We will now consider in more detail the preparation of mashes from starch-containing substances.
Gelatinizing Apparatus. These comprise either ordinary vats, into which steam at low pressure is admitted (see Fig. 4), cookers and stirrers such as shown in Fig. 1 and 45 or the Henze steamer (Fig. 2.)
An example of a cooking and mashing apparatus and its connections is shown in Fig. 1. This is the vacuum cooker put on the market by the
Vulcan Copper Works Company, of Cincinnati Ohio. This consists of a cylindrical steel vessel the interior of which is fitted with stirrer arms attached to a shaft making about sixty revolutions per minute. The steam enters the vessel at the bottom by means of pipes conducting it from a manifold, or header, in the same manner as is shown in the apparatus illustrated in Fig 45. Attached to each pipe at its point of entrance is a check valve to spray the steam through the mash. A thermometer for registering the temperature and a water gauge are placed in the manifold. The grain enters the cooker from the grain hopper by way of a spout. The cylinder has been previously supplied with hot water and during the mixing of the meal with the hot water the mass is constantly stirred. The malt is mixed with water in the small grain tub which is provided with a stirrer. The malt mash is admitted into the cooker and the mass thoroughly mixed by the arms. After the mashing, the product passes off to the drop tub and from thence to the mash coolers where it is cooled to the proper temperature for fermentation. The gearing for agitating the malt mash and the grain or potato mash is evident from the drawing.
The pressure steamers used in mashing are shown in Fig. 2. They comprise a cylindrical vessel preferably conical or partly conical, provided with steam entrance pipes, air valves and a manhole. At the bottom of the cone forming the lower end of the steamer is a grating located in an exit pipe provided with a valve. One of the steam entrance pipes is so located that the steam is forced in at the top of the cylinder while the
other allows steam to enter at the bottom of the cylinder. The device is provided with a pressure gauge and an air cock.
In use the body of the apparatus is partly filled
COflfl MEAL hopper.
COflfl MEAL hopper.
(To fact pagt 10)
(To fact pagt 10)
with water and the material to be treated. This is acted upon by a steam pressure of two atmospheres, which is later increased to three, steam entering by the lowermost pipe, passing up through the water and potatoes thoroughly agitating the same and passing away by the steam gauge. After standing at the last pressure for ten or fifteen minutes the lower steam inlet is closed; the upper inlet and the blow-out valve are opened. The steam is then increased to its highest point or about four atmospheres and the lower valve is opened. The disintegrated material is forced out by the steam through the grating at the bottom of the cone. This comminutes it and pulps it before it passes into the preparatory mash tub. Blowing out requires about 40 to 50 minutes. Steaming and blowing out together cover a space of two hours. The pressure of the steam before blowing out should be such that the steam is constantly being blown off through the safety valve. Thus the mass in the steamer is agitated and the material entirely disintegrated and gelatinized.
Process. Into these apparatuses the Potatoes and corn or grain first ground into mash, or even corn or grain unground, if the pressure is high enough, are disintegrated and cooked by steam under high pressure. During this process the starch becomes partially dissolved and partially gelatinized, which occurs when a pressure of some 65 pounds has been attained, with a temperature of about 300°F.
Saccharifying. It is now necessary to saccharify the gelatinized mass. This is accomplished by adding to it a certain amount of malt, whereby maltose or sugar is formed through the action of the diastase. The amount of maltose so created is in proportion to the amount of malt used, the length of time it is acting, the dilution of the mash, and the existence of a proper temperature. The temperature best fitted for this action lies above 122°F., but in order to entirely dissolve the starch a temperature of 145°F. should be used. In addition, at this higher temperature, the bacteria inimical to fermentation are destroyed. A higher temperature than 145°F. should not be allowed, except in extraordinary cases as it injures the effectiveness of the diastase.
Apparatus. The mixture of the malt with the mash may either take place in the heater and cooker itself (see FIG. 2) or in a preparatory mash vat.
In the first instance, the malt is allowed to enter the cooking cylinder when the temperature of the mash is around 145°F. The mash is stirred until thoroughly mixed when the product is drawn into a receptacle called a drop tub and later reduced to a proper fermenting temperature.
When the Henze type of steamer is used, the pulped mash (see Page 121) is blown into a pre-
FERMENTATION IN GENERAL. 15
Paratory mash vat, at the proper temperature. It is left to stand at this temperature for a period varying from twenty minutes to an hour and a half.
Cooling the Mash. Saccharification takes place at a temperature above 122°F., but the proper fermenting temperature is only about 63°F. to 68°F., and hence some means must be adopted for cooling the hot mash to this temperature and for so cooling it in a relatively short time,
Cooling may be accomplished by submitting the mash to currents of air; to contact with cold water coils or by the use of ice. One of the simplest coolers of the first class is shown in Fig. 3.
This consists of a shallow panlike tank A having means for introducing and drawing off the mash. Rotating in the center of the tank is a vertical shaft C carrying radiating stirrer arms B. Braces M
extend to the middle of these arms and the arms carry. a number of blades or paddles b, which extend down into the mash. Above the arms, mounted loosely on the same shaft, but rotating in the opposite direction, are fans H supported by arms J which create air currents over the agitated mash. These fans move at a much faster rate than the stirrers B.
A simple form of driving gear is shown. The main shaft C is rotated by a large bevel gear D, meshing with a small pinion E on the end of a driving shaft F, which is driven by a belt. This shaft also carries a bevel gear L, which meshes with a bevel gear K mounted on a sleeve. This sleeve surrounds and rotates freely on the central shaft C, being supported at its lower end in ball bearings mm, mounted on the shaft. This combination gives opposite rotation to the faces and stirrer arms and at different speeds. The driving mechanism can be of course varied.
Another simple method of air cooling would be to let the mash run down a series of enclosed steps or chutes, the casing being kept cool by an air blast. Mashes may be even cooled by mere stirring by paddles, but this takes a long time and much labor.
The preparatory mash vats used to-day are almost all provided with stirrers formed of hollow blades capable of a rapid stirring movement through the mash. Through the hollow blades cold water is forced. Mash vats of this kind should have the following qualities. They should be strongly built, particularly as regards the stirrers so as to be used with thick mashes. They should thoroughly and uniformly stir and mix the mash and they should be capable of cooling the mash within an hour, and should be so constructed as to be easily cleaned.
By using coils of pipe which may be inserted or withdrawn from the mash tub, and through which cold water is forced, the mash may be effectively cooled, but the best plan for quick cooling is to bring
a comparatively thin layer of the mash in contact with the coils. This may be conveniently done by using a system of comparatively large water pipes enclosing small pipes for the passage of the mash.
This should be arranged in a stand like the coils of a radiator with an incline from the inlet end of the top pipe to the outlet end of the lowermost pipe. As stated, the small pipe carries the mash, the large pipe the water. Preferably the mash flows downward while the water is forced upward in a contrary direction by means of a pump or a high level reservoir. The cooled mash should flow into the fermenting tank at a temperature of about 68°F.
There are many varieties of mash cooling apparatuses on the market of more or less complication suited to the needs of large and expensive plants,
The form of cooler best to be used depends upon the circumstances of each case and whether thick or thin mashes are to be distilled, The cooler should, however, be capable of thorough cleansing so that no portion of one mashing be carried to another.
Fermentation is an obscure and seemingly spontaneous change or decomposition which takes place in most vegetable and animal substances when exposed at ordinary temperatures to air and moisture. While fermentation broadly covers decay or putrifaction, yet it is limited in ordinary use to the process for producing alcoholic liquors from sacchariferous mashes.
Fermentation is brought about by certain bodies called ferments—these are either organized, as vegetable ferments such as yeast, or unorganized as diastase,—the enzyme of germinated malt. The last is used to convert starch into maltose, the first is used to convert maltose into fermentable sugar. The organized ferments are either to be found floating freely in the air under the name of wild yeast or are artificially produced. If a solution of pure sugar be allowed to stand so that it can be acted on by the organisms in the air, it will remain unaltered for a long time, but finally mold will appear upon it and it will become sour and dark-colored. If, however, a suitable ferment is added to it, such as yeast, it rapidly passes into a state of active fermentation by which the sugar is split up into alcohol and carbon dioxid, the process continuing from 48 hours to several weeks according to the temperature, the amount of sugar present, and the nature and quantity of the ferment. Fermentation cannot occur at a temperature much below 40°F., nor above 140°F. The limits of practical temperature, however, are 41° to 86°F. Brewer's yeast is chiefly employed in spirit manufacture.
The most striking phenomena of fermentation are the turbidity of the liquid, the rising of gas bubbles to the surface, and the increase in temperature, the disappearance of the sugar, the appearance of alcohol and the clearing of the liquid. At the end a slight scum is formed on the top of the liquid and a light colored deposit at the bottom. This deposit consists of yeast which is capable of exciting the vinous fermentation in other solutions of sugar. The lower the temperature the slower the process, while at a temperature above 86°F. the vinous fermentation is liable to pass into other forms of fermentation to be hereafter considered.
There are many theories of fermentation, of which the two most important are those of Pasteur and Buchner. The first teaches that fermentation is caused purely by the organic life of the yeast plant and is not a mere chemical action, whereas the second view most largely held to-day is that fermentation is a purely chemical change due to certain unorganized substances called "enzymes" present in the yeast.
The theory need not detain us. It is sufficient that the yeast plant in some manner acts to decompose the saccharified mash into alcohol and carbonic acid gas.
Yeast is a fungus, a mono-cellular organism, which under proper conditions propogates itself to an enormous extent. There are many races or varieties of yeast each having its peculiar method of growth.
For our purposes we may divide the yeast races into two classes, wild yeast and cultivated yeast. Originally any of the yeast races were supposed to be good enough to effect fermentation but to-day every effort is made to procure and use only those races which have the greatest power to decompose sugar. It was for this reason that the old distiller kept portions of his yeast over from one fermentation to the next. This was yeast whose action they understood and whose abilities were proven. This yeast so kept was open, however, to the chance of contamination and yeast to-day is as carefully selected and bred as is a strain of horses, or dogs, or plants.
After getting a portion of selected pure yeast for breeding purposes, it may be sowed, that is, propagated very carefully in a yeast mash, in sterilizing apparatus, where all chance of contamination by bacteria or wild yeast is avoided. From this bed of mother yeast, or start yeast, the yeast for the successive yeast mashes is taken.
The preparation of the various varieties of yeast mashes is too lengthy to be set forth except in special treatises on the subject, but the ordinary method of yeasting is as follows, reference being made to Fig. 5, which shows the apparatus used in the yeasting and fermenting departments of a distillery, as installed by the Vulcan Copper Works, of Cincinnati. The yeast tubs are shown to the left of the illustration. They are each provided with cooling coils and stirrers.
The yeast mash we will assume is composed of ,equal parts of barley malt and rye meal. Hot water at 100°F. is first put into the mash tub. The rake or stirrers are then rotated and the meal run in slowly. The stirring is continued for twenty minutes after the meal is all in, during which the mash has become saccharified.
The mash is then allowed to stand for about twenty hours, and to grow sour by lactic fermentation. The lactic acid so produced protects the mother yeast from infection by suppressing wild yeast and bacteria. During this period great care is taken to prevent the temperature of the mash falling below 95°F. and consequent butyric and acetous fermentation following. After it has so stood the sour mash is cooled by cir culating water in the coils and stirring until it is reduced to from 59°to 68°F. depending on whether the mash is thin or thick. Start yeast during the cooling of the mash when at above 86°F. is added and stirred in. For the next twelve hours the yeast ferments and when a temperature of 84°F. has been attained the mash is cooled to 65°F. at which temperature it is maintained until allowed to enter the fermenting tubs through the pipe leading thereto from the yeast tub.
There are four principal kinds of fermentation: alcoholic, acetous, lactic and viscous.
Alcoholic Fermentation. This may be briefly described as follows: The mash in the fermenting vat having been brought to the proper temperature, the ferment is thrown in, and the whole is well stirred together.
The proper pitching temperature varies with the method of fermentation adopted, the length of the fermenting period, the materials of the mash, its thickness or attenuation. It must always be remembered that there is a great increase in the temperature of the "beer" during fermentation and that the temperature at its highest should never under any circumstances, become greater than 86°F. and with thick mashes that even a less heat is desirable. Therefore the pitching temperature should be such that the inevitable rise due to fermentation shall not carry the temperature to or beyond the maximum point desired
for the particular mash being treated. It is to accurately control the pitching temperature and the fermenting temperature that the fermenting tanks are provided with cooling appliances.
In about three hours' time, the commencement of the fermentation is announced by small bubbles of gas which appear on the surface of the vat, and collect around the edges. As these increase in number, the whole contents are gradually thrown into a state of motion, resembling violent ebullition, by the tumultuous disengagement of carbonic anhydride. The liquor rises in temperature and becomes covered with froth. At this point, the vat must be covered tightly, the excess of gas finding an exit through holes in the lid; care must now be taken to prevent the temperature from rising too high, and also to prevent the action from becoming too energetic, thereby causing the contents of the vat to overflow. In about twenty-four hours the action begins to subside, and the temperature falls to that of the surrounding atmosphere. An hour or two later, the process is complete; the bubbles disappear, and the liquor, which now possesses the characteristic odor and taste of alcohol, settles out perfectly clear. The whole operation, as here described, usually occupies from forty-eight to seventy-two hours. The duration of the process is influenced, of course, by many circumstances, chiefly by the bulk of the liquor, its richness in sugar, the quality of the ferment, and the temperature.
Acetous Fermentation. This perplexing occurrence cannot be too carefully guarded against. It results when the fermenting liquor is exposed to the air. When this is the case, the liquor absorbs a portion of the oxygen, which unites with the alcohol, thus converting it into acetic acid as rapidly as it is formed. When acetous fermentation begins, the liquor becomes turbid, and a long, stringy substance appears, which after a time settles down to the bottom of the vat. It is then found that all the alcohol has been decomposed, and that an equivalent quantity of acetous acid remains instead. It has been discovered that the presence of a ferment and a temperature of 68° to 95°F. are indispensable to acetous fermentation, as well as contact with the atmosphere. Hence, in order to prevent its occurrence, it is necessary not only to exclude the air, but also to guard against too high a temperature and the use of too much ferment. The latter invariably tends to excite acetous fermentation. It should also be remarked that it is well to cleanse the vats and utensils carefully with lime water before using, in order to neutralize any acid which they may contain; for the least trace of acid in the vat has a tendency to accelerate the conversion of alcohol into vinegar. A variety of other circumstances are favorable to acetification, such as the use of a stagnant or impure water, and the foul odors which arise from the vats; stormy weather or thunder will also engender it.
Lactic Fermentation. Under the influence of lactic fermentation, sugar and starch are converted into lactic acid. When it has once begun, it develops rapidly, and soon decomposes a large quantity of glucose; but as it can proceed only in a neutral liquor, the presence of the acid itself speedily checks its own formation. Then, however, another ferment is liable to act upon the lactic acid already formed, converting it into butyric acid, which is easily recognized by its odor of rank butter. Carbonic anhydride and hydrogen are evolved by this reaction. The latter gas acts powerfully upon glucose, converting it into a species of gum called mannite, so that lactic fermentation—in itself an intolerable nuisance—becomes the source of a new and equally objectionable waste of sugar. It can be avoided only by keeping the vats thoroughly clean; they should be washed with water acidulated with five per cent. of sulphuric acid. An altered ferment, or the use of too small a quantity, will tend to bring it about.
The best preventives are thorough cleanliness, and the use of good, fresh yeast in the correct proportion.
Viscous Fermentation. This is usually the result of allowing the vats to stand too long before fermentation begins. It is characterized by the formation of viscous or mucilaginous matters, which render the liquor turbid, and by .the evolution of carbonic anhydride and hydrogen gases the latter acting as in the case of lactic fermentation and converting the glucose into mannite. Viscous fermentation may generally be attributed to the too feeble action of the ferment. It occurs principally in the fermentation of white wines, beer, and beet-juice, or of other liquors containing much nitrogenous matter. It may be avoided by the same precautions as are indicated for the prevention of lactic fermentation.
Periods of Fermentation. The operation of fermentation may be conveniently divided into three equal periods.
The first or pre-fermentation period is that when the yeast mixed into the mash is growing; the temperature should then be kept at about 63 to 68°F. during which time the yeast is propagated. The growth of the yeast is manifested by the development of carbonic acid gas and by a slight motion of the mash. When alcohol is produced to an extent of say five per cent. the growth of the yeast stops
The second period of chief fermentation then begins. Carbonic acid is freely developed and the sugar is converted into alcohol. The temperature at this time should not exceed 81.5°F. The second period of fermentation continues about 12 hours, when the last period commences.
During the third period or after fermentation there is a lessening of the formation of carbonic acid and a lowering of the temperature. In this stage the mash is kept at a temperature of 77° to 81°F. In order to conveniently regulate the temperature of the mash the vat may be provided with a copper worm at the bottom thereof, through which cold water is forced. This, however, need only be used for thick mashes. There are also various kinds of movable coolers used for this purpose.
There are a number of different forms which fermentation may take. The insoluble constituents of the mash in the process of .fermentation are forced to the surface, and form what may be termed a cover. If the carbonic acid gas bubbles seldom break this cover it indicates that the conversion of the sugar into alcohol and carbonic acid is proceeding very slowly and imperfectly. If, however, the cover is swirling and seething, and particularly if the cover is rising and falling with every now and then a discharge of gas, it is an indication that the conversion is properly proceeding. Foaming of the mash is to be prevented, as the froth or foam flows over the mash tank and considerable loss is sustained. It may be prevented by pouring a little hot lard into the vat, or petroleum, provided its odor will not interfere with the use of the alcohol when distilled.
Water is added in small quantities near the termination of the second period of fermentation. This dilutes the alcohol, in the mash and lessens its percentage, and thus the further growth of the yeast is permitted.
After fermentation the mash takes either the form of a thick diluted pulp or of a thin liquor. Again the reader is reminded that the mash after fermentation contains alcohol mixed with water—and that the next step in the process—distillation is necessary merely to separate the alcohol from the water.
There is always some loss in the process of fermentation; in other words, the actual production is below the theoretical amount due. Theoretically one pound of starch should yield 11.45 fluid ounces of alcohol. With a good result 88.3 per cent. of this theoretical yield is obtained; with an average result of 80.2 per cent. and with a bad result only about 72.6 per cent. or less.
Fermenting Apparatus. It remains now to describe briefly the vessels or vats employed in the processes of fermentation. They are made of oak or cypress, firmly bound together with iron bands, and they should be somewhat deeper than wide, and slightly conical, so as to present as small a surface as possible to the action of the air. Their dimensions vary, of course, with the nature and quantity of the liquor to be fermented. Circular vats are preferable to square ones, as being better adapted to retain the heat of their contents. The lid should close securely, and a portion of it should be made to open without uncovering the whole. For the purpose of heating or cooling the contents when necessary, it is of great advantage to have a copper coil at the bottom of the vat, connected with two pipes, one supplying steam and the other cold water.
Iron vats have also been used, having a jacketed space around them, into which hot or cold water may be introduced. As wooden vats are porous and hence uncleanly they have to be constantly scrubbed and disinfected. It is advisable to cover the interior with linseed oil, varnish or with a shellac varnish. The diameter of the coil varies according to the size of the vat.
The room in which the vats are placed should be made as free from draughts as possible by dispensing with superfluous doors and windows; it should not be too high and should be enclosed by thick walls in order to keep in the heat. As uniformity of temperature is highly desirable, a thermometer should be kept in the room, and there should be stoves for supplying heat in case it be required. The temperature should be kept between 64°F. and 68°F.
Every precaution must be taken to ensure the most absolute cleanliness; the floors should be swept or washed with water daily, and the vats, as pointed out above, must be cleaned out as soon as the contents are removed. For washing the vats, lime-water should be used when the fermentation has been too energetic or has shown a tendency to become acid; water acidulated with sulphuric acid is used when the action has been feeble and the fermented liquor contains a small quantity of undecomposed sugar. Care must be taken to get rid of carbonic anhydride formed during the operation. Buckets of lime-water are sometimes placed about the room for the purpose of absorbing this gas; but the best way of getting rid of it is to have a number of holes, three or four inches square, in the floor, through which the gas escapes by reason of its weight. The dangerous action of this gas and its effects upon animal life when unmixed with air are too well know to necessitate any further enforcement of these precautions.
The beer obtained by mashing and fermenting consist essentially of volatile substances, such as water, alcohol, essential oils and a little acetic .acid, and of non-volatile substances, such as cellulose, dextrine, unaltered sugar and starch, mineral matters, lactic acid, etc.
The volatile constituents of the liquor possess widely different degrees of volatility; the alcohol has the lowest boiling point, water the next, then acetic acid, and last the essential oils. It will thus be seen that the separation of the volatile and non-volatile constituents by evaporation and condensation of the vapors given off is very easily effected, and that also by the same process, which is termed distillation, the volatile substances may be separated from one another. As the acetic acid and essential oils are present only in very small quantities, they will not require much consideration.
The aim of distillation is to separate as completely as possible the alcohol from the water which dilutes it. Table I shows the amount of alcohol contained in the vapors given off from alcoholic liquids of different strength, and also their boiling points.
A glance at this table shows to what an extent an alcoholic liquor may be strengthened by distillation, and how the quantity of spirit in the distillate increases in proportion as that contained in the original liquor diminishes. It will also be seen that successive distillations of spirituous liquors will ultimately yield a spirit of very high strength.
As an example, suppose that a liquid containing five per cent. of alcohol is to be distilled. Its vapor condensed gives a distillate containing 42 per cent. of alcohol which, if re-distilled, affords another containing 82 per cent. This, subjected again to distillation, yields alcohol of over 90 per cent. in strength. Thus three successive distillations have strengthened the liquor from five per cent. to 90 per cent.
It will thus be clear that the richness in alcohol of the vapors given off from boiling alcoholic liquids is not a constant quantity, but that it necessarily diminishes as the ebullition is continued. For example a liquor containing seven per cent. of alcohol yields, on boiling a vapor con taining 50 per cent. The first portion of the distillate will, therefore, be of this strength. But as the vapor is proportionally richer in alcohol, the boiling liquor must become gradually weaker, and, in consequence, must yield weaker vapors. Thus, when the proportion of alcohol in the boiling liquid has sunk to five per cent., the vapors condensed at that time will contain only 40 per cent.; at two per cent. of alcohol in the liquor, the vapors yield only 28 per cent., and at one per cent., they will be found when condensed to contain only 13 percent. From this it will be understood that if the distillation be stopped at any given point before the complete volatilization of all the alcohol the distillate obtained will be considerably stronger than if the process had been carried on to the end. Moreover, another advantage derived from checking the process before the end, and keeping the last portions of the distillate separate from the rest, besides that of obtaining a stronger spirit, is that a much purer one is obtained also. The volatile, essential oils, mentioned above, are soluble only in strong alcohol, and insoluble in its aqueous solutions. They distill also at a much higher temperature than alcohol, and so are found only among the last products of the distillation, which results from raising the temperature of the boiling liquid. This system of checking the distillation and removing the products at different points is frequently employed in the practice of rectification.
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