New winemaking processes have risks, writes Haydn Shaughnessy
If you went looking for the contents of your favourite wine, you're unlikely to find them listed on the bottle. Uniquely among modern food and drinks, labelling the contents of a wine bottle is not required.
Because wine ingredients have never been labelled, consumers and regulators appear equally unconcerned. A properly labelled wine, however, may now have to concede that it contains carcinogens. In addition, many wines are now affected by what scientists call biogenic amines, toxins that directly affect health.
Making a wine is becoming problematic and the reason is global warming.
"There are two major problems," says Prof Ken Fugelsang of California University at Fresno in the US.
Fugelsang, the author of Wine Analysis and Production, is a recognised authority on wine stability and microbiology.
"There are two major problems, although there are many more. Higher temperatures mean the grape spends more time on the vine, which leads to a higher sugar content.
"Warmer climates present an increasingly hostile environment for yeasts and that translates into problematic fermentation."
What Fugelsang is referring to is the fact that yeasts live naturally on grapes. When they are healthy they trigger the wine's fermentation - the process that develops alcohol from sugar. Excess heat from the sun kills the yeasts.
In hot climates that means it is necessary for winemakers to introduce engineered yeasts in order to ferment their wines. No yeast, no wine.
These engineered yeasts and cultures are responsible for the production of biogenic amines.
"Biogenic amines," explains Peter Somer, head of wine research at microbiology specialist Christian Hansen, "resemble a allergic reaction and they're present in all fermented foods."
They cause the flushed feeling some people get when drinking red wine. They can cause palpitations, constrictions in the throat or other allergy-type symptoms.
"They come from free amino acids in the grapes and the addition of co-factors [ the artificial yeasts and cultures] to help fermentation," says Somer.
In other words, because of heat - and more wine areas are becoming hotter - winemakers are using cultures to trigger fermentation. These cultures in turn trigger what appears to be an allergic reaction in humans.
"I certainly get an asthma-like reaction," says Monica Murphy, whose job is to taste wines for Dublin wine merchants Febvre. "I have a kind of occupational asthma."
"It's not an allergy," Somer warns. "It is like an allergy but it is a toxin."
Nor is it particularly well understood.
We can be sure though that wine is likely to contain toxins when grapes that are high in sugar combine with artificial yeasts.
But at what level of sugar/alcohol are toxins likely to appear?
According to Fugelsang, it is 12.5 per cent alcohol - the strength of what is now a relatively weak wine. "There are problems around the world where grapes are harvested over 13 per cent; 14 per cent is at the extreme."
Increasingly, wines exceed 12.5 per cent alcohol.
Peter Somer says winemakers are asking his company for cultures that will trigger wine fermentation at 17 per cent alcohol. In other words, the natural strength of grapes is exceeding the capacity even of artificial yeasts to ferment them, an indicator of how serious the problem is becoming.
That problem is not so evident to the consumer because few wines reach the shop at these high strengths. Wineries are increasingly using de-alcoholisers to strip alcohol out of wine. And in some areas of the world, regulators allow winemakers simply to add water to the wine.
Mike Finnegan of the Wine Development Board of Ireland says: "I have not seen wine at 16 or 17 per cent alcohol; 14.5 per cent would seem to be the limit."
And diluting wines with water? "Yes, I'm aware there are different regulations around the world," he says, but points out that the Wine Development Board would not be in a position to comment on the technicalities of wine production.
Health risk number two is more serious than an amine toxin. Wine now regularly contains a known carcinogen: ethyl carbamate.
Ethyl carbamate production is in part a result of vineyards using fertilisers. Fertilisers increase nitrogen levels in the ground which ultimately develop into ethyl carbamate.
But two wines from the same patch of land and with the same nitrogen levels can produce different ethyl carbamate levels, warns Prof Sanliang Gu, also of California University, Fresno, an expert in ethyl carbamate production.
"If a wine is exposed to high temperature at any point, it increases the likelihood of the wine's ethyl carbamate level going up."
There is an argument that says changing consumer tastes means winemakers are now tempted to macerate and ferment wines at higher temperatures, to extract a more fruity juice. Not all observers of the wine trade agree with this.
"Why would a winemaker want to heat a wine?" asks Monica Murphy. "Most of them are desperate to keep the temperature down."
However, Murphy acknowledges that one leading global brand pasteurises their wine, which means heating it to 62 degrees Celsius.
It is not unknown in Spain and France to heat wines to create aromas that resemble those of the New World.
Jean Claude Paret, a winemaker at Chateau La Fauconnerie in the Montagne St Emilion, says: "It is happening. Heating during maceration and fermentation is happening. The wine will not be fresh but the wine will have the fruit, the jam." Paret deplores the practice because it kills what he calls the freshness of the wine. Nonetheless, it produces those strong fruit flavours that Irish buyers enjoy.
But the health risks lie not just in production. A recent study showed that when wine is shipped, for every 14 degrees Fahrenheit that it increases in temperature, the ethyl carbamate levels double.
Gu points out that it has also been discovered that storage is as important as fermentation in determining ethyl carbamate levels. So whether it is in the production of wine, the storage of wine or the transportation, a danger of increased carcinogens exists.
How much ethyl carbamate is too much for our health?
"The world seems to be watching the US on this and we produce at a limit of 14-15 parts per billion," says Fugelsang. "It's not difficult to achieve that with reasonable management and fertilisation."
With wine currently at uncertain risk from ethyl carbamate production, is there a case for regulation? Monica Murphy thinks so: "I certainly think that if people are finding there are chemical changes in wine, there should be regulation."
Fugelsang has been expecting regulation for more than a decade. "We've been studying the problem [ of fermentation] since the early 1990s and every year we expect to see regulations put in force, but so far it hasn't happened."
He observes also that the problem can be resolved by identifying strains of yeast that limit the potential for ethyl carbamate production.
"If everything was regulated tomorrow we'd be looking for those strains that eliminate the problem," says Fugelsang, putting forward the strongest possible case for regulation, perhaps without knowing it.