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U. S. DEPARTMENT cfcs'- ' 




■Has beon rev. 
— see rev.od. 

binders at 
end of file. 

IXEGAK t-an he made from any I'rnil, or, in fuel, 

* 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 scale on the farm, or on a still larger 
scale in the factory, the production of vinegar is the 
result of two distinct fermentation processes an 
alcoholic fermentation followed by an acetic fer- 

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 fruits, large quantities of which are 
wasted each year in the United States. 

WiWliiilgliin, !).('.. Issiiril June, 19LM 


By Edwin L,eFevke, Scientific A.isi&tunt, Microbiological Laboratory, Bureau 

of Chemistry. 



Vinegar 1 

Material used, 2 

Fermentation r> 

After treatment 14 

Causes of failure 10 

Darkening of vinegar 21 


Animal parasites 22 

Vinegar liees 23 

Test*. ....... 2:t 

Acid strength of vinegar-- 2(i 

Federal regulations governing inanu- 

fneture and sale of vinegar 28 


VINEGAR was first made from wine, as its name indicates, at 
a remote period. Biblical writers mentioned it and Hippocrates 
used it as n 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 had soured. For this 
reason it was known as alegar. Although this name lias 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 
juice is largely used for this purpose and cider vinegar is considered 
the standard for household purposes. Other fruits 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 is 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. 
Sugar is the base of vinegar production. Any watery solution of a 
fermentable sugar may be transformed into vinegar under favorable 
conditions. Many fruit juices are well suited to this purpose, as 
they contain sugar 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 is brought about by the action of yeasts which change the sugar 
into alcohol and carbon dioxide gas. This is the alcoholic 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 acetification. 


2 Farmers' Bulletin Vi2k. 

The following recognized varieties of vinegar are classified ac- 
cording to the material 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 fruit 
juices, notably those of grapes, peaches, oranges, persimmons, pine- 
apples, and some berries, are satisfactory. Any fruit or vegetable 
containing enough sugar will serve the purpose. 

Malt vinegar made bv 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- 
tation of solutions of sugar, sirup, or molasses. 

Corn-sugar vinegar made bv the alcoholic and subsequent 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. 


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


Nearly all varieties of apples contain enough sugar to make vine- 
gar of the required strength. This was well shown in three series 
of tests conducted bv 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 more than 13 per cent. In one series, including 58 
varieties, in which two or more samples of each variety were analyzed 
(a total of 40G samples), the average sugar content was 18.34 per 
cent ; in no sample was the sugar content less than 10 per cent. In 
a second series of 72 varieties, in which only one sample of each 
variety was analyzed, the average sugar content was 18.16 per cent; 
in only four of the varieties did the sugar content 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. Snmmw 
apples therefore are not suitable for vinegar making. \\ mdtall 
apples lmiY well be used for this purpose, provided they are not train 
summer varieties and were properly matured at the time of tailing. 
Green 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. 


vinegar, but they must be pressed soon after freezing and before 
any rotting occurs. 1 Contrary to the usual belief, sweet apples tire 
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 used to some extent in the commercial production or 
vinegar. By passing water through several successive tanks of this 
material 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 he produced in this way. Such vinegar, however, is not made 
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. 2 


Vinegar of unexcelled quality can be made from the grapes (Vitis 
vinifera) grown in Europe and on the Pacific coast of the United 
States. The white wine vinegar made from whole white grapes or 
from the pulp of purple or red grapes is excellent in quality. This 
must not be confused with what in commerce was formerly 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 superiority over all other classes of 


Grape juice contains a very much higher proportion oi 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 
"•allons 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 
"•rapes grown in the Southern States. Juice from four varieties of 
These grapes (16.5° Brix) gave by household methods vinegar which 
contained an average of G.G per cent of acetic acid. 


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. 

» \ U l>amh and Edith Wilson. Vinegar Fermentation and Home Production of 
Cider Vinegar. Iowa Agr. Expt. Sta. Bui. 218 (102.-;), p. 5. 
2 11 S DeRt Agr., Food Inspection Decision 140 (11112). 

•F. T. Blolettl. Grape Vinegar. Calif. Agr. Expt. Sta. Bui. 227 (1912), 20 pp. 


Farmers' Bulletin Vi2h. 


"While tlic average sugar content of peaches is somewhat lower than 
that of apples, certain varieties contain enough sugar for vinegar 
making. -Juicy varieties of the Carman 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 juice ferments readily and vinegar of good flavor can often 
be made from peaches which would otherwise be allowed to decay. 


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


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 Kiefl'er, which have a 
low sugar content, if well ripened may be made to produce a satis- 
factory vinegar. 6 


Vinegar which can readily be made by household methods from 
raspberries, blueberries, and doubtless other berries may be very 
acceptable for certain purposes. Experiments in the Bureau of 
Chemistry have shown that vinegar made from red raspberries will 
retain indelinitelv the odor and flavor of the fruit, which makes it 
desirable for llavoring food. Vinegar made from berries is dark, 
but it can easily he made clear or " bright " (p. 15). 


Vinegar of excellent flavor can be made from unmarketable honey 
or honey washings. When honey is used for this purpose, it must, 
of course, be diluted by the addition of water until it contains about 
l. r ) per cent of sugar. As heat must be employed in the process of 
dilution, it will lie necessary to use cultures of yeast and acetic 
bacteria (p. !.!). The dilution of the honey also reduces the chem- 
ical elements which are necessary for the growth of the yeasts and 
bacteria. In order to supply the essential elements, especially nitro- 
gen and phosphates, certain chemicals should be 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, L! ounces: potassium tartrate. 2 ounces. 

' W. IV lilgelow and II. C Gnro. Studios on lVaclios. V. S. Pcpt. Ajrr.. Cliem. Bui. 
1)7 i umro. :rj pp. 

1 11. C. (lore. The l'l-opai-atiou of Vinegar from Kleffer Tears. In J. Am. Chein. Soc. 
(1007), vol. -'!). p. 730. 

Making Vinegar. 



Maple-sirup skimmings or maple sirup which lias been scorched 
may be used for making vinegar. Like honey, this must be diluted 
until it contains about 15 per cent of sugar, or until it weighs 9 
pounds to the gallon. To each 30 gallons of the diluted simp, 2 
ounces each of ammonium sulphate and sodium phosphate are added. 
These chemicals, which are neither expensive nor injurious in the 
quantities called for. are not to be regarded as adulterants." 


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


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 lirst diluted with hot water and then sub- 
jected to alcoholic fermentation. The u low wines" which arc ob- 
tained by distilling the fermented product are then run through 
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 aroma and flavor of fruit vinegars. For 
this reason it is \v ' commonly preferred for table use, but is exten- 
sively used for pic' ling and preserving. 


The methods of making vinegar dill'er decidedly, depending upon 
whether it is made in .small quantities as a household product, in 
larger quantities as a farm product, or in much larger quantities 
requiring the elaborate equipment of a commercial plant. The lirst 
two methods will be discussed in detail: the last method, which in- 
volves many technical details, can not be fully treated here. 


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 
immediate use or for canning may often be turned into a useful prod- 
uct at a merely nominal cost. Experiments in the Bureau of Cheui- 

" Directions for Mnkine a Good Flavored Ciller Vinegar. Mich. Agr. Expt. Sta. Special 
l'.ul. IIS (lOtl)l. LM pp ; A. E. Vinson. Holler Vinegar. In Ariz. Agr. Expt, Sta. l!ul. 57 
(1007), pp. 247-'205. 


Farmers' Bulletin 1'tlh. 

istry have shown that vinegar of legal strength (4 per cent acetic 
acid) can be made from nil of the fruits listed on page 2, although 
it may not be possible to use 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 home 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 3 to 
C 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 lwifore the alcoholic fermentation has 
taken place. The proper method, therefore, is to make a yeast in- 
oculation 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 juico only. Even with apples, 
however, it is probable that a more complete utilization of sugar 
would result if the alcoholic fermentation were carried out in the 
crushed fruit, . . 

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


]{ipe fruit should, of course, always l>e selected. Overripe fruit is 
not to he barred; in fact, in some instances it is preferable, so long 
as decayed portions, which would introduce objectionable flavors and 
organisms, are carefully removed. Juicy poaches are best, although 
almost any kind can he utilized. 

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


A cake of compressed veast which has been mixed in a small por- 
tion of the juice 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 exclude light. The mash is stirred daily 
to break up surface crusts, prevent the formation of molds, and 
insure a more complete fermentation. Stirring also prevents the 
action of acetic bacteria. As a rule from 4 to 6 days are necessary 
for this fermentation. 


When the alcoholic fermentation is complete the juice is separated 
from the mash. Usually 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 

Making Vinegar. 


of vinegar," which is composed almost entirely of acetic bacteria, 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). 


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 equal quantity by 
weight of water added to the persimmon mash will usually give the 
desired sugar content. 

The plan outlined is believed to. offer the lwst 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. 


Vinegar as ordinar- 

Fia. 1. — Suitable receptacles for making vinegar In tho 

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


Almost any apples may be used except those which are green or 
rotten. If partly rotten apples are used the rotten spots should be 
cut out and the apples washed. Dirty apples should bo 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- 

03147°— 24 2 

g Farmers' Bulletin 7424. 

hh of (lie iuioo extracted. From 2 to 3 gallons of juice should be 
obtained from a bushel of apples. The " press cloth type oi press 
is the most ellicient for this purpose. Full direct ions lor pressing 
apples are given in Farmers' Bulletin 1'2<>4. 

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 sii"ar and oilier solids. The addition of such juice to the 
juice from iirst pressings may reduce the sugar content oi the whole 
to a do-ree which would not permit the, production of a satisfactory 
vinwr' If the vinegar is made for sale, Federal food regulations 
rec|ime that the addition of water in the process of manufacture 
must be plainly indicated on the label. 


After being expressed, the juice should stand for a day or two in 
looselv covered barrels or other covered receptacles for sediment a- 
t ion. after which it is carefully drawn oil', preferably by the use of 
a siphon (p. l. r >), and transferred to other containers for alcoholic 
fermentation. These barrels should not be Idled over three-fourths 

full. • , ii i p 

Compressed yeast is added in the proportion ot 1 small cake lor 

each f> gallons of juice. The yeast should first be thoroughly macer- 
ated uCni least a'quart of the juice and this should be well stirred 
into the whole. If a pure culture of a specially cultivated yeast is 
to be used, this should be prepared and added as directed on page IS. 


The second or acetic ferment at ion may be (lone in any one of the 
three following ways. The selection of the process will, of course, 
depend upon individual conditions. 

SLOW HAliliKI. l'KOCK.sS. 

After ihe alcoholic fermentation is complete, as shown by a test 
(p. iif>), the juice should be carefully drawn oil' from the containers 
in which the alcoholic fermentation look place, without disturbing 
the sett linns at the bottom, and passed into barrels for the final or 
acetic fermentation. The barrels should have been Iirst thoroughly 
cleaned and soaked with strong vinegar and placed on their sides 
with the bungholes up. They are Idled about two-thirds full. 1 he 
aim being to expose as large a surface of juice as possible to the air. 
About o gallons of good vinegar is then added to each barrel to 
hasten the change to acetic acid. For this purpose a fresh un- 
pasteurized vinegar is much to be preferred, but if it is not ob- 
tainable any good strong vinegar will do. 

The alcohol of the yeast- fermented juice is now turned into acetic 
acid. In order that ibis change shall take place rapidly, the juice 
must be in contact with the air. For Ibis reason the bungholes 
should be left open. Additional holes should be bored in the ends 
of the barrels to afford a free circulation of air. Pieces of cheese- 
cloth or well-varnished line wire screen should be tacked over all 
openings to keep out insects and dirt. The temperature should 
not be lxdow 70°F.. if practicable. 

Making Vinegar. 


Acetification should be allowed to proceed until a strong vinegar 
is produced. Such a vinegar can he recognized by its taste, but it is 
Hindi 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 
juice is kept at the proper temperature, the time required to convert 
the alcohol in the juice into acetic acid should not be more than 3 
to C mouths. 


The process of acetification may be made continuous by, adopting 
the following plan. 7 which is essentially the Orleans method that has 
been used from lime immemorial in the Orleans district of France: 

A 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. about an inch below the 
stave containing the biinghole, another hole (B) of the same size. 
The holes are covered 
with mosquito bar or 
well-varnished fine 
wire screen to keep 
out the small vinegar 
or fruit 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 
half of the w a y 
through. A piece of 
bent glass tubing, about one-half inch in diameter and long enough 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 circulation of air and about 3 gallons of fresh, unpasteurized 
vinegar is poured into it. The clear yeast-fermented juice is now 
run in until the surface of the liquid' is nearly level with the air 
hole (A). Better results would probably be obtained by adding the 
juice in the fractional parts of one-fourth to one-third at intervals of 
a week. An additional advantage would be secured in all of these 
operations if (he 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 surface until the acetification has gone far 
enough. When 4.5 to 5 per cent of acetic acid has been produced 
the vinegar is drawn off through the spigot, leaving about 8 gallons. 
The transfer of the vinegar should be made slowly so as not to break 
the film. 


-Converter for continuous process. A 
2-incli holes: ('. spK'ol. 

' Adapted from Farm-Made Cider Vinegar, Iowa State Dairy and Food Commission 
Bui. 12 (l'Jiro. 


Farmers' Bulletin lk2h. 

Kiu. 3. — (ionorator 
for rolling Ren- 
orator process. 
A. rack made of 
;i by \ i n c h 
slats: li. 2 by 
4 inch KniUMjrt, 
for rack ; <\ i>o- 
sitlon of rack In 

A new supply of ycast-fennented juice is now slowly lunin 
through the funnel which leads to the Iwltom of the converter, l his 
should he done carefully so as not to disturb the surface film lne 
film will rise on the surface of the liquid and start fermentation 

P T^on verier made from a 50-jrallon barrel should convert from 
100 to 150 gallons of yeast-fermented juice into vinegar m a. year. 


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 
more work and attention than the slow barrel method, but by pro- 
viding for a greater circulation of air it greatly hastens acetilication. 

An ordinary vinegar barrel is made into a generator s as follows 
(h> 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 (» inches below the buiighole, a compartment which is 
to be, filled with beechwood shavings or corncobs (C). A quick way to 
do this is to make a rack of slats W inches wide by one-halt 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 in such lengths that the rack will be at least G inches 
below the bung (B). The 2 bv 4's are usually joined at the bottom by 
a crosspiece 1 by 2 inches. After this rack is 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 

r '-l>roducts from Citrus Fruits. U. S. Dept. Agr. Cir. 232 (1922), 

» IS. SI. Chace. 
pp. 4, 5. 


Making Vinegar. 


to the 2 by 4's, grooves or dowels should be used, or, if more con- 
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 possible, 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 beeehwood 
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 boles through the 

Pig. 4. — Generator for quick or generator proeesB. 

12 Farmers' Bulletin ih2h. 

shavings out of the bnnghole, the juice dripping from the shavings 
comes in contact with the air. as a result of which the process ot 
acetilicalion is greatly hastened. _ 

As the fermentation progresses, a good deal of heat is developed. 
To obtain the best results the temperature of the upper portion of 
the generator should he kept at about 85° F. The temperature can 
be lowered by inserting some of tlie 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 generator is rolled every day and the temperature is main- 
tained at from 80° to 85° F.. the juice may he converted into good 
vinegar by this method in from GO to 90 days. 


The farm method of making vinegar is necessarily slow, for the 
reason that onlv 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 van-outiiniing material like wood shavings, coke, or corncobs 
which has been inoculated with acetic bacteria and through which a 
current of air is constantly rising. Such an apparatus is known as 
a general or (fig. 4) and this method is called the quick 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 reason generators are always used where 
vineuar is produced commercially in large quantities. As this 
method is a continuous process which calls for an extensive equip- 
ment and trained supervision, it is not practicable for farm use. 


Cleanliness is essential in all methods. Anything that will pro- 
duce liialferinentation or oil' flavors should be avoided. To this end 
all utensils and receptacles must be kept clean. Not only must the 
barrels 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 he used for this purpose. Old vinegar and 
molasses barrels und new barrels should not be used until they have 
been well washed with boiling water or steam. 

Barrels which have been used for grain alcohol, whisky, or brandy 
are well adapted for vinegar making. These liquors are antiseptic 
to most microbes, but in small quantities they are not antagonistic to 
the growth of yeasts or ucetic bacteria and will not impart unde- 
sirable flavors or odors to vinegar. 


Experience has thoroughly demonstrated the value of the use of 
starters in making vinegar. Yeasts and acetic bacteria are prac- 
tically always present in fruit juices, but they often occur only in 
limited numbers or more often are of undesirable or inactive types. 

Making Vinegar. 


Better results arc obtained by the addition of active strains. This 
is especially important in the alcoholic (yeast) fermentation where 
a prompt and rapid fermentation is desirable. 

Ordinary compressed yeast, obtainable almost everywhere in this 
country, is a satisi'actoiy 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- 
teurized vinegar should be used, for the reason that such vinegar 
usually insures the addition of the essential organism. Vinegar 
should be added as a starter in any event, however, whether or not 
it contains 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 desire to use pure cultures winch have been culti- 
vated especially for vinegar production these directions are given. 9 

The cultures should bo 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. From these a starter in a 2-quart fruit jar is prepared for each 
barrel as follows : 


Wash the jar thoroughly and sterilize il in boiling water. 

Immediately till the jar half full with boiling apple juice. If no sweet 
juice is available, slice live or six ripe apple.* in - quarts of water and boil 
until the fruit is soft. Add 4 tnblespooni'uls of molasses or 2 tablospoonfuls 
nf sugar and strain about 1 quart of the boiling juice into the fruit jar. 

Cover the jar immediately with a few folds of cloth, sterilized with bulling 
water, to keep out .norms front the air. 

When the liquid has cooled to 75° If., shake the bottle labeled " vinegar 
yeast " and empty the contents into the jar. 

Keep Hie jar at a temperature of 70° to SO" F. 

When foaming is very active, empty the contents of the jar into the barrel 
of sweet juice, (.'over the bunghole with a thin cloth to keep out dust, without 
cutting off the air. 

Immediately after lhe active foaming in the barrel ceases, send to the bac- 
teriological laboratory for the acetic culture and prepare it as follows: 


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

Pasteurize the liquid in the jars by bringing it just to the boiling point in 
hot water; then allow it to cool to 75° I<\ Do not let it boil. 

Add the culture labeled "vinegar bacteria" to the jar. cover as before, and 
keep it at. a temperature of 80* V. 

Do not disturb this jar. Mother of vinegar ( llticlcrium <i<vli) will appear 
on the surface of the liquid in a week or so as a smooth grayish-white glisten- 
ing til in. If molds develop do not use the starter but send to (he bacteriological 
laboratory for another. 

When this film is one-sixteenth to one-eighth inch thick, lift it out of the 
jar with a (dean boiled splinter of wood, add the contents of the jar to the 

fl Adapted from direct ions ^iven by the Washington State Agricultural Uxperimont 
Stntlon for preparing pure cultures for vinegar making. 


Formers' Bulletin 

barrel siiid float Hie film on the surface of the liquid, using the splinter as a 
raft It is verv important that this film he flouted on the surface. 

Do not disturb the barrel from now on except to remove small quantities 
from time to lime to test the strength of the vinegar (page 25). 


After vinegar lias boon properly fermented anil 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 important 

during acetifica- 
tion, is now to the 
same degree unde- 

sirable. Free 
p o s n r e to 


would mean that 
the acetic and pos- 
sibly other types 
of microorganisms 
would continue to 
tict. As a result 
the acid would be 
a 1 1 a c k c d a n d 
sooner or later the 

Fin. 5.- Siphoning oft* the vlnauar. A. glass tube; 13, rubber hose. 

vinegar would he 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 oft', filtered, and bot- 
tled. When made under'farin 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 


Vinegar has a raw, biting taste when first made but it Incomes 
more mellow during storage. The flavor and aroma characteristic of 
the best grades of vinegar made from apple and grape juice arc due 

Making Vinegar. 


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


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. 11ns 
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 
of rubber hose (B). This 
process should be repeated if 
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 sal*, 
however, good commercial 
practice demands that it be 
perfectly clear or bright. 

Juices 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 may be due to the 
presence of finely divided par- 
ticles or colloidal substances 
held in suspension, or to the 
presence of bacteria or the 
products of bacterial activity 

Fig. C. — Filter over top of barrul. 

Certain strains of acetic bacteria 
show a marked tendency to produce cloudiness of the medium m 
which they grow. Tn order, therefore, that a vinegar may be 
perfectly clear and bright, it is usually necessary to resort to filtra- 
tion or to the use of clarifying agents. 


The common method of securing a perfectly clear vinegar is by 
of filtration, which usually is effectual if properly done, 
n the quantity of vinegar to be filtered is not large, it 



be passed through a filter made by folding a large piece of cm 
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. T). It may be neces- 


Farmers' Bulletin ik2k. 

sary to pass the vinegar through a filter of this kind several times 
to make it clear or bright. The efficiency 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. Hence 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 refiltration. 

When largei' quantities of vinegar are to be filtered, as in com- 
mercial production, filters of more or less elaborate construction are 
used. These usually operate by suction and filtration is made through 

various substances, such as 
cloth, paper or cotton pulp, 
or d i a t o m a c eons earth. 
Metals which are readily at- 
tacked by acetic acid must 
be avoided in the pails of 
the filter which come in con- 
tact with the vinegar. 


In some vinegars which 
are persistently cloudy fil- 
tration alone may not be 
effectual for clarification. 
In such cases a clarifying 
agent, either alone or as an 
aid to filtration, must be 
used. An inert insoluble 
substance is preferred for 
this purpose. 

Diatomaceons earth, com- 
monly used for clarifying 
vinegar, has a high adsorb- 
ing power and when prop- 
erly selected and prepared 
has no undesirable effect on 
the product. If this earth 
contains calcium carbonate 
it should be rejected. The 
organic matter usually pres- 
1-1.;. 7. kiii.t ha*. fit to sonic extent can be re- 

moved by heating the earth 
to redness. It should be added to the vinegar in the proportion of 
one-half to 1 ounce to the gallon (4 to fi pounds to 100 gallons), well 
stirred in order to form an intimate mixture with the vinegar, and 
at once filtered through a cloth containing a thin moist layer of the 
same earth. 

Animal charcoal or some of the vegetable carbons are sometimes 
used for clarifying vinegar. These, however, usually contain alka- 
line salts, which, to some extent at least, lower the acidity of the 
vinegar, and may also have an unfavorable effect on its flavor. An- 
other objection to the use of carbons is that the finer particles filter 
out with difliculty and, unless the filtering is very carefully done, 

Making Vinegar. 


they may on standing form a deposit on the sides and bottoms of 

As the carbons are active decolorizing as well as clarifying agents, 
they are sometimes used for clarifying grape vinegars made from 
dark wines which might otherwise be unmarketable, 10 They must, 
however, be used with caution and only after a preliminary test to 
determine the quantity necessary in eacli case. They are to be thor- 
oughly stirred into the vinegar just before filtration. 

When vinegar is made in the home from fruits like prunes and 
various berries which give a dark-colored product, the color need 
not be removed. It is only necessary that the vinegar should he 
made clear or " bright." 

Gelatinous or albuminous substances which produce a heavy pre- 
cipitate when mixed with vinegar have long been used and are widely 
recommended as a means of clarification. When it is desired to 
clarify vinegar in this way one-half ounce of a good grade of edible 
gelatin to a barrel of vinegar should be used. The gelatin must 
first be covered with about a quart of water, allowed to stand for a 
few hours, and heated until completely dissolved. The solution is 
then added to the vinegar and mixed thoroughly by stirring. After 
standing for some time the gelatin settles, leaving a clear liquid. 
The clear liquid should be siphoned off (p. l. r >) and the sediment 
drained off and filtered. The success of this method of clarification 
depends upon the perfect precipitation of the gelatin which results 
from the presence of tannin. In many vinegars tannin is present in 
such small quantities that more tannin must be added if clarification 
is to be accomplished by the use of gelatin. The tannin (about one- 
fourth the quantity by weight of gelatin used) should be added 
several hours before the gelatin is added. 

Ordinarily a clear vinegar may be obtained by the use of agents 
which act chemically and under certain conditions their use may be 
justifiable (p. 22). " This method of clarification, however, is open 
to the following serious objections: (1) It means the addition of a 
foreign substance which goes into solution in the vinegar and may 
have an unfavorable influence on the flavor of the product; (2) these 
agents act slowly and their use involves loss of time and extra labor 
and expense: the addition of some of these materials favors the 
growth of microorganisms and is therefore objectionable unless fol- 
lowed at once by pasteurization. 


Pasteurization is always to be considered as one of the measures 
for preserving vinegar and maintaining its strength. The deteriora- 
tion of vinegar is usually the result of the continued activity of the 
acetic organisms. Even'after filtration or clarification, vinegar con- 
tains bacteria which upon being exposed to the air grow and multi- 
ply, making the vinegar "mothery" and perhaps cloudy. This con- 
dition may be prevented by pasteurization, which is sometimes done 
as soon as' acetification is completed. As the same end may be accom- 
plished by storage in air-tight containers which are completely filled, 
however/pasteurization is usually deferred until the vinegar is trans- 
ferred to its final containers. 

">1<\ T. Dlolcttl, loc. clt. 


Farmers' Bulletin U2b. 

The, proper temperatures for the pasteurization of vinegar range 
from 140° to 1G()° F. Experience lias shown that if properly car- 
ried out a temperature of 140° F. is effectual for this purpose, but 
it is the minimum — no lower temperature can be depended upon to 
produce the desired result. On the other hand, a temperature of 
100° F. should not be exceeded, for the reason that it is not required 
and may cause an unnecessary loss of acetic acid by evaporation. 

Under household or farm conditions pasteurization may be accom- 
plished by simply heating the vinegar to the required temperature 
in kettles or other large containers. Only the best unchipped 
enameled ware should be used. The entire volume of the vinegar 
must he brought to an even temperature. This can be done by stir- 
ring during the heating process and by using a reliable thermometer. 

After being cooled to about 70° F., the vinegar is 
at once transferred to the final containers, which 
should have been previously sterilized in hot water 
or steam. They should he filled full and im- 
mediately sealed with sterilized stoppers. 

Vinegar may be 
readily pasteurized 
after it has been trans- 
ferred to the final con- 
tainers by submerging 
the tightly sealed con- 
tainer in water and 
heating to the required 
temperature. For pas- 
teurizing on a small 
scale, an ordinary tin 
w a s h boiler, with a 
wooden rack in the bot- 
tom to permit circula- 
tion of w a t e r and 
having a long-stemmed 
thermometer suspended through a hole in the cover, makes a very 
satisfactory outfit. 11 Jars or bottles should be placed in the boiler 
either on their sides or invented in order to insure the destruction of 
any organism on the stoppers. 

For pasteurizing vinegar on a larger scale or in large containers, 
a pasteurizing tank is necessary. Vinegar pasteurized in this \v&y 
will not reach the desired temperature as soon as the surrounding 
water. This additional time, which is proportional to the size of the 
containers, varies from 5 minutes for a pint container to 25 minutes 
for one holding 2 gallons. Allowance must also be made for the 
expansion of liquids from heat. Containers, therefore, should not 
bo filled entirely full. A rise in temperature from G0° to 140° F. 
would cause an expansion of about 2 per cent in volume. 

Under commercial conditions vinegars are usually pasteurized by 
the continuous method. The vinegar is heated to the required tem- 
perature by being passed thirnigh coils of pipe surrounded by steam 
and then to other coils covered by cold water, which again cools it to 


(linns containers for vinegar. 

11 J S Cnldwell. Vnrm Hnnufnotiirc of Unfermonted Apple Juice. V. S. Dept. Agr. 
Farmers' Hul. 1204 (l'J22), pp. 33-34. 

Making Vinegar. 19 

about 70° F. Under the usual factory procedure, vinegar that has 
been properly aged is first filtered, then pasteurized, and poured at 
onee into the final containers. . 

Pasteurization also is believed to assist the maturing of vinegar, 
civinir it a softer and more pleasing taste and aroma rhis it prob- 
ably does by hastening the combination of the residual alcohol in the 
vinegar with the acetic acid, thereby favoring the formation ot esters. 


After vinegar has been properly aged, filtered, and pasteurized, 
it should he finally packed in small containers. This is the best way 
to preserve it for home use and is, the most acceptable form in which 
it can be offered for sale to the ordinary consumer. The common 
method of keeping vinegar in the barrels in which it was stored after 
acetification and drawing out from time to time the quantities 
needed for immediate use is not a good practice; it permits the en- 
trance of air and interferes with the sedimentation of the vinegar^ 

For the final packing of vinegar, receptacles which arc most suit- 
able in form and size and which will not be attacked by the vinegar 
should be selected. Metal containers, of course, are not to be consid- 
ered. The most suitable containers are glass bottles, jars, or pigs. 
(Fig. 8.) They should ho filled full and tightly sealed. 

Vinegar made in small quantities by household methods may be 
stored in bottles. These are also largely used under commercial 
conditions to supply customers who want to buy only in small quan- 
titics. Ordinary glass-top fruit jars can be utilized m the home. 
Perhaps the most desirable containers for both home and commercial 
use are glass jugs, which may be obtained in almost every size up 
to 2 gallons capacity, the 1-gallon jug being a favorite. _ 

As stoppers for all these containers, except the fruit pvrs, ordinary 
wood corks may be used, but they should bo of the best material 
and free from cracks. Corks are greatly unproved by being soaked 
in hot paraffin. Paraffined corks should not be used to seal con- 
tainers holding hot vinegar, however, for the reason that the paraffin 
would probably liquefv and soil the surface of the pack. When the 
vinegar is packed for sale, the corks should he well driven in and 
heated paraffin should be poured over the top. Glass-stoppered 
bottles are desirable for vinegar made in small quantities in the 
household, but they are often difficult to obtain and quite expensive. 
When fruit jars are used, only those which have glass covers should 
be selected. Metal covers should never he used for sealing vinegar. 
Even those which are cork-lined are undesirable. 

After vinegar has been packed, the containers should be properly 
labeled. When it is made for sale, printed labels giving the follow- 
in<>- information are desirable: (1) Name and address of manufac- 
turer; (2) kind and quantity of vinegar which the container holds; 
(3) strength, expressed as nearly as possible in grains (p. 27) or 
in percentage of aeetie acid, or preferably in both. 


The chief causes of failure in making vinegar are: (1) The use of 
material having too low a sugar content; (2) failure to recognize the 
fact that the making of vinegar involves two distinct fermentations 


Farmers' Bulletin lh2h. 

(alcoholic and acetic) and that the lirst must he completed before, the 
second begins; and ('i) failure to stop acetilication at the proper 
time. All of these causes have been discussed elsewhere in this bulle- 
tin and the remedy indicated. 

Various mal fermentations due to the presence of undesirable or 
destructive microorganisms also cause failure. All material used 
for making vinegar is contaminated to some degree with undesirable 
organisms which may have a harmful effect on the fermenting juices 
and may even grow at the expense of the desirable organisms. The 
only sure means of preventing such a result is to sterilize the raw- 
material and use pure cultures. This, however, is usually neither 
possible nor desirable. 

Malferinentations may be caused by false yeasts, molds, or unde- 
sirable bacteria. The lnycodernuu, yeastlike organisms which nearly 
always accompany fruits and fruit juices, often develop upon ex- 
posure to the air, forming a scum on the surface of the. juice. These 
organisms, which are known as - M yeodermn vini. often called 
wine flowers, like the true yeasts, multiply by budding, but, unlike 
the true yeasts, grow only in the presence of oxygen, for which 
reason they are called aerobic, and have no fermenting value. They 
live on the medium on which they grow, being destructive to both 
fixed acids and alcohol. The presence of mycodernue is objectionable 
in all of tlio fermentation industries and the scum formed by them 
should be removed whenever possible. This scum, which at lirst 
is thin, whitish, and smooth, grows rapidly, soon becoming thick, 
rough, and heavily wrinkled. It should not be confused with the, 
acetic iilin which at lirst usually occurs as greasy looking spots on 
the surface and gradually spreads, becoming a grayish veillike 
covering over the entire surface. As a rule the acetic film later 
becomes a smooth, leathery membrane, which eventually sinks* by 
its own weight, only to be succeeded by another similar formation. 
This membrane is made up of acetic bacteria and a gelatinous ma- 
terial given oil by them. 

Mold spores are often present in fruit juices and under favorable 
conditions, either alone or in combination with false yeasts and 
aerobic bacteria, may grow on the surface of fermenting juices. As 
molds have an unfavorable action on the flavors of these juices, 
their growth should always be prevented if possible. 

The bacteria which may complicate a fermentation are usually the 
kind that can grow in the absence of oxygen — the so-called anaerobic 
type. The lactic group, the one most commonly found, is nearly 
always present to some extent in fruit and vegetable juices. If 
these bacteria occurred in large numbers they would undoubtedly 
cause cloudiness, increased acidity, and undesirable changes and 
Harm's. Other forms of bacteria, such as the butyric or even 
putrefactive types, may develop in juices, especially in those of low 
acidity. Unless speedily checked, these organisms may soon produce 
changes which make the juices worthless. The development of 
fleet ic bacteria before the acetilication stage is. of course, very 

All these organisms usually appear before or during the alcoholic 
stage. As a rule they can be prevented by securing at the start an 
active alcoholic fermentation. This is accomplished by adding at 
once a culture of active yeasts and by subjecting the fermenting 

Making Vinegar. 


juice to such favorable conditions as will render their growth rapid 
and certain. In this way they quickly gain precedence over all 
other organisms and the sugar in the juice is utilized before other 
organisms have an opportunity to attack it. The large quantity of 
carbon dioxide formed by an active yeast , fermentation doubtless 
has a tendency to check the growth of all other organisms. Above 
all, it is important to secure complete utilization of the sugar before 
the acetic bacteria, which are always present to some extent, have 
an opportunity to form much acetic acid. The presence of even 
0.5 per cent of acetic acid interferes seriously with the growth of 
veasts and 1 per cent is almost prohibitive. 

The failure of yeasts to grow in a. juice which is ordinarily a fa- 
vorable medium is probably due to a high acid content, or. m some 
instances, to the presence of an antiseptic agent added to prevent 
fermentation. It is useless to add more yeast to a juice of this kind. 
The only thing that can be done is to dilute it with fresh juice to a 
point where veasts will grow and then add another culture. 

Sometimes "failure occurs during the acetic fermentation. A cot lo- 
cation may be slow in starting or may stop entirely, owing to the 
fact that 'the acetic bacteria are present only in small numbers or 
that those present are of a weak strain or of an objectionable type, 
like the Bacterium xyUnwn. In most cases failure is due to the 
fact that the medium is unfavorable to the growth of the acetic bac- 
teria or that the temperature and air conditions are not favorable. 
As a rule acetic bacteria will grow in a medium which is only 
weaklv acid or even slightly alkaline, but a more prompt and vigorous 
growth can usually be obtained in a decidedly acid medium. For this 
reason the addition of vinegar is always advisable, especially in the 
case of juices or solutions which are normally low in acid. The 
addition of vinegar also is a protection against the growth of un- 
desirable organisms until enough acid is formed by oxidation of the 
alcohol present. 

The solution to be fermented must contain the proper nourishment 
for both yeasts and acetic bacteria. The presence of sugar for the 
yeasts or of alcohol for the bacteria alone is not suflicient to insure 
'their growth. Nitrogenous matter in some form must be present to 
make "these organisms function properly. Fruit juices usually con- 
tain enough nourishment for the growth of yeasts and acetic bacteria, 
but not all the sugar solutions used for making vinegar do (pp. 4. 5). 

Temperature is an important factor in making vinegar. If too 
high or too low this mav be a cause of failure. Most yeasts do their 
work best at from 75° to 80° F., and most strains of acetic bacteria at 
from 80° to 86° F. As evaporation is likely to occur at these tem- 
peratures, somewhat lower ones are often preferred. If very much 
lower than those stated, the fermentations are certain to be slow. In 
general, it may he said that a very hot room or a very cold cellar is 
a poor place in which to make vinegar. 


Vinegar usually becomes darker with age. This slow darkening 
may be due to the presence of oxydase (an organic substance which 
promotes oxidation), just as fruits, vegetables, and fruit juices are 


Farmers' Bulletin UM. 

darkened when exposed to the air. Moderate darkening which comes 
on gradually in vinegar usually need cause no great concern. 

In many cases darkening doubtless is due to the presence of small 
quantities* of iron and tannin. The presence in large quantities of 
iron or tannin or both may cause the vinegar at once to become very 
dark and in extreme cases even densely black. Tannin, a normal con- 
stituent of nearly all fruit juices, is present, in small quantities at 
least, in vinegar made from these juices. Tannic substances may 
also be extracted from new barrels in which vinegar is stored, espe- 
cially when they have not been properly cleaned. Iron salts are not 
a normal constituent of vinegar, but they may be present as a result 
of the action of acetic acid on iron during the process of manu- 
facture. They may also gain entrance through sod which clings to 
the fruit from which the vinegar is made. In nearly every case 
excessive darkening of vinegar is the result of the presence .of iron 
salts. The inky blackness commonly caused by the combination in 
solution of iron salts and tannin occurs when iron salts are present 
in a fruit vinegar. The degree of blackening depends entirely upon 
the quantity of iron salts present. It is important, therefore, to pre- 
vent the entrance of iron salts into vinegar in every way possible. 
Darkening from this cause can usually be removed by " fining" with 
gelatin (p. 17). 

While animal charcoal and vegetable carbons are usually effective 
in removing color from solutions (p. 10), then' use as decolorizing 
agents for vinegar is open to several serious objections. 

Free exposure to air undoubtedly favors the darkening of vinegar, 
regardless of what special cause is operating to produce this result. 
This constitutes another reason for protecting vinegar from exposure 
to air as far as possible. 



Vinegar may become infested with small worms (Anguilhila accti 
(Muel.) Much), commonly called vinegar eels. Although very small, 
they can be seen with the unaided eye by holding the vinegar in a 
small glass before a strong light. They are harmless when taken 
internally, but very objectionable from an aesthetic standpoint. As 
these eels are apparently found only in vinegar or in connection 
with fruits or other substances which are undergoing acetic fermen- 
tation, they undoubtedly spread from such sources. They usually 
occur around the edges of acetic liquids and in the surface of the 
film. When sufficiently numerous they may destroy the film, caus- 
ing it to sink, thus interfering with acet ification. When very numer- 
ous they may give rise to a putrid decomposition which makes the 
vinegar unfit for use. 

Vinegar eels are readily killed by heat, a temperature of 130° F. 
being sufficient for their destruction. Heat, therefore, in some form 
is the best means of getting rid of them. They are easily removed 
from finished vinegar by filtration, followed by pasteurization. Bar- 
rels, tanks, and generators which contain them should be sterilized 
by steam. 

Making Vinegar. 



Unless great care and cleanliness are observed in connection with 
vinegar production, mites (Tyrogh/phus longiorlt. and Tyroghjpkus 
siro Gerv.) may appear in large numbers and prove very trouble- 
some. They are undoubtedly identical with the mites often present 
in cheese and other food products. 12 Under favorable conditions 
of warmth and moisture, these mites breed with great rapidity, and 
unless proper precautions are taken they may enter vinegar casks and 
generators, spoiling the contents. 

Alites are readily destroyed by the use of hot water or steam, it 
a room becomes badly infested, it should be cleaned, fumigated with 
sulphur, and thoroughly washed with kerosene emulsion. The en- 
trance of mites into vinegar casks may ho prevented by painting a 
ring of turpentine or kerosene oil around the openings. 


Several species of light-brown flies (DrosopMki spp.) breed in the 
juices of decaying fruits and also around the openings of vinegar 
containers or wherever they find vinegar exposed to the air. These 
are known as fruit or vinegar flies. If very numerous, the larva) 
of these flies may get into the vinegar and cause its deterioration. 
They may also be responsible for the introduction of the Bacterium 
xyUmnii, an undesirable member of the acetic group. 13 

' The presence of these flies may be prevented to a great extent 
by cleanliness and by avoiding the spilling of vinegar and the leakage 
from casks. The importance of keeping all openings in casks well 
screened has already been mentioned. 


Sultstances with such names as "vinegar bees" and "California 
bees" are sometimes advertised for use in making vinegar. As ex- 
travagant claims have been made for some of these preparations, a 
word of caution about them should be given. These so-called " vine- 
gar bees" are not insects, as the name implies, but a combination of 
yeasts and bacteria in a suitable medium. As the "bees" are usually 
the result of chance inoculation, the yeasts present are not as a rule 
actively fermenting strains and the bacteria are ordinarily a mixed 
culture which may^contain harmful as well as desirable types. Molds 
also are often present. Even if the "bees'" should contain none but 
desirable microorganisms — that is, yeasts-and acetic bacteria — their 
use would still be fundamentally wrong, for the reason that they 
would bring about the simultaneous action of alcoholic and acetic 
ferments which is to be avoided (p. 19). 


In making vinegar certain tests are necessary for accurate results. 
Unfortunately there are no simple tests which are dependable. Tt 
is not safe to assume that the alcoholic fermentation is complete 

"I, 0 Howard and C. h. Marlatt. The Principal Household Insects of the United 
States. U. S. Dept. A«r., Div. Ent. liul. 4 (18»C). PH. 100-111. 

"(!. Bertraud. Preparation bloculmlque du sorbose. In Compt. rend. (18S6), vol. 122, 
pp. 000-005. 


Farmers' Bulletin UM. 

when bnbbl ing- or frothing ceases; nor can tasting during the acetic 
fermentation be depended upon to show when the acetic fermenta- 
tion has gone far enough. Reliable tests are needed to determine 
(1) the sngar content of the material from which the vinegar is to 
be made, (2) the quantity of alcohol formed during the first fer- 
mentation, and the quantity of acetic neid formed during the 
second fermentation. The}' call for additional ap- 
paratus not ordinarily found in the home or on 
the, farm. 


A quantitative chemical analysis is necessary to 
determine accurately the sugar content of the juice 
or solution used in making vinegar. Very few 
persons can make a test of this kind; moreover, 
great accuracy is not usually required. Ordinarily 
this information can be obtained with a sufheient 
degree of accuracy by the use of a sugar hy- 
drometer 14 which shows the sugar content of 
any pure sugar solution. (Fig. 9.) 

This test should, of course, be made before fer- 
mentation begins. The hydrometer should be 
cleaned thoroughly and dried each time before 
being used and it should be handled with clean, 
dry hands or with a clean cloth. The juice to be 
tested should be quite fluid — that is, it should not 
contain enough solid matter to make it thick or 
slimy: otherwise, the resting point of the hydrom- 
eter will be uncertain. A small quantity of the 
juice is poured into a glass cylinder, and the 
hydrometer is dropped in carefully. (Fig. 
The instrument must float freely and touch neither 
the bottom nor walls of the cylinder. 

To determine the correct reading, put the eye 
on a level with the surface of the liquid and note 
where the true surface intersects the scale. The. 
lihn of liquid which is drawn by capillarity np 
around the neck must be disregarded. 

The specific gravity of juices varies with the 
temperature. Therefore the juice must he brought 
to the standard temperature for which the hy- 
drometer is adjusted (usually G0° F.) or a tem- 
perature correction should be made. This cor- 
rection is very nearly 0.1 per cent for every '.)° 
F. above or below the standard. Tf the lempera- 
this correction must be added: if it is lower, it must 

I'm. !». Sum 


t lire is highei 
be subtracted. 

The approximate percentage of sngar in fruit juices which corre- 
sponds to the hydrometer reading is shown in Table 1. 

As fruit juices contain substances other than sugar which increase 
the reading, the true sugar content of these juices is always from 
0.5 to 2.5 per cent less than that indicated by the hydrometer. 

" KltliiM" :i lirlx or a n.illini; hydrometer may bo used. A Brlx hydrometer, graduated 
from o t" !!<>, Is well adapted to tills purpose. 

Making Vinegar. 



As a result of the utilization of sugar during fermentation, the 
hydrometer reading gradually approaches the zero point. This in- 
strument, therefore, may be used to determine the progress of a 
fermentation and its probable completion. When the quantity of 
material to be fermented is small enough to admit of its being 
weighed accurately, this information may also be obtained, with 
perhaps a greater degree of accuracy, by weighing the fermenting 
mass from day to day, thereby determining the loss of weight duo 
to the escaping carbon dioxide. When loss of weight has practically 
ceased, the fermentation may he regarded as complete. 

When the fermentation of a juice or sugar solution is complete 
it no longer contains sugar. This has been converted into alcohol 
and carbon dioxide gas, the alcohol remaining in the liquid and the 
gas passing into the atmosphere. The fermented juice should then 
contain a quantity of alcohol which approaches closely to that indi- 
cated by the original hydrometer reading. (Table L.) The exact 
quantity of alcohol resulting from a fermentation can be determined 
only by distillation. 15 


The acid strength of a vinegar can be determined accurately only 
by titration against an alkaline solution of known strength. For 
this purpose normal sodium hydroxide is ordinarily used. The sim- 
plest way to do this is to measure carefully with a pipette 10 cubic 
centimeters of (he vinegar to be tested into a porcelain evaporating 
dish, adding a few drops of a 0.5 per cent solution of phenolphthalein 
in 50 per cent alcohol as an indicator. The normal sodium hydroxide 
is then run in very slowly, preferably using a 50 cubic centimeter 
burette graduated in tenths of a cubic centimeter. As the sodium 
hydroxide is being added the juice should be stirred constantly. 
When the entire well-stirred mixture shows a permanent faint pink 
tint the neutral point has been reached. 

The exact quantity of sodium hydroxide required to neutralize 
the mixture in the dish, multiplied by 0.6, gives the number of 
grains of acid per 100 cubic centimeters, calculated as acetic, present 
in the vinegar. For example, if the burette reading shows that 7.5 
cubic centimeters of sodium hydroxide is required to neutralize the 
mixture, the grams of acetic acid in 100 cubic centimeters of the vine- 
gar would be 4.5, which, for convenience's usually stated as 4.5 per 

As any laboratory method of determining the acid strength of 
vinegar is somewhat complicated and calls for apparatus and chemi- 
cals which are not always available, it may be better to use some 
form of vinegar tester. In that shown in Figure 10 the quantity 
of acetic acid is determined by the volume of gas given off when 
bicarbonate of soda (baking soda) is treated with a measured quan- 
tity of the vinegar to be tested. 

A quantity of vinegar is measured in the small tube (A) and 
poured into the bottle (B). A small quantity of sodium bicarbonate 

IB Alcohol determinations are not essential and are seldom made except in the com- 
mercial production of vinegar. Those who desire to make such a test should consult the 
methods of the Association of Official Agricultural Chemists or books relating to analyti- 
cal chemistry. 


Farmers' Bulletin i'lH. 

(about 1 gram), taken with the scoop (C), is introduced into the 
bottle (B) in such a way that it does not come in contact with the 
vinegar until after the bottle has been tightly closed with the cork 
(1)). Vigorous shaking will cause the soda and vine- 
gar to unite, with the resulting formation of carbon 
dioxide gas. This gas passes through the rubber 
tube (E) and causes the water within the reservoir 
(F) to rise in the graduated cylinder (G). The 
stronger the vinegar the more gas will be given off 
and the higher the water will rise in the cylinder, 
which is graduated in such a way that the acid 
strength of the vinegar may be read off directly, 
either in grains (p. 27) or in percentage of acid. 

The following precautions should be observed in 
making this test: (1) The bicarbonate of soda used 
must be pure, a reliable brand of baking soda being 
satisfactory. (2) The soda must be introduced in 
such a way that none of it comes in contact with the 
vinegar until after the bottle is tightly corked. (3) 
There must be no leaks in the apparatus. The pres- 
ence of leaks can be determined by allowing the col- 
umn of water to remain for a few minutes in the 
cylinder after making a determination. If the col- 
umn does not fall during this time there are no im- 
portant leaks. (4) Neither very cold nor very 
hot water should be used; the instrument is made 
for use with water at ordinary temperatures. 

The apparatus and chemicals required for 
making these tests may usually be procured 
through local druggists, or they may be ob- 
tained from dealers in laboratory apparatus and 





Based on the molecular weight, 
H'ivn 100 parts of sugar should give 
about 51 parts of alcohol and 49 
parts of carbon diox- 
ide gas. As small 
quantities of s u g a r 
are, consumed as food 
for the yeasts or may 
be lost in the produc- 
t i o n of other sub- 
stances, however, no 
more than 45 to 47 
parts of alcohol are 

oretieally, again, 100 parts of alcohol should yield about 130 
of acetic acid. Because of evaporation and other causes, how- 
less than 120 parts are obtained. Hence, starting with 100 
of sugar, it is possible, under very favorable conditions, to get 
50 to 55 parts of acetic acid. In order to insure a vinegar with 

Fin. in. — Vinegar tester. 

Making Vinegar. 27 

4.5 per cent of acetic acid, a juice which gives a hydrometer read- 
ing of about 12 should be used. (Table 1.) 

Table 1 .—Hydrometer readings (Brix or nailing) of fruit juices, approximate 
percentages of sugar before fermentation, awl percentages of atcohol that 
can he irroduced. 

or Hail- 



11 V. 

ii y- 
dro me- 


or Ball- 



or Ball- 





Per cent. 



Per cent. 











12. 5 









12. 7 

6. 3 




13. 1 




12. » 

6. 4 





10. 8 



13. 2 

6. 6 

11. 2 


4. 3 

13. 6 

11. 1 


16. 1 


6. 8 

11. 6 







13. 8 









14. 1 


11. 9 




11. 8 



14. 3 

7. 1 
















The percentages of sugar given in Table 1 are 2.5 less than those 
indicated by the hydrometer readings. While this difference is not 
true of all fruit juices, it is true of many. Analyses of a large num- 
ber of apple juices made by the Bureau of Chemistry have shown 
that the nonsugar solids usually constitute about 2.5 per cent of the 
juice. This difference affords a safe basis for the estimation of the 
probable results of a fermentation. The percentages of alcohol by 
weight given are half the sugar content. Common experience has 
shown that this is the usual result of a normal fermentation. As 
the percentage of acid formed by acetification as a rule exceeds by 
little, if any, the percentage of alcohol present, it is possible by a 
. very simple calculation to estimate from the hydrometer reading of 
a fruit juice the strength of the vinegar it will produce. For ox- 
ample, if the hydrometer reading of a juice is 12.5, subtract 2.5 to 
get the percentage of sugar. This result, divided by 2, gives 5 as 
the probable percentage of acetic acid which should be obtained in 
the linished vinegar. Owing to various causes which have been ex- 
plained in this bulletin, such a result is by no means always obtained. 
The only method for determining the actual strength of the vinegar 
obtained is the use of a test for acidity. 

The acid strength of vinegar is determined by finding the acidity 
of the vinegar in terms of grams of acetic acid per 100 cubic centi- 
meters. Since the specific gravity of vinegar is but slightly greater 
than that of water, 100 cubic centimeters of vinegar weigh little 
more than 100 grams. Grams per 100 cubic centimeters is therefore 
nearly but not quite the same thing as percentage by weight. The 
difference is so slight that it is usually disregarded by manufacturers 
and dealers and the strength of the vinegar is stated as 4, 5, or G per 
cent, etc. 

The grain system of expressing the strength of a vinegar is also 
often used. As now used in this country, the grain, which is the 
unit of this system, is equivalent to 0.1 gram of acid per 100 cubic 
centimeters of vinegar. A 4 per cent vinegar therefore is a 40-grain 
vinegar; a 6 per cent vinegar is a 60-grain vinegar; etc. 


Farmers' Bulletin ih2k. 


Vinegar may be made in the home and on the farm without a per- 
mit if it is to he consumed only in the home or on the farm where it 
is made. 1 f it is to he oll'ered for sale the maker must obtain a per- 
mit from the eollector of internal revenue of his district. As the 
regulations governing the making of vinegar for sale are subject to 
change, anyone planning- to make vinegar on a commercial scale 
should first obtain the most recent information about the laws from 
the Federal prohibition director of the State. 

All vinegar which is shipped from one State to another or is 
oll'ered for sale in any possession or Territory of the United States 
or the District of Columbia should meet the requirements of the 
Federal food and drugs act. This information ma}' he obtained from 
the Bureau of Chemistry, United States Department of Agriculture, 
"Washington, D. C. 

As practically all States have laws governing the sale of vinegar, 
anyone interested in its commercial production should obtain the 
regulations from the State food commissioner. 

In general, it may be said that the law requires that vinegar 
oll'ered for sale in the United States should contain at least 4 per 
cent of acetic acid.