle is often finished before you have a chance to truly get your head around what has passed your lips.
The elements that make champagne so dazzling are often misunderstood, or barely given a moment of thought, but with a little more insight, they may make you pause a moment the next time you’re handed a glass.
“Along with the grape variety used, how ripe the grapes are (or aren’t), and the amount of dosage liquor added before it is corked, the time spent on lees has a significant olfactory impact on the wine.”
Méthode Champenoise is one of the most involved processes in winemaking … and it takes a long time. For sparkling winemakers, a crystal ball would be helpful at times, as the wine placed inside a bottle often doesn’t smell or taste in the way anticipated upon release some two, seven or even 20 years later.
Much of the evolution in a wine's character is due to the yeast that carries out primary and secondary fermentations. Along with the grape variety used, how ripe the grapes are (or aren’t), and the amount of dosage liquor added before it is corked, the time spent on lees has a significant olfactory impact on the wine. ‘Lees’ is the fancy way of describing yeast sediment that falls to the bottom of the bottle once secondary fermentation is complete. The yeast autolysis characters, to which we commonly refer, are derived from these lees. I’ll return to this point later.
Yeast deposits left on the bottom of the bottle following second fermentation at G.H. Mumm.
Yeast lees are also produced during primary fermentation, when freshly pressed grape juice is converted to base wine. This occurs either in stainless steel tanks or oak barrels (as in the manner of
Pol Roger versus Krug). Yeasts are incredible organisms, not only because they produce alcohol, but also because they scavenge oxygen and impart a textural component to the palate of the wine.
Champagne and sparkling base wines are actually rather subtle in aroma, but highly architectural in structure. They build more body, flavour and aroma once secondary fermentation takes place and the wine becomes sparkling.
“Most champagnes are made using a neutral yeast strain, aspiring to citrus, soft red fruits, and minerality, rather than to big fruity or tropical aromas in the base wine, which can become heavy after the second ferment.”
Primary fermentation can be spontaneous, using airborne or grape skin derived yeast that are present in the atmosphere. Alternatively, fermentation can be induced by adding one of the selected yeast strains that are commercially available. Different yeast strains contribute to the release of various aromatic compounds depending on the variety being fermented. Most champagnes are made using a neutral yeast strain, aspiring to citrus, soft red fruits, and minerality, rather than to big fruity or tropical aromas in the base wine, which can become heavy after the second ferment.
To add texture and complexity on the palate of the base wine, the primary ferment lees can be re-suspended into the base wine during ageing and before blending and bottling. If the ferment was undertaken in barrel, this occurs by bâtonnage, where each barrel is stirred weekly or monthly to keep the lees in suspension. If the base wine is in tank, lees can be mixed back in via pumping (this is known as a 'pump over').
Re-suspending lees has other benefits, too; they keep the wine fresh and help prevent oxidation.
What many people don’t know is that champagne is very low in added sulphur, which is often used in wineries to prevent oxidation and microbial spoilage. With sparkling wine/champagne, sulphur can prevent the second fermentation from happening. Or if it does, it can be a stressed fermented, creating ‘off’ odours.
Measuring chardonnay sugar levels at Jacques Lassaigne in Montgueux.
Let’s now return to the yeast autolysis discussion. The term autolysis refers to the breakdown of the yeast cytoplasmic constituents into sizes small enough to escape the cell wall as they die and release into the wine. These constituents include peptides, which are good for bubble formation, and amino acids which can be aromatic precursors. With time, aromatic molecules may form with other wine components. The increase in amino acids, attributed to the autolysis process, begins after around nine months and continues for about two years. It is believed that the toasty, nutty, and biscuit-like aromas in aged champagne results from this process. However, I have not yet found a document that relates a specific aroma to its autolytic precursor.
“The increase in amino acids, attributed to the autolysis process, begins after around nine months and continues for about two years.”
For producers wanting to develop these later characters in their champagnes, time spent on lees in the bottle can take a minimum of seven years. For purists, wanting to show varietal or vineyard aspects, disgorging the wine sooner will minimise autolytic characters.
I personally think autolytic aromas can be elusive, as some champagnes I have tried with eight years on lees (or more) don’t show any of these typically toasty characters (Agrapart), while others are brimming with them (Charles Heidsieck). Naturally, this leads to an entirely different discussion around how varietals develop aromatically, independently of yeasts. In my opinion, pinot noir develops more of those toasty/nutty characters than chardonnay so it’s possible there are more aromatic precursors available in this varietal. Time will tell following some trials I am running on this very topic.
So, for now, it’s best to simply enjoy those beautiful bubbles and, next time, take a moment to consider the work of yeast in creating that delicious drop.
Photography by Victor Pugatschew and Stephane Gautier
