With the exception of fervent teetotalers, few people manage to get through the end of year festivities without trying at least one glass of alcoholic beverage. In the next few days, it is almost certain that someone will offer you glass of sparkling wine or of champagne, the original one from France, if the family finances are in the black and the exchange rate well-behaved for a toast. At a lunch or dinner with a climate of commemoration, a glass of wine will appear, just to keep company. And at an informal meeting with friends, there will pop up on the table a bottle of beer, the fermented beverage that Brazilians prefer. Drinking moderately does no harm to health. But you have to be on the alert: as bad as going over the limit is consuming products of a doubtful quality or authenticity. Buying a pig in a poke. The problem is that, in the world of beverages (and of food), it is not always easy to distinguish a counterfeit product unless you are a specialist in the subject. Or can count on thehelp of carbon atoms, the most abundant chemical element on Earth.
In the last five years, Brazilian researchers have been studying the degree of adulteration in domestic and foreign products, using an analysis of the quantity existing, in their content, of the stable, heavier, form of the carbon atom, the isotope denominated carbon 13 (13 C), much rarer than the light carbon 12 (12 C). The relationship between the number of atoms of these two kinds of carbon may denounce the adoption of some illegal, or at least not much divulged, procedures in the course of manufacturing drinks. According to the ingredients used in its formulation, each kind of product should show a standard isotopic signature, which reflects the proportion of atoms of the scarce carbon 13 compared with the abundant carbon 12. If in a sample of a beverage this ratio, called d13 C (delta carbon 13), is distant from its standard isotopic signature, it is a sign that the product has been targeted for some heterodox interference. Or ethylic pranks, like the excessive use of sugarcane to step up the alcoholic content of wines, or the abundant use of corn to replace barley malt in beers. “The isotopes never lie”, explains agronomist engineer Luiz Martinelli, from the Nuclear Energy in Agriculture Center, of the University of São Paulo (Cena/USP), in Piracicaba, upstate São Paulo. “With them, it has become easier to catch falsifications.”
Martinelli recently coordinated or took part in four studies which made use of stable carbon isotopes to gauge possible adulterations in wines, beers and brandies. The results of this work are reasonably worrying, although not alarming. There is no need to banish alcohol from the Christmas dinner or from seeing in the New Year. The alterations revealed in the studies do not increase (nor diminish) the risks to health inherent in the excessive consumption of alcohol. They arouse questions of another order. Some kinds of manipulation simply infringe Brazilian legislation. Others blemish the authenticity and the natural characteristics of the products. And yet others merely make explicit production methods that are rarely released to the consumer in a clear manner. A few examples of the ruses documented by the analyses with the stable carbon isotopes, a method officially recognized by the Ministry of Agriculture in the analysis of Brazilian wines and beverages derived from grapes since February 2001:
– About three quarters of the carbonic acid gas, or carbon dioxide (C02) present in three Brazilian sparkling wines of the medium sweet kind, the bubbles of which should be the fruit of the natural fermentation of their sugars, were probably injected into the bottles industrially. A perfectly legal procedure provided that the manufacturer lowers the product to the inferior category of gasified beverage, instead of sparkling. A Portuguese producer went even further. The bubbles of its sparkling wine, of the brut kind (not sweet) contained, in part, carbon acid gas coming from the air, evidence of failures in the process for preparing it. The study analyzed 75 sparkling wines from ten countries, of which 33 were made in Brazil, and was published in March this year in the Journal of Agricultural and Food Chemistry .
– At least one quarter of the 228 bottles analyzed of commercial brands of Brazilian wine showed a quantity above that permitted by the legislation of alcohol not derived from the fermentation of the sugar naturally present in the must (juice) of the grape. In these cases, it was found that over 3 degrees Gay-Lussac (G. L.) a measure of alcohol content of all the ethanol present in these drinks derived from an over-generous and for this reason illegal quantity of sugarcane added to the grape must during fermentation. What calls attention is the fact that only a little more than one quarter of the beverages that were outside the specifications 17 of 64 belonged to the most popular category of the so-called table wines. The majority of the samples with an excess of sugarcane alcohol came from some renowned producers of fine wines from Rio Grande do Sul. In this legal category, the products have to be made exclusively with varieties of grapes of the Vitis vinifera species, ideal for making wine. Adulteration proved to be more common in white wines than in red. On the positive side, one is left with the finding that almost 75% of the wines analyzed were within the law, which is more of an obligation than properly a merit. “I don’t know if the situation has got better or worse, in term of adulterations”, says Danilo Cavagni, the president of the Brazilian Viticulturists Union (Uvibra). “But the tests with isotopes are an advance. To set an example and to separate the good producers from the bad, perhaps it should be a case of closing down any company where irregularities are found.” The study by Cena is still being drafted and will shortly be submitted for publication in some magazine.
– Do you know that story of beer made with pure malt barley, the most noble (and expensive) ingredient of the chilled lagers? It does even exist, but it is a rarity in these parts. In a comparison with products from Europe, North America, Japan and Australia, the Brazilians were champions in the use of non-malted cereals probably corn in their composition, in their primitive extract. Of 31 Brazilian makes analyzed, 28 contained this cereal in their composition. On average, corn accounted for 48.7% of the dry raw material in the beers made in the country. The beers with malt closest to the pure form were the European ones. In Brazil, since November 2001, up to 45% of the malt may be replaced by several kinds of brewers adjuncts, the technical name given to starches, sugars and other cereals (usually unmalted) that can go into the composition of beer. Before that date, the maximum limit for the use of these adjuncts was even higher, 49%. As the study worked with samples of Brazilian beer collected before the end of 2001, when the law was more benevolent with the producers installed here, one can say that, apparently, the majority of them was in accordance with the legislation when the study was done. Apparently, because the analysis of carbon 13 does not reveal the use of another beer adjunct much used in Brazil, which is rice. “Producing beer outside the legal specifications is fraud”, says Marcos Mesquista, the superintendent of the National Beer Industry Union. “When this happens, the authorities can seize the merchandise and even close the factory.” The study coordinated by Americans and with the participation of Cena/USP, came out in September last year in the Journal of Agricultural and Food Chemistry.
– Amongst the samples of five Brazilian makes of brandy analyzed, none of them was a product made exclusively from the distillation of wine or of fermented grape juice. The most expensive had less alcohol derived from sugarcane, but even so were not pure. In the popular category defined by Brazilian legislation as ginger brandy, in which the law allows any plant to be used to generate alcohol, all the ethanol in the beverages came from sugarcane. This work was published at the end of 1999 in the Food Research International magazine.
These tricks, which winegrowers and master brewers comment on only in whispers, without any ado, are today unequivocally revealed with the help of a mass spectrometer, a device capable of measuring the mass and the relative concentration of atoms and molecules, and the analysis of carbon isotopes (and of other chemical elements). The methodology is used in the whole world, including in the ambit of the European Union, to control the authenticity of beverages, above all wine. “It would be difficult for any Brazilian producer to contest this kind of analysis today”, comments researcher Luiz Rizzon, from Embrapa Grapes and Wine, in Bento Gonçalves, in Rio Grande do Sul, who took part in the studies with wines. Obviously, the technique is not perfect, and some forms of fraud are not detected just with the use of stable carbon isotopes. Sometimes, to catch certain forms of adulteration, like the falsification of the geographical origin of a product, recourse has to be taken to tests with a basket of isotopes ofvarious chemical elements, such as oxygen and hydrogen. Anyhow, the use of examinations with carbon isotopes in beverages and in foodstuffs like honey is already an advance in inspecting for adulterations.
The logic behind this technique lies in peculiarities of carbon atoms and of the process of photosynthesis in plants. There are three types of carbon atoms, these isotopes: carbon 12, carbon 13 and carbon 14 (14 C). They have practically identical chemical characteristics and their number of protons in the atomic nucleus is absolutely the same (6, in fact). But they display visible differences in their physical properties. This is because the atomic mass of each isotope is slightly different. Some are lighter, and others, heavier. For the analyses carried out with beverages and food, researchers are only interested in determining the proportion of the rare and heavier13 C in relation to the abundant and lighter12 C, precisely the two carbon isotopes that are stable and do not alter in a spontaneous fashion (14 C, much used in dating fossils, is radioactive and unstable).
What do photosynthesis, plants and beverages have to do with all of this? Let us leave physicochemistry aside for a moment, to dive a bit into plant physiology. Under the action of sunlight, plants carry out photosynthesis. They transform water and carbon dioxide into organic compounds (sugars, carbohydrates, etc.) which provide them with energy for surviving. According to their type of photosynthesis, they are divided into two groups, the C3s and the C4s. That is where the story of carbon isotopes comes in. During photosynthesis, both the C3 plants and the C4s absorb much more carbon 12 than carbon 13. But, in the C3 plants, like the wine grape and barley for beer, this characteristic is still more marked than in the C4s, amongst which are included sugarcane and corn, traditional sources of sugar, alcohol and carbohydrates for many alcoholic drinks. Accordingly, in the C3 plants, the rare13 C is even more scarce than in the C4s. Put another way, from the carbon isotopes point of view, the products derived from C3 farm crops are lighter than those that originate from C4 plants.
Several international studies show that the C3 plants and their byproducts have a d13 C (the delta carbon 13 level), between -26 and -32. In the C4 plants, the values vary from -11 and -14. The level is expressed in this way, with negative values and per thousand (?), because of the formula used for calculating it. “When we find intermediate numbers, between these two ranges, we conclude that the product has components both from C3 plants and from C4 ones”, Martinelli comments. It is also possible to calculate how much of the beverage is derived from C3 plants and how much from C4s. Take an example. In a wine totally made from the fermentation of grape must (a C3 plant), or in a beer with pure barley malt (also C3), the d13 C should be between -26 and -28. In the case of Brazilian wine, this requirement has the force of law.
The Ministry of Agriculture defined, almost three years ago, that the d13 C of pure Brazilian wine, standard, is 27.86. If the alcoholic content of the beverage has been strengthened to the maximum level provided for by law (3 degrees G.L.), this ratio should come to between -22 and -24. “In this range, I consider that the wines are suspects for adulteration”, explains the researcher from Cena/USP. “Above this, there has certainly been some exaggeration in chaptalization.” The raising of the alcoholic level by the addition of sugar not originating from the vine during the process of fermentation of the must is a procedure known as chaptalization. Some wines analyzed in the study by Martinelli’s team had a d13 C of -17. This allows one to say that more than half of its alcohol originated from sugarcane sugar.
Chaptalization is a centuries-old practice that should not scandalize anyone. Used very parsimoniously, it may even improve the quality of the wines, in that the alcohol gives a beverage smoothness and viscosity. It is prohibited in some countries, like Italy, but adopted and regulated in others, including in France, the homeland that makes the best red, white and sparkling (including Champagne, of course) wines in the world. And some of the worst ones as well. Although forbidden or limited in many wine-growing zones, usually in those of a hot climate, in which the grape finds it easier to mature (and thus to generate more sugar), chaptalization has always been of difficult effective control for the authorities, before the adoption of isotopic analyses. The reason is simple: from the chemical and gustatory point of view, ethanol is ethanol, regardless of its origin having been sugar from sugarcane, from beet (much employed in Europe in chaptalization) or from grapes. “Tasting a wine, there is no way of knowing how much of its alcohol derives from the fermentation of sugarcane sugar and how much comes from the sugar of the grape itself”, claims Mauro Zanus, from Embrapa Grapes and Wine. “The central issue is that chaptalization indicates that the grapes used in the wine had not reached an ideal degree of maturity.”
According to Carlos Ducatti, the coordinator of the Stable Environmental Isotopes Center of the São Paulo State University (Unesp), in Botucatu, who started to work with carbon 13 analyses to monitor adulterations in vinegars some four years ago, it used not to be rare for this kind of analysis to catch Brazilian wines with over 50% of alcohol derived from sugarcane in the recent past. “Today, the situation has improved”, Ducatti says. “The producers know that we have a way of showing the botanical origin of the alcohol”.
The researcher from Unesp assisted the Ministry of Agriculture in preparing the legislation that instituted the use of carbon isotope analyses to monitor the degree of chaptalization in Brazilian wine. Its center is one of the two that can supply this kind of report for the ministry. The other is the enology laboratory of the Brazilian Wine Institute (Ibravin), in Caxias do Sul, an entity maintained with funds from the Secretariat for Agriculture of Rio Grande do Sul. “Since 2002, when we started to work, we have practically only detected an excess of chaptalization in table wines”, explains Regina Vanderlinde, the head of Ibravin’s laboratory. “Our target now is to inspect for more forms of adulteration, by means of tests with isotopes from other chemical elements.”
Addition of Sugarcane Sucrose in Brazilian Wines: An Isotopic and Chromatographic Approach (nº 02/02285-8); Modality Regular Line of Research Grants (Fapesp); Coordinator Luiz Antonio Martinelli Cena/USP; Investment R$ 18,008.75