What’s with the Dimple?
You have your wine and are admiring the bottle. So what’s with the dimple in the bottle’s base? The first reaction of most people is it’s to help sustain the pressure of sparkling wines. There’s some degree of credibility to that story, but it becomes less so when you discover the ‘real’ reason behind it.
Wine Bottle Punt
The dimple is termed the ‘punt’, or sometimes the ‘kick-up’, that much seems to be agreed upon. After that it starts to become anybody’s guess and mixture of folklore and technological reasons. The simplest explanation is it stops the bottle toppling over, harking back to a time when bottles were blown using a blowpipe. The method left a ‘punt-mark’, the scar where the blowpipe is snapped off the glasswork. If left on the base of the bottle it would never have sat properly on the table, so it was pushed up into the bottle. The result was a much less wobbly bottle.
Other theories include it was easier for the servants to hold the bottle with their thumbs when they poured the wine. Seems it would have been easier to find servants with ‘grippier’ fingers than redesign the wine bottles? But then it is sooo hard to find good help, such a tiresome business. Similarly, it is also speculated it provides a good grip when bottles of sparkling wine are riddled to remove lees from the bottle. Considering the pittance labourers were once paid, it seems unlikely anyone would have cared if their jobs were even more of a drudge. So why introduce a punt to help them out?
Also on the list of possibilities is the deep trench at the bottom of the bottle allows sediments to accumulate, thereby avoiding gunge being slopped into one’s glass. Again, so tiresome.
Other explanations tend to be coincidental, rather than deliberate. The punt may make the bottles less likely to resonate during transport, reducing the chances of shattering. It also has the effect of making the bottle appear larger (because it is) to compensate for the loss of volume the punt causes.
Rather than a great scientific intrigue behind the punt, it looks like there are only the stories people have created to make the story of wine just that little bit richer. I’ll drink to that.
Sequencing Flavour
A couple of years ago, a team of French and Italian researchers identified the sequence of DNA that creates that most lovely of grapes, the Pinot Noir. Being the first fleshy fruit crop to be sequenced, and only the fourth flowering plant, this was pretty big news, both at Nature and the BBC.
While the sequencing occurred several years ago, back in 2007, try as I might I was unable to find out if full analysis of the sequence had yet been completed. This does not mean it hasn’t happened yet, and rather might reflect more on my search-skills, so if anyone knows of a published analysis, then let me know.
One of the big roadblocks in studying genomes these days is not the sequencing but the actual analysis that needs to be performed afterwards. This is a problem not only with grapes, but with any kind of work which generates a lot of data, and with over 30,000 genes identified in Pinot Noir, it would be no wonder if a lot of time had to be spent working out what they all did.
Such an analysis would be incredibly interesting not only for the pure, unadulterated joy of learning, but for informing the breeding of new strains with improved flavours (a practice that has been going on for centuries, otherwise known as ‘viticulture’, though in this case there would be a little more genetic information floating around to inform breeding decisions), as well as for developing better pest resistance within grape strains – removing the need to be spraying all those pesky CFC-filled pesticides around our countrysides. Sadly, grapes, due to their inbreeding and fragility, are among the most sprayed of all crops, with over 12 applications of pesticide generally needed a season.
I hope that with increasing numbers of winemakers turning to organic methods and trying to avoid the excessive use of pesticides, winemakers will be open to the idea of modifying grape genomes in order to make pest resistance inherent in the grape, rather then bathing the grapes in dangerous, environmentally unfriendly chemicals.
Of course, modifying the genes doesn’t guarantee the quality. The flavours produced in grapes are incredibly reliant on their environment – the soil, the sunshine, the terroir. Nurture plays such a massive part in the production ofgood wine, so just having a grape with great genes simply won’t do the trick.
Here’s to the future of wine!
Science & Wine (And Sebastian the Crab)
by Tom McFadden
We here at “scienceofwine.com” like to interpret our mission quite broadly. We’re interested in just about any intersection between science and wine, not just the methodology behind the growing and fermenting of grapes.
Ecology, psychology, climate science, and economics are all fair game for scienceofwine.com.
A recent article in the New York Times provides fodder for our expansive approach. Reporter Alan Tardi tells the story of Piero Lugano, Italian wine-maker who ages his bottles under the sea.
The New York Times covers wine from many angles.
The article points out that…
1. Underwater storage has some upsides for wine aging: perfect temperature, no light, a lack of air, constant pressure, and gentle rocking that keeps yeast particles circulating. To quote Sebastian, from The Little Mermaid, “Life it is better down where it’s wetter.” And if that song wasn’t already stuck in your head, it is now.
2. The project required approval from ocean scientists at the University of Genoa. Originally the scientists were concerned about the fragile ecosystem, but realized that the project would ultimately demonstrate their “philosophy of a positive synergy between man and nature.” This quote hints at a key debate within environmentalism – whether “the natural world” should be held separate in (increasingly smaller) reserves, or whether humans should figure out a way to sustainably live and operate alongside nature.
3. Since the vineyards are conditioned by their proxmity to the sea, wines from the region have a “lean, crisply acidic, minerally, almost salty” taste. This represents the concept of terroir, from the French “terre” meaning land, denoting the way in which soil, climate, and other physical qualities affect a wine’s taste.
From soil to serotonin, the world of wine constantly crosses science. We look forward to covering it all.
Snap, crackle…
There is something about champagne that will never quite let my heart be still. As much as I loathe cheap sparkling wine, I love quality sparkling and of course, champagne itself. And what do I love the most, I hear you, oh Attentive Reader, plea to hear? Well, the magic of the fizz, of course. There really is something truly amazing in the beauty of the bubbling pour, the satisfaction of seeing a cork arcing gracefully through grateful air, the fizzing energy exciting the atmosphere of a party diving through waves of golden champagne.
But what is the secret to this magic? Well, that’s a lot more than one late-night post can handle. But I will introduce you to three of my favourite parts of the myth-ridden traditional technique, now regulated by the ‘Appelation d’origine controlee’. As I said, I’m not so interested in the cheaper wines, but you can see here that there are other methods.
The first of my favourite steps of the traditional technique is that of ‘autolysis’, and of how champagne so well entices. (Yes, I tried to rhyme. Did it work for you?)
The fermentation of wine is a delicate process. Each type of grape wants to be coddled in it’s own favourite way, and winemakers must learn each grape’s needs and desires.
The amount of sugar in each type of grape will vary, and even within a certain variety of grape, the amount of sunshine the plant receives during the gestation and the length of time taken in the ripening of its fruit will determine how much sugar is produced.
The photosynthesis that occurs in the leaves of the grapevine produces energy which moves sugar (in this case, sucrose) molecules into the developing fruit – meaning that the more sunshine a grapevine gets, the more sugar will accumulate in its grapes.
In an even more fun twist of the sugar cane, during the ripening of the grapes, this first type of sugar, sucrose, is turned into two different types of sugar, glucose and fructose.
This change in the sugar type is performed by an enzyme called invertase. Invertase removes some parts of the sucrose, changing what type of sugar it is. These ‘parts’ are the water molecules (yep, good old H2O) that are attached to the sucrose. These water molecules are split into their separate components, water and oxygen, in a process called ‘hydrolysis’, quite literally ‘water-splitting’, with ‘hydro-‘ referring to ‘water’, and ‘lysis’ referring to ‘splitting’.
Normal fermentation involves yeast added by the winemaker to the blend of grapes. The yeast feeds off the glucose and fructose in the ripened grapes, converting the sugars into alcohol and carbon dioxide.
Once the yeast runs out of sugar (or, in fact, other nutrients such as nitrogen, or if the alcohol level in the wine becomes too high), it dies. The way that the yeast cell dies is what is called ‘autolysis’. Like we learnt before, ‘lysis’ means ‘splitting’, and in this combination with ‘auto’, we are talking about a process of ‘self-splitting’. Quite simply, the yeast cell kills itself, unable to cope with the harsh conditions of its now hostile environment. After autolysis, the yeast cells sink to the bottom of the fermentation vessel. These dead, sunken yeast cells are called the ‘lees’.
In order to capture that magical melting sensation of a quality velvety champagne in your mouth (sounds weird, I know), the champagne has to be fermented with these lees. The bubbles of champagne, or sparkling wine, are made by this secondary fermentation, over a time period of anything from a couple of months to many years (the ‘Appelation d’origine controlee’ I mentioned earlier enforces a minimum 15-month second fermentation).
Two of the best words in all of the wine production fiefdom start rolling off the tongues of winemakers once they have guided their precious grapes through the secondary fermentation stage – ‘riddling’ and ‘disgorging’. Come on. Tell me you don’t love ‘em, I dare you.
Riddling is basically just fancy stirring. The sediment needs to be moved up to the bottleneck, but if it’s moved up too fast then the sediment will mix back into the liquid and not be able to be removed until it has finished settling out again. While automated systems now exist, no machine will ever be so poetic as ‘the riddler’: that dear gentleman entrusted with the 15-day long process of the turning of the bottles, each only 1/8 of a turn at a time.
The other fantastic word of the wine world that I have chosen to mention, disgorging, is not so disgusting as it sounds. Following riddling, once the sediment is all up in the bottleneck, the bottle is immersed in a cryogenic bath and then upended and the cap removed – so that all the frozen sediment in the neck falls out. This leaves the sparkling wine or champagne clear, rather than cloudy like in the good old ancient days.
The disgorging is the second to last step before the bottle is closed with the final cork, which is secured to the neck with one of those fun wire caps I love twisting off, because it is so joyfully followed by that ever so satisfying,
Dr. Corkero Strikes Again!
by Tom McFadden
When you go backpacking (what you New Zealanders call “tramping”) you’ve got to make decisions. My recent three-day tramp on Stewart Island was no exception.
We embark on the trail hoping for kiwi sightings.
Is it worth packing that extra heavy jacket? Nope. Is it worth lugging a portable boombox so that we can listen to science raps in the wilderness? Absolutely not.
But is it worth lugging two bottles of wine the entire way? Of course. Patrick bravely took on the extra weight for the good of our hut-sleeping evenings.
A beautiful walk through a marsh. With a bottle of wine.
Us looking at birds! With a bottle of wine.
Now granted, this was not the nicest bottle of wine. But apparently, no bottle of wine is too humble for the dastardly works of Dr. Corkero.
Zoe captured this photo of Dr. Corkero in action.
Yes ladies and gentlemen, we suffered the very fate that Zoe had explained so eloquently in a post on “corked wine” few months ago. A fungus had contaminated the wine-making process at some point and jettisoned 2,4,6-trichloroanisole (TCA) into our bottle. The smell was awful. The taste was worse. And this bottle was capped, not corked. Have you no shame, Corkero?
Luckily, the views were spectacular. Even with no wine in our bloodstream.
Until next time Dr. Corkero. When I vow to do battle with you via a bowl and a plastic wrap. Until next time.
Stuck on You
A good grafter, at least in the UK, would indicate someone was willing to work hard and put in a decent day’s work. When you move to the world of plants, a ‘good grafter’ takes on a more specific meaning. Grafting is a case of having your cake and eating it. Often plants are bred for desirable characteristics, and plant breeding over the last 1,000 years or so has refined this to a fine art. The problem is a plant breeder might have produced a grape with perfect ripening characteristics, but with a root system which would make a radish blush. Grafting of human body parts requires brutal immuno-supressant drugs to have even a reasonable chance of working. Plants on the other hand are a lot more accommodating with a wide range of scions (above ground variety) being able to be grafted to any one stock plant (root system).
Usually a grape variety would be grafted onto a root stock because it provides an improvement in growth and grape production. This could be due to better nutrient uptake or simply being better suited to local conditions. Varieties of Vitis vinifera native to North America are resistant to local soil-borne pests, but tend to produce wine unsuited to the European palette. The solution is to graft European grape varieties onto native North American root stocks. Grafting won’t however solve all incompatibilities between environment and grape. Vintners in Oregon had little success with Chardonnay grapes imported from California, irrespective of how they grafted them to local root stocks. The scions were unsuited to the colder Oregon conditions and failed to thrive. Whereas imports from Burgundy, which has a closer match in climate, did.
Plants produce their water and nutrient conducting vessels at their vascular cambium layers, a ring of actively propagating cells which ring their stems. Leaving old cells behind them and generating new cells in front. Seen as growth rings in trees when sawn down. For a grant to ‘take’, both the plants’ vascular cambiums must come into close contact. This is the function of the variety of grafts used by horticulturalists, to provide a continuous water and nutrient conducting network between the stock and scion plants – plus a strong mechanical connection.
Plant Graft Types
Plants also have a complex network of plasmodesmata running throughout them. These are essentially tiny finger-like projections of their cell membranes which poke through neighbouring cell walls. The result is a continuous cellular network. It is through this network the stock and scion plants ‘communicate’ and explains why maturation can be dramatically sped up by grafting young scions to mature stock plants. The latter triggering early maturation in the former by the transmission of its phyto-hormones (plant hormones). The partners in the graft will have intermingling of their plasmodesmata, each snaking through the other’s cell walls. There is also evidence of direct connection between them, as evidenced by the transmission of phytohormones and the like. There’s more going on in your grafted vines than you might think when you start looking at their phyto-hormones. So, if your wine seems particularly hard to understand, perhaps unreasonably sharp – maybe it’s a victim of another plant’s PMT?
Don’t Rock the Brain-Damage Boat.
In a perfect turn of events for someone involved in writing a blog about wine, I am no longer supposed to drink. Nor was I supposed to use a computer for six weeks. Oh Hallelujah! Neither of these bans, thankfully, are part of a permanent state of affairs, but the good Doctors’ orders remain for now as “no alcohol for 6 months, it would be best if it were more”.
Me? Not imbibe any alcohol?! God help us all.
Let’s not aim for 6 months right now. Please, no. I will be working in shorter timeframes, something like when you go for a jog and tell yourself you will run to at least that next lamppost before you start walking.
Fair enough if you want to ask why. Or maybe you don’t. Either way, I’m more than happy to hear the sound of my own voice. I’ll keep it short though – my skull tried to occupy the same dimensions in space and time as a car. In a shocking turn of events, the car won. Fun, huh?
We all know that when you’re sick, or on most medications, you shouldn’t drink alcohol (especially not to excess), but why is that? Your body can’t handle it, you might say. Right, right, but…why? My doctor tells me brain damage. My brain has been damaged by my head trauma. (“Well, that explains a lot” I hear the snide reader snigger). And, he says, by drinking alcohol at my usual levels, I would also wreaking irreversible damage on my brain cells.
How do brain cells become damaged as a result of drinking alcohol? The effect that alcohol has on the body, the whole sensation of being “drunk” (see also: wasted, smashed, intoxicated, rummy) occurs after your liver is overcome. This means that more alcohol is getting through to your brain. And this, the breaching of the defences, is VERY, VERY BAD.
When you’re in good health, your champion of a liver pumps poisonous alcohol out of your system like nobody’s business. Most glasses of wine you are served in a restaurant or bar will hold about 150mL of liquid. Although the alcohol content varies between wines, a good rule of thumb is that a normal-sized serving of wine will be about 1.5 standard drinks. The Alcohol Advisory Council of New Zealand recommends that men drink no more than 6 standard drinks and women no more than 4 in one session. In a week, men should drink no more than 21 and women no more than 14. More than this, and you’re considered to be binge drinking. In Australia, recommendations (this one’s a pdf) are for even fewer drinks.
Think about the last time you got really drunk. How many drinks do you think you had? What happened to you? I’m going to bet that walking in a straight line became an effort, your vision started blurring, you started seeing double, your words slurred together, your reaction times stretched out way beyond normal and quite likely your memory of that night was a little patchy the next day. Motor function and mental capacity – now what controls these? The brain. So, obviously, the alcohol is having some negative effect on your brain…somehow.
In the short term, alcohol interferes with the communication between your neurons – distracting the receptors on cells so that they can’t receive signals they normally would. Chemical accelerators are slowed and inhibitors are sped up. This causes those effects of sluggishness that we ran through earlier. Alcohol is a depressant for this reason – it makes your central nervous system run slower.
That’s just the short term. In the long term, excessive alcohol consumption will quite literally shrink your brain.
Most of the cells in our body are able to regenerate and recover from damage (check out the healing process on your finger after a paper cut). It used to be thought that brain and spinal cord cells couldn’t recuperate from damage. But, in an exciting turn of scientific events in the 1990’s, a series of papers overturned the idea that brain cells can’t regenerate. They showed that, in fact, this process (called neurogenesis) does occur. Whoopah!
Unfortunately, these repairs never seem to take a person fully back to normal. These brain cells, or neurons, mostly form during early development – so if you’re destroying them when you’re 25, 30 or older then you’re in for some serious cognition and memory problems if you go too far at all those keg parties.
So how does this alcohol-induced brain damage relate to concussion? Well, being concussed is a lot like being drunk. When I was first concussed, I had all the above symptoms of being drunk – trouble walking, blurred vision, slurred speech, long reaction times, no memory, plus the added bonus of throwing up. Oh, and yeah, that can happen when you’re drunk too. There are some important differences though. Yes, being concussed is something like being drunk. But just take out all the fun parts. No friends, no gaiety, no music. Plus, you’re already feeling the next morning’s hangover, and, buddy, trust me when I say: It is here to stay.
Basically, the drunk and the concussed are already in the same brain-damaged boat and neurons are leaking out the hull. So why bother rocking it with a delicious glass of wine?
(And remember, if you don’t like this post, or any of my posts following…I HAVE BRAIN DAMAGE. Deal with it, folks. Or, tell me your thoughts. Whatever makes your soul sing.)
Napa Valley vs. Climate Change
Great cartoon by Neil Wagner on today’s topic. See more of his "What on Earth?" strip at www.sciencefriday.com/blog/
The same themes come up again and again in the public discourse on climate change. Weather versus climate. Prevention versus adaptation. The idea that cold regions may actually benefit from a bit of warming (Russian leaders famously embraced this idea, before becoming the “poster children” for the perils of global warming).
All these themes are present in a recent article in the Napa Valley Register reporting on how local winemakers have responded to scientists’ predictions of how climate change will impact the region.
The reaction of the PR guy to the climate predictions is, in short, that the Napa Valley brand will not be tarnished. The last few summers in the Valley have actually been cooler, not warmer, than average. And if temperatures do begin to rise, wine growing technology has always been dynamic and will continue to adapt. This seems both a reasonable data-based assessment, and an optimistic spin from someone vested in the Napa Valley brand.
But it also hints at a position you hear more and more often, even from frustrated greenies. Our attempts to prevent climate change are failing. And even if significant political action is taken, there is so much momentum in the system that we will soon have no other option but to adapt via technological solutions. A recent article in the Telegraph takes this argument to an extreme (complete with a nice sensationalist headline about “Playing God”).
Yet technological adaptation is indeed critical. So much so that it is the very first paragraph of the Stanford study that the Napa winemakers were responding to:
Although governments continue to consider policies to constrain the level of greenhouse gas (GHG) concentrations in the atmosphere, it is becoming increasingly clear that some adaptation to climate change will be required in the coming decades. The expected need for adaptation arises in part from the recognition that inertia in the climate system is likely to create continued climate change after GHG stabilization. Further, policy negotiations are focused on GHG levels that guarantee further global warming. While these targets are relatively moderate compared to unconstrained warming, they are not likely to avoid high-impact regional and local climate change.
In a recent discussion of this viewpoint with some of my fellow students, we decided in a fit of youthful idealism that society must continue to innovate on all fronts. Yes, we should dream up new ways to adapt to climate change. But it is just as important that we continue to dream up technological, societal, political, and behavioral solutions that cut emissions and prevent the root cause of the problem.
So yes, winegrowers should be confident in their ability to innovate and adapt to a changing climate. But they should also be striving to reduce their own environmental impact, and lessen the size of the problem they will soon be forced to solve.
[And just in case you need a quick refresher on weather vs. climate, see this video.]
Frankenstein Wines?
Genetically modified Pinot / Champagne / Shiraz … why not? Your favourite foods are probably courtesy of a little genetic modification in any case. So why not your favourite tipple? It’s not that you’d be swigging down grapes from Chateau Frankenstein, and in the cold light of day, the wine industry resembles a paint factory more than an artisan winemaker’s premises.
The issue of GM (genetically modified) wines largely comes down to is one of perception. Traditional wine makers are appalled at the thought of the predictability of GM grapes and GM yeasts. The finesse of reading the growing conditions, the grape’s sugar levels and the wine making itself – all lost in the lifeless world of zombie wines. Or is it? Very few wines are made as they would have been 200, or even 100 years ago, even wines with excellent vintages. Quantity wise, most wines don’t rely upon wild yeasts on the skin of the grapes for fermentation, they add commercially available strains of Saccharomyces cerevisiae. They also add industrial enzymes to hurry along the fermentation process. This isn’t to say all these wines are inferior (or superior) to all artisan wines. The point is they are accepted – GM wines are not.
Franken-grape
In 2000, a group in France called the Terre et Vin du Monde (land of wine and the world) called for a ten year moratorium on GM vines or yeast. The French government never agreed. By 2004 a test planting of 70 vines in Alsace, genetically modified to resist the soil nematode Xiphinema index, was underway. The nematode causes the the highly destructive fan leaf disease in grapes. The Terre et Vin du Monde were not impressed, claiming it would destroy 100 years of winemaking by removing diversity from the region. No matter that Xiphinema index can remove up to 80% of the grape harvest. Apparently pouring highly toxic pesticides and herbicides onto the grapes and their environs didn’t cause any harm either? So much for the sacred ‘terroir’ (the soil, geography and climate – how they impart a special ‘sense of place’ upon the wine).
In the European Union, consumers have been vigorously opposed to GM food, yet, they happily eat cheese … so? For most cheese manufacturers, calf rennet has been replaced by chymosin, hooray, no more dead calves on your conscience. Chymosin is a milk coagulating enzyme, found in a fungus. To be useful to cheese makers it’s genetic manufacturing machinery was inserted into a bacterium – which happily churns out chymosin. Cue the cheese makers. The cheese isn’t labelled as GM, simply because the GM component is classified as as ‘processing aid’ and doesn’t appear in the final product. Most consumers probably never consider this level of greyness. If your running shoes don’t have a small, under-paid child attached to them when you buy them, you ignore the potential that such a child may have been a ‘processing aid’. The same EU regulation which allows the cheese makers to side step GM issues also allows wine makers to do the same thing with GM yeast, if they chose to. Opponents point out that, theoretically, some modified yeast cells could make it into the final product.
Yeasts are well on their way to changing how wines are made. Easy to modify and rapid reproduction cycles make them an ideal organism to tinker with. In view of the generally rabid opposition of wine makers to GM yeasts, researchers have a cunning plan. By using the lab-based GM yeasts, they hope to then use traditional methods to breed the same characteristics in non-GM yeasts. How … yesterday?
Other innovations involve hybridising with S. cerevisiae with other Saccharomyces species which cannot ferment grape juice, but which impart a host of new flavours, such as mazipan, nuts, butter and soap. One wild species (S. cariocanus) was found on fruit flies in Brazil. Another, S. mikatae, normally lives on dead leaves. With so much new diversity ready to be introduced to the world of wine, it seems to fit the traditionalist’s view that variation is what they strive to protect. GM practices can introduce variety quicker than any other method. Could it be the traditionalists want to maintain diversity only so long as it doesn’t change? If so, please let those of us with shallow pockets enjoy the fruits of GM wines. It could mean our cheap plonk romps all over their fine wines with regards to aroma, flavour, mouth feel – and maybe no hangover. But that’s another GM story …
Will You Have an Isotope With That?
How do you know the bottle of sparkling wine you’ve just paid good money for hasn’t been ‘manufactured’ to match marketing requirements? The answer my friend, isn’t blowing in the wind, but it may be in the bubbles – or an isotope of bubbles.
As an avid reader of this blog, you’ll know sparkling wines are produced using a second fermentation. If it’s done in the bottle it’s termed Traditionalle or Chapmenoise. If it occurs in a large pressurised tank it’s termed Charmat. Like many things we consume, wines which were once produced in very traditional ways are now possible to replicate by all manner of food science technologies. Evidence for this comes from the third method of producing sparkling wines: pump CO2 gas into the wine under pressure. In an effort to control the many pretenders, most wine producing countries have legislation to describe how the fermentation steps are done and the final composition of the wine. For example, Brazil allows sugar to be added in the first fermentation to increase the alcohol content. It also allows sugar to be added to the second fermentation to adjust the sweetness to match the wines description. Californian producer in the US are only allowed to add sugar during the second fermentation. European legislation is stricter still, allowing sugar to be added only in accordance to local wine types and method of production.
One way to determine the history of a sparkling wine is to see if the sugar has been added at the right stage of the process. The difficulty with this fine idea is knowing if the sugar came from the grapes (the first fermentation) or from added sugar (the second fermentation). As it turns out, the common sources for added sugar are sugar cane and corn starch, or sugar beet. The first two plants are C4 plants, mainly tropical grasses, the first organic molecule they from from atmospheric CO2 contains four carbon atoms. Sugar beet belongs to a group of with a less efficient photosynthetic pathway termed C3 plants. Most temperate plant species, including grapes, belong to this group. Incase you’ve had a long day, their first organic molecule in the photosynthetic process contains three carbon atoms.
Normal run of the mill carbon is C12, but a small proportion of carbon is C13, which means its atom contains 13, rather than the usual 12 neutrons in its nucleus (C14 is the radioactive form). The usual proportions of C12 is 98.89%, and C13 – 1.11%. Due to their slightly different photosynthetic pathways, C3 and C4 plants accumulate C13 in different proportions from the atmosphere. C4 plants incorporate less C13 than C3 plants. Therefore if cane sugar or corn starch has been added to the second fermentation it will alter the C13:C14 ratio. If the CO2 comes from a pressurised gas bottle, that too will leave a C13 signature in the wine consistent with fossil fuels. It must then be clearly labelled as a gassified wine, not a sparkling wine. In this detective story, the bubbles themselves can also give the game away.
Studies have shown that many sparkling wines have mixed sugar parentage in both the first and second fermentations. The C4 plant signature shows many of them also have added cane sugar in the second fermentation.
So, science can help you rest assured your vino is what it says it is. But if the label says $5.99, you sure as hell don’t need stable isotope analysis to know what you’re getting.