Glycosyltransferase

[Jeff Grossman]

This too-cute article describes a chemical mechanism for how smoke taint can be unobservable on grapes and grape juice but come out after fermentation.

Makes me wonder if this is part of the terroir equation. After all, there has never been evidence that the roots uptake anything interesting from the ground... perhaps it is the berries themselves stashing things that float by on the breeze?

 

[mark e]

originally posted by Jeff Grossman:
After all, there has never been evidence that the roots uptake anything interesting from the ground...

And what might you mean by "interesting"? Besides stomata and roots where is there interesting uptake?

 

[Oswaldo Costa]

In Jamie Goode's Flawless there's a chapter on smoke taint. I don't recall anything about it coming out after fermentation, but no longer have the book with me to check.

 

[mark e]

originally posted by Oswaldo Costa:
In Jamie Goode's Flawless there's a chapter on smoke taint. I don't recall anything about it coming out after fermentation, but no longer have the book with me to check.

On p. 135 he says "it emerges during the winemaking process."

 

[MLipton]

Surpringly accurate for a popular science article. Two quibbles. One is that most glycosides, especially phenolic glycosides, can be cleaved non-enzymatically by simple exposure to acid. So, simply rupturing the grapes and breaking down compartmentalization might be enough to deglycosylate the odorants. Secondly, the author confuses gases with vapors. A vapor is properly a suspension of a liquid in a gas, just as a fume is a suspension of a solid in a gas. A common example of a vapor is water vapor such as we see in clouds and coming out of a tea kettle (and which is commonly misnamed steam, the term for gaseous water).

Mark Lipton

 

[MarkS]

originally posted by Jeff Grossman:
perhaps it is the berries themselves stashing things that float by on the breeze?

I've always wondered what wines made from grapes grown by the Port of Long Beach would taste like.

 

[Jeff Grossman]

originally posted by mark e:

originally posted by Jeff Grossman:
After all, there has never been evidence that the roots uptake anything interesting from the ground...

And what might you mean by "interesting"? Besides stomata and roots where is there interesting uptake?

My point -- and it is supported around here somewhere by Dougherty -- is that vine roots in Chablis, say, are not extracting limestone from the ground. They are pulling exactly the same nutrients that vine roots everywhere do: lots of water and a smidgen of elemental nitrogen, phosphorus, potassium (and a few others). No particles of ancient seashells mixed in the xylem, no Kimmeridgian clay in the phloem. Mycorrhizal relationships may influence what the vine does, and the specific fungus that grows may depend on soil properties, but that's not the same as saying that the soil directly changes the taste of the wine.

 

[Jeff Grossman]

originally posted by MLipton:
Surpringly accurate for a popular science article.

That's good to hear. Thanks for the peer review.

 

[mark e]

originally posted by Jeff Grossman:

originally posted by mark e:

originally posted by Jeff Grossman:
After all, there has never been evidence that the roots uptake anything interesting from the ground...

And what might you mean by "interesting"? Besides stomata and roots where is there interesting uptake?

My point -- and it is supported around here somewhere by Dougherty -- is that vine roots in Chablis, say, are not extracting limestone from the ground. They are pulling exactly the same nutrients that vine roots everywhere do: lots of water and a smidgen of elemental nitrogen, phosphorus, potassium (and a few others).

The same doesn't mean the exact same quantities though. I don't believe that very minor differences in mesoclimate would account for the striking differences in wine characteristics that you see, say, from adjacent vineyards in the Mosel.

 

[Oswaldo Costa]

This is a hugely important issue where uncertainty still reigns, despite the bold claims made by Alice Feiring's latest about the impact of the mineral composition of soils on wine flavor. Most people would agree that this is true, yet Joe D. claimed there was no scientific proof (i.e., no pathways have been identified for this particular effect).

 

[Jayson Cohen]

originally posted by Oswaldo Costa:
This is a hugely important issue where uncertainty still reigns, despite the bold claims made by Alice Feiring's latest about the impact of the mineral composition of soils on wine flavor. Most people would agree that this is true, yet Joe D. claimed there was no scientific proof (i.e., no pathways have been identified for this particular effect).

I have wondered whether that book would have been different with Joe around. Joe was one of Alice’s mentors, and I think his presence / possible challenge to the science fiction would have potentially tempered the claims. Or maybe not.

 

[Jayson Cohen]

originally posted by MLipton:
Surpringly accurate for a popular science article. Two quibbles. One is that most glycosides, especially phenolic glycosides, can be cleaved non-enzymatically by simple exposure to acid. So, simply rupturing the grapes and breaking down compartmentalization might be enough to deglycosylate the odorants. Secondly, the author confuses gases with vapors. A vapor is properly a suspension of a liquid in a gas, just as a fume is a suspension of a solid in a gas. A common example of a vapor is water vapor such as we see in clouds and coming out of a tea kettle (and which is commonly misnamed steam, the term for gaseous water).

Mark Lipton

Interesting. Physicists are pedestrian and tend to use gas and vapor interchangeably. For example, either a gas or vapor of sodium atoms. Maybe that is sloppiness.

 

[MLipton]

originally posted by Jayson Cohen:

originally posted by MLipton:
Surpringly accurate for a popular science article. Two quibbles. One is that most glycosides, especially phenolic glycosides, can be cleaved non-enzymatically by simple exposure to acid. So, simply rupturing the grapes and breaking down compartmentalization might be enough to deglycosylate the odorants. Secondly, the author confuses gases with vapors. A vapor is properly a suspension of a liquid in a gas, just as a fume is a suspension of a solid in a gas. A common example of a vapor is water vapor such as we see in clouds and coming out of a tea kettle (and which is commonly misnamed steam, the term for gaseous water).

Mark Lipton

Interesting. Physicists are pedestrian and tend to use gas and vapor interchangeably. For example, either a gas or vapor of sodium atoms. Maybe that is sloppiness.

Far be it from me to criticize my physical brethren of semantic sloppiness, but if people are using the terms interchangeably they need to be taken to the intellectual woodshed {insert emoticon here}.

Mark Lipton

 

[Greg Hirson]

originally posted by MLipton:
Surpringly accurate for a popular science article. Two quibbles. One is that most glycosides, especially phenolic glycosides, can be cleaved non-enzymatically by simple exposure to acid. So, simply rupturing the grapes and breaking down compartmentalization might be enough to deglycosylate the odorants. Secondly, the author confuses gases with vapors. A vapor is properly a suspension of a liquid in a gas, just as a fume is a suspension of a solid in a gas. A common example of a vapor is water vapor such as we see in clouds and coming out of a tea kettle (and which is commonly misnamed steam, the term for gaseous water).

Mark Lipton

When my labmates were developing an analytical method to measure glycosidically bound aroma compounds, they used both b-glycosidases and acid hydrolysis. The b-glycosidases better preserved the aroma compounds from acid-induced rearrangements, but the acid treatment was quite harsh in that case.

 

[Ian Fitzsimmons]

originally posted by MLipton:

originally posted by Jayson Cohen:

originally posted by MLipton:
Surpringly accurate for a popular science article. Two quibbles. One is that most glycosides, especially phenolic glycosides, can be cleaved non-enzymatically by simple exposure to acid. So, simply rupturing the grapes and breaking down compartmentalization might be enough to deglycosylate the odorants. Secondly, the author confuses gases with vapors. A vapor is properly a suspension of a liquid in a gas, just as a fume is a suspension of a solid in a gas. A common example of a vapor is water vapor such as we see in clouds and coming out of a tea kettle (and which is commonly misnamed steam, the term for gaseous water).

Mark Lipton

Interesting. Physicists are pedestrian and tend to use gas and vapor interchangeably. For example, either a gas or vapor of sodium atoms. Maybe that is sloppiness.

Far be it from me to criticize my physical brethren of semantic sloppiness, but if people are using the terms interchangeably they need to be taken to the intellectual woodshed {insert emoticon here}.

Mark Lipton

In atmospheric science, water vapor is unambiguously water in gas phase; fog, steam, and clouds are composed of condensed, liquid-phase water droplets. Water vapor pressure (partial pressure of gas-phase water in air) is a key concept.

Merriam and Wikipedia cleave to the general definition of vapor as gas-phase, for what it's worth, as do a couple of popular online chemistry dictionaries. I don't know what reference is gold standard for chemistry terminology.

 

[Christian Miller (CMM)]

originally posted by Jeff Grossman:

originally posted by mark e:

originally posted by Jeff Grossman:
After all, there has never been evidence that the roots uptake anything interesting from the ground...

And what might you mean by "interesting"? Besides stomata and roots where is there interesting uptake?

My point -- and it is supported around here somewhere by Dougherty -- is that vine roots in Chablis, say, are not extracting limestone from the ground. They are pulling exactly the same nutrients that vine roots everywhere do: lots of water and a smidgen of elemental nitrogen, phosphorus, potassium (and a few others). No particles of ancient seashells mixed in the xylem, no Kimmeridgian clay in the phloem. Mycorrhizal relationships may influence what the vine does, and the specific fungus that grows may depend on soil properties, but that's not the same as saying that the soil directly changes the taste of the wine.

You're leaving out one mechanism - what if the underlying soil, bedrock or whatever affects the behavior of the vine (canopy, flowering, yield, stress levels, etc.), which in turn affects the levels of various molecules that impact flavor or aroma? (It does.) Doesn't require any uptake or translocation of minerals or whatever.

That said, I think I already remarked on the contrast between the amount of words and debate on underlying geology vs. the paucity of discussion of microflora in the soil. Smoke taint is adding discussion of airborne influences. As you might guess, there's a lot of research going on right now - the concept of "hidden" smoke taint has growers and grape buyers very very nervous and is already roiling the market.

 

[Ian Fitzsimmons]

I puzzle from time to time over the contrasting views that, on the one hand, vines take up nothing from the soil, except universal nutrients, in constant proportion from location to location; and, on the other, that soil type is a key determinant of the place-specific expression of a particular variety (or blend). The idea of terroir is not exclusively linked to the soil composition of a particular location, but local soil is very widely considered to be a key element of a particular terroir - not least by the vignerons themselves. The strict identification of Kimmeridgian soil with Chablis-specific expression of Chardonnay is a case in point.

If the soil composition in no way biases the composition of material uptake from soil into vine, then the flavor and aromatic characteristics typically attributed to soil - minerality, slatiness, iron - must be caused solely through indirect mechanisms, such as those Christian lists.

Joe's view notwithstanding, however, it seems plausible that some non-nutritional molecules would be entrained with the flow of nutrient solution from soil to vine, tinting the flavor profile of the grapes one way or another. In this case, which molecules are entrained, and in what proportions, would be related to the various compounds present in the local soil. In this vein, I recall a good post in Berserkers several years ago, which explained how an abundance of - I think - calcium ions in soil could cause the sensation of salinity (or minerality) in wine made from the fruit of wines grown in it.

I wonder what the boys at UC Davis have to say on the subject - this seems like the kind of thing a well-trained plant physiologist would be able to explain without breaking a sweat.

 

[robert ames]

originally posted by Ian Fitzsimmons:
I puzzle from time to time over the contrasting views that, on the one hand, vines take up nothing from the soil, except universal nutrients, in constant proportion from location to location; and, on the other, that soil type is a key determinant of the place-specific expression of a particular variety (or blend). The idea of terroir is not exclusively linked to the soil composition of a particular location, but local soil is very widely considered to be a key element of a particular terroir - not least by the vignerons themselves. The strict identification of Kimmeridgian soil with Chablis-specific expression of Chardonnay is a case in point.

If the soil composition in no way biases the composition of material uptake from soil into vine, then the flavor and aromatic characteristics typically attributed to soil - minerality, slatiness, iron - must be caused solely through indirect mechanisms, such as those Christian lists.

Joe's view notwithstanding, however, it seems plausible that some non-nutritional molecules would be entrained with the flow of nutrient solution from soil to vine, tinting the flavor profile of the grapes one way or another. In this case, which molecules are entrained, and in what proportions, would be related to the various compounds present in the local soil. In this vein, I recall a good post in Berserkers several years ago, which explained how an abundance of - I think - calcium ions in soil could cause the sensation of salinity (or minerality) in wine made from the fruit of wines grown in it.

I wonder what the boys at UC Davis have to say on the subject - this seems like the kind of thing a well-trained plant physiologist would be able to explain without breaking a sweat.

not sure where uc davis is nowadays, but 25+ years ago their take on
1) terroir's influence on wines, and
2) french oac laws
was that it was a load of bollocks created by the french to protect their products.

 

[Jeff Grossman]

originally posted by Ian Fitzsimmons:
...it seems plausible that some non-nutritional molecules would be entrained with the flow of nutrient solution from soil to vine...

You're writing gibberish. Stop it.

I am not a plant scientist but I can still read a textbook:

There are two methods by which nutrients get into plant cells, diffusion and active transport.

Diffusion happens when the concentration of the substance is greater outside the cell than inside the cell. This is how plants acquire water. Root hairs do not have the same sort of cell walls as pretty much every other part of the plant so water molecules can just follow the gradient. But, as the concentration of mineral ions in a root hair is usually 10,000 times greater than its environment, ions don't get in with the water; their gradient pushes them away!

The plant must actively work to acquire elemental ions. Root hairs emit H+ ions into the soil around them. These ions pry elements off the surface of wads of clay, and also bind to element anions to make them positive. (It's good to make them positive because they are then attracted to the root hair, which is a little negative from having shed all those H+ ions.) When the elemental ion brushes against a matching protein on the surface of a root hair cell, the protein deforms to snatch it up and push the ion inside. (This actually consumes energy; the cell burns ATP to do this, hence it is active transport.)

There appear to be a finite number of receptor proteins for Element X on any given mass of root hairs, so making more of Element X available only changes uptake to a limit.

There are also some complicated mechanisms for giving back water and ions but the text was getting over my head.

 

[Oswaldo Costa]

I wish Eric would chime in. As a scientist by training, though not a microbiologist, he seems well placed to opine.