Before getting on to disgorgement dates, we need to do a little preparation …
Base wines, destined to become champagne, are generally produced in bulk in tank. They are then blended, and subject to a second slow fermentation at below 12C, in bottle, under a crown cork or crown cap – a beer type bottle closure; and then allowed to continue ageing on the dead yeast cells or lees in a process called yeast autolysis or self-digestion. This engenders a range of so-called autolytic flavours in the wine, adding to its complexity, including biscuit, bread, brioche, pastry, toast and yeast. Autolysis starts a few months after the second fermentation ends, and can continue for typically 4-6 years.
A crown cork rather than cap, is used with prestige and deluxe cuvees, this allows, in contrast to the metal cap, a minute gas exchange, oxygen in and CO2 out, which together with yeast autolysis, encourages the development of tertiary aromas, transforming floral fruity notes of young wines into riper, nuttier toasty aromas (CIVC, Champagne, from terroir to wine). These flavours are further enhanced and added to (if a dosage is used then there is the maillard reaction between the amino acids generated during autolysis, and the dosage sugars) post-disgorgement, when a slug of oxygen is admitted to the bottle and ageing changes from autolytic to oxidative.
Tom Stevenson, says in Christie’s Encyclopedia, that autolytic flavours develop only after oxidative disgorgement. Is it only oxidation at disgorgement that allows the flavour precursors generated by autolysis to manifest themselves in the wine’s flavour profile then?
Mary Gorman-McAdams MW, in her web log, said that autolytic character develops whilst on lees and not after disgorging …
So more than one opinion – I put this quandary, in a private email, to a top UK sparkling winemaker. And I don’t mind sharing this with you, as apparently his view is starting to gain a bit of momentum in Champagne. His feeling is that the flavours of autolysis are not from the breakdown of the yeast, rather from the ageing of the character (of the wine) made by the yeast acting on the fruit during second fermentation. This ageing happens slower pre-disgorgement and faster post disgorgement, owing to the different rates of oxygen ingress from the closure (that is pretty much anaerobic pre-disgorgment, under a crown cap; and a little aerobic post-disgorgement). No doubt there are French research papers on this issue, but nothing that I have found more recent than 2003, and they are in abstract form only.
The longer a wine spends on its lees, the fuller and richer it becomes. In any event, autolysis is most active in the first 3 to 5 years, with little effect beyond, until at 10 years on the lees, there is no further effect on flavour.
There are minimum legal requirements for ageing Champagne on its lees – 15 months for non-vintage and 36 for vintage. Or that’s what is mostly, yet not quite accurately quoted – the Champagne Authority, the CIVC, states that, for an NV wine there must be at least 15 months from the start of the second fermentation to shipping, of which 12 must be on the lees. IN PRACTICE this is 2 to 3 years. For vintage wines, it is a minimum of 3 years on the lees, but IN PRACTICE this is 4-10 years+.
This ageing period, after some manipulation to collect the lees next to the cork, which may continue with prolonged storage upside down (sur pointe), ends with disgorgement, that is the removal of the dead yeast cells. This is followed by topping up with a dosage of sugar and reserved wine, to achieve the desired sweetness, before fitting the final cork and wire (muselet). The wine is then rested to allow the wine and dosage to integrate, before shipping.
There has been debate for a number of years on the topic of disgorgement date, this relates not only to vintage Champagne, and then whether the date should be on the bottle. There are two main disgorgement options:
- Historic disgorgement – occurs early on, after perhaps 4-6 years on the lees
- Recent disgorgement – occurs after a lengthy period on the lees, perhaps 10 years +
But not forgetting that NV wines are disgorged as batches on demand, to maintain freshness, perhaps monthly. But is there a difference between an NV from a lot disgorged in January and another from the same lot in December? Theoretically, every disgorgement will produce a unique wine, perhaps the dosage wine is adapted to correct to the house style – more research is needed. Indeed, Bollinger disgorge their RD vintage wine twice a year by subscription demand – perhaps the best thing to do is to buy, if one has a proper cellar, a crate at its first release.
- Decanter Panel tasting. 2013. Vintage Champagne 1992 and 1993. Decanter, January 2013.