Peter May
Pinotage Advocate
3812
Mon Mar 20, 2006 11:24 am
Snorbens, England
Brian Gilp wrote:Mark Lipton wrote:The barrels do breathe and let oxygen in, albeit at a slow rate.
Has this been proven to be true? I know it is generally believed to be true but I do recall reading once a text on wine making where the author disputed this claiming that all the oxygen pick up came during the topping up process and not through the barrel staves.
TomHill wrote:Brian Gilp wrote:Mark Lipton wrote:The barrels do breathe and let oxygen in, albeit at a slow rate.
Has this been proven to be true? I know it is generally believed to be true but I do recall reading once a text on wine making where the author disputed this claiming that all the oxygen pick up came during the topping up process and not through the barrel staves.
Yup.....Brian has it right. Back in the early '70's, DickPeterson (then Tchelichev's asst at BV) did the experiment in which he put a vacuum gage
on bungs and found, if the bung had a good seal, that it drew a vacuum in the barrel as the wine evaporated. Dick asserted that any O2 pickup
came from the topping up process, rather than any O2 "breathing" thru the pores in the wood.
So where does the head space develop in the barrel as the wine ages?? Beats heck out of me. I assume there must be some
evaporation outwards from the hydrostatic pressure.
Tom
Paul Winalski
Wok Wielder
8030
Wed Mar 22, 2006 9:16 pm
Merrimack, New Hampshire
Peter May wrote:Every single Champagne house I've visited has emphasised that their Champagne doesn't need any more aging, that all the necessary aging has been doen in the winery and that the wine is ready to drink now. (with which I disagree, always keeping Champagne for at least 6 months and often for years).
Mark Lipton wrote:But, but, but... Tom, oxygen is a smaller molecule than water in most regards. How is that water can make it out of the barrel but oxygen not find its way in? Makes no physical sense to me.
Mark Lipton
TomHill wrote:
Let's assume you have a spherical cow.....errrrrr....an infinite slab of semi-permeable oak. On one side you have O2 (or air) at one atmosphere
of pressure. On the other side you have water at X atmospheres of pressure (whatever the hydrosrstatic pressure is at the bottom of a 2 foot column
of water (wine). Presumably X >>> 1 atmosphere. Now we have a simple transport problem that any idiot should be able to calculate.
(I'd do the calculation...but I forgot how to use the LL3 scale on my treasured Post slide rule)!!!!!
Does the water at the wine/oak interface vaporize and then is forced thru the slightly permeable 1-D slab??? Does the water at the wine/oak
interface vaporize and leak thru the joints/cracks between the staves?? I'm not at all sure. But I can envision the outflow of water vapor overwhelming
any ingress of O2 thru this slightly porous membrane.
Clearly, there is loss of water/wine from an initially full barrel. What's the mechanism for this loss?? Again...don't know. But as the wine is lost,
I'm assuming the headspace is replaced by volatiles/water vapor from the wine which is (assuming a good bung seal) at a pressure << 1 atmosphere.
I'm sure you've visited wineries to barrel sample. Almost always, when the winemaker pulls the bung, you can hear the sucking sound as air rushes into
the headspace. This is consistent w/ Peterson's work way back when. But I don't recall his paper positing a mechanism for the loss of wine from the barrel.
Tom
Mark Lipton wrote:More to the point, we all know the difference between barrel-aged white wines and SS-aged whites. The latter are more crisp and reductive whereas the former are rounder and more developed. It isn't just a matter of oak tannins, is it? I've always attributed those differences in part of slow oxygenation in barrel.
Paul Winalski
Wok Wielder
8030
Wed Mar 22, 2006 9:16 pm
Merrimack, New Hampshire
Howie Hart
The Hart of Buffalo
6389
Thu Mar 23, 2006 4:13 pm
Niagara Falls, NY
Paul Winalski wrote:I suspect evaporation occurs two ways: between the staves of the barrel, and through the oak itself. Wood is a semipermeable membrane.
-Paul W.
Ben Rotter
Ultra geek
295
Tue Sep 19, 2006 12:59 pm
Sydney, Australia (currently)
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