A Practical Handbook on the Distillation of Alcohol from Farm Products. F. B. Wright
CHAPTER II.
THE PREPARATION OF MASHES, AND FERMENTATION.
Alcohol may be produced either from, (1) farinacious materials, such as potatoes or grains, (2), from sacchariferous substances such as grapes, sugar beets, sugar cane, or the molasses produced in sugar manufacture.
THE PREPARATION OF STARCHY MATERIALS.
=Saccharification.= =Preparatory Mashing.= With starchy materials it is first necessary to convert the starch into a sugar from which alcohol can be produced by the process of fermentation. This is called saccharification.
=Gelatinizing.= The first step in this process is gelatinizing the starch;—that is, forming it into a paste by heating it with water, or into a liquid mass by steaming it under high pressure. The liquid or semi-liquid mass is then run into a preparatory mash vat and cooled.
=Saccharifying.= The disintegrated raw materials or gelatinized starch in the preparatory mash vat is now to be "saccharified" or converted into sugar. This is effected by allowing malt to act on the starch. This malt contains a certain chemical "ferment" or enzyme, called "diastase" ("I separate").
This is able under proper conditions to break up the gelatinized starch into simpler substances—the dextrins—and later into a fermentable sugar called maltose.
=Fermentation.=—The maltose or sugar in the "mash" is now to be converted into alcohol. This is accomplished by fermentation, a process of decomposition which converts the sugar into carbonic acid and alcohol. Fermentation is started by yeast, a fungus growth, which in the course of its life history produces a matter called zymose which chemically acts on the sugar to split it up into carbonic acid gas and alcohol.
Yeast may be either "wild" or cultivated. If the mash is left to stand under proper condition the wild yeast spores in the air, will soon settle in the mash and begin to multiply. This method of fermentation is bad because other organisms than yeast will also be developed—organisms antagonistic to proper fermentation. As a consequence, pure or cultivated yeast is alone used.
This yeast is cultivated from a mother bed in a special yeast mash and when ripened is mixed with the mash in the fermenting vat. At a temperature between 50° F. and 86° F. the yeast induces fermentation, converting the sugar of the mash into carbon dioxid which escapes, and alcohol which remains in the decomposed mash, or "beer" as it is termed in the United States.
It now remains to separate the alcohol from the water of the beer with which it is mixed. This is accomplished by distillation and rectification, as will be fully described in the chapters following.
PRODUCTION OF ALCOHOL FROM SACCHARIFEROUS SUBSTANCES.
Substances such as grape juice, fruit juice, sugar beets, cane sugar and molasses already contain fermentable sugar. Saccharification is therefore not needed and juices or liquids from these matters are either directly fermented as in the case of sugar cane, or—as in the case of sugar beets—the sugar in juice is transferred by yeast into a fermentable sugar.
MASHING STARCHY MATERIALS.
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. 44), cookers and stirrers such as shown in Fig. 1 and 45 or the Henze steamer (Fig. 2.)
[Illustration: FIG. 1.—Vacuum Mash Cooker. (To face page 10)]
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.
[Illustration: FIG. 2.—Henze Steamer.]
In use the body of the apparatus is partly filled 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 about 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 mass (see Page 121) is blown into a preparatory mash vat,