. Current Eamments@ EUGENE GARFIELD INSTITUTE FOR SCIENTIFIC lNFORMATION~ 3501 MARKET ST PHILADELPHIA PA 19104 Enology. Part 1. Fortifying an Ancient Art with Modem Science Number 29 )UIY 20, 1987 For the past few years, Philadelphia has content falls much below 7 or 8 percent, the been experiencing a restaurant “boom’ ‘— beverage approaches what is now called a a renaissance of creative dining establish- “wine cooler, ” a combination of undistin- ments. 1.2In addition to exotic foods pre- guished wine and unfermented fruit juice. pared in unusual or extravagant ways, a sig- The alcohol content of wines varies, of nificant part of this gastronomic revolution course. In some cases, with grapes that are has been the prominence of wine as a part very high in sugar, alcohol levels may reach of the meal and an accompanying increase 14 percent; others can be as low as 7 per- in interest in types of wines and how they cent.5 (p. 43) The alcohol content of cham- are served. pagne and sparkling wines generally ranges One of my own favorites is Piesporter, a from 10 to 12 Percents (p. 178-90) If the term that, according to the Encyclopedia of bottle indicates alcohol content above 14 Wine by the eminent wine writer Frank percent, then a neutral brandy has beerradd- Schoonmaker (1905-1976), refers to wines ed (as in port, sherry, and other dessert produced in the village of Piesport in the wines). j (p. 191-203) Wines that have not Moselle Valley of the Federal Republic of only a relatively high alcohol content (15 Germany-although some wines labeled percent or more) but also other natural fla- ‘‘Piesporter” may come from “less cele- vors—including herb flavors-are called brated townships nearby. ” Schoonrnaker aperitifs.5 (p. 204-1 1) described Piesport as “one of the small yet Goldtropfchen wines are sweet because deservedly one of the most famous not all of their natural grape sugars have wine-producing” sites along the Moselle and been converted into alcohol during fermen- called genuine Piesporter wine “wonderful- tation; they have no synthetic or natural ly delicate and fragrant, fruity, with an in- sugar added to sweeten them. While my comparable distinction all its own.”3 A tru- more sophisticated friends continue to ‘‘ed- ly great Moselle wine is created by a selec- ucate” me to the virtues of other wines, my tion process that involves picking grapes col- particular chemical makeup doesn’t react onized by the “noble mold” Botrytis cin- well to dry wines or stronger alcoholic erea, which grows naturally on late-harvest- drinks. Some of these friends helped in ed grapes and depletes them of their mois- preparing this report, including my neighbor ture, thus concentrating their inherent sugar and good friend, wine enthusiast Arthur and flavor. ‘r Bayard; Arthur Seidel, patent attorney and As a matter of fact, my preference for scholar extraordirraire; and Morley Kare, Piesporter is even more spexitic-piesporter director of the Monell Chemical Senses Goidtropfchen (Golden Drops), of which Center, just across the street from lSl@. there are at least a dozen brands that I’ve Wine is the subject of considerable sci- encountered. But to paraphrase the Ameri- entific interest. Part 1describes some of this can humorist Will Rogers, I never met a published scientific research. Part 2 will Goldtropfchen I didn’t like. These sweet, discuss the leading centers of enology re- white wines are about as low in alcohol as search around the world. I imagine, how- you can get in a true wine—if the alcohol ever, that there is considerable “research” 190 in this field that remains unpublished. Most broadest sense, “wine” refers to the fer- likely, these trade secrets remain closely mented juice of any piant product; wine guarded because patents provide less than made from dandelions, a common iawn pest a generation of protection. For most inven- in North America, is popular in some parts tors, this is inadequate incentive. of the US, and the Japanese produce a wine, called sake, from fermented rice. Another popuiar Japanese fruit wine is made from Just What Is Wine? piums. It is ciose to a sherry in taste, and Wine has been a part of human cuiture for I’ve encountered at least a dozen brands in millemia. The word “wine” derives from Japanese and Chinese restaurants in the US. the ancient Greek word oinos, from which Fermentation, of course, is the process came the Latin vthum and the Old and Mid- that makes wine possible. The chemistry of die Engiish forms of the word, win and wyn, fermentation-the conversion of a moiecule respectively. b /Uso derived from oinos is of grape sugar (glucose) to two molecules the far more modern word ‘‘ecology, ” the of alcohoi (ethanoi) and carbon dioxide— science of wine and wine making. T was first described by French chemist Jo- “Wine” usually refers to the fermented seph Louis Gay-Lussac in 1810.1o.11How- juice of grapes-specifically, to the juice of ever, Louis Pasteur demonstrated in i 857 the Old World wine grape, Vitis viru’’era.8 that the process is due to the metabolic ac- (Vitis, the name of the genus to which this tions of yeast ceiis (generaiiy of the Sacchar- plant belongs, is the Latin word for omyces cerevisiae species). 12.ls The chem- “grapevine”; vinifera is the species icai equation for this process is reproduced name.g) The variations of V. vinifera, in Figure i. which range from light greenish yellow But wine is a compiex liquid whose final through russet, pink, red, reddish violet, and flavor is influenced by numerous factors. Of purplish black, account for the vast majori- course, the amount of time the wine is ai- ty of fine grape wines. Other factors con- lowed to ferment is one such factor, but tributing to the diversity of these wines (as there are many others that affect flavor be- well as those made from other grapes) in- cause they affect the maturation of the clude the climate and soil conditions under grapes. These inciude moisture, suniight, which the grapes are grown, the techniques soil conditions (such as rninerai content), as of the wine makers, and the actuai processes well as any fungi, molds, and diseases that used during vilification (the conversion of may attack the vines (and thereby affect the juices into wine). ripening process). Even the temperature of But while V. vinifera is the fruit of choice the grapes when they are picked can influ- for most “noble” or distinguished wines— ence the flavor of the finai product. 11Not that is, those rhat are aged in the bottie— surpnsingiy, two of the 1986 1S1research most wines are produced from hybrid vines. fronts we identified in reiation to wine and Wines are produced from an array of grape wine making concern the yeast S. cerevis- varieties. For instance, the Concord grape iae (see Table 1). Three other fronts de- (V. kdwusca)–aiso known as the wild scribe new methods for the chromatograph- American fox grape and a native of the ic and spectrai analysis of the various con- eastern US—is one of the main alternatives stituents of wine. to V. vinifera.s (p. 25) The juice of other grape varieties, such as the Muscadines (V. Resemch-Frortt Data rotwtdifolia) and the desert grape (V. gir- diana), as weii as V. rupestris, V. ber,!an- In i986 there were 27 pubiished papers dieri, and V. riparia-ail of which are na- concerning’ ‘Computer regulation of sugar tive to North America-is aiso used occa- metabolism in yeast” (#86-0359). Waiter sionally to make wine, aithough their main Beyeler, Swiss Federai institute of Technol- use iies in serving as rootstock or as the ogy, Zurich, coauthored two of the four core parents of hybrid grape varieties.s (p. 25)$ papers that identified this topic. With col- In fact, the juice of any fruit can be fer- leagues Arthur Einsele and Arntin Fiechter, mented to produce wine. Indeed, in its he wrote a paper in i 98i describing a new, Tstbte 1: The 19S6 SCP /SSCP research fronts on vxrious aspects of enology. A =number of core papers. B=rtumber of citing papers. Nmrtber Name AB 86-0359 Computer regulation of sugar metabolism in yeast 4 27 86-0360 Ethanol-sensitive mutants of .%charomyces cerevisiae 4 35 86-2020 Current trends in wine tdsnology 16 131 86-6056 Determination of wine components by gas chromatography 2 13 86-8351 HPLC and spsctrd methods for separation of phenolic compounds 2 15 to keep track of the rate at which glucose Figure 1: The chemicaf equation for the conversion of was being metabolized and could add glu- glucose to alcohol. cose as needed to keep the level optimaJ. IT 1 glucose (CCH,20J ~ 2 ethanol (CH3CH20H) + A]ba also coauthored one of the four core 2C02 + about 56 kilocalories of energy papers for the research front on ‘‘Etha- nol-sensitive mutants of .$accharornyces cerevisiae” (#86-0360). His 1%8 paper dis- computerized prob for measuring fluores- cusses the growth rates of a specific strain cence in cultures of microorganisms. 14Ul- of S. cerevisiae under various concentra- traviolet light is used to cause the nicotin- tions of alcohol. la Alcohol, the natural arnide adenine dinucleotide phosphate product of fermentation, inhibits the meta- (NADP, which mediates oxidation and re- bolic activity of the yeast cells in concen- duction by carrying electrons) contained in trations of more than 20 percent. This in- yeast microorganisms to fluoresce; by hibitory effect was also the subject of two measuring the intensity of this fluorescence, core papers coauthored by D.