Presented beiore the Divisioii of .igrioultural a n d Food Chemistry a t t h e 90th Meeting of t h e American Chemical Society, San FranC I B C O , Calif., .\uourrt 19 t o 23. 1935.
iymposium on the
'hemistry and Technology A
of Wine Vinification in OST Califorilia wines are made troiii the V i t i s vinijerera variety of grapes, characterized by their neutral flavor, as contrasted with the Vilis labrusca or American varieties grown chiefly eayt of the Rocky Mountains. According to European standards the Vitis l a b r u m varieties, with their strong flavors, are not desirable for wine making but are best when blended with California wines and w e d in the manufacture of champagnes and sparkling wines Grapes ripen in California during the fall months. The vintage season usually lasts from August until well into Sovernber. When the wine grapes are ripe, they have an average dissolved-solids content of 22" to 2.2" Brix or Balling. of which about 2.5 to 3 per cent are di-olved yolid- other than sugars, consisting of minerals. pectin matter;, tannin, and other material. From the point of view of the wine maker, the pulp of t,he grape is the most important part. The sugars in grapes are reducing sugars and have the properties of aldehydes and ketones. At mat,urity equal quantities of glucose and levulose are found in the must. The sugars are formed in the leaves of the vine with the act'ion of sunlight. The nonsugar substances in solut,ion in the must are mainly free and combined a c i d s , m i n e r a l s , tannin, coloring matter, nitrogenous substances, and pect'in TYPICiL FEK\IE~TI;\L substances. CELLIR AT SHEW4YJONES \ ~ I \ E R I , SFIOWISG Of t,lie organic acids presFROTH ON TIVKS I IF FERent, which are formed in the ME\TIVG \YIUE DUE TO leaves by the oxidation of C ~ R R O YDIOYIDE:FORc a r b o h y d r a t es , tartaric, N4TIOU citric, and malic acids are T h e conveyor in t h e ioreg r o u n d i s f o r c a r r y i n ga u a y t h e the most abundant and the grape pomace which I - usually nios t important,, although shoveled i n t o t h e c o n r e y o r b y hand. H a l f w a y d o u n t h e conformic, glycolic, glyoxalic, >eyer is seen t h e swing s p o u t which supplies m u s t t o a n y of hydrochloric, sulfuric, and t h e 4 adlacent t a n k s from t h e 6p h o s p h o r i c acids are also inch m u s t l i n e s h o u n at the top. 1733
California Wineries E. \ I . BROWS A ~ VICTOR D DEF. HENKIQUES
5heB ail- Jones, hc., Lodi, Calif.
BEIZ~G DUblPED INTO .i HOPPER I T THE SHEWAN-JONES \FINERY TO BE CONVEYED TO CRCSHER AXD STEMMER,AND THESCE TO BE PUMPEDBY (;RWES
5IEiUS
OF
MUST
PUMPS INTO I Y THE
FERMENTING T&!iKs CELI,+R
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INDUSTRIAL AND ENGINEERING CHEMISTRY
BEINGFILLEDFOR SHIPYERT I S THE SHEWAN-JONES \$-INERY
A CELLAR O F
Lower l e f t , Sweetland-type diatomaceous-earth pressure filter for preliminary rough filtration.
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most important step because more wine is spoiled a t this point than anywhere else; but with an intelligent understanding of the control of fermentation it is possible to produce a sound mine, even from grapes which may not be of the finest quality. Grapes, as they come from the vineyards, are covered with various yeasts n-hich cause fermentation; each yeast produces various amounts of alcohols, acids, odors, and tastes. The true wine yeasts, Saccharomyces ellipsoideus, form endospores and have the power t o produce comparatively large amounts of alcohol-under ordinary commercial conditions up to 15 per cent by volume, and under favorable conditions as high as 19 per cent by volume. These fresh grapes are also covered with wild yeasts which predominate over the true yeasts. Bacteria which produce disease conditions are also present. The so-called wild yeasts are usually producers of low alcohol, high volatile or acetic acid, and disagreeable flavors, and they also interfere with normal fermentation. Xodern wine making aims a t controlling the fermentations so that a sound wine will be the result. This is accomplished in several ways, although the common object is to allow the wine yeast, Saccharomyces ellipsoideus, to predominate in the fermentation. It has been found that the wild yeasts and bacteria are more sensitive to controlled doses of sulfurous acid than are the mine yeasts. While the grape musts are being pumped into the fermentation tanks, sulfurous acid, in solution or as potassium metabisulfite, a t the rate of 75 to 150 mg. per liter is added. This tends to paralyze these n-ild yeasts, and then about 5 per cent of an actively fermenting pure culture is added which rapidly multiplies and predominates the fermentation, giving the desired results of complete conversion of the sugars to alcohol with a minimum of volatile acids or disagreeable flavors. Pure Yeast Culture A simple, effective, pure yeast apparatus for winery use can be made by setting up two small tanks one above the other. The tanks are both equipped with coils for heating and cooling. They are sterilized by steam or by boiling water. The upper tank is used to sterilize and cool the must which is then dropped by gravity flow into the lower tank which is inoculated with a laboratory pure culture of yeast. After active fermentation has started, the “starter” is drawn from the lower tank into the fermenting tanks, and more sterile, cooled grape must is dropped into the lower tank from the upper tank as needed in order to maintain an active fermentation in the lower tank and to replace the must which has been drawn off for use in starting the fermenting tanks.
present. The acids of the must keep the numerous compounds of sulfur, phosphorus, and alkaline earth bases in solution in the plant juice. Grapes contain very little free tartaric acid, since the acid radical unites quickly with the potassium ions present to form the less dissociated cream of tartar. It is this substance which is responsible for the main portion of the acidity of must and wine. The mineral content of must is composed of compounds of the above acids with the minerals present in the must-potassium, calcium, magnesium, manganese, iron, and aluminum. Cream of tartar is probably the most abundant of these mineral salts. The tannin and coloring matter of most grape varieties is contained primarily in the skins. The tannin is of the enotannin type and is largely bound up with the coloring compounds. The degree of oxidation of these compounds causes variation in the coloratiop, solubility, and chemical compositions. Tannin and coloring matter are extracted from the must during fermentation largely through the action of acids and alcohol. The pectin substances in wine exist in the grapes and the must, and have a marked relationship to the mellowness and smoothness of the wine, particularly from very ripe grapes and from those varieties which produce small berries.
Wines may be divided for general purposes into dry wines and fortified wines. I n dry wines the sugars of the grape juice have been almost completely converted into alcohol and other products of fermentation and can be subdivided into red dry wines such as clarets and Burgundies, and into white dry wines such as Rieslings and Chablis; fortified wines, usually known to the trade as sweet wines, can be subdivided into red sweets such as port, and white sweets such as angelica and muscatel.
Ferment ation
Manufacture of Wines
Grapes are picked and hauled to the wineries where they are run through a crusher, which usually consists of rollers to macerate the grapes without crushing the seeds and is provided with a series of revolving blades to remove the stems. The pulp (or must) is pumped into open tanks in the fermenting house through pipe lines where most of the fermentation of the wine takes place. The fermentation of the wines is a
DRY RED WIXE. This mine is made from red or black grapes. They are macerated and stemmed by being run through the crusher, and the resulting must is pumped into open fermenting tanks generally from 3000 to 10,000 gallons capacity. Since red wine gets most of its color from the skins of the grapes, the juice is allowed to ferment upon these skins. As the must is being pumped into the tank, sulfurous acid is
General Classification of Wines
NOVEMBER, 1935
IKDUSTRIAL AND ENGINEERING CHEMISTRY
added-about 75 mg. per liter for sound grapes and u p to 150 mg. per liter for less sound grapes. This addition of sulfurous acid tends to hold the wild yeasts arid bacteria temporarily in check; as soon as the tank is full (mithin a few hours) a starter of a n active culture of pure yeasts of from 3 to 5 per cent of the volume of the juice is added which sets up a rapid fermentation. Fermentation is accompanied by (1) the formation of a cap consisting of the skins and seeds which rise to the top due to the rapid evolution of carbon dioxide and ( 2 ) by a rise in temperature. This temperature rise is approximately 0.5" F. (0.3" C.) for each degree Brix of the original must. I t is necessary to control this rise of temperature in some manner. Teast is most active around 85" F. (29" C,), d i i l e at 105" F. (41" C.) the yeast apparently ceases action and the wine become:, "stuck." Although the yeast i:: sbill fairly active at, 95" F. (35" C.), fermentation a t this t,emperature produces a n "off-taste." As the yeast weakens, certain bact'eria become active and produce volatile acids. Cooling is accomplished in several ways, either by means of cooling coils in the tanks or of heat interchangers, or even by adding blocks of ice to the juice. As mentioned before, the escaping carbon dioxidt? gas causes the stems to rise to the top to form a cap, and, since most of the color and also t'annin is extracted from this; cap, it is either submerged under the juice daily by punching or held submerged by a grabing. The color of red wine is thought to be due to a group of enolic acids, more or less in combination with tannin and similar in their propert'ies to enotannin. The removal of color from the skins is greatly aided by the alcohol formed during the fermentation and by the acids present in the grape juice. Although sulfurous acid a t first has a tendency to bleach this color, upon aeration (with its accompanying oxidation) the color becomes more firmly set and has not the tendency to precipitate later. One method of making red wine is to dram off part of the juice and heat it' to 125-130" F. (52-54" C.) and pump this juice back over the skins. This tends to extract the color and tannin t'o a greater degree. The juice is then cooled, sulfurous acid is added, and it is given a starter, consisting of about 5 per cent of its volume of pure yeast culture, and fermented. Twice daily, Brix readings and temperatures are taken; if the fermentation shows a tendency to slow up, HYDRAULIC PRESSES FOR GRAPE POXACE ; C.4R FOR P R E S S B A S K E T IN BACKGROUXD
Ccurielru, Dicision o/ F r u i t Producta, C n i z e r s t t y of California
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the juice is aerated, usually by pumping from the bottom and spraying over the top of the juice in the tank. When nearly all of the sugar has been fermented, the wine is drawn off and run into closed tanks in the storage cellar where the yeasts gradually ferment the small percentage of sugar remaining in the wine. This process usually requires 2 or 3 week.. The wine is now ready for cellar t r e a t m e n t that is, methods devised to clear the wine, hasten its aging, and improve its palatability. DRYRHITE XIKES.White wines are made either from white grapes or from the juice of red grapes which has been drawn off the pornace before the juice has had sufficient time to extract the color from the skini. I n using white grapes, one method of wine making is to allow the must to start fermenting on the skins after addition of sulfur dioxide and pure yeast in order that the cap will rise to the surface; this procedure facilitates the drawing off of a greater amount of "freerun" juice which gives a better product than the juice expressed from the pomace by pressure. Another rrietliod is t o draw the juice irnrnediately and add sufficient sulfurous acid to paralyze temporarily all fermentation organisms. Thib dosage will allow much of the sediment to sink to the bottom of the tank, after which the juice is ''racked" off, and pure yeast culture is added. About one ounce of tannin for 100 gallons of juice is often added to white wine during fermentation in order to help precipitate the albuminoid matter. during fermentation and to improve the flavor. Also, skimming the scum from the surface is good practice. In some of the finer grades of white wine3 the juice is fermented in closed containers using a bubble trap. In using this method care must be taken to prevent the wine from overheating. The residual skins, or pomace, are either pressed to free them from as much juice as possible; or a' is usually the case, when the winery producing dry wines also produces fortified wines, the pomace is covered with a small amount of water and allowed to ferment, producing a weak, alcoholic wine which is used in the distillery to produce high-proof brandy used in the manufacture of fortified wines. Another method d i i c h applies to red as well as white wines, is the "superquattro" or "Semichon" method or plus-four method. The growth of most wild yeasts is inhibited by a n alcoholic content in excess of 4 per cent by volume; thus in the plus-four method one-third of a tank containing, for example, 12 per cent of alcohol by volume, is added to twothirds of a tank of fresh juice, giving the new tank a starting alcoholic content of 4 per cent. This amount of alcohol then prevents the growth of wild yeasts, and fermentation is accomplished by selected yeasts. A serious objection to the Semichon process of fermentation is that, if a tank of fermenting must becomes infected with tourne' or some other wine disease bacteria which is not held in check by the 4 per cent of alcohol, in a very short time the entire winery becomes infected because of the mixing of wines from the different fermenting tanks. At present the Semichon process is very little used, if at all, in California. The recommended procedure is to control fermentation through the use of sulfur dioxide which not only keeps in check the wild yeasts but also the harmful bacteria which thrive in wines with an alcoholic content of over 12 per cent. White wines are generally fermented a t lower temperatures than red wines, and are removed to the cellar to "finish-off" while still containing more residual sugars than do red wines. SAUTERNE TYPE. Sauternes are white wines containing a small amount of sugar (up to 3 or 4 per cent). The juice is handled as are other white wine juices and is allowed to ferment until nearly dry. Then the fermentation is checked by adding sulfurous acid; care must be exercised not to ex-
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INDUSTRIAL AND ENGINEERING CHEMISTRI-
ceed the limitd of 325 mg. sulfurous acid per liter, set by the Food and Drug Administration. Sauternes are often made by taking a dry white wine, sweetening it to the proper degree with grape concentrate, and adding sufficient sulfurous acid to prevent it from fermenting. Probably one of the best ways to make sauterne is to take a well-flavored and sound dry white wine and sweeten it to the desired degree with fortified juice or with fortified concentrat'e made from Seniillonor grapes with similar flavor. The alcohol content must be kept under 14 per cent by volume to avoid extra tax hy the Bureau of Internal Revenue. The wine is then dosed with about 300 mg. per liter of sulfur dioxide and pumped into oak barrels [placed in a heated room x i t h temperature brought up to 120-130" F. (49-54' C . ) ] for approximately one week. This process imparts a small amount of oak flavor and also produces certain desirable esters which enhance the flavor. After removing the wine from the hot house, it is refrigerated and filtered. SWEETOR FORTIFIED WINES. These wines contain a coiisiderable amount of sugar, and high-proof brandy has generally been added to give them betx-een 20 and 21 per cent alcohol content. The grapes from which these sweet wines are made are characterized by greater sugar and less acid content than those from which dry wines are made. They also should contain less tannin. In the case of red sweet wines, such as port, the grapes are crushed and the juice is fermented on the skins. Sound procedure calls for the use of sulfurous acid and pure yeast with the usual attention paid to keeping the fermenting juice a t an optimum t'emperature [in the case of sweet wines, about 90" F. (32' C.)]. With sweet wines it is best to insure a rapid fermentation; aeration by pumping the juice over the skins is a good method, but it also extracts color. The use of sulfur dioxide helps materially in setting the extracted color and preventing it from oxidizing to a large extent and later precipitating in the bott'les. As soon as the juice is partially fermented, usually to about 12" Brix, it is removed to the fortifying room d i e r e , under the supervision of a United States gager, it is fortified by adding
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to it brandy of 180-192 proof, called "high-proof." This high-proof or fortifying brandy is distilled from the wine pressed from the pomace or from the weak water washes previously mentioned. The addition of this brandy to the wine checks further fermentation. It also causes the coagulation of a considerable amount of albuminoid and pectin matter which settles rapidly to the bottom of the tank. White sweet m-ines are made similarly to the dry whites except that, as in the case of fortified sweet reds, the fermentation is checked by the addition of high-proof brandy. Often, if the fermentation proceeds too far, it is permissible, within certain limits, to make up this deficiency by the addition of pure grape concent'rate. SHERRYTYPE. California sherry is a fortified white wine containing a small amount of sugar and having a cliaracteristic rancio flavor due to baking. It is made in the same way as white wines, but the fermentation is checked when the juice shows a Brix value of from 1" to 2". It is then fortified to nearly 21 per cent aclohol by volume. If the wine is soundthat is, low in volatile acid content and not too high in tannin -the baking will determine the quality of the sherry. This baking i. done in sherry houses or by means of steam coils in the tanks. Heating with sunlight in solaria is not practiced in California to any extent. In the sherry houses the whole room is heated between 130" and 140' F. (54" and 60' C.) over a period of 3 to 4 months, or the heat may be applied by means of coils in large tanks through which circulates hot water or steam. This heating turns the wine a dark amber color, with the formation of esters and aldehydes, and the caramelization of the sugars which, together with high oxidation, gives the characteristic sherry or rancio flavor. The methods of manufacturing California sherry can probably be improved, since sherry baking is essentially a caramelization and esterifying process. Mycoderma uini is not used in California so far as the authors know. This Feudoyeast or film yeast, called "wine flowers," which is allowed to grow on the wine in Spain, forms ethyl acetate and probably also acetaldehyde and gives the Spanish sherry a desirable bouquet. Experiments by means of oxygen, electricity (either of high voltage or electrolysis), or combinations of both together with various means of heating are being t'ried and give indications of success.
Cellar Treatment After the various wines have passed through the first stage, they are pumped into tanks in the cellar to be made marketable. This process is known as "aging" and consists of removing the suspended materials; in ridding the wine of substances which will later precipitate. such as cream of tartar,
L4RGE-CAP.iCITY
BAUDELOT-TYPE WINE COOLER, SHEWAN-JONES WINERY
Courtesy Division of Fruit Products, ~ n i v e r s i i z l of California The cylinder at the top is the tubular type of heater using steam or hot water for heating; the lower section i s the double-tube type of heat interchanger in which the incoming nine cools the outgoing, and in which the incoming wine i s preheated.
The wine is passed through the coils of nickel pipe i s cooled by brine 'which i s circulated over the nine soils, and subsequently falls over coils containing d i r e c t l y expanding ammonia.
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IKDUSTRIAL AND ESGINEERING CHEMISTRY
pean who handles his wine with great care in order that he may not disturb the sediment in the bottle. It was necessary then, not only to quick-age the newly made wines and to have them brighter, but to insure that they would stay bright in the bottles. Many means of accomplishing this are employed either singly or in qombinations. Among them are pasteurization, refrigeration, freezing, sunlight, electricity, ultraviolet light, oxygen, ozone, agitation, and aeration together with clarifications and filtration. Sweet fortified wines react to these severe treatments much more satisfactorily than do the more delicate dry wines. It is possible to put out a fairly good sweet wine in 4 months. The newly fortified wine is racked off the lees, filtered through a coarse filter, and pasteurized a t 180” F. (82’ (3.). This treatment tends to coagulate protein matters and smooth out the raw alcohol, probably by causing some oxidation and esterification. The wine is then centrifuged to remove more suspended matters to bring about further mixing and oxidation. It is then chilled down to just about the freezing point and held a t a low temperature for about 3 weeks to a month. A small amount of oxygen as gas is bubbled into the wine while cold. This refrigeration will remove most of the potassium acid tartrates. The wine is then racked and clarified with some clarifier. Either a claylike bentonite or an organic fining agent such as gelatin or isinglass may be used for this purpose. After 2 weeks the wine can again be filtered through
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No. 11
a coarse filter and allowed to rest for a few weeks more when, just previous to barreling, it is filtered through a fine filter employing either asbestos or asbestos-paper pulp disks. It is necessary that the metal content of the mine be below the amount which nil1 cause hazing or clouding. Freezing the wine t o slush ice and then allowing it to thaw has proved quite satisfactory.* Wine which has been frozen to slush ice, thawed, and filtered remains brilliant in the bottle much more surely than wine which has been merely chilled. This process also eliminates the necessity for the use of a clarifying agent. It is believed that one cause for the extreme stability of this frozen wine is due to the dehydration, by freezing, of proteins to insoluble forms. Overoxidation is t o be avoided, especially in the case of dry wines. It is best to refrigerate dry wines and then to adjust the total acid content and clarify with some form of gelatin using tannin in slight excess of the amount necessary to combine with the fining agent. The wines may then be considered finished and are ready for a final polishing, for filtration into barrels or bottles, and thence for marketing. RICCEIVED August 29, 1935. 1
Reported b y M. A. Joslyn i n April, 1934, a n d being investigated b y [ I N D . ENQ.CEEM, 27, 33 (1935)l.
M. A. Joslyn a n d G L. Marsh
Manufacture of Champagne and Sparkling Burgundy F. 31. CHAJIPLIN
H. E. GORESLINE
Pleasant Valley Wine Company, Rheims, N. Y.
Bureau of Chemistry and Soils, Washington, D. C.
D. K . TRESSLER
New York State Agricultural Experiment Station, Geneva, N. Y.
HAMPAGXE, a distinct type of sparkling wine, originated in the Abbey of Hautvillers, near Epernay, France, in the seventeenth century. According to the rather meager historical records available, Dom Perignon, then cellar man a t the abbey, observed that, if wine containing a small amount of residual sugar was bottled, tightly stoppered, and stored for several months, it acquired radical changes in character. When opened it effervesced abundantly and possessed an added and agreeable bouquet and flavor.
For centuries previous to this time the wines of the district had been famous for their exceptional qualities, but they had been nonsparkling. Early accounts mention the “sparkling clearness and whiteness” of Dom Perignon’s product. It is therefore assumed that he introduced the method of removing the sediment from the bottles, which a t the present time is one of the most important steps in the “champagnization” process. The meaning of the word “champagne” is a moot question. The French hold that it can be applied only to wines produced from grapes grown in the Champagne district and made effervescent by the champagnization method of slow fermentation in the bottle. However, sparkling wines are made by exactly the same method in many countries of the world and are allowed by lam to be called “champagne,” provided the same process is used.
