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Home and Farm Food Preservation
Chapter XIV - Vinegar Manufacture

Waste fruits, inferior honey, and other sugar containing materials not suitable for sale or use otherwise can often be made into satisfactory vinegar. The waste cores and peels from canneries and fruit driers can be turned to profit, in this way. Vinegar is used in enormous quantities for ketchup and pickles in addition to the large amounts used as table vinegar.

Vinegar making is a fairly simple process, provided the fundamental principles involved are well understood.

79. General Principles. Vinegar making depends on two fermentation processes. The first is a transformation of sugar into alcohol, and carbonic acid gas by yeast. The second is the conversion of the alcohol into acetic (" vinegar ") acid. The second fermentation cannot take place before the first and must follow the first. If it should start before the yeast fermentation is complete, it will stop the yeast fermentation and give an inferior vinegar. Vinegar manufacture depends on making these two fermentations as efficient as possible, and in keeping them separate. In the following paragraphs the methods of controlling the two fermentations are discussed.

80. Raw Materials. Any substance containing 10% or more sugar, or a substance easily changed to sugar, or any fermented liquid containing 4% or more alcohol can be made into vinegar in the household. Industrially starch and distilled alcohol are also used. Fruit juices, dried fruits, fruit-sirups, partially fermented jelly, honey, and spoiled wine can all be used. Watermelons do not contain enough sugar.

81. Crushing Fruits for Vinegar. Fruits used for vinegar should be thoroughly crushed in a food chopper or fruit crusher. The crushed fruit should be placed in a crock or wooden barrel, for yeast fermentation, before pressing. Grapes and berries in small lots are easily

crushed by the hands. Very ripe peaches, pears, apricots, and plums, are easily crushed with the hands or with a potato masher. Apples require the use of a crusher or grinder. Yeast should be added to the crushed fruit. See paragraph 84 on addition of yeast.

82. Diluting Honey. To each cup of honey add four cups of water and one-half a cup of any fruit juice. Honey does not ordinarily contain enough yeast food to cause a good fermentation. The fruit juice furnishes this necessary food. Yeast must be added as directed in paragraph 84.

83. Preparation of Fruit Cores and Peels and Dried Fruits for Vinegar Making. Cores and peels, give good results if two cups of water is added to each cup of fruit, the mixture boiled until the fruit is tender, pressed and sweetened with one half a cup of sugar to each four cups of juice. Dried fruits contain about 60% of sugar. They may be used for vinegar making if four pints of water is added to each pound of fruit. The mixture is allowed to soak twenty-four hours. It is then heated to boiling and allowed to cool. The fruit may then be pressed and the resulting juice used for vinegar. Yeast should be added in the way described in paragraph 84.

84. Addition of Yeast and Control of Alcoholic Fermentation. The crushed fruit, diluted honey, and fruit juice prepared as described in paragraphs 81, 82, and 83 must be allowed to pass through an alcoholic fermentation. This is caused by yeast. Time materials contain yeast that will cause fermentation, but usually the fermentation will be very poor and an inferior product will usually result because the yeasts naturally present are not of the proper varieties. Therefore, good yeast should be added.

All containers and other utensils coming in contact with the juices or fruits must be clean. Never under any circumstances add vinegar or vinegar mother to fresh juices before fermentation. They should only be added after yeast fermentation is complete.

If large amounts of vinegar are to be made, suitable yeast may be obtained from the College of Agriculture, University of California, Berkeley, California. This will be sent for one dollar, prepaid, with directions for use. It is more satisfactory than bread yeast.

To crushed fruit, compressed yeast is added at the rate of one cake per three gallons of crushed fruit. The yeast must be broken up thoroughly in the juice or crushed fruit. This can be done by mixing the yeast with a little juice or water and then stirring the yeasty liquid in with the crushed fruit.

Fruit juices and diluted honey are allowed to ferment until there is no longer any gas given off and until all taste of sugar disappears. This will be in about three weeks at room temperature.

Crushed fruits should be allowed to ferment about a week. This will soften them so that the juice may be pressed out easily. During fermentation, the crushed fruit should be stirred frequently and should be screened or covered with a cloth to keep out vinegar flies. The fruits are then pressed and the juice allowed to ferment until all the sugar is destroyed. Yeast fermentation proceeds most rapidly at warm temperatures. A temperature of about 800 to 900 F. is the most favorable. At temperatures above 105 F., fermentation ceases and at temperatures below 60 F., it proceeds extremely slowly. At 83 to 90 F. fermentation will usually be complete in two weeks or less. Because a warm temperature is so favorable, the stoneware crock or other container should be kept in a warm room, except in hot summer weather.

Vinegar flies often gather around fermenting fruits or juices. Their presence is objectionable, both because of their appearance, and the fact that they may infect the material with vinegar bacteria. Vinegar bacteria form vinegar acid which seriously interferes with and may stop yeast fermentation. It is essential that yeast fermentation run to completion in order that a strong vinegar shall be formed. The flies may be kept out of barrels or jars by the use of cheesecloth covers.

85. Pressing Fermented Fruits. The same equipment can be used as described under paragraph 29, "The Pressing of Fruits for Fruit Juice." If only a small amount (less than five gallons) of crushed fruit has been fermented, it may be pressed through a cheesecloth. Usually a great deal of the juice may be poured off after fermentation is complete; this is especially true of soft fruits.

The pressed juice should be placed in clean containers. Alcoholic fermentation will continue for several days after pressing.

86. Removal of Sediment. When alcoholic fermentation is over, the yeast and coarse fruit, pulp, etc., will settle out. When this has occurred the fermented liquid should be drawn or poured off the sediment, because this material will affect the flavor of the vinegar. Usually settling will have taken place in a month after the start of alcoholic fermentation or within two weeks after alcoholic fermentation is over. A hose is used to syphon off settled fermented liquids from barrels; the liquid may simply be poured from a crock or jar into another similar clean container.

87. Adding Vinegar Starter. When the alcoholic fermentation is complete (but not before) the vinegar fermentation should be started by the addition of a small amount of vinegar. Never add vinegar until yeast fermentation is complete. This is when gas is no longer given off and there is no longer a taste of sugar. This may be (lone by adding one pint of barrel vinegar or new vinegar from a grocery store to each gallon of fermented liquid after drawing it off from the yeast sediment. To fermented orange juice add one quart of vinegar per gallon. If there is any vinegar on hand from previous home made lots, it may be used. The addition of several pieces of "vinegar mother" also greatly assists the start of vinegar fermentation.

The vinegar adds millions of vinegar bacteria which multiply rapidly in the alcoholic liquid and it also increases the vinegar or acetic acid so that molding and growth of "wine flowers" cannot take place. Mold and wine flowers often spoil alcoholic liquids to be used for vinegar unless vinegar is added.

88. Vinegar Fermentation. Vinegar fermentation must not be allowed to start until after alcoholic fermentation is complete. Starting the vinegar fermentation is described in the preceding paragraph.

The mixed vinegar and alcoholic liquid must he so placed that a large surface is exposed to the air. If the liquid is in a bottle the bottle should be filled only two- thirds full and must not be corked. A cloth only should be placed over the mouth of the bottle to keep out insects. A stoneware crock or glass fruit jar can be used. It should be covered with a cloth only. If a barrel is used, leave the bung open and fill the barrel only two- thirds or three-fourths full. The arrangement in Fig. 49 is very good.

Vinegar fermentation proceeds must rapidly in a warm room at 75 to 90.F. At this temperature, vinegar will usually form in about three or four months. It will then be ready for filtration and use.

During the vinegar fermentation the liquid should be Protected from vinegar diseases and pests as described in paragraph 84.

89. Vinegar Generators. The rate of vinegar fermentation depends on the amount of surface exposed to the air and to the temperature. Vinegar generators enormously increase the surface and hence speed up the rate of fermentation accordingly.

The most common type of generator is a wooden cylinder 8 to 12 feet high and about 30 to 40 inches wide. This is usually filled with beechwood shavings. Corn cobs, or rattan shavings may also be used. Charcoal or coke in large pieces may be used for distilled alcoholic liquids, but not for fruit juices because the material would soon become clogged with sediment.

The acidified fermented juice is run through the above generator slowly (not more than twenty-five gallons per day). It is distributed over the perforated head of the generator by a tilting trough and trickles down over the shavings. Air is admitted through air holes near the bottom of the generator. Heat is generated by the fermentation and the temperature in the generator is maintained at 80 to 85 F. by regulating the rate of flow of liquid and air supply. A mixture of one part vinegar and three parts fermented liquid enters the top of the generator and vinegar issues from the bottom. The time for the liquid to flow through the generator is only a few minutes.

Considerable skill and experience are necessary to successfully operate vinegar generators and their use is recommended only for relatively large installations.

A simple generator for farm use can be constructed of a barrel filled with beechwood shavings and fitted with two wooden spigots and hole at each end. To operate this generator, it is filled half full with fermented juice acidified with one gallon of vinegar to each three gallons of liquid. The upper spigot is left open. The barrel is turned halfway over several times daily, closing the lower spigot and opening the upper spigot each time. Air enters holes in centers of ends of the barrel and flows out the upper spigot furnishing air to the liquid and vinegar bacteria on the wet shavings in the upper part of the barrel. A form of revolving generator is also used commercially.

The operation and construction of vinegar generators is very well described in a circular published by the Hydraulic Press Manufacturing Company of Mt. Gilead, Ohio. This company will send the above circular free on request.

Vinegar fermentation should be watched carefully and when the vinegar is strong enough for use it should be placed in completely filled containers such as barrels or bottles. Where very large amounts of vinegar are made, the vinegar should be analyzed for acid content. The instrument shown in Fig. 51 is used by vinegar factories. Directions for its use accompany it. It can be used by anyone.

90. Aging of Vinegar. Vinegar is greatly improved in flavor by storing for one year in well-filled closed wooden barrels. It does not age very well in well-filled bottles and may deteriorate in open barrels and tanks after reaching its maximum strength. The bacteria form acid so long as any alcohol is left. When all of the alcohol is changed to acid, they attack the acid itself if the vinegar is exposed to air and may completely destroy all the acid or seriously lower the quality of the product. Hence the necessity for storing it in well-filled closed containers when the maximum acid content is reached. This point is determined by analysis with instruments shown in Fig. 51 if a large quantity of vinegar is made. In the household the taste will serve as a guide.

91. Clearing the Vinegar. If the vinegar is for home use it may be made sufficiently clear by straining through heavy cloth.

If it is to be sold, it may be necessary to clarify it by the methods outlined in Recipe 95. However, vinegar made in small quantities usually becomes clear after settling several months and only the sediment need be filtered or strained.

92. Vinegar Diseases and Pests.

(a) Wine Flowers. This disease is caused by a film yeast growing on freshly fermented fruit juices and is seen as a white powdery or wrinkled and easily broken film. It is easily distinguished from vinegar mother because vinegar mother is thick, slimy, almost colorless, and tough. Wine flowers destroy the alcohol of the liquid and (10 not form any acid. They are especially dangerous in fermented orange juice or other fermented juices of low alcohol content. If vinegar at the rate of one or two pints to every gallon of fermented liquid is added when yeast fermentation is complete, there will be little danger of injury by wine flowers. Pure yeast added to the fresh juice before fermentation, also reduces the possibility of growth of wine flowers.

(b) Lactic Acid Bacteria. These grow in fermented liquids producing disagreeable flavors and cloudiness. They can be controlled as directed for wine flowers.

(c) Vinegar Eels. These are small nematode worms just large enough to be seen in the vinegar when it is held to the light in a small glass tube or small tumbler. They are not especially harmful to health but their appearance is not pleasing. They may infest generators so badly that the generators cannot be used until the eels have been killed.

They may be killed by heating the vinegar to 120 F. in an agateware pot or by heating in some other way. Generators infested with eels are sterilized by live steam. Tanks in which infested vinegar has been stored should he steamed or sulphur should be burned in them several times so that the fumes will kill the eels. They can also be removed by close filtration. Eels will seldom appear in very small lots of vinegar, but are very common in vinegar factories where they usually do not become numerous enough to require repressive measures.

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