First off, no snarky responses to the effect of “because they’re older.” I mean a vintage that is substantially darker than neighboring vintages from the same chateau.
The case that has raised this question: I have the 1988, 1989, 1998, and 2003 Lafaurie-Peyraguey’s in my cellar (don’t have a picture handy at the moment, sorry). The 1998 and 2003 are very similar in color currently, orangish-gold; the 1988 is actually lighter than both of them, and is currently deep golden yellow with no orange yet showing; but the 1989 is substantially darker than any of them, and is fully going bronze already (from my experience, it’s color is about 10 years older than I’d expect - slightly darker than my 1981 Rieussec for example, which is only starting to bronze). I have found at least one image online that verifies that the color of my bottle the 1989 is typical (http://www.thewinedoctor.com/weekend/lafauriepeyraguey89.shtml) - it’s not a result of poor storage (although I admit that I only just acquired it and the provenance is unclear)
I had always assumed that this was a question of residual sugar vs acid: that higher RS stickies darken faster, but those with higher acid relative to RS darken more slowly. Is this accurate, or is there something else going on?
And I am wagering that if multiple bottles of the various vintages are brought into play, the discrepancy would decline.
Although I’m in a poor position to argue this as I just had 3 bottles of 89 Suduiraut show up at my office and they’re all a very uniform deep orange/bronze.
Okay, so here are some nit-picky questions: is it just that wines with higher botrytis start out darker, or do they darken at a faster rate over time, or both? And is there any insight into why botrytis causes this (I mean at a biochemical level)?
Even with botrytis being the primary factor, do sugar and/or acid still play a role? You would expect them to.
You can definitely have variation between bottles from the same chateau in the same vintage. I have noticed a quality difference between these (sometimes the darker color means poorer storage, sometimes it’s variation from the bottling or natural variation).
Some vintages are darker than other vintages, ie: 1988 is always lighter than 89 or 90. I don’t know the molecular basis of this, but it makes sense that botrytis would be linked to this. The darker color doesn’t necessarily mean its better or worse, just different.
Kind of a long shot answer here but it may have to do with sugars and other compounds. When some sugars degrade, they can combine with other things to produce more interesting compounds, some of which are responsible for caramel color, etc.
To the degree that there are vintage variations in color, it may have to do with the specific types and amounts various sugars and amine and other compounds. Brix measures solids in in the juice. With grapes, you’re usually trying to measure carbohydrates, particularly sucrose.
But even if you pick at the same brix, specific levels and types of sugars, acids, and all the other compounds in a grape can vary with vintage - you have differing amounts of things that might constrain browning. Someone smarter than I can probably explain it better.
