Part 2

A small part of the sugar was made into alcohol and this alcohol was at once changed to acetic acid by the "mother" present; this acetic acid killed the yeast so that no more sugar could be changed to alcohol and no more alcohol being found, no more acetic acid could be made by the "mother." We have a weak, worthless something neither vinegar nor hard cider with considerable unfermented sugar still present and incapable of further fermentation because no yeast can develop in the weak acetic acid solution.

_The Acetic Acid Fermentation._

The second step in vinegar making is the change of the alcohol of the hard cider into the acetic acid of the finished product. This is accomplished by the acetic acid germ, another microscopic plant still smaller than the yeast. In some peculiar way it is able to bring about a union between the alcohol of the hard cider and the oxygen of the air so that the alcohol is transformed into acetic acid and water.

As soon as the alcoholic fermentation, described in the preceding section, is completed, draw off the clear liquid, being very careful not to disturb the sediment in the barrel. Wash out the barrel thoroughly and replace the hard cider. It is believed that removing this sediment permits the acetic acid to form somewhat more quickly, and furthermore, the sediment may undergo decomposition and impart a disagreeable flavor to the cider. Again, these dregs may harbor living bacteria which either destroy acetic acid or interfere with its formation.

This done, we are now ready to introduce the acetic acid [Page 12] germs. This may be carried out in a number of different ways, but preferably by means of a pure culture of a desirable organism which has been selected because of its ability to produce strong acetic acid and to impart an agreeable flavor to the vinegar. In place of the pure culture starter, one may add two to four quarts of good cider vinegar containing more or less "mother" for each barrel. The introduction of a desirable organism is left to chance in this case. A serious objection to this latter method is that sometimes one introduces foreign organisms with the "mother" which may prove detrimental to the vinegar. The pure culture starter is free from this objection. On the whole, the indiscriminate use of "mother" alone is to be discouraged, since the popular idea of what constitutes "mother" is apt to be wrong. Pure "mother" is made up exclusively of acetic acid bacteria and is recognized as the thin, white, glistening, gelatinous membrane that forms on the surface of vinegar. It seldom becomes one sixteenth of an inch in thickness and should be translucent or white in color, It is entirely distinct from the thick, tough, dark brown, slipping, leathery masses which form in vinegar and are usually regarded as "mothy of vinegar." Such accumulations contain the acetic acid germ, in all probability, but in an impure state. In addition to this organism there may be present yeast cells and numerous bacteria which are positively harmful to the vinegar. Often these growths undergo decomposition and give the vinegar a flavor of rotten oranges. Again the germs present may cause the partial or complete loss of the acid, particularly if the barrels are not full and tightly stoppered. All things taken into consideration, the use of this sort of "mother" is a rather dangerous procedure.

With the acetic fermentation, as with the alcoholic, the higher temperatures favor the changes. Experimental work shows that hard cider to which no acetic acid bacteria were added other than those that came from the air, and kept at 65 degrees F., when six months old, contained 7.03 per cent. of acetic acid, while that held at 55 degrees F. showed only 3.63 per cent.

The addition of some kind of an acetic acid starter, either as a pure culture of the acetic organism or as good vinegar, hastens the fermentation and reduces appreciably the time required for making marketable vinegar.

For most satisfactory results we would recommend using the pure cultures and holding the vinegar at a temperature of 65 to 75 degrees F. Under these conditions, salable vinegar can be obtained in three to six months in place of two to three years, as is often [Page 13] the case. Theoretically, 100 parts of alcohol should give about 130 parts of acetic acid, but in actual practice this will probably fall below 120.

When the acetic acid has reached 4.5 to 5 per cent., fill the barrels as full as possible and cork tightly. In this way, contact of the air with the vinegar is cut off and the acetic acid organisms soon cease their activity. If this is not done and the acetic and other bacteria are allowed to develop indefinitely, there is apt to be a reverse reaction resulting in a partial or complete loss of the acetic acid. Such vinegar is, of course, worthless.

_Clarification of Vinegar._

For those who desire an extra fancy product of extraordinary brightness, suitable for bottling, it will be necessary to subject the vinegar to a special process of clarification known as fining. According to Bioletti*, the best results are obtained by using isinglass. This is employed at the rate of from one-half to three-fourths of an ounce of isinglass to each one hundred gallons of vinegar.

* Bioletti, Frederic T., Grape Vinegar, Bull. 227, California Exp. Sta., 1912.

"The isinglass is cut into small pieces and soaked for twelve to twenty-four hours in a little water containing acetic or tartaric acid equal in weight to the isinglass used. When thoroughly soft it is then rubbed several times through a fine sieve, gradually adding a little more water until a perfectly fluid liquid is obtained. This fluid is then well mixed with a little vinegar and thoroughly stirred into the cask. With some vinegars it is necessary to add a little tannin, from one-half to one-seventh the amount of the isinglass used. This tannin should be added at least twenty-four hours before the finings.

When the finings have settled and the vinegar is perfectly bright it is ready for bottling."

_Pure Cultures for Vinegar Making._

Reference has been made above to the use of pure cultures, both yeast and acetic acid bacteria, for vinegar making. For a little more than one year, the Bacteriological Laboratory of the Colorado Experiment Station has been supplying these at fifty cents (50c) per set, post paid, sufficient for one barrel, to those who care to give them a trial. Full printed directions for their use are included. These cultures have been selected because of certain properties which they possess which make them especially suited to the vinegar industry. No guarantee, either expressed or [Page 14] implied, goes with the cultures, since it is not the purpose of the Experiment Station to exploit these products, but rather to distribute them at the cost of production for experimental purposes. Inasmuch as one of the cultures is to be added to the sweet cider, the set should be obtained a few days, not longer, before the cider is to be made.

Requests for cultures should be addressed to the Bacteriological Laboratory, Colorado Experiment Station, Fort Collins, Colorado, and should be accompanied by a remittance of fifty cents (50c).

_Directions For Using Pure Cultures in Making Vinegar Preparation of Yeast Culture._

1. For each barrel of sweet cider, sterilize one two-quart Mason jar by washing thoroughly and boiling for five minutes in clean water.

2. Cover the top of the jar with a single layer of clean muslin or cheese cloth just removed from boiling water and secure it in place by a string tied about the neck of the can.

3. Select 6 or 8 medium sized _ripe_ apples; pare and quarter or slice them; add one quart of water and boil till soft; strain liquid through clean cloth while hot into Mason jar, first removing the cloth covering from the top.

4. Make up the volume of liquid to approximately one quart with boiling water; add 4 tablespoonfuls of sugar and replace the cloth immediately.

5. When the liquid has cooled thoroughly, partly remove the cloth covering and add the contents of the culture bottle marked "Yeast." Replace the cloth. Just previous to opening the culture bottle, shake thoroughly and immerse the lip and cork only, ten second in boiling water. Do not touch the lip while removing cork.

6. Keep the jar in subdued light at a temperature of 75 degrees F. to 90 degrees F. After two to four days the foaming characteristic of alcoholic fermentation should appear.

7. After four to six days, add the entire contents of the _yeast_ jar to the barrel of freshly made _sweet_ cider. _The barrel must not be more than two-thirds full;_ it should be placed on its side, and the bung-hole be left open, or, better, plugged loosely with a tuft of clean cotton batting.

8. Keep the barrel at 75 degrees F. to 85 degrees F.

[Page 15]

_Preparation of Acetic Culture._

1. Three to four weeks after the yeast culture has been added to the cider prepare the Acetic Culture in precisely the same manner as described for the yeast in paragraphs 1 to 6 above. See that all of the culture is removed from the bottle; rinse with a little cooled boiled water if necessary. Do not shake the jar while the culture is developing.

2. By the end of one to two weeks, a white, gelatinous film or membrane should be visible on the surface of the liquid. This is a growth of acetic acid bacteria and constitutes the "Mother of Vinegar."

3. When this acetic membrane is well formed, which will require about two weeks, with a clean sliver of wood, previously dipped into boiling water, remove the membrane from the jar, but do not lay it down; pour the contents of the jar into the barrel of cider, now fermented, to which the yeast was added some five or six weeks before; next drop the sliver with the attached acetic film into the barrel through the bung-hole. The wood will serve to float the acetic membrane on the surface of the hard cider and thereby hasten its development by keeping it in contact with the air.

4. Keep the barrel at 65 degrees F. to 75 degrees F. till the vinegar has formed.

5. When vinegar of satisfactory quality has been obtained, in three to six months, draw off and store at a cool, even temperature in casks which are kept full and tightly bunged.

6. Both of these cultures can be propagated indefinitely by employing a small portion of the jar cultures in the same manner as the original bottle starters.

TRANSCRIBER'S NOTES:

1. Italics in the original text have been indicated by underscores at the beginning and end of the italicized text, for example, "_italicized text_". 2. Bold face in the original text has been indicated by equals signs at the beginning and end of the bold face text, for example, "=bold face text=".