UMIVEBSITY OF CALIFORNIA PPBLICATIOH8 
 
 COLLEGE OF AGRICULTURE 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BERKELEY, CALIFORNIA 
 
 VINEGAR FROM WASTE FRUITS 
 
 BY 
 
 W. V. CRUESS 
 
 BULLETIN No. 287 
 
 October, 1917 
 
 UNIVERSITY OF CALIFORNIA PRESS 
 
 BERKELEY 
 
 1817 
 
Benjamin Ide Wheeler, President of the University. 
 
 EXPEEIMENT STATION STAFF 
 
 HEADS op divisions 
 
 Thomas Forsyth Hunt, Director. 
 
 Edward J. Wickson, Horticulture (Emeritus). 
 
 Herbert J. Webber, Director Citrus Experiment Station; Plant Breeding. 
 
 Hubert E. Van Norman, Vice-Director; Dairy Management. 
 
 William A. Setchell, Botany. 
 
 Myer E. Jaffa, Nutrition. 
 *Bobert H. Loughridge, Soil Chemistry and Physics (Emeritus). 
 
 Charles W. Woodworth, Entomology. 
 
 Ealph E. Smith, Plant Pathology. 
 
 J. Eliot Coit, Citriculture. 
 
 John W. Gilmore, Agronomy. 
 
 Charles F. Shaw, Soil Technology. 
 
 John W. Gregg, Landscape Gardening and Floriculture. 
 
 Frederic T. Bioletti, Viticulture and Enology. 
 
 Warren T. Clarke, Agricultural Extension. 
 
 John S. Burd, Agricultural Chemistry. 
 
 Charles B. Lipman, Soil Chemistry and Bacteriology. 
 
 Clarence M. Haring, Veterinary Science and Bacteriology. 
 
 Ernest B. Babcock, Genetics. 
 
 Gordon H. True, Animal Husbandry. 
 
 James T. Barrett, Plant Pathology. 
 
 Fritz W. Woll, Animal Nutrition. 
 
 Walter Mulford, Forestry. 
 
 W. P. Kelley, Agricultural Chemistry. 
 
 H. J. Quayle, Entomology. 
 
 D. T. Mason, Forestry. 
 
 J. B. Davidson, Agricultural Engineering. 
 
 Elwood Mead, Bural Institutions. 
 
 H. S. Reed, Plant Physiology. 
 
 W. L. Howard, Pomology. 
 IFrank Adams, Irrigation Practice. 
 
 C. L. Roadhouse, Dairy Industry. 
 
 William G. Hummel, Agricultural Education. 
 
 John E. Dougherty, Poultry Husbandry. 
 
 S. S. Rogers, Olericulture. 
 
 David N. Morgan, Assistant to the Director. 
 
 Mrs. D. L. Bunnell, Librarian. 
 
 Division of Viticulture 
 F. T. Bioletti W. V. Cruess 
 
 J. R. Zion 
 
 * Died July 1, 1917. 
 
 f In co-operation with office of Public Roads and Rural Engineering, U. S. 
 Department of Agriculture. 
 
VINEGAR FROM WASTE FRUITS* 
 
 By W. V. CRUESS 
 
 Fruit, unsuitable for sale fresh, for drying or for canning, may 
 often be used for vinegar making or for the manufacture of acetic- 
 acid from which to produce acetone, used in the manufacture of high 
 explosives. A ton of apples, grapes, or most deciduous fruits, will 
 yield from MO to 175 gallons of juice suitable for vinegar making. 
 Oranges will yield about 100 to 125 gallons. Apples will yield about 
 75 pounds of acetic acid per ton, grapes about 150 pounds, and 
 oranges about 50 pounds. At 15 cents per gallon, the vinegar from 
 a ton of apples or grapes is worth approximately $23, and from a 
 ton of oranges $15. Grapes contain nearly twice as much sugar as 
 apples, and the vinegar is correspondingly stronger. The figures 
 given are based on the assumption that the grapes are not diluted 
 with water. At $2 per gallon for acetone, the acetone from a ton of 
 apples is worth about $7, of grapes about $13, and of oranges 
 about $4.50. 
 
 There is usually a local demand for vinegar and those having 
 surplus fruit can make vinegar for their own and for their neighbors' 
 use. It is often possible to build up a profitable local trade and then 
 gradually increase the output, so that a business of considerable size 
 can finally be established. Profits in vinegar making are moderate 
 and the prospective manufacturer should realize this fact before 
 undertaking it on a large scale. Acetone for explosives is also in 
 demand, but its manufacture involves the installation of extensive 
 equipment and it should, therefore, be undertaken only on a large 
 scale and in a locality within easy reach of a large supply of cheap 
 fruit. The Fresno and other vineyard districts have large amounts 
 of cull and second-crop grapes and raisin seeds suitable for acetone 
 production, while citrus districts like Redlands or Riverside have a 
 large supply of cull oranges not utilized at present, but which are 
 suitable for this purpose. 
 
 It is proposed here to discuss briefly the principles of vinegar 
 manufacture rather than to describe large-scale equipment. If the 
 principles are thoroughly understood, methods of applying them to 
 large or small-scale manufacture can be devised. Acetone is pro- 
 duced by the destructive distillation of calcium or sodium acetate 
 
 * Supplementary to " Grape Vinegar" (Bull. 227, by F. T. Bioletti). 
 
170 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 formed from acetic acid obtained by the distillation of vinegar. 
 Vinegar making is, however, one of the principal steps in the process 
 and should be well understood. 
 
 Fig. 1. — Waste apples, peels, and cores used in vinegar making. 
 
 Raw Materials. — Vinegar for table use requires fairly sound and 
 clean fruit. For acetone manufacture, the condition of the fruit is 
 not important. Any of the common California fruits, except lemons, 
 can be used and also inferior dried fruits. Cannery waste, such as 
 peels and cores, will make a satisfactory vinegar if clean ; otherwise 
 it may be used for acetic acid or acetone. 
 
 Crushing. — Crushers suitable for grapes and all varieties of fruits 
 without stones are available in sizes varying from those suitable to 
 a small kitchen to those having a capacity of 100 tons of fruit per day. 
 The fruit should be thoroughly crushed to facilitate fermentation and 
 pressing. Orange juice will ferment more satisfactorily if it is free 
 
 from the oil of the skins. 
 The oil may be recov- 
 ered from oranges on a 
 large scale by methods 
 described in Depart- 
 ment Bulletin 399 of 
 the United States De- 
 partment of Agricul- 
 ture, Washington, D. C. 
 The oranges may then 
 be crushed after the oil 
 cells are removed by the 
 methods given in that 
 Fig. 2. — Filling a rack and cloth press. bulletin. 
 
VINEGAR FROM WASTE FRUITS 
 
 171 
 
 Pressing before Fermentation. — If vinegar for table use Is to be 
 made from grapes, they should be pressed as soon as crushed to avoid 
 color and an astringent taste from the skins and stems. Apples are 
 usually pressed as soon as crushed, but a larger yield of juice is 
 obtained and pressing is more complete if they are allowed to undergo 
 a partial fermentation before pressing. Oranges and other fruits 
 will press much more satisfactorily if fermented before pressing. 
 Hand presses for small-scale operations may be had for about fifteen 
 to twenty-five dollars. Larger presses to be run by hydraulic pressure 
 will cost from $150 to $1000 or more. The basket and the rack and 
 cloth types of presses are 
 best suited to vinegar 
 manufacture; the contin- 
 uous press does not work 
 so satisfactorily. 
 
 ALCOHOLIC FERMENTATION 
 
 A. Growth of Pure 
 Yeast. — The manufacture 
 of vinegar requires two 
 fermentation processes. 
 The first causes the trans- 
 formation of the SUffar of ^S- 3. — Elevator, crusher and vats for fermentation 
 
 ° of crushed fruit before pressing. 
 
 <fche fruit or juice into 
 
 alcohol. This is brought about by yeast. The second changes the 
 alcohol into acetic acid and is caused by vinegar bacteria. 
 
 The alcoholic fermentation must be complete before the acetic or 
 "vinegar" fermentation is allowed to start, or otherwise the yeast 
 fermentation will be stopped by the acetic acid and unfermented 
 sugar will remain in the vinegar. Such a condition results in weak 
 vinegars of poor quality and low yields of acetic acid or acetone. 
 
 Alcoholic fermentation will occur naturally by the growth and 
 activity of yeasts present on the fruits themselves. Such a fermen- 
 tation is, however, ver}^ uncertain, usually very wasteful of sugar, 
 and results in vinegars of varying and uncertain quality. 
 
 Selected pure j^east is necessary to insure uniform, complete fer- 
 mentations, with maximum yields of alcohol and minimum waste of 
 sugar. Pure yeast may be obtained for $1 per culture by writing 
 to the Division of Viticulture, Hilgard Hall, University of California, 
 Berkeley. The method of using the yeast is described below: 
 
 1. The yeast as received from the University is in solid form in 
 a bottle plugged with cotton. A bottle of sterile fruit juice accom- 
 
172 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 panies the yeast. Remove the cotton plug and fill the yeast bottle 
 about three-quarters full with sterile juice from the other bottle. 
 Replace the cotton plug at once. 
 
 2. Leave the yeast bottle in a warm place until the juice is fer- 
 menting rapidly, as indicated by the formation of gas bubbles. Three 
 or four days are usually sufficient. 
 
 3. When the yeast is fermenting, sterilize three to five gallons 
 of fresh juice by heating it to boiling in a covered agate ware or 
 aluminum pot and let it cool overnight. 
 
 4. Then add the contents of the yeast bottle and mix the yeast 
 and juice by pouring the juice back and forth a few times with a 
 
 dipper sterilized by 
 dipping in boiling 
 water. Everything 
 that comes in contact 
 with the yeast or juice 
 must be scrupulously 
 clean and sterilized by 
 boiling water or steam. 
 Set aside in a warm 
 place for three or four 
 days. It will then be 
 in vigorous fermenta- 
 tion. This will be 
 enough to start 40 gal- 
 lons of juice as de- 
 scribed in step 5. 
 
 5. Prepare a clean 50-gallon barrel for yeast growth by removing 
 one head and washing the barrel out with hot water and "sal soda' : 
 or soda ash, followed by rinsing with boiling hot water. Heat about 
 40 gallons of juice to 165 degrees Fahrenheit or higher. This can 
 be done by placing a steam hose in the juice in the barrel or by 
 heating the juice in 5-gallon pots on a stove. A dairy thermometer 
 may be used to test the temperature. Allow the juice to cool in the 
 barrel to 90° F. or lower. Large tin buckets of cold water may 
 be floated in the juice to cool it quickly. They must be clean. 
 
 6. When the juice has cooled, add the three or four gallons of 
 fermenting juice previously prepared. Aerate and mix the yeast 
 and juice in the barrel by pouring it back and forth with a dipper 
 sterilized in hot water. 
 
 7. Aerate the juice five or six times daily in the same way until 
 it is fermenting rapidly. This will be in three or four days. It is 
 
 Fig. 4.— A small hand press. 
 
VINEGAR FROM WASTE FRUITS 173 
 
 then ready for use. This 40 gallons of yeast will be enough for 1000 
 to 2000 gallons of fresh juice. If more is needed, several more 
 barrels of sterile juice may be started from the first barrel. 
 
 B. Starting the First Fermentation Vats. — 1. As soon as the yeast 
 is working rapidly in the yeast barrel, crush the fruit to be fermented. 
 To each ton of crushed fruit add three-quarters of a gallon of 6 per 
 cent sulfurous-acid solution and mix it in bv stirring. This solution 
 may be bought from the manufacturer for 20c to 25c per gallon. 
 Potassium meta-bi-sulfite may be used instead, but at present is ver} 7 
 expensive. A solution made by dissolving one pound in a gallon 
 of water is used in the same way and the same amount as the 6 per cent 
 sulfurous-acid solution. 
 
 a- 
 
 Fig. 5. — Growing yeast in 50-gallon barrels. a. Barrels with sterilized juice. 
 
 b. Barrels with yeast growing in juice. 
 
 If apples or grapes are being used, press them and transfer the 
 juice to fermentation vats, tanks or barrels. Other fruits as soon as 
 crushed are placed directly in the fermentation vessels. The pressed 
 apple pomace is placed in a separate vat; it contains juice that may 
 be recovered by pressing after fermentation. 
 
 2. A few hours after sulfiting, add five to ten gallons of the yeast 
 to each ton of crushed fruit or each 200 gallons of juice and mix 
 thoroughly. 
 
 3. If crushed fruit is being fermented, stir it once daily during 
 fermentation to prevent molding and vinegar fermentation in the 
 top of the fermenting mass. 
 
 C. Starting Other Vats. — When this first vat is in fermentation it 
 may be used to start other vats. To the second vat add a half -gallon 
 
174 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 of 6 per cent sulfurous-acid solution per ton of crushed fruit or per 
 200 gallons of juice. Then add 20 gallons of the rapidly fermenting 
 juice or crushed fruit from the first vat per ton of crushed fruit and 
 mix. When this vat is fermenting other vats may be started from 
 it in the same way that the second was started from the first and the 
 same system may be applied to all succeeding vats. If the yeast at 
 any time seems to work poorly, a new start should be obtained from 
 the University. 
 
 Pressed apple pulp or pomace is fermented by adding fermenting 
 juice to it in a vat. Use about 10 gallons to each 100 gallons of 
 pomace. It is pressed again after fermentation. A great deal of 
 juice can be obtained in this way. 
 
 D. Pressing Fermented 
 Fruits. — If the fruits have not 
 been pressed before fermenta- 
 tion they should be pressed 
 after about four days' fermen- 
 tation. Fermentation before 
 pressing softens the fruit and 
 greatly increases the yield of 
 juice. Usually a great deal of 
 the fermented juice may be 
 
 -c,. a -r T . n , ■, - ', • n . .. drawn off before pressing so 
 
 Fig. 6. — Vats of crushed fruit in fermentation. ^ to 
 
 that only the residual pulp need 
 be pressed. Press thoroughly and transfer the juice to tanks or 
 barrels to finish fermenting. 
 
 E. Completion of Fermentation. — The juice is allowed to ferment 
 until practically all of the sugar is converted into alcohol and carbonic 
 acid gas. If conditions are favorable this will be in about three weeks 
 or less. It is complete when there is no taste of sugar present and 
 when gas is no longer given off. The progress of the fermentation 
 can be watched by means of a Balling sugar tester or hydrometer. 
 This instrument indicates approximately the amount of sugar present. 
 The Balling hydrometer may be obtained from any chemical supply 
 house directly or through a drug store for about 75c. A tall glass 
 or tin cylinder will also be needed. To make the test pour the juice 
 into the cylinder, insert the hydrometer and read the per cent of sugar 
 indicated at the surface of the liquid. 
 
 The vats and all apparatus coming in contact with the juice should 
 be clean. Each vat should be started with yeast from the preceding 
 vat or from a pure-yeast apparatus as described above. If these 
 precautions are observed good fermentations will result. 
 
VINEGAR FROM WASTE FRUITS 175 
 
 F. Storage after Fermentation. — The fermented juice should be 
 allowed to settle for two to three weeks after alcoholic fermentation 
 is over. This is to rid it of yeast and pulp, etc. During this settling- 
 process the tanks or barrels should be kept full to prevent growth of 
 
 'wine flowers' 1 on the exposed surface. Closed tanks should be 
 employed. 
 
 G. Racking. — When the yeast and sediment has settled, the fer- 
 mented juice must be ' ' racked ' ' ; that is, drawn off from the sediment 
 into other tanks or barrels. This can be done by means of a faucet 
 near the bottom or by syphoning with a hose from the top and by 
 pumping, or running by gravity into the new tanks, according to 
 conditions and equipment. The sediment may be discarded, filtered 
 or allowed to settle in barrels. By the last method more fermented 
 juice may be recovered from the otherwise waste sediment. 
 
 If left in the juice, the sediment may give a bad flavor and inter- 
 fere with acetic fermentation and the clearing of the vinegar. 
 
 DISTILLATION BEFORE ACETIC-ACID FERMENTATION 
 
 Where the fermented juice contains a great deal of suspended 
 matter and where it is desired to make a vinegar of very high acid 
 strength to be used in the manufacture of acetic acid or acetone, the 
 fermented juice should be distilled. This will separate the alcohol 
 from the impurities of the juice and a fairly high acetic acid can be 
 made by passing this distilled liquid through generators. It is cus- 
 tomary to carry out this distillation in large continuous stills which 
 give a distillate of about 10 per cent alcohol. Distillation, however, 
 is only used in large establishments and the equipment necessary is 
 too expensive for the small-scale manufacturer. With the distillation 
 process it is possible to recover all of the alcohol from the pressed 
 fermented pomace by washing or leaching with water and then dis- 
 tilling the alcoholic wash. If fruits are to be used on a very large 
 scale for the manufacture of acetic acid and acetone, it is recom- 
 mended that the distillation process be installed because all of the 
 alcohol is then recovered and a purer acid obtained. 
 
 ACETIC-ACID FERMENTATION 
 
 A. Acidification. — The transformation of the alcohol in the fer- 
 mented juice is carried on by vinegar bacteria. They will not work 
 efficiently and will not start quickly unless the fermented juice after 
 alcohol fermentation is acidified and inoculated with vinegar bacteria. 
 These two objects are accomplished by the addition of new vinegar 
 to the fermented juice after it has been racked, or to the alcoholic 
 distillate from the still. The fermented liquid should be acidified 
 
176 
 
 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 with at least one gallon of strong new vinegar to each three gallons 
 of the fermented juice. This new vinegar will carry with it large 
 quantities of vinegar bacteria which will heavily inoculate the fer- 
 mented juice and cause a rapid start of vinegar fermentation. After 
 acidifying in this way, the vinegar fermentation is carried out by 
 either one of the processes described below : 
 
 B. Slow Process. — The slow process is carried out in barrels or 
 other containers and requires several months to a year for completion. 
 It is greatly hastened by the addition of vinegar as noted under ' ' A. ' : 
 If it is carried out in barrels, they should be filled about three-quarters 
 full. The bung of the barrel should be removed and the bunghole 
 covered with a wire screen or a cheesecloth to keep out insects. At 
 each end of the barrel, slightly above the level of the liquid, two holes 
 
 ^^ 
 
 1 
 
 I 
 
 a 
 
 ^\^\W\^ 
 
 Fig. 7. — Barrel arranged for slow process of vinegar fermentation, a. Three- 
 quarter inch holes at each end of barrel, covered with screen or cheesecloth, b. 
 Bunghole. c. Wooden spigot, d. Level of vinegar. 
 
 should be bored each about one inch in diameter. These holes should 
 also be screened to keep out vinegar flies, etc. The barrels should 
 be kept in a warm place and should not be disturbed during the 
 vinegar process. The vinegar is simply allowed to remain in the 
 barrels until it has reached its maximum strength. About three- 
 quarters of the vinegar can then be drawn off into other barrels and 
 newly fermented and settled juice can be added to the remaining 
 one-fourth of the vinegar. This new lot of fermented juice and 
 vinegar is then allowed to acetify. This process can be repeated 
 indefinitely, starting the new lot of fermented juice each time with 
 one-fourth of the new vinegar left in the barrels. This method is 
 known as the "Orleans" process and is the best of all slow processes. 
 It is a mistake to simply allow the vinegar fermentation to depend 
 on chance because great risk is run of having the vinegar completely 
 
VINEGAR FROM WASTE FRUITS 177 
 
 spoiled or of getting an inferior product. This is especially true of 
 orange vinegar. 
 
 C. Testing the Vinegar. — The vinegar fermentation, whatever 
 process employed, should be watched carefully by testing the acid 
 strength from time to time. If this is to be done very accurately, 
 a standard sodium-hydroxide solution and the necessary instruments 
 should be obtained from a reliable chemical supply house which will 
 furnish the equipment with instructions for use. The Leo Acid 
 Tester is simpler and sufficiently accurate for factory use. This small 
 instrument can be obtained from any of the chemical supply houses 
 directly or through a local druggist. The cost is about five dollars 
 or less. It gives the strength of the vinegar in ' ' grains. ' ' The Pure 
 Food Law requires that a vinegar shall have at least 4 per cent acid 
 or be "40-grain vinegar." It can be above this and usually is if 
 it is a pure vinegar. A good tester is necessary in the manufacture 
 of any considerable quantity of vinegar. Directions accompany the 
 Leo Tester. Bulletin 227 of this station also tells how to use it. 
 
 The vinegar fermentation should continue until there is no further 
 increase in acid. This indicates that it is complete. A good cider 
 vinegar should reach a strength of "60 grains." A wine vinegar 
 should reach "75 to 100 grains.' A good orange vinegar should 
 reach at least "45 to 50 grains.' A "distilled" vinegar made from 
 an alcoholic distillate containing 10 per cent alcohol will reach "90 
 to 95 grains. ' A distilled vinegar can be made only by the generator 
 process.* 
 
 D. Generator Process. — The rate of vinegar fermentation depends 
 upon the amount of air supplied to the vinegar bacteria. Vinegar 
 generators merely increase the amount of surface of vinegar exposed 
 to the air. The surface is a great many times that which would be 
 exposed in an ordinary barrel. Therefore, the rate of acidification 
 is enormously increased. Most generators consist of an upright tower 
 filled with beechwood shavings or other suitable material, such as 
 rattan shavings or coarse coke or charcoal. For fruit juices, beech- 
 wood shavings will be found best. Figure 8 shows a plan of a 
 generator. 
 
 To use the generator, it is first filled with clean beechwood shavings. 
 The shavings are then wet by running strong new vinegar through 
 them until they are saturated. The generator is equipped with a 
 tilting trough C which distributes the vinegar over the head, from 
 which it flows down over the shavings through numerous holes. This 
 
 * See also ' ' Cider Vinegar by the Quick Process, ' ' published by the Hydraulic 
 Press Mfg. Co., Mt. Gilead, Ohio. Sent free on application to above address. 
 
178 
 
 UNIVERSITY OF CALIFORNIA- — EXPERIMENT STATION 
 
 vinegar should be run through the generator several times until the 
 shavings are saturated. The alcoholic liquid which has been acidified 
 with one-fourth its volume of new vinegar is then started slowly 
 through the generator. The usual rate of flow is not more than 25 
 gallons per day of 24 hours. At first, the liquid issuing from the 
 generator will not be strong vinegar, but after three or four days 
 of running, the vinegar bacteria will multiply in the shavings suf- 
 
 sa«as>*«S!?**»i?ss*s!a«: ^is*ssas»i««sa«sa«i\* 
 
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 ■> n,\^\w i t^s^ ta&^at ^Lsai sss 
 
 m% 
 
 m^f 
 
 i 
 
 8 
 
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 m 
 
 Fig. 8. — Upright generator. A. Supply pipe. B. Cover. C. Tilting trough. 
 D. False head. E. Main chamber filled with shavings. F. Thermometer. G. 
 False bottom to support shavings. H. Air inlets. I. Outlet. 
 
 ficiently to cause a rapid fermentation so that finally the vinegar as 
 it comes through at the rate of 25 gallons per day or less will come 
 out vinegar of the maximum strength possible with the raw material 
 being used. The rate of flow and the air supply which comes through 
 the small inlets at the bottom of the generator are so regulated that 
 a temperature of about 80 to 85 degrees F. is maintained. A ther- 
 mometer, inserted as shown in the drawing, near the center of the 
 generator, will indicate the temperature. 
 
 With clear juice and careful manipulation, the generator can be 
 kept running for six or seven months without cleaning. It will in 
 time, however, become clogged with sediment so that it will not act 
 
VINEGAR FROM WASTE FRUITS 
 
 179 
 
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 711 
 
 Fig. 9. — Revolving generator for factory use. a. Air inlet. b. Air inlet 
 with regulating wooden plug. c. Thermometer, d. Wall of outer chamber which 
 encloses cylinder e. e. Revolving cylinder filled with beechwood shavings. /. 
 Air inlets to e. g. Shaft and pulley to rotate e; e rotates about once per hour. 
 h. Liquid, usually about 500 gallons, i. Beechwood shavings. .;'. Supports for 
 
 generator. 
 
 
 <5> 
 
 r/// 
 
 
 yhzzzzzzzzzfizzzzzm y/////a y///////a \ // / // /a y///////a ^zzzzzzzzA n 
 
 (t </ 
 
 YA ////A v///////a ^zzzzzzn V/////A Y// /// /A 
 
 Fig. 10. — Rotating generator made from barrel filled with beeclnvood shavings. 
 a. Air inlets at ends of barrel. ~b. Wooden partitions in barrel perforated to allow 
 passage of air. c. Shavings, d. Vinegar, e. Upper spigot, open. /. Lower spigot, 
 closed. As barrel rotates / becomes upper and e lower spigot. #.3X6 inch 
 skids for barrel. 
 
180 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 efficiently. It must then be stopped and the shavings washed in hot 
 water. They can then be dried in the sun and returned to the gen- 
 erator. The filled generator should never be stopped for more than 
 twenty-four hours at a time because the shavings will become diseased 
 and moldy if the generator is not kept in operation. 
 
 A type of generator that need not be cleaned so often is the hori- 
 zontal revolving type. This generator consists of a cylinder filled 
 with shavings. It is enclosed in a wooden air-tight box with air inlets. 
 The lower half of the cylinder is immersed in acidified fermented 
 juice, the upper half is exposed to the air. The cylinder rotates 
 slowly. Acetification takes place in the exposed upper half. The 
 Temperature is maintained at 80-85 degrees F. by regulating the air 
 inlets and rate of turning. The generator usually holds about 500 
 gallons (see fig. 9). A simple form of rotating generator is a barrel 
 filled with shavings. Air vents are made in the centers of the heads 
 of the barrel. It is filled half full of acidified fermented juice. It 
 is turned half way over several times daily to expose new shavings 
 to the air (see fig. 10). 
 
 Distilled vinegar, which is made from an alcoholic distillate of 
 fermented fruit juice or other material, is made in generators filled 
 with beechwood shavings, or, better, with pieces of charcoal or coke. 
 Charcoal and coke cannot be used for undistilled fruit juices because 
 they soon become inactive through the accumulation of sediment. 
 
 Aging. — When the vinegar has reached its maximum strength, 
 either by the slow or the generator process, it must be aged before it 
 is at its best quality for table use. The aging process takes place 
 during storage and results in an improvement in flavor and in clear- 
 ness. The best vinegar is aged at least a year before it is put on 
 the market. The aging should take place in tanks or in barrels 
 which are kept full and closed. 
 
 CLARIFICATION AND FILTRATION 
 
 Well made vinegar from good material will very often clear suf- 
 ficiently during the aging process to make it suitable for bottling. 
 Usually; however, it will be necessary to aid the clearing by filtration 
 or by the addition of some clarifying substance. 
 
 A. Clarification. — Two substances are in common use for the 
 clarification of vinegar, viz., fish isinglass and Spanish clay. Isinglass 
 is the more expensive, but produces the most perfect clearness. The 
 usual amount of isinglass necessary to clarify cider vinegar is about 
 one ounce per hundred gallons, although this will vary considerably 
 
VINEGAR FROM WASTE FRUITS 181 
 
 with the condition of the vinegar. The isinglass is weighed out and 
 broken up into small pieces. It is then mixed with one gallon of 
 vinegar for each ounce of isinglass. It is allowed to soak until the 
 isinglass becomes swollen and soft. Warming the mixture will aid 
 in dissolving the isinglass. The isinglass is then broken up very 
 thoroughly and mixed with the vinegar until a solution free from 
 lumps is obtained. The mixture should be passed through a fine 
 sieve and the lumps retained well broken up. This solution of 
 isinglass is then added to the vinegar at the rate of one gallon for 
 each hundred gallons of vinegar to be clarified. It must be empha- 
 sized that the isinglass must be made into a very smooth solution 
 
 Fig. 11. — A small barrel arranged to mix clay, or other clarifying agent, and 
 
 water by agitation. 
 
 before it is used. Otherwise, the clarification will be imperfect. 
 The vinegar and isinglass are then mixed thoroughly in a barrel or 
 tank by stirring. The mixture is allowed to stand until the isinglass 
 settles, leaving a clear liquid above. The clear vinegar can then be 
 drawn off with a hose or from a faucet. The sediment can be 
 drained off and filtered. 
 
 Spanish clay is used in a similar way. It is mixed with water 
 at the rate of one pound to each gallon of water, and allowed to soak 
 for several days until it becomes soft. It is then worked up with the 
 hands or by continuous agitation to give a thin, smooth mud or sus- 
 pension of clay. The clay must be broken up very finely. The device 
 shown in fig. 11 shows a convenient method of mixing the clay and 
 water in a rotating ten-gallon barrel. 
 
182 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 They are placed in this barrel which is set rotating slowly. Within 
 a few hours the mixing is complete. For each 100 gallons of vinegar 
 to be clarified, the amount of clay will be from three to six pounds; 
 that is, from three to six gallons of the one pound per gallon clay 
 solution. This solution is mixed with the vinegar by stirring and 
 is allowed to settle in the same way as directed for isinglass. 
 
 The amount of clay to be used will vary with the cloudiness and 
 condition of the vinegar. Where an attempted isinglass clarification 
 has failed the vinegar can be treated successfully with Spanish clay 
 later, or often isinglass and clay may be added together with good 
 results. 
 
 B. Filtration. — Where large amounts of vinegar are to be made, 
 clarifying often becomes impracticable and filtration is resorted to 
 because of its cheapness and because very large volumes can be 
 handled rapidly. Any of the standard types of filters, such as the 
 Karl Kieffer, the International, or the Seitz Filter, can be used suc- 
 cessfully for vinegar, if the interior of the filter is heavily coated 
 with tin to protect it from the action of the acid. For small-scale 
 operations, a cloth bag filter, costing five to ten dollars, can be used. 
 The efficiency of the bag filter is increased if a small amount of 
 infusorial earth (Kieselguhr) is added to the vinegar before filtration. 
 
 Bottling. — For bottling purposes vinegar should be aged and per- 
 fectly bright. If the operations previously described have been car- 
 ried out successfully, the vinegar will be in this condition. Bottles 
 should be filled full and well corked so that bacteria will not grow 
 in the vinegar and cause it to become cloudy. Vinegar clarified with 
 isinglass will remain bright in the bottles more satisfactorily than 
 vinegar clarified with Spanish clay. Ordinary grape juice bottles 
 or other type of Crown finish bottles make very satisfactory containers 
 for vinegar, because the capping is less expensive and troublesome 
 than corking and the appearance is attractive. 
 
 VINEGAR DISEASES 
 
 Lactic Bacteria. — Fermented fruit juices that have not been fer- 
 mented with pure yeast usually develop lactic-acid bacteria. These 
 bacteria are also known as "tourne bacteria" and are very common. 
 They produce a disagreeable taste, cloudiness and lactic acid in the 
 fermented juice. These persist in the vinegar and reduce its quality. 
 The lactic-acid bacteria can be avoided if pure yeast and a small 
 amount of sulfurous acid are used in the way described. 
 
VINEGAR FROM WASTE FRUITS 183 
 
 Wine Flowers. — If the fermented fruit juice is left in open tanks, 
 it will become coated with "wine flowers," a form of wild yeast that 
 destroys alcohol and flavor and causes cloudiness. It can be avoided 
 by storing the fermented juice in filled and closed barrels or tanks 
 and its development can be checked in open tanks by the addition of 
 one gallon of new vinegar to each three gallons of fermented juice, 
 as 'directed under vinegar fermentation. 
 
 Vinegar Eels. — Vinegar often becomes infested with small nema- 
 tode worms known as "vinegar eels." These little eels are about an 
 eighth of an inch long and can be seen by holding the vinegar in a 
 glass to the light. They destroy the acid and are very unpleasant 
 in appearance. If the fermented juice or vinegar in the factory 
 becomes badly infested, all the juice and all of the tanks must be 
 sterilized by heat to rid the factory of them. Vinegar infested with 
 eels can be sterilized by heating to about 130 degrees F., at which 
 temperature the eels are killed. Tanks and barrels that have been 
 infested should be sterilized by steam. The same applies to generators 
 which often become contaminated with this pest. A sterilizer can 
 be made by surrounding a piece of tin pipe, 10 feet or more in length, 
 with a steam jacket made of iron pipe. The vinegar or cider, etc., 
 is passed through the tin pipe, which is heated by steam. The hot 
 vinegar or fermented juice can be cooled by passing it through a 
 coil of tin pipe immersed in water. 
 
 SUMMARY 
 
 1. Vinegar making depends on two fermentations. The first is 
 fermentation of the sugar to alcohol and carbonic acid gas by yeast. 
 The second is the transformation of the alcohol into acetic acid by 
 vinegar bacteria. The fermentations must be kept separate and 
 distinct to get good results. 
 
 2. Pure yeast and a small amount of sulfurous acid should be used 
 to insure good alcoholic fermentation and to eliminate lactic bacteria. 
 
 3. Most fruits can be pressed most satisfactorily if crushed and 
 fermented before pressing. 
 
 4. The fermented juice should be stored several weeks to rid it 
 of yeast and other solid particles and should then be "racked'' or 
 drawn off the sediment before vinegar fermentation commences. 
 
 5. To the racked juice, should be added one-fourth its volume 
 of new vinegar to start acetic fermentation and prevent vinegar 
 diseases. 
 
184 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 
 
 6. The acidified fermented juice may then be made into vinegar 
 by the slow process in barrels or by the quick process in generators. 
 Vinegar fermentation requires an abundance of air. 
 
 7. The progress of the acetification should be watched by the Leo 
 tester or other means. 
 
 8. The vinegar should be aged for a year before sale if a high 
 quality is desired. 
 
 9. Vinegar may be clarified by isinglass or Spanish clay, or by 
 filtration. 
 
 10. Lactic-acid bacteria injure the quality of vinegar, but are 
 avoided if pure yeast is used; wine flowers destroy alcohol, but are 
 prevented if the fermented juice is acidified with one-fourth its volume 
 of new vinegar; vinegar eels are destroyed by heating the fermented 
 juice or vinegar to 130 degrees F. 
 
 Publications. — Write to the State Pure Food and Drug Labora- 
 tory, University of California, Berkeley, for a copy of the State Food 
 and Drug Regulations. 
 
 Bulletin 213 and Circulars 119 and 140 of the Experiment Station, 
 obtainable free of charge on written application to the Dean's Office, 
 College of Agriculture, Berkeley, will be found of great assistance 
 in the use of pure yeast and control of alcoholic fermentation. 
 
 A chapter in Marshall's Microbiology on vinegar manufacture, by 
 Prof. F. T. Bioletti, may also be consulted. 
 
STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION 
 
 REPORTS 
 
 1897. Resistant Vines, their Selection, Adaptation, and Grafting. Appendix to Viticultural 
 Report for 1896. 
 
 1902. Report of the Agricultural Experiment Station for 1898-1901. 
 
 1903. Report of the Agricultural Experiment Station for 1901-03. 
 
 1904. Twenty-second Report of the Agricultural Experiment Station for 1903-04. 
 
 1914. Report of the College of Agriculture and the Agricultural Experiment Station, July, 
 
 1913-June, 1914. 
 
 1915. Report of the College of Agriculture and the Agricultural Experiment Station, July, 
 
 1914-June, 1915. 
 
 1916. Report of the College of Agriculture and the Agricultural Experiment Station, July, 
 
 1915-June, 1916. 
 
 1917. Report of the College of Agriculture and the Agricultural Experiment Station, July, 
 
 1916-June, 1917. 
 
 BULLETINS 
 
 No. 
 
 230. 
 241. 
 242. 
 
 244. 
 246. 
 248. 
 
 249. 
 250. 
 251. 
 
 252. 
 253. 
 
 255. 
 257. 
 261. 
 
 262. 
 
 263. 
 264. 
 265. 
 266. 
 
 267. 
 
 Enological Investigations. 
 
 Vine Pruning in California, Part I. 
 
 Humus in California Soils. 
 
 Utilization of Waste Oranges. 
 
 Vine Pruning in California, Part II. 
 
 The Economic Value of Pacific Coast 
 
 Kelps. 
 Stock-Poisoning Plants of California. 
 The Loquat. 
 Utilization of the Nitrogen and Organic 
 
 Matter in Septic and Imhoff Tank 
 
 Sludges. 
 Deterioration of Lumber. 
 Irrigation and Soil Conditions in the 
 
 Sierra Nevada Foothills, California. 
 The Citricola Scale. 
 New Dosage Tables. 
 Melaxuma of the Walnut, "Juglans 
 
 regia." 
 Citrus Diseases of Florida and Cuba 
 
 Compared with Those of California. 
 Size Grade for Ripe Olives. 
 The Calibration of the Leakage Meter. 
 Cottony Rot of Lemons in California. 
 A Spotting of Citrus Fruits Due to the 
 Action of Oil Liberated from the Rind. 
 Experiments with Stocks for Citrus. 
 
 No. 
 
 268. 
 
 270. 
 
 271. 
 272. 
 273! 
 
 274. 
 
 275. 
 
 276. 
 277. 
 278. 
 279. 
 280. 
 
 281. 
 
 282. 
 
 283. 
 284. 
 285. 
 286. 
 287. 
 
 Growing and Grafting Olive Seedlings. 
 
 A Comparison of Annual Cropping, Bi- 
 ennial Cropping, and Green Manures 
 on the Yield of Wheat. 
 
 Feeding Dairy Calves in California. 
 
 Commercial Fertilizers. 
 
 Preliminary Report on Kearney Vine- 
 yard Experimental Drain. 
 
 The Common Honey Bee as an Agent 
 in Prune Pollination. 
 
 The Cultivation of Belladonna in Cali- 
 fornia. 
 
 The Pomegranate. 
 
 Sudan Grass. 
 
 Grain Sorghums. 
 
 Irrigation of Rice in California. 
 
 Irrigation of Alfalfa in the Sacramento 
 Valley. 
 
 Control of the Pocket Gophers in Cali- 
 fornia. 
 
 Trials with California Silage Crops for 
 Dairy Cows. 
 
 The Olive Insects of California. 
 
 Irrigation of Alfalfa in Imperial Valley. 
 
 The Milch Goat in California. 
 
 Commercial Fertilizers. 
 
 Vinegar from Waste Fruits. 
 
 No. 
 113. 
 114. 
 115. 
 121. 
 
 124. 
 126. 
 127. 
 128. 
 129. 
 131. 
 133. 
 134. 
 135. 
 136. 
 137. 
 138. 
 139. 
 
 140. 
 
 141. 
 
 142. 
 
 143. 
 
 144. 
 145. 
 
 147. 
 148. 
 150. 
 151. 
 
 Correspondence Courses in Agriculture. 
 
 Increasing the Duty of Water. 
 
 Grafting Vinifera Vineyards. 
 
 Some Things the Prospective Settler 
 Should Know. 
 
 Alfalfa Silage for Fattening Steers. 
 
 Spraying for the Grape Leaf Hopper. 
 
 House Fumigation. 
 
 Insecticide Formulas. 
 
 The Control of Citrus Insects. 
 
 Spraying for Control of Walnut Aphis. 
 
 County Farm Adviser. 
 
 Control of Raisin Insects. 
 
 Official Tests of Dairy Cows. 
 
 Melilotus Indica. 
 
 Wood Decay in Orchard Trees. 
 
 The Silo in California Agriculture. 
 
 The Generation of Hydrocyanic Acid 
 Gas in Fumigation by Portable Ma- 
 chines. 
 
 The Practical Application of Improved 
 Methods of Fermentation in Califor- 
 nia Wineries during 1913 and 1914. 
 
 Standard Insecticides and Fungicides 
 versus Secret Preparations. 
 
 Practical and Inexpensive Poultry Ap- 
 pliances. 
 
 Control of Grasshoppers in Imperial 
 Valley. 
 
 Oidium or Powderv Mildew of the Vine. 
 
 Suggestions to Poultrymen concerning 
 Chicken Pox. 
 
 Tomato Growing in California. 
 
 "Lunjrworms." 
 
 Round Worms in Poultry. 
 
 Feeding and Management of Hogs. 
 
 CIRCULARS 
 
 No. 
 152. 
 
 153 
 
 154, 
 
 155. 
 156. 
 157. 
 158. 
 160. 
 161. 
 162. 
 
 164. 
 165. 
 
 166. 
 167. 
 168. 
 
 169. 
 170. 
 
 171. 
 172. 
 173. 
 
 174. 
 175. 
 
 176. 
 
 177. 
 
 178. 
 
 Some Observations on the Bulk Hand- 
 ling of Grain in California. 
 
 Announcement of the California State 
 Dairy Cow Competition, 1916-18. 
 
 Irrigation Practice in Growing Small 
 Fruits in California. 
 
 Bovine Tuberculosis. 
 
 How to Operate an Incubator. 
 
 Control of the Pear Scab. 
 
 Home and Farm Canning. 
 
 Lettuce Growing in California. 
 
 Potatoes in California. 
 
 White Diarrhoea and Coccidiosis of 
 Chicks. 
 
 Small Fruit Culture in California. 
 
 Fundamentals of Sugar Beet under 
 California Conditions. 
 
 The County Farm Bureau. 
 
 Feeding Stuffs of Minor Importance. 
 
 Spraying for the Control of Wild Morn- 
 ing-Glory within the Fog Belt. 
 
 1918 Grain Crop. 
 
 Fertilizing California Soils for the 1918 
 Crop. 
 
 The Fertilization of Citrus. 
 
 Wheat Culture. 
 
 The Construction of the Wood-Hoop 
 Silo. 
 
 Farm Drainage Methods. 
 
 Progress Report on the Marketing and 
 
 Distribution of Milk. 
 Hog Cholera Prevention and the 
 Serum Treatment. 
 
 Grain Sorghum Seed. 
 
 The Packing of Apples in California.