LOUIS PASTEUR, FATHER OF MODERN OENOLOGY

While the biologist earned royal access to the science pantheon for his remarkable work on pasteurization and vaccination, it is interesting to note that, as a great wine lover, he was also a benefactor to winemaking. "For thousands of years, winemaking remained the exclusive business of the winemakers. Techniques handed down from generation to generation with the aim of producing excellence: selection of the soils, grape varieties, working the vines... Almost magical rituals that were carried out in the mystery of the cellars", recall the biologists François Gros and Béatrice Salviat, reference authors on the subject. At 41 years old, Pasteur was already known for his research on fermentation. His work complemented the existing theories, developed thus far by chemists. "Contrary to current ideas, Pasteur asserts that this process is a "work of life" and not of decomposition, because it is triggered exclusively by the action of living beings." Indeed, how else can we explain, if not by a mystery of divine order, that the grape must spontaneously start to bubble in the press without any fire being lit under the vat? It took until the 18th century for science to provide a better understanding of the natural mechanisms at work in winemaking. Already convinced of the role of microorganisms in fermentation, Louis Pasteur withdrew to his family home in Arbois, now owned by the Academy of Sciences, in order to carry out a mission entrusted to him by Emperor Napoleon III, mainly to deal with diseases of the vines. "Each time he studied a sample of altered wine, Pasteur found, alongside ordinary yeast, ferments that are distinct to this yeast, of course, and of different morphologies according to the type of disease. He concludes that these unusual germs are responsible for the diseases observed and that they cause alterations resulting from fermentation." A giant step forward for oenology, Pasteur thus identified the four microbes that, by developing in the wine, alter its taste qualities.

BIRTH OF PASTEURISATION

Pasteur first imagined adding antiseptic substances to wine in order to kill undesirable germs while preserving the organic elements of the wine. But the experiments prove inconclusive. He then turned to another solution, recommending heating the wine to high temperatures in the absence of air. As far as wine was concerned, it would eventually be abandoned because of a major drawback: even though it enables perfect conservation, it kills the wine by preventing the fermentations that take place after bottling and allow its maturation. Pasteurisation of the wine has therefore gradually been replaced by rigorous hygiene during the harvest and vinification. "We now know how to avoid the four "bad" microbes discovered by Pasteur (there are no more today), which multiply in the wine and, on the contrary, favour the development of the "good" microbes by playing on the temperature of the wine, its exposure to the air or by adding sugar or chemicals, all within limits defined and controlled by the State." Pasteur made considerable progress in the way wine is made and stored, so much so that many winemakers still consider Pasteur a benefactor of winemaking today, and even the founder of modern oenology. There is no doubt that this recognition would delight the scientist. For although Louis Pasteur made a decisive contribution to the elucidation of the mysteries