GERSTEL Solutions No. 7 (pdf; 1,86 MB)

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GERSTEL Solutions Worldwide Report To perfect the composition of a wine, scientists start by separating the score of flavors into single notes. In their quest for a bouquet of fragrant high notes, scientists at the Research Institute Geisenheim rely on some rather unusual methods. Lab on the slopes Flavor from trash cans In a German vineyard, scientists of the Research Institute of Geisenheim practice an unusual, but very sophisticated type of viticulture using hundreds of trash cans. The Geisenheim wine researchers are systematically pursuing the lofty goal of creating perfectly balanced wine. They must follow an intricate path so that factors which could influence the taste or cause off-odor is addressed in the vineyard, not in the cellar. ficial quality inspection: „We want to find out why lately, in some German white wines such as Riesling, Kerner and Müller-Thurgau an off-odor develops with increasing age” explains Prof. Otmar Löhnertz. The expert oenologist explains that the trash cans are used to better observe the complicated wine system and to influence the development of plants and grapes by changing various parameters. “In the trash cans, we investigate the development of the vines by specifically varying the intensity of sunlight, the supply of nutrients and the precipitation”, says Prof. Löhnertz. „We now strongly suspect that climatic stress is the cause of UTA.“ A plant is stressed by factors such as strong UV radiation, high temperatures like those experienced in Europe in the summer of 2003, and by a shortage of nutrients in the soil. The undesirable flavor that can originate from stress conditions is formed by young wine just a few months after fermentation. In small doses, 1-AAP »We suspect that climatic stress is the cause of the atypical aging (UTA) off-odor.« Prof. Otmar Löhnertz, Research Institute Geisenheim Searching for off-odors A white wine contains 800 to 1000 different taste and flavor components, a red wine even more. In their laboratories, the Geisenheim scientists try to break down the flavor into its individual components. Most recently, they identified „atypical aging flavor“ (UTA), which is caused by the presence of 2-aminoacetophenone (2-AAP). Wines containing 2-AAP are flat and appear excessively aged with a distinct fragrance note of mothballs. It has been due to the 2-AAP that some Riesling wines didn’t pass the ofis a pleasant flavor with a fruity note. Increase the dose, however, and the unpleasant “mothball” odor comes to the forefront. The “aging” flavor is not only found in German vineyards, this research will apply to all wines that have problems with UTA. Not every grape variety is right for every vineyard From a scientific point of view, wine quality depends mainly on two initial factors: 12 GERSTEL Solutions Worldwide – May 2007
GERSTEL Solutions Worldwide Report tion, winegrowers must be familiar with the wine’s flavor compounds, and how these are formed based on both soil conditions and microclimate. Once these substances are determined, and the mechanism on how they are generated is known, their formation can be directly influenced. Additionally, if a winegrower sets out to produce top quality wines, he must reduce the crop size. The idea behind this is simple: The flavor compounds that are generated by the vines are shared between fewer grapes and so they are available in higher concentrations; in turn, the flavor of each grape becomes more pronounced. „We are trying to optimize the fruit flavor“, says Prof. Löhnertz. When leaves are removed from the Riesling vines, for example, the grapes are exposed to more sunlight which helps produce larger amounts of the compounds that are responsible for the fruity flavor. However, mistakes and pitfalls must be avoided in many parts of the process. Otmar Löhnertz mentions that winegrowers often seek his advice on how to address risks to product quality. „We are especially contacted by winegrowers that lack the chemical analysis capabilities in their cellars.” climate and soil conditions. Thus, winegrowers have to carefully consider which grape varieties are best suited for their growing area. Planting a Riesling in a warm climate zone, like California or South Africa, would result in significantly less flavor compounds being formed. The wine would never develop the characteristic fruity freshness. Red wines, on the other hand, have difficulties in Germany, even though the hot summer of 2003 prompted renewed discussion on whether it would be possible to cultivate a strong, full-bodied red wine in northern regions as well. Quality at the expense of quantity The soil type in which a vine grows in part determines the flavor of a wine. But, by what mechanism does this happen? To answer this ques- Analyzing flavors is like decomposing a musical score into single notes. The Geisenheim Research Institute maintains a number of laboratories dedicated to flavor analysis. Researchers inject flavor extracts of wines into high resolution gas chromatography systems, trying to determine every nuance of the extract by separating it into hundreds of individual components. It is like decomposing a large musical score into single notes: high or low, dominant or subtle. The only difference is that this performance is not rendered by musicians, but by chemists, who sniff out the flavor note and assign a sensory attribute to each molecule. In doing so, it is possible to link chemical analysis with olfactory sensing in an ideal way, enabling sensory wine analysis. The effluent from the GC column is split so that it arrives simultaneously at the nose and at another detector, usually a mass spectrometer since it is capable of specific compound identification. The compounds are presented to the nose through the use of an Olfactory Detector Port (ODP), and trained personnel determine the identity and intensity of the flavor compounds both of which are recorded as part of the analytical data file. Wine flavors dictated by the market GC/ODP analysis can help to understand the flavor composition of good wines, but can of course also be used when products are recreated “synthetically”, helping to create flavors with popular appeal for mass market consumption. According to the Geisenheim experts, international mass markets seem to require less personality than ever. Instead, global trends are set by wine gurus like the French oenologists Michel Rolland, who is a dominating figure in wine circles on every continent and by the American Robert Parker. A winery, whose product receives a positive review in Parker’s Wine Advocate magazine, can pop the Champagne corks and celebrate. Such is the critic’s influence on the market. Hence, many wine makers comply with Parker’s preferences. In this case, GERSTEL Solutions Worldwide – May 2007 13
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GERSTEL Solutions No. 7 (pdf; 1,86 MB)

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