GIFT OF 
 
UNIVERSITY OF CALIFORNIA 
 
 COLLEGE OF AGRICULTURE 
 
 BERKELEY 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BENJ. IDE WHEELER, PRESIDENT 
 
 THOMAS FORSYTH HUNT, DEAN Al 
 
 H. E. VAN NORMAN, VlCE-DlRECTO 
 
 UNIVERSITY FARM S 
 
 CIRCULAR No. 108 
 
 OCTOBER, 1913 
 
 GRAPE JUICE, 
 
 By F. T. BIOLETTI. 
 
 This short account of methods of preserving unfermented grape juice 
 is prepared in answer to the very numerous inquiries received at the 
 Station on this subject. No attempt is made to explain in detail all 
 the methods and appliances necessary for preparing grape juice on a 
 commercial scale. Only the fundamental processes and principles are 
 discussed together with enough detail to enable anybody to devise 
 means to conserve small quantities for domestic use, or to judge of the 
 efficacy of industrial methods or installations. 
 
 OUTLINE OF PROCESS. 
 
 Gathering and Care of the Grapes. 
 
 Extraction of Juice. 
 
 Stemming, Crushing, Draining, Pressing. 
 
 Preliminary Clearing or Defecation. 
 
 Sulfiting,, Settling, Racking, (Fining?). 
 
 Final Clearing. 
 
 Pasteurizing, Settling, Addition of Acid, (Fining?), Filtering. 
 
 Conservation. 
 
 Bottling, Corking, Sterilizing. 
 
 The various steps in the process have two objects to preserve the 
 juice from spoiling and to make it permanently clear. Both objects 
 should be accomplished with as little change of the flavor of the fresh 
 juice as possible. If the juice is for home consumption and perfect 
 clearness is not necessary, the process can be shortened and simplified. 
 It can be still further simplified by adopting the methods used for 
 ordinary preserving of fruit. In the last case, the fresh flavor of the 
 juice is destroyed and it is not relished by most people. 
 
 1. Gathering the Grapes. Only good, sound grapes, carefully gath- 
 ered in a cleanly way should be used. It is best to gather them in the 
 morning while cool, or to leave them all night exposed to the open sky 
 to cool off before crushing. ^ ." 
 
2 
 
 2. Crushing and Stemming. The cool grapes should be thoroughly 
 broken and the pulp crushed by passing between rollers or by some 
 similar method. The seeds should not be broken nor the skins macer- 
 ated too much or the juice will be harsh, astringent and difficult to clear. 
 On the other hand, if the pulp is not well broken up, the yield of juice 
 will be low. 
 
 3. Separation of Juice. A considerable portion of the juice will 
 run off if the crushed grapes are allowed to stand for a few hours in a 
 drainage cage. This cage may be the press basket, a box furnished with 
 a false bottom of slats, an open fermenting vat with a good strainer 
 at the bottom, or some similar device. 
 
 After draining, the crushed grapes are pressed to extract more of the 
 juice. A cider press or any of the presses used in wineries may be used 
 for this purpose, with the exception of the ordinary continuous presses, 
 which are not advisable, as they macerate the grapes too much and pro- 
 duce a turbid juice that is difficult to clear. The fresh grapes have a 
 tendency to squirt out through the interstices of the press, especially if 
 the stems have been removed, as is generally done directly before or 
 after crushing. This can be prevented by lining the bottom and sides 
 of the press basket with grape stems as it is being filled. Clean straw 
 is sometimes used for the same purpose. 
 
 For the best results, the pressing should be slow and gradual. A 
 lever press gives excellent results on a small scale. The pressed 
 "pomace" may be forked over and pressed a second or third time. 
 If any water is to be used, it is best sprinkled on the turned pomace 
 before the second and third pressings. 
 
 4. Defecation. The free run and the press juice are more or less 
 cloudy, owing to floating particles of skin, pulp, etc. If the grapes are 
 clean and sound, this may not injure the flavor noticeably and for home 
 use it may be bottled immediately and sterilized as explained later. 
 It is very much improved, however, in appearance and somewhat in 
 flavor, by a preliminary "defecation" or clearing. This is obtained 
 by allowing the juice to remain undisturbed in casks or open vats 
 until the grosser particles settle and form a sediment. 
 
 This defecation requires from twelve to forty-eight hours, usually 
 about twenty-four to thirty-six. It will therefore be from two to three 
 days after the crushing of the grapes before the clear juice is obtained. 
 During this time, there is danger of fermentation starting, which would 
 spoil the juice. If the grapes are cold when crushed and the weather 
 remains cool, the juice can sometimes be cleared successfully in this 
 way. It is usually necessary, however, to take measures to prevent 
 fermentation. There are two methods of doing this. One is to put the 
 jnice ia+o a ?o':d '.storage room below 50 F. If the grapes are in poor 
 
condition or the juice warm, it may be necessary to have the room much 
 colder than this. The other method is to paralyze, temporarily, the 
 fermentation organisms with sulfurious acid. 
 
 The best way of applying the latter method is the use of potassium- 
 metabisulfit. This is used in the form of a ten per cent solution in 
 water at the rate of from 5 ounces to 10 ounces of the sulfit to one ton of 
 grapes or two hundred gallons of the juice. The sweeter and warmer 
 the juice the more sulfit is needed. 
 
 The best way of applying the sulfit is to add the solution gradually 
 to the crushed grapes as they fall from the crusher or into the drainage 
 box. In this way, the ferments are prevented from making even 
 a commencement of development and a smaller quantity of sulfit will 
 suffice. The use of sulfit must not be considered as a substitute for 
 care in handling and keeping the grapes cool, but only as an additional 
 precaution against injurious fermentation. The juice should be as cool 
 as is practicable, but may be defecated perfectly by this means if it does 
 not rise above 70 F. 
 
 The sulfit must be carefully measured and evenly distributed. If 
 too much is used, it will injure the flavor of the juice. If too little, it 
 may not accomplish its object. An excess of ten or twenty per cent 
 over the amounts indicated will do little or no harm and would still be 
 several times less than the legal limitations for dried fruits and wine. 
 
 Defecation by means of sulfurous acid is not only simpler but better 
 than by means of refrigeration. It not only prevents injurious fer- 
 mentations more effectually, but it prevents undue oxidation of the 
 juice during the processes of preparation. Oxidation is one of the main 
 causes of the loss of the finer flavors of the fresh juice. This is not 
 prevented but rather increased by refrigeration. 
 
 5. Pasteurization. The prevention of fermentation by means of the 
 metabisulfit is only temporary and, even in cold storage, fermentation 
 will develop slowly unless the juice is kept close to the freezing point. 
 The clear juice, therefore, must be separated from the sediment as soon 
 as it has settled and before even the commencement of fermentation has 
 occurred. At the end of forty-eight hours, at the latest, therefore, it 
 should be drawn off. Even though it still appears cloudy, most of the 
 gross sediment will have settled. 
 
 In many cases, it will be nearly bright, and, if intended for domestic 
 use, it is best to bottle and sterilize it at this point. However bright it 
 may be at this point, it is not safe to bottle it for commercial use, as it 
 will become cloudy again in bottle. This new cloudiness is due to 
 crystallization and precipitation ; that is, the becoming solid of certain 
 substances which are at first dissolved in the juice. The chief of these 
 substances is the bitartrate of potash or cream of tartar. These sub- 
 stances precipitate slowly, often requiring weeks, or even months. 
 
In order to give the substances time to deposit, the juice is pasteur- 
 ized to kill the ferments which have been only temporarily paralyzed 
 by sulfiting or refrigeration. 
 
 This pasteurizing is sometimes applied to the fresh juice without 
 preliminary defecation. This involves heating the juice while it still 
 contains all its gross sediment. This results in deterioration of flavor, 
 difficulty in clearing, and clogging of the pasteurizer. 
 
 Pasteurizing is heating to a degree and for a time sufficient to kill 
 all ferments which are in the juice and are capable of injuring it. 
 
 The killing of the germs depends both on the degree of temperature 
 reached and on the time during which this degree is maintained. A 
 momentary heating to 175 F. will kill most yeasts and molds com- 
 monly found in grape juice, but at 140 F., some of the resistant spores 
 would escape. If the must is heated to 140 F. and kept at that 
 temperature for several hours, the effect would be equal to 175 F. for 
 a minute. 
 
 The lower the temperature of pasteurization the less the flavor of 
 the juice is injured. It must be high enough, however, to insure keep- 
 ing. In practice, with present methods, it is necessary to heat at least 
 to 160 F. If the must is sulfited and run hot into sterilized casks of 
 at least fifty gallons capacity where it will keep hot for some hours, 
 this temperature should be sufficient. If the heated must cools rapidly 
 as when put in bottles, or if the casks are imperfectly sterilized before 
 filling, a higher temperature will be needed. The flavor of the juice is 
 not seriously injured below 175 F. when sulfit is used. 
 
 For domestic purposes, the pasteurizing is best done by placing the 
 fruit in large fruit jars or demijohns and heating them, surrounded 
 by water, in a boiler, as is done in bottling fruit. Two thermometers 
 should be used, one in one of the jars, and the other in the water of 
 the boiler. The thermometer in the jar should reach to the bottom 
 where the juice heats more slowly. The covers should be placed loosely 
 over the jars and the boiler should be covered. The water in the boiler 
 should not exceed 175 or 180 F. and as soon as the thermometer in 
 the jar indicates 160 F. at the bottom, the fire should be removed, 
 the covers of the jars screwed down tight and the juice allowed to cool 
 slowly in the covered boiler. These jars may then be kept like those 
 containing preserved fruit. If placed upright, the solids eliminated 
 will form a sediment at the bottom and the clear juice above may be 
 decanted for immediate consumption, or placed in bottles, corked and 
 sterilized as described later. 
 
 On a large scale, some form of continuous pasteurizer is more con- 
 venient. Some of those used for wine are suitable, providing the tubes 
 or other passages through which the liquid runs are not too small. 
 Pasteurizers having a great length of narrow tubing rapidly become 
 
clogged and the viscid nature of the juice renders the flow difficult 
 and irregular. In pasteurizing wine, the hot liquid must not come in 
 contact with the air. With grape juice, this precaution is not neces- 
 sary, especially if sulfit has been used. Too much exposure to the air, 
 however, should be avoided, or the juice may acquire an oxidized taste. 
 The heated wine should pass directly from the pasteurizer into 
 recently sterilized casks. These casks should be sterilized by means of 
 steam and plugged with a wooden bung wrapped with a piece of cloth 
 such as ordinary cotton sheeting. Both bung and cloth should be 
 thoroughly sterilized with boiling water and by soaking in a two per 
 cent sulfit solution. The filled casks are then placed on skids, firmly 
 wedged to prevent movement, and allowed to settle for several weeks. 
 
 D 
 
 Air-filtering Bung for Settling Casks. 
 S, stave of cask ; J, surface of grape 
 juice ; B, wooden bung ; T, metal fun- 
 nel to hold cotton with tube passing 
 through the bung ; C, tightly packed 
 sterilized cotton ; D, loose fitting metal 
 cap of funnel. 
 
 The colder the room in which they are kept, the less danger there will 
 be of fermentation and the more rapidly the juice will get rid of its 
 cream tartar. 
 
 The juice will have to settle for several weeks and unless the work 
 is all done carefully, it runs the risk of fermenting. If the casks have 
 been properly sterilized and the juice run in at 160 F., they will be 
 completely free from any germs which could cause fermentation. As 
 the juice cools, however, air will be drawn into the cask by the decrease 
 of volume and, with this air, some fermentation germs may enter. 
 
6 
 
 This may be prevented by use of a device which filters the air through 
 a tight plug of sterilized cotton as it enters. Such a device is shown 
 in the figure. 
 
 This air-filtering bung should be put in place of the regular bung 
 as soon as the cask is fixed on its skids and before the juice has had 
 time to cool in the least. The best way, where practicable, is to 
 pasteurize directly into the casks after they have been fixed in their 
 permanent resting places and to insert the air-filtering bung the moment 
 the cask is full. 
 
 These air-filtering bungs will be effective only if carefully made and 
 properly handled. The bung hole of the cask should be smooth and 
 regular and each should have its own bung fitted exactly. The metal 
 tube through the bung should fit close so that no air will pass between 
 it and the Avood. If it is threaded so as to screw into the bung it will 
 make an air tight joint. 
 
 Before using, both filtering funnel and bung should be sterilized. 
 
 The funnels are first filled with clean surgeon's cotton, packed fairly 
 tight and the loose metal caps put in place. They are then rolled 
 in pieces of manila paper kept in place by folding over the ends. The 
 wrapped funnels are then heated for an hour in an oven hot enough 
 to just slightly char the paper. A number of wrapped funnels may 
 be sterilized in a metal box and kept in this box until needed. 
 
 The bungs are sterilized by dipping in boiling water and then soak- 
 ing until needed in a 2 per cent solution of sulfit. 
 
 If the funnels and bungs are carefully handled, they can be inserted 
 into the casks without danger of contamination. As soon as a bung is 
 inserted into a filled cask, it is tapped in firm and the cask immedi- 
 ately rolled a little on one side. The cask should be rolled over 
 sufficiently to immerse the lower end of the bung in the hot juice but 
 not so far that there is danger of wetting the cotton in the funnel. 
 
 With all these precautions, a cask of juice may occasionally ferment. 
 In such cases, the juice can be used for vinegar. With intelligent 
 care, few or none of them should spoil in this way. The air-filtering 
 bung acts as a safety valve for the occasional cask which ferments and 
 which without this outlet might blow out a head. 
 
 6. Final Clearing. A few weeks of settling, after pasteurizing, 
 will sometimes render the juice perfectly bright. In this case, the 
 permanency of the brightness should be tested. This may be done by 
 heating a corked bottle of the clear juice to 160 and then allowing it 
 to stand for several days in a cool place. If the juice remains clear, it 
 may be bottled. If it becomes cloudy, it should be allowed to stand 
 several weeks longer. 
 
 In some cases the juice will not become clear even after prolonged 
 settling. It is then necessary to filter it before bottling. It should 
 
be tested by filtering a few bottles, heating and allowing to stand as 
 explained above before bottling the whole quantity. 
 
 In nearly all cases, even when the brightness appears permanent by 
 these tests and the juice is put in the bottles clear, there will be a 
 further deposit with time. This should be very slight, however, and 
 should consist only of fine crystals of cream of tartar. The formation 
 of these crystals in the bottle will be prevented if a small quantity of 
 citric acid is added to the juice before filtering. The addition of this 
 acid is also nearly always advisable to improve the flavor of the juice, 
 which with ripe vinifera grapes tends to be lacking in acidity. Tartaric 
 acid will improve the flavor in the same way but will not prevent the 
 formation of crystals. From one to two pounds of citric acid to a 
 hundred gallons of juice is all that is needed. 
 
 7. Sterilizing. The clear filtered juice should pass directly into 
 bottles which should be corked and sterilized without delay. 
 
 The bottles should be carefully cleaned and sterilized with boiling 
 water before filling. It is even more important that the corks should 
 be thoroughly sterilized. The sterilization of the corks is more difficult 
 as resistant mold spores may be lodged in the crevices. It can be 
 accomplished by immersing the corks for five nmmtes in boiling water 
 to which has been added 1 per cent of copper sulfate. The corks should 
 then be kept in 2 per cent solution of metabisulfit until used. Where 
 caps are used, there is also danger of molding unless they are sterilized. 
 Copper sulfate can not be used in this case as it would attack the metal 
 of the caps. Boiling in pure water for fifteen minutes can be recom- 
 mended. 
 
 As soon as the clear juice is bottled and corked, it should receive its 
 final sterilization. This can be done by any means which raises the 
 temperature of the juice in every part of the bottle to 160 F. This 
 temperature should be maintained for at least five minutes. If the 
 bottles are placed upside down or in such a position that the cork will 
 be wet with the juice during sterilization, less trouble will be experi- 
 enced from subsequent molding of the corks. 
 
 The bottles must not be filled too full or the expansion of the juice 
 in heating will drive out the cork or burst the bottle. An air space 
 of about 1| inches in the neck is necessary. Even then the corks may 
 be driven out by the compressed air, so it is necessary to fasten them in 
 by tying with string or with some of the devices made for this purpose. 
 When the sterilizing is done in a closed sterilizer or l i autoclav, ' ' fasten- 
 ing the corks is not necessary. 
 
 8. Fining. The clearing of the juice may be much facilitated and 
 hastened in many cases by "fining." This consists in adding to the 
 juice a minute quantity of a substance which will coagulate and settle 
 in the liquid*, carrying down with it all the particles of solid matter 
 
which cause the cloudiness. This fining can be applied at the time of 
 the first pasteurization or just before the final filtration and bottling. 
 
 In the first case, just as soon as the juice is cleared by defecation, it 
 should be drawn off, thoroughly mixed with the finings and pasteurized 
 into the settling barrels immediately.* In the second case, the juice 
 from the settling casks is drawn off, mixed with finings and pasteurized 
 again into other casks. After remaining until clear, it is bottled 
 directly and sterilized. Instead of allowing it to settle after this 
 pasteurization, it may be passed while still hot through a filter and 
 bottled directly. When this is done, the juice often becomes cloudy 
 again a short time after bottling. If the juice after fining and heating 
 is allowed to stand for a few hours it can often be made permanently 
 clean by filtering. 
 
 The usual method is to fine the juice after settling for several months. 
 In this case, an extra heating is necessary just before bottling. If the 
 fining is done before settling this extra heating is unnecessary. 
 
 9. Materials Used for Fining. The materials used in fining wine can 
 be used for grape juice. The amounts used, however, will differ, owing 
 to the greater cloudiness of the juice and the presence of albuminoid 
 matters. 
 
 The commonest finings used for wine is equal amounts of tannin and 
 gelatin. If gelatin is used in grape juice, a much larger amount of 
 tannin will be necessary. Good results have been obtained by the 
 use of 5 ounces of tannin and 2 ounces of gelatin to 100 gallons. Two 
 to three ounces of tannin without the gelatin would probably be effec- 
 tive in some cases as the tannin would form a precipitate with the 
 albuminoid matters of the juice. The tannin should be completely 
 dissolved in a little hot water and thoroughly mixed with the juice 
 before adding the gelatin. The gelatin should then be dissolved in 
 hot grape juice and thoroughly stirred into the juice. These finings 
 can be recommended for use before settling. 
 
 Dried egg albumen at the rate of 4 ounces to 100 gallons of juice 
 without tannin may be used for the late fining but has not given good 
 results before settling. 
 
 The best results for early fining, before settling, were obtained by 
 the use of Lactocol or Casein at the rate of from two to six ounces per 
 100 gallons, according to the character of the juice. Lactocol is more 
 convenient to use as it dissolves easily in warm water. Casein has to 
 be dissolved with the aid of sodium carbonate or other alkali. Silicate 
 of soda at the rate of 2 to 4 ounces per hundred gallons gave fair results. 
 
 Whenever the juice does not become bright by itself, fining is advis- 
 able. Even though the fining is not completely successful in clearing 
 the juice, its use much facilitates the final filtration. 
 
 *The juice may be filtered a few hours after heating with the finings. It will 
 usually remain bright after this but will deposit cream of tartar. 
 
OUTLINE OF RECOMMENDED METHODS. 
 
 1. Domestic Method 
 
 Separation of Juice 
 
 Sulfiting, Defecation and Settling 24 to 48 hours 
 
 Bottling and Sterilizing for 30 minutes at 165 F. 
 
 2. Industrial Method 
 
 Separation of Juice 
 
 Sulfitiug, Defecation and Settling 24 to 48 hours 
 
 Removal of Juice from Sediment 
 
 (Addition of Finings) 
 
 Heating to 165 F. 
 
 Settling for one week to three months. 
 
 Removal of Juice from Sediment 
 
 (Addition of Citric Acid) 
 
 Filtering (if necessary) 
 
 Bottling 
 
 Sterilization at 160 F for twenty minutes. 
 
 VARIETIES OF JUICE. 
 
 Much variety in color and flavor can be given to Califorman grape 
 juice by the use of different varieties of grapes and by modifications 
 in the methods of manufacture. 
 
 The finest and most highly flavored juice can be made only from 
 thoroughly mature grapes, in perfect condition, of the best varieties. 
 However, any variety of vinefera grapes, even if not in the best con- 
 dition, such as good table grape culls, if treated carefully as described, 
 will produce a very acceptable juice of much higher quality than most 
 of that which appears in the market either under a Californian or an 
 Eastern label. Much of the juice is defective in flavor and appearance 
 because of overheating and over exposure to the air or other unsuitable 
 treatment. 
 
 Where a choice is possible, grapes of high acidity should be used. 
 This does not mean unripe grapes, for the full delicious flavor of the 
 grapes does not develop until the grapes are quite mature. It 
 means grapes which retain their acidity even when they are ripe. Any 
 grape which will make good wine will make good grape juice and the 
 best for one purpose is the best for the other. An exception should be 
 made of the Pierce and other Labrusca varieties, which make good 
 grape juice but are unsuitable for wine. 
 
 Many Californian grapes tend to be very rich in sugar and rather 
 low in acidity. This makes the juice more acceptable to some palates. 
 To others, it is a defect, especially if the juice is diluted with water, 
 when consumed. Most juice can be improved by the addition of a little 
 citric acid, as already indicated. The excessive sweetness of the juice 
 would be remedied by diluting with water, but it would seem more 
 advisable to allow the consumer to do this to his own taste. 
 
 The color of the juice can be modified in several ways. It may be 
 made nearly water white or dark red. Many tints between these, vary- 
 ing from greenish yellow to golden or pink, may also be obtained. The 
 2 CiRlOS 
 
10 
 
 lightest colors are obtained by moderate aeration before sulfiting and 
 as little aeration as possible after. By this means, juice without any 
 reddish tint can be made even from red grapes. In this case, the 
 aeration must be sufficiently prolonged to destroy any color which gets 
 into the juice during the crushing and pressing of the skins and the 
 sulfite should be added as soon as the coloring matter is oxidized. This 
 oxidation is shown by the change of the pink color of the juice to 
 brownish and the formation of minute brown solid particles of 
 oxidized coloring matter. 
 
 Eed juice can be made in three ways. One is to use grapes with 
 colored juice such as the Bouschets. Such juice will be pink or light 
 red. Another way is to heat the crushed red grapes before the com- 
 plete separation of the juice and defecation. This may be done by 
 heating all the grapes in a boiler or by heating a portion of separated 
 juice and pumping it on to the skins. A temperature of- 120 F. of the 
 whole mass is sufficient to extract the color in several hours. At higher 
 temperatures, the extraction is more rapid. This method is not 
 advisable, as it exposes the hot juice too much to the air, makes it very 
 astringent and injures the flavor. A better method is to separate and 
 defecate the juice as usual and to color it with a deep red juice made 
 from the skins of dark colored grapes. This red juice is made as 
 described above after draining off some of the free run of juice. 
 
 In this way, the fresh flavor of the juice is injured very little by 
 the small quantity of heated red juice added. 
 
 Varieties of Grapes. As already indicated^ palatable grape juice can 
 be made from any of our ripe grapes. For the best results, however, 
 some care must be exercised in the choice, blending and degree of ripe- 
 ness of the varieties. 
 
 What is required is full acidity and flavor. Up to a certain stage, 
 the riper the grapes the fuller the flavor but the lower the acidity. 
 Most of our varieties do not attain their full flavor until they have 
 reached a stage of ripeness representing at least 22 Balling. For a 
 good fresh-tasting juice, the acidity ought to be about the equivalent 
 of .7 per cent to .8 per cent of tartaric acid. 
 
 The average composition of Californian grapes, based on seven 
 hundred analyses of many varieties from many sections, is 23.4 Balling 
 and .58 per cent acid. These grapes were gathered as nearly as possible 
 when they were at the best stage for wine-making. To obtain a juice 
 of the composition desired for grape juice, most varieties would have 
 to be gathered less ripe than this. Varieties which retain their acidity 
 to an advanced stage of ripeness are particularly suitable for grape 
 juice as are also varieties with a high special flavor. 
 
11 
 
 A list of such varieties, together with some typical analyses is given 
 in the following table : 
 
 SOME VARIETIES SUITABLE FOR GRAPE JUICE. 
 
 Variety 
 
 Composition 
 
 
 Coast region 
 
 Interior 
 
 
 Ripe 
 
 Overripe 
 
 Kipe 
 
 Overripe 
 
 Sugar 
 
 Acid 
 
 Sugar 
 
 Acid Sugar 
 
 Acid 
 
 Sugar 
 
 Acid 
 
 Varieties with Special 
 Flavors. 
 Muscat of Alexandria 
 
 
 
 21.83 
 
 .74 
 
 27.20 
 
 .54 
 
 Traminer 
 
 
 25.10 
 
 25.45 
 23.96 
 24.10 
 
 .38 
 .46 
 .46 
 .41 
 
 Riesling, Franken 
 
 21.92 
 22.15 
 
 .50 
 .66 
 
 24.40 .50 
 
 i 
 
 Riesling, Johannisberg 
 Semillon 
 
 
 21.50 
 21.50 
 
 .63 
 .68 
 
 25.90 
 25.50 
 25.50 
 
 26.03 
 
 23.80 
 23.24 
 25.12 
 
 22.30 
 26.90 
 26.10 
 23.50 
 
 .32 
 .37 
 .39 
 
 .41 
 
 .45 
 .45 
 .62 
 
 .43 
 .64 
 .47 
 
 .56 
 
 Colombar 
 
 
 Cabernet Sauvignon 
 
 21.95 
 22.00 
 
 20.50 
 17.20 
 21.50 
 
 21.60 
 21.93 
 20.20 
 20.00 
 
 .77 
 .64 
 
 .80 
 .99 
 .92 
 
 .92 
 .80 
 1.39 
 1.07 
 
 25.34 
 24.79 
 
 23.10 
 22.60 
 25.20 
 
 23.70 
 26.50 
 23.25 
 25.90 
 
 .50 
 .44 
 
 .77 
 .79 
 .86 
 
 .69 
 .70 
 1.15 
 .66 
 
 Means _ 
 
 22.31 
 
 18.60 
 19.60 
 22.40 
 
 21.20 
 
 .64 
 
 .61 
 
 .56 
 
 .77 
 
 .65 
 
 Varieties with High Acid. 
 Folle Blanche 
 
 Burger 
 
 West's White Prolific 
 
 Varieties with High Acid and 
 Color. 
 
 Bouschet, Alicante 
 
 Gamai, Tpintm*ifir 
 
 Gros Mansenc 
 
 24.35 
 21.90 
 
 .88 
 .70 
 
 St. Macaire 
 
 Alicante Ganzin 
 
 Means 
 
 20.42 
 23.20 
 21.07 
 
 .98 
 .75 
 
 .87 
 
 24.32 
 26.50 
 24.63 
 
 .80 
 .65 
 .64 
 
 21.34 
 2S-.59 
 21.83 
 
 .70 
 .64 
 
 .65 
 
 24.42 
 28.34 
 25.29 
 
 .52 
 .39 
 .45 
 
 Zinfandel 
 
 Means of all _ 
 
 
 This table shows that all the highly flavored varieties are somewhat 
 lacking in acidity when ripe whether grown near the coast or in a 
 warmer region. The acid varieties have sufficient acidity when grown 
 in the coast region even when overripe. In the warmer regions, how- 
 ever, even these varieties lose too much of their acidity if allowed to 
 become overripe.. The best quality would probably be obtained by 
 blending the juice of highly flavored varieties when they were fully 
 ripe with acid varieties gathered while the acidity was still high. For 
 example: A mixture of Muscat showing 25 Bal. of sugar and .55 
 per cent acidity with West's White Prolific, showing 20 Bal. of sugar 
 and .95 per cent acidity would give a juice of 22.5 Bal. and .75 per 
 cent acidity. The Prolific would supply the acid and the fully ripe 
 Muscat the flavor. 
 
 A series of tests of the sugar and the acid in Muscat grapes at various 
 stages of ripeness gives an example of the changes which take place in 
 the ratio between sugar and acidity. 
 
12 
 
 COMPOSITION OF MUSCAT GRAPES AT VARIOUS STAGES OF RIPENESS. 
 
 ill 
 
 Edible - 21.8 
 
 f 25.5 
 
 Eipe -i 26.2 
 
 I 26.8 
 [27.2 
 
 Overripe -i 29.1 
 
 133.2 
 
 Acidity 
 Sugar (as 
 
 iBal.*) tartaric) 
 
 .72 
 
 .63 
 .62 
 .50 
 .54 
 .54 
 .70 
 
 "With a sugar content of 21.8 Bal., the grapes were edible and the 
 acid sufficiently high but the full Muscat flavor had not developed. 
 When the sugar had risen to 25.5 Bal. the flavor was fully developed 
 but the acidity was a little low. This was the best stage to gather these 
 grapes for grape juice. As they got riper, the acidity fell until at full 
 ripeness (the stage for raisin making), nearly one third of the acidity 
 was lost. The apparent increase of acidity with overripeness does not 
 indicate a gain of acid but simply concentration due to evaporation of 
 water. 
 
 As a general rule, the grapes for flavoring should be gathered when 
 the sugar reaches 23 to 25 Balling and the grapes for acidity when 
 it reaches 19 to 21 Bal. 
 
 Eastern Varieties. Grape juice made in New York and other eastern 
 states is sold in large quantities even in California. Various samples 
 show variations in quality, but they all differ from the Californian 
 juices in their higher acidity and their strong Labrusea flavor. We 
 can obtain the acidity by gathering our grapes with the low percentage 
 of sugar customary in the East. The Labrusea flavor we can obtain 
 only by growing the Eastern grapes. These grapes, Concord. Isabella, 
 Catawba, etc., do very well in the cooler parts of California, bearing] 
 larger crops of sweeter grapes than they do in most Eastern vineyards. 
 The Pierce, an improved Isabella, would probably be very suitable for| 
 producing a Californian grape juice of the Eastern type. 
 
 Which would be more profitable, to produce grape juice from 
 Labrusea varieties, thus taking advantage of a market already estab-l 
 lished, or to develop the market for juice made from our Californian 
 varieties, experience alone can determine. There can be little doubt 
 that both kinds of grape juice can be produced here profitably when 
 the manufacturers adopt methods which will insure the* conservation! 
 of the good qualities of our grapes. 
 
Makers 
 
 Syracuse, N v 
 
 288520 
 
 r T ! 
 
 UNIVERSITY OF CALIFORNIA LIBRARY 
 
 UNIVERSITY OF CALIFORNIA LIBRARY 
 
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