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AGRICULTURE FARMERS’ BULLETIN No. 1424 Bh epee ec Ren REET NIION ES PE Be mumins been reve { --see reveode

| | MAKING

VINEGAR IN THE HOME AND ON

Nee can be made from any fruit, or, tu fact, from any material which contains enough sugar and is in no way objectionable.

Whether it is done on a small scale in the home, on a larger seale on the farm, or on a still larger scale in the factory, the production of vinegar ts the result of two distinct fermentation processes-~ an alcoholic fermentation followed by an acetic ter- mentation,

By using the materials and following the methods discussed in this bulletin, vinegar of good quality may readily be made from apples, peaches, grapes, and other truits, large quantities of which are wasted cach year in the United States.

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Washington, D.C. Issued Jane, 1924

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MAKING VINEGAR IN THE HOME AND ON THE FARM.

By Epwin LeFevre, Scientific Assistant, Microbiological Laboratory, Bureau of Chemistry.

CONTENTS.

Page. Page. Winégat- 22-226 2.0 Soe eo olus es. 2 1 | Animal parasites.-_..-~ .-_____. oe, Materlal used.______.-_ eRe S.c2e2 2 | Vinegar bees __ ee 23 Fermentation. -—. 2 5 | Tests __ 23 After treatment. —__ = 2 14 Acld strength of vinezar__ 26 Causes of failure. ____ 19 | Federal regnlations governing manu- Darkening of vinegar_ 21 facture and sale of vinegar— : 8

VINEGAR.

INEGAR was first made from wine, as its name indieates, at

a remote period. Biblical writers mentioned it and Hippocrates used it as a medicine. By the sixteenth century vinegar from grapes was being produced in France for home consumption and for export. In England vinegar was first made from malt liquors, a method of disposing of ale and beer which had soured. For this reason it was known as alegar, Although this name has long since become obsolete, malt vinegar is still the standard in the British Isles. It is not known just when vinegar was first made in the United States. certainly very early as a home product. Here apple jnice is largely used for this purpose and cider vinegar is considered the standard for household purposes. Other frits and vegetables, however, are coming more and more into favor for making vinegar, Spirit vinegar, now manufactured in large quantities in the United States, is extensively used for pickling purposes. There are few homes in which vinegar in some form is not used for flavoring, pre- serving, or pickling. ;

Vinegar 1s essentially a dilute solution of acetic acid, made by fermentation processes, containing salts and extracted matter. These additional substances, the exact nature and quantity of which depend upon the material used, give the product its distinctive quality. Sngar is the base of vinegar production, Any watery solution of a fermentable sugar may be transformed into vinegar under favorable conditions. Many fruit jiices are well suited to this purpose. as they contain sngar in the proper proportion and other necessary or desirable substances. ;

All vinegar is made by two distinct biochemical processes. both of which are the result of the action of microorganisms. The first pro- cess 18 brought about by the action of yeasts which change the sugar into aleohol and carbon dioxide gas. This is the aleoholic fermenta- tion. ‘The second process results from the action of a widely dis- tributed group of bacteria which have the power of combining oxygen with the alcohol, thereby forming acetic acid. This is the acetic fermentation, or acetifcation.

9 Farmers’ Bulletin 1424.

The following recognized varieties of vinegar are classified ac- cording to the wnaterial from which they are made and the methods of manufacture:

Vinegar made by the alcoholic and subsequent acetic fermentation of the juices of various fruits. Although apple juice is most com- monly used for making vinegar in the United States, other frit juices, notably those of grapes, peaches, oranges, persiinmons, pine- apples, and some berries, are satisfactory. Auy fruit or vegetable containing enough sugar will serve the purpose.

Malt vinegar made by the alcoholic and subsequent acetic fermen- tation, without distillation, of an infusion of barley malt or other cereals in which the starch has been converted into maltose.

Sugar vinegar made by the alcoholic and subsequent acetic fermen- tution of solutions of sugar, sirup, or molasses.

‘orn-sugar vinegar made by the alcoholic and snbsequent acetic fermentation of a solution of cornstarch sugar or of glucose prepared from cornstarch.

Spirit or distilled vinegar made by the acetic fermentation of dilute distilled alcohol.

MATERIAL USED.

Anything may be used for making vinegar, so long as it contains enough sugar and is in no way objectionable. It would be difficult to describe in detail all the materials which are available for this purpose. The following are most commonly used in the United States:

APPLES.

Nearly all varieties of apples contain enou h sugar to make vine- gar of the requived strength. This was well shown in tliree series of tests conducted by the Bureau of Chemistry on apples representing a large number of varieties grown during 1909, 1910, and 1911 in New York, Ohio, Virginia, Michigan, Missouri, and Washington. The average sugar content of the apples grown on grafted stock was found to be nore than 18 per cent. In one series, including 58 varieties, in which two or more samples of each variety were analyzed (a total of 406 samples), the average sugar content was 13.54 per cent; in no sample was the sugar content less than 10 per cent. In a secoud series of 72 varieties, in which only one sample of each vaviety was analyzed, the average sugar content was 13.16 per cent; in only four of the varieties did the sugar coutent fall below 10 per cent. In a series of 75 samples of seedlings. natural fruit, the average sugar content was 12.71 per cent, the sugar content of none of the samples falling below 10 per cent.

Winter apples have the highest and summer apples the lowest average sugar content, with fall apples intermediate. Summer apples therefore are not suitable for vinegar making. Windfall apples nay well be used for this purpose, provided they are not from stimmer varieties and were properly matured at the time of falling. freen apples are incapable of yielding a satisfactory_vinegar, be- cause much of their starch has not been transformed into sugar. Frosted or frozen apples have been used successfully for making

Making Vinegar. 3

vinegar, but they must be pressed soon after freezing and before any rotting occurs.t Contrary to the usual belief, sweet apples are not richer in sugar than sour apples; in fact, some varieties may contain less than the average quantity. The sweet taste of these apples is due not to the presence of larger quantities of sugar but to a deficiency in inalic acid, the acid normally present in apples.

Evaporated apple chops and the evaporated cores and parings obtained from apple-canning factories and apple-drying establish- ments are now uscd to some extent in the commercial production of vinegar. By passing water through several successive tanks of this inaterial it is possible to obtain a sweet solution which serves for the production of vinegar. If the dried stock used for this purpose is clean and made from sound material, vinegar of satisfactory quality may be produced in this way. Such vinegar, however, is not inade from the expressed juice of apples, so that when offered for sale it must be marked to show the material from which it is made.’

GRAPES.

Vinegar of unexcelled quality can be made from the grapes (Vitis vinifera) grown in Kurope and on the Pacific coast of the United States. Lhe white wine vinegar made from whole white grapes or from the pulp of purple or red grapes is excellent in qnality. This inust not be confused with what in commerce was fomnerly incor- rectly called white wine vinegar,” which is simply a spirit vinegar. Grape vinegar can compete commercially with cider vinegar only on the score of merit and if it is to be sold at a profit “it must be made in such a manner as to produce and preserve those qualities to which it owes its reputation for smperiority over all other classes of vinegar.” ®

Grape juice contains a very much higher proportion of sugar than apple juice; hence a much stronger vinegar can be made from it. The California Agricultural Experiment Station has shown that a ton of California grapes (20° Brix) can give on an average 150 gallons of juice, which will yield 135 gallons of vinegar containing 9.8 per cent of acetic acid. The Bureau of Chemistry has shown that vinegar of excellent quality can be made from the muscadine grapes grown in the Southern States. Juice from fonr varieties of these grapes (16.5° Brix) gave by honsehold methods vinegar which contained an average of 6.6 per cent of acetic acid.

ORANGES.

The Bureau of Chemistry has shown that a very acceptable vinegar can be made from oranges, either on the household scale or on a commercial scale. Cull oranges will give a vinegar which not only is equal to the best grade of vinegar but can be made commercially at a cost which in some markets permits competition in price with apple vinegar.

Be eS he i ee SS

24, RB. Lamb and Edith Wiison. Vinegar Fermentation and Wome Production of

Cider Vinegar, lowa Agr. Expt. Sta. Bui, 218 (1925), p. 5. 211, §, Dept. Agr., Food Inspection Decision 140 (1912)

23° J Blolettl Grape Vinegar. Calif. Agr. Expt. Sta, Bul. 227 (1912), 26 pp.

4 Farmers’ Bulletin 1424. PEACHES.

While the average sugar content of peaches is somewhat lower than that of apples, certain varieties contain enough sugar for vinegar making. Juicy varieties of the Camman type are best adapted for this purpose. The peaches should be tree-ripened if possible, for tree-ripened peaches apparently contain more sugar than those picked while green and allowed to ripen during shipment or storage.* Peach jnice ferments readily and vinegar of good flavor can often be made from peaches which would otherwise be allowed to decay.

PERSIMMONS.

Persimmons, which grow in nearly all parts of the United States, but most abundantly in the Southern States, are exceedingly rich in sugar. Experiments condueted in the Bureau of Chemistry have shown that they may be utilized for making vinegar. In using frints like persimmons and figs, which have a high sugar and low moisture content, water must be added in order to seeure the proper con- centration,

PEARS.

Grown in great abundance in many places, pears also may be utilized for making vinegar. Investigations in the Bureau of Chem- istry have shown that even varieties like the Mieffer, which have a low sugar content, if well ripened may be made to produce a satis- factory vinegar.®

BERRIES.

Vinegar which can veadily be made by household methods from raspberries. blueberries, and doubtless other berries may be very neceptable for certain purposes. Experiments in the Burean of Chenustry have shown that vinegar made from red raspberries will vetain indefinitely the odor and flavor of the fruit. which makes it desirable for lavoring food. Vinegar made from berries is dark, but it can easily be made clear or * bright * (p. 15).

HONEY.

Vinegar of excellent flaver ean be made from uninarketable honey or honey washings. When honey is used for this purpose, it must, of course, be dilited by the addition of water mntil it contains about {5 percent of sugar. As heat must be employed in the process of lution, it will be necessary to use cultures of yeast and acetic bacteria (p. bz). The dilution of the honey also reduces the chem- ical elements which are necessary for the growth of the veasts and bacteria. in order to supply the essential elements, especially nitro- gen and phosphates, certain chemicals should he added. The fol- lowing formula is suggested for a barrel of vinegar: Strained or extracted honey. 40 to 45 pounds: water, 30 gallons: ammonium phosphate, 2 ounces: potassinm tartrate, 2 ounces.

W. oD. Bigelow and IT. C. Gore. Studies on Peaches. VU. 8. Dept. Agr, Chem. Bul. OF (190500. 32 pp. SIL. CG. Gore, The Preparation of Vinegar from Kleffer Pears. Jn J. Am. Chem. Soc. (1907), vol. 29. p. 759.

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Making Vinegar. 5 MAPLE PRODUCTS.

Maple-sirup skimimings or maple sirup which has been scorched may be used for making vinegar. Like honey, this umst be diluted until it contains about 15 per cent of sugar, or until it weighs 9 pounds to the gallon. To each 80 gallons of the diluted simp, 2 ounces each of ammonium sulphate and sodimn phosphate are added. These chemicals, which are neither expensive nor injurious in the quantities called fov, are not to be regarded as adultevants.°

WATERMELONS.

Watermelons have been used successfully for making vinegar, but the juice must be concentrated to about half its original volume to give the proper sugar content.

GRAINS.

Grains, chiefly coru, barley, rye, and oats. are largely utilized for the production of spirit and malt vinegar, The stareh which they contain is first converted into sugar. usually by the action of malt (sprouted barley). Malt vinegar is made from the sugary solntion or wort obtained by steeping crushed malt in warm water.

MOLASSES.

Molasses, either alone or in combination with grain extracts, is widely used as a basis for making spirit vinegar. Crude molasses, known as blackstrap, is first diluted with hot water and then sub- jected to alcoholic fermentation, The “low wines” which are ob- tained by distilling the fermented product are then run throngh generators and converted into spirit vinegar, Much of the spirit vinegar now used is made from alcohol obtained as a by-product from the manufacture of other products, notably compressed yeast.

Distilled or spirit vinegar which is made in this way is nearly colorless and lacks the aronia and flavor of frmt vinegars. For this reason it is ne’ conmionly preferred for table use, but is exten- sively used for pic! ling and preserving.

FERMENTATION.

The methods of making vinegar differ decidedly, depending npon whether it is made in small quantities as a household produet. im larger quantities as a farm product. or in much larger quantities requiring the elaborate equipment of a commercial plant. ‘Phe first two methods will be discussed in detail: the Jast method, which in- volves inany technical details, can not be fully treated here.

HOUSEHOLD METHOD.

Fruit enough to make all the vinegar for a year's supply is wasted in many homes. Surplus or inferior grades of fruit not desired for ininiediate use or for canning nity often be turned into a useful pred- uct at a merely nominal cost. experiments in the Bureau of Chem-

6 Directions for Muking 1 Good Flavored Clder Vinegar. Mich. Agr. Expt. Sta. Special

Bul. 98 (1920), 24 pp ; A. E. Vinson. Wleney Vinegar. Jn Ariz. Agr. Expt. Sta. Bul. 57 (1907), pp. 247-255.

6 Farmers’ Bulletin 1424.

istry have shown that vinegar of legal streneth (4 per cent acetic acid) can be nade from all of the fruits listed on page 2, although it may not be possible to nse all varieties. In order to avoid disap- pointment, a test should be made to determine the sugar content of each lot of fruit before beginning the operation (p. 24). In making vinegar for hone consumption and not for sale the need of a product of full legal strength is not imperative.

The best receptacles for making vinegar in the home are stone jars. These should always have straight sides and open tops and should be provided with covers. (Fig. 1.) Jars holding from 8 to 6 gallons are ordinarily used for this purpose.

With most of the fruits used it is impossible or inexpedient to separate the juice from the pulp before the alcoholic fermentation has taken place. The proper method, therefore, is to make a yeast in- uculation into a mash of the fruit. With some fruits, like apples, oranges, or pineapples, from which the juice can be readily ex- pressed, it may be better to use the juice only. Even~with apples, however, it is probable that a more coinplete utilization of sugar would result if the alcoholic fermentation were carried out in the crushed frnit.

The following method which calls for peaches may be used, with a few minor variations, for making vinegar from other fruits,

PREPARATION OF MASH.

Ripe fruit should, of course, always be selected. Overripe frnit is not to be barred: in fact, in some. instances it is feforables so long us decayed portions, which would introduce objectionable flavors and organisins, are carefully removed. Juicy peaches are best, although almost any kind can be ntilized.

Enough peaches (approximately 1 bushel) to fill a 4-gallon stone jar about two-thirds fnll when made into a mash are cut in two aud crushed with a potato masher. The stones need not be

removed. ALCOHOLIC FERMENTATION.

A cake of compressed yeast which has been mixed in a small por- tion of the jnice is added to the jar of peach mash. The jar is cov- ered with a double layer of cheesecloth to prevent the entrance of insects and with a cover to exclnde light. The mash is stirred daily to break np surface crusts, prevent the formation of molds, and insure a more complete fermentation. Stirring also prevents the action of acetic bacteria. Asa rule from 4 to 6 days are necessary for this fermentation.

ACETIC FERMENTATION.

When the alcoholic fermentation is conrplete the juice is separated from the mash. Usnally by this time separation has to a great extent been accomplished by the ‘action of the yeast and straining through cheesecloth is all that is necessary. Complete separation may re- quire the use of a hand press.

After the juice has been returned to the jar a starter (p. 13) in the form of vinegar is added in the proportion of 1 part to 4 parts of the juice and the jar is covered as before. Within a few days a thin coating or film will appear on the surface of the juice. This mother

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Making Vinegar. 7

of vinegar,” which is composed almost entirely of acetic hacteria, is essential for a successful fermentation. Great care, therefore, should be taken not to cause it to fall by stirring or agitation.

During the acetic fermentation frequent tests should be made to determine the increase in acidity (p. 25). As soon as this has reached its maximum, the vinegar is filtered (p. 15) and bottled (p. 19).

VARIATIONS.

This procedure may need to be varied in some respects for differ- ent fruits. For example, when fruits which have very high sugar contents, like persimmons, are used it is necessary to add water to the mash before inoculating with yeasts. An eqnal quantity by weight of water added to the persinimon mash will usually give the desired sugar content.

The plan outlined is believed to. offer the best method of making vinegar in the household. It is the simplest and the least expensive and gives satisfactory results. Anyone who has a supply of sur- plus fruit, 2 or 3 large stone jars, a few cakes of compressed yeast, and 3 or 4 quarts of good vinegar to act as a starter can in this way make all the vine- gar that is required by an ordinary family for a year. Vinegar with an acetic acid strength of 4.5 per cent has been made from peaches by this method in 13 days.

FARM METHOD. Vinegar as ordinar Vig. 1.—Sultable receptacles for making vinegar in the @ =

: home. ily produced on Ainer- ican farms is nade from apple juice, although there is no good reason why grapes, peaches, or pears should not be used when their prices are not prohibitive.

PRESSING THE FRUIT.

Almost any apples may be used except those which are green ov rotten. If pactly rotten apples are used the rotten spots should be cut out and the apples washed. Dirty apples should be washed. Dirt. grass, or leaves should not be allowed to go into the press with the apples; they will injure the flavor of the vinegar and may retard the process.

The apples should not be ground too fine; they should be crushed rather than ground. Too fine grinding makes it difficult to press out the juice. Pressing must be done slowly and as much as possi-

93147°—24 2

8 Farmers’ Bulletin 1424.

ble of the juice extracted. From 2 to 3 gallons of juice should be obtained froma bushel of apples. ‘Phe press cloth ? type o { press is the most ellicient for this purpose. Full directions for pressing apples ave given in Farmers’ Bulletin 1264. ;

Second pressings from fresh pomace may be made when desired. If water is added to the pomace, however, the resulting juice will be low in sugar and other solids. The addition of such juice to the juice from first pressings may reduce the sugar content of the whole toa degree which wonld not permit the production of a satisfactory vinegar. Hf the vinegar is made for sale, Federal food regulations require that the additjon of water in the process of manufacture must be plainly indicated cn the label.

ALCONOLIC FERMENTATION.

After being expressed, the jnice should stand for a day or two in loosely covered barrels or other covered receptacles for sedimenta- tion. after which it is carefully drawn off, preferably by the use of a siphon (p. 15), and transferred to other containers for alcoholic fermentation. ‘Phese barrels should not be filled over three-fourths full. ~

Yompressed yeast is added in the proportion of 1 small eake for each 5 gallons of juice. ‘The yeast should first be thoroughly macer- ated in-at least a quart of the jnice and this should be well stirred into the whole, Ef a pnre culture of a specially cultivated yeast 1s to be used. this should be prepared and added as directed on page 15.

ACETIC FERMENTATION.

The second or acetic fermentation may be done in any one of the three following ways. ‘The selection of the process will, of course, depend upon individual conditions.

SLOW BARKEL PROCESS,

After the alcoholic fermentation is coniplete, as shown by a_ test (p. 24), the juice should be carefnlly drawn off from the contamers mowhich the aleoholic fermentation tock place, withont disturbing the vettlings at the bottom, and passed into barrels for the fia] or acetic fermentation. ‘Phe barrels should have been first thoroughly cleaned and soaked with strong vinegar and placed on their sides with the bungholes np. They are filled about twe-thirds fill, the nim being to expose as large a surface of juice as possible to the air. About 3 gallons of good vinegar is then added to each barrel to hasten the change to acetic acid. For this purpose a fresh un- pastenrized vinegar is much to be preferred, but if it is net ob- tainable any good strong vinegar will do.

The aleohol of the yeast-fermented juice is now turned into acetic acid. In order that this change shall take place rapidly, the jmice inust be in contact with the air. For this reason the bingholes should be left open. Additional holes should be bored in the ends of the barrels to afford a free cirenlation of air. Pieces of cheese- cloth or well-varnished fine wire sercen shonld be tacked over all openings to keep out insects and dirt, The temperature should not be below 70°F... if practicable.

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Making Vinegar. 9

Acetification shonld be allowed to proceed until a strong vinegar is produced. Such a vinegar can be recognized by its taste, but it is much safer to determine the degree of acidity by tests as the aceti- fication progresses (p. 25). Tf a good starter has been added and the jnice is kept at the proper temperature, the time required to convert the alcohol in the jnice into acetic acid should not be more than 3 to 6 months.

CONTINUOUS PROCESS.

The process of acetification may be made continuons by adopting the following plan,’ which is esseutially the Orleans method that has been used from time immemorial in the Orleans district of France: barrel holding about 50 gallons is made into a “converter” (fig. 2). In one end of the barrel, just above the center, a 2-inch hole (A) is bored and in the other end. abont an inch below the stave containing the bunghole, another hole (B) of the saine size. The holes are covered with mosquito bar or well-varnished fine wire screen to keep out the small vinegar or frnit flies. The spigot (C) is fitted in place. With the aid of a hot iron, a hole is bored through the cork used for closing the bung. Tn this hole is fitted the stem of a short glass or rubber funnel, running about

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. 2ineh holes: €, spigot. throngh. A piece of bent glass tubing, about one-half inch in diameter and loug enongh to reach within 3 inches of the bottom of the barrel, is also fitted in the hole. .

The finished converter is blocked firmly into place where there is a free creation of air and about 8 gallons of fresh. nupastenrized vinegar is poured into it. The clear yeast-fermented juice is now rnn in until the surface of the liquid is nearly level with the air hole (A). Better resnlts wonld probably be obtained by adding the jnice in the fractional parts of one-fonvth to one-third at intervals of a week. An additional advantage would be secured in all of these operations if the juice were heated to 85° or 90° F. before being poured into the converter,

The converter is allowed to stand without disturbing the film which forms on the swrface until the acetification has gone far enough. When 4.5 to 5 per ceut of acetie acid has been produced the vinegar is drawn off through the spigot, leaving about 3 gallons. The transfer of the vinegar should be made slowly so as not to break the film.

‘Adapted from Farm-Made Cider Vinegar, lowa State Dairy and Food Commission Bul. 12 (1915).

10 Farmers’ Bulletin 1424.

Kia. 38.——Generator ——— = for rolling gen- \4 \& erator process, | A, rack made of

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barrel.

A new supply of yeast-fermented juice is now slowly run_in through the funnel which leads to the bottom of the converter. This should be done carefully so as not to disturb the surface film. The film wilt rise on the surface of the liquid and start fermentation promptly,

A converter made from a 50-gallon barrel should convert from 100 to 150 gallons of yeast-fermented jiice into vinegar in a year.

ROLLING GENERATOR PROCESS.

The so-called rolling generator process, which greatly shortens the time required for acetilication, approaches more nearly the com- mercial process of making vinegar in generators. This plan requires inore work and attention than the slow barrel method, but by pro- viding fora greater circulation of air it greatly hastens acetilication.

An ordinary vinegar barrel is made into a generator ® us follows (fig. 8): After one head of the barrel has been removed, a small rack is built into the barrel in such a way as to make throughout its length, about 6 inches below the bunghole, a compartment which is to be filled with beechwood shavings or corneobs (C). A quick way to do this is to make a rack of slats 3 inches wide by one-half inch thick, set into grooved end pieces, with about one-half inch of space between them (A). At each end this rack is supported by a 2 by 4 inch piece cut im such lengths that the rack will be at least 6 inches below the bung (B), The 2 by 4’s are usually joined at the bottom by a crosspiece 1 by 2 inches. After this rack 1s set in place and the compartment is filled with cobs or shavings. the barrel is reheaded and three 1-inch holes are bored obliquely downward in each end, so that the openings come just beneath the bottom of the rack holding the shavings or corncobs. In constructing the rack and fastening it

a $$ pe ih Chace. By-Products from Citrus Frults. U. S. Dept. Agr. Cir. 232 (1922), pp. > *

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Making Vinegar. 11

to the 2 by 4’s, grooves or dowels should be used, or, if more eon- venient, the rack may be held together by hardwood pegs. Iron or other metallic nails should not enter into the construction.

When used for the first time or after it has been standing idle for any length of time, the generator should be thoroughly scalded with hot water or steam. After the generator has been completely drained, about 1 gallon of fresh unpasteurized vinegar is poured into it. All the holes are tightly plugged, and the generator is turned to allow the vinegar to run over and saturate the shavings. The generator should then be filled about half full with yeast-fermented juice. Several times each day, if poss:ble, but at least once a day, all the holes should be closed with wooden pegs and the generator rolled over, so that the bung is at the bottom, and shaken three or four times to bring the juice thoroughly in contact with the beechwood shavings or corncobs. The generator is then rolled back into its original position and the wooden pegs are replaced by cotton plugs. As there is a circulation of air from the end holes throngh the

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12 Farmers’ Bulletin 1424.

shavings out of the bunghole, the juice dripping from the shavings comes in contact with the air, as a result of which the process of acetification is greatly hastened.

Ag the fermentation progresses, 2 good deal of heat is developed. To obtain the best results the temperature of the upper portion of the generator shonld be kept at abont 85° I. The temperature can be lowered by inserting some of the pegs to cut down the air current passing in at the holes. ‘To raise the temperature the supply of air is increased by removing some of the pegs.

If the geucrator is rolled every day and the temperature is main- tained at from 80° to 85° F., the juice may be converted into good vinegar by this method in from 60 to 90 days.

COMMERCIAL METHOD (QUICK VINEGAR PROCESS).

The far method of making vinegar is necessarily slow, for the reason that only the surface of the alcoholic liquid is exposed to the air. It is possible to greatly hasten the production of acetic acid by allowing the alcoholic mixture to trickle slowly through a tall wooden vat containing material like wood shavings. coke, or corncobs which has been inoculated with acetic bacteria and through which a curvent of air is constantly rising. Such an apparatus is known as a generator (fig. 4) and this method is called the quiek or generator process of making vinegar,

By using generators more vinegar can be made in a few days than could be made in as many months or even years by the ordinary farm procedure. For this veason generators are always used where vinegar is produced commercially in’ large quantities. As this method is a continuous process which calls for an extensive equip- nent and trained supervision, it is not practicable for farm ise.

CLEANLINESS.

Cleanliness is essential in all methods. Anything that will pro- duce malfermentation or off flavors should be avoided. To this end all utensils and receptacles must be kept clean. Not only must the bavrels be clean but they must also be free from anything which will impart undesirable flavors or odors to the vinegar, Barrels which have been used for storing paints, oils. varnishes, or industrial alcohol should never be used for this purpose. Old vinegar and molasses barvels and new barvels should not be used until they have been well washed with boiling water or steam,

sarrels which have been nsed for grain alcohol, whisky, or brandy are well adapted for vinegar making. These liquors are antiseptic to most nicrobes, but in small quantities they are not antagonistic to the growth of yeasts or acetic bacteria and will not mpart unde- sirable thivors or odors to vinegar.

USE OF STARTERS.

Experience has thoronghly demonstrated the value of the use of starters ino making vinegar. Yeasts and acetic bacteria are prac- tically always present in frmit jiices, but they often occur only in lanited numbers or more often are of undesirable or inactive types.

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Making Vinegar. 13

Better vesults are obtained by the addition of active strains. This is especially important in the aleoholic (yeast) fermentation where w prompt and rapid fermentation is desirable.

Ordinary conpressed yeast, obtainable almost everywhere in this country, is a satisfactory starter for the alcoholic fermentation and should be used when it is impossible to obtain cultures which have been especially cultivated for vinegar production.

As a starter for the acetic fermentation, the best results are un- doubtedly obtained by the addition of vinegar. If possible, unpas- tenrized vinegar should be used, for the reason that such vinegar usually msures the addition of the essential organism. Vinegar should be added as a starter in any event, however. whether or not

it coutains living bacteria, and even when a pure culture of acetic bacteria is used.

When pasteurized juices or sugar solutions, which do not contain the essential organisms, are used for making vinegar, the addition of active cultures is of course essential.

For those who desive to use pure cultures wluch have been culti- vated especially for vinegar production these directions ave given.?

The cultures should be obtained only from sources which insure their reliability. Such cultures are furnished by several of the State experiment stations and by some commercial laboratories. Yeast cultures should be obtained about a week before they are to be

used, Front these a starter ina 2-quart fruit jar is prepared for each barrel as follows:

STARTER FOR ALCOHOLIC FERMENTATION.

Wash the jar thoroughly and sterilize it in boiling water.

TInnnediately fill the jar dndf full with boiling apple juice. If no sweet juice is available, slice five or six ripe apples in 2 quarts of water and beil until the fruit is soft. Add 4 tablespoentuls of molasses or 2) tablespooutuls of sugar and strain about 1 guart of the boiling juice iuto the fruit jar.

Cover the jar immediately with a few folds of cloth, sterilized with boiling water, fo keep out germs from the air

When the liquid has cooled to 75° EB. shake the bottle Jabeled vinegar veast ? and ecinpty fle contents into the jrr.

Keep the jar at a temperature of 70° to SO° FF.

When fonming is very active, empty the conteuts of the jar into the barrel ot sweet juice. Cover the bunghole with a thin cloth to keep ont dust. withent cutting olf the air.

Innnediately after fhe active foaming in the barrel ceases. send to the bae- tericlogical laboratory for the acetic culture and prepare it as follows :

STARTER FOR ACETIC FERMENTATION.

Draw off a quart of the yeast-fermented juice into as many jars as there are barrels te be inocnlated. Observe the foregoing precautions for the jars clean and sterile,

eat the liquid in the jars by bringing it just to the boiling point in hot water: theu allow it te cool T5° BB. Do not let it beil.

Add the eulture labeled “vinegar bacteria” to the jar. cover as before. and keep it at a taaperature of sa° EF,

Po not disturb this jar. Mother of vinegar (Bacteria acetiy will appear on the surtace of the liquid ina week or so as a smooth grayish-white glisten- ing film. It molds develop do not use the starter but send to (ie bacteriotogics] laboratory for another,

When this filmi is one-sixteenth to one-eighth ineh thick, litt if out of the Jar with a clean boiled splinter of wood, add the contents of the jar to the

keeping

* Adapted from directions piven by the Washington State Agricultural Uxperiment Statlon for preparing pure culures for vlnegar making.

14 Farmers’ Bulletin 1424.

barrel, und float the film on the surface of the liquid, using the splinter as a raft. It is very important that this film be flouted on the surface.

Do not disturb the barrel from now on except to remove sinall quimntlties from time to (ime to test the strength of the vinegar (page 25).

AFTER TREATMENT.

After vinegar has been properly fermented and has reached the desired degree of acidity, it is most important to see that it does not deteriorate in strength or quality. To this end, it must not be exposed to the air. The presence of air, which was so inportant

during acetifica-

tion, 1s now to the

same degree unde- B sirable. Free ex- posure to air would mean that the acetic and pos- sibly other types of inicroorganisms would continue to act. As a result the acid would be attacked and sooner or later the

Ma. 5.- Siphoning off the vinegar. A, glass tube; B, rubber hose,

vinegar would be reduced to a worthless condition. ‘To prevent this, it is necessary only to keep the vinegar in completely filled containers, tightly sealed.

When vinegar is made under household conditions, as soon as it reaches the desired acidity it should be decanted off, filtered, and bot- tled. When made under farm conditions and stored in barrels or in kegs, the containers should be kept completely filled, tightly bunged, and stored, preferably in a cellar where a cool, even temperature prevails.

AGING. Vinegar has a raw, biting taste when first made but it becomes

more mellow during storage. ‘The flavor and aroma characteristic of the best grades of vinegar made from apple and grape Juice are due

Making Vinegar. 15

to the esters which are formed during storage. Storage for from six months to a year is required for vinegar to attain its highest quality.

CLARIFICATION.

The aging of vinegar is valuable for the additional reason that it affords a chance for settling. In many cases vinegars which: are not clear at the end of fermentation will become clear on standing.

After vinegar has been held in storage for several months it should be “racked off,” that is, drawn off carefully, so as not to disturb the sediment, and with as little exposure to the air as possible. This is best done by the use of a siphon. (Fig. 5.) For this purpose the glass tube (A) described on page 9 may be utilized by simply attach-

ing to the upper end a piece ——— f rubber | B). Th a TT 7 of rubber hose (3B) his fen qi |

ap

process should be repeated if a gysns

the vinegar is to be held in storage very long. Usually this will yield a product which is fairly clear and for home use may be all that is desired. If intended for sale. however, good commercial practice demands that it be perfectly clear or bright. Jnices from certain fruits, notably that from most va- rieties of apples, show a marked tendency to_ clear during fermentation. Others. like that from peaches, do not, and often can be made perfectly clear only with great difficulty. Cloudiness in vinegar nay be due to the presence of finely divided par- a ticles or Teidal substances accet cae held in suspension, or to the Fic. 6.——Filter over top of barrel. presence of bacteria or the products of bacterial activity. Certain strains of acctic bacteria show a marked tendency to produce cloudiness of the medium in which they grow. In order, therefore, that a vinegar may be perfectly clear and bright, it 1s usnally necessary to resort to filtra- tion or to the use of clarifying agents.

FLLTRATION.

The common method of secnring a perfectly clear vinegar is by means of filtration, which usually 1s effectual if properly done.

When the quantity of vinegar to be filtered is not large, it may be passed through a filter made by folding a large piece of canton {flannel so as to give three or four thicknesses. This may be simply placed over a convenient receptacle (fig. 6) or it may be made up in the form of a cone-shaped filter bag (fig. 7). It may be neces-

16 Farmers’ Bulletin 1424.

sary to pass the vinegar through a filter of this kind several times to make it clear or bright. The efliciency of a cloth filter, and in fact of practically all filters, depends upon the gradual filling up of the pores of the filtering medium by particles of the material passing through it. Tlence perfect clarification is not often accom- plished by one filtration, or at least the first portion to pass through is not clear and must be poured back for refiltvation.

When larger quantities of vinegar are to be filtered, as in coin. mercial production, filters of more or less elaborate constriction are used. These usually operate by suction and filtration is made through various