26 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



pletely converted into maltose. The form 

 of the mashing apparatus and the tem-^ 

 peratures at which the several operations 

 are conducted are modified as may be 

 necessary to fit the peculiarities of the 

 raw materials. 



In this country maize is the chief 

 starchy material used in the manufac- 

 ture of alcohol. It is mashed in a sort 

 of kettle known as a vacuum cooker. 



The vacuum cooker is a horizontally 

 placed cylindrical vessel made of steel 

 boiler plate, and has a capacity of about 

 40 gallons for every bushel of grain to 

 be mashed in one charge. Just below 

 the center of each end it is provided 

 with stuffing boxes, through which a shaft 

 passes. The latter carries several rakes 

 or stirring arms inside the shell; outside 

 it is provided with a strong toothed wheel, 

 arranged for chain drive. Thermometers 

 and try cocks are mounted in each end 

 of the shell, and if the cooker is large a 

 third thermometer is set in the middle 

 of the side. In a row along the bottom 

 are several small steam-inlet valves so 

 constructed that while steam can pass 

 freely into the cooker the contents of the 

 latter can not run back into the steam 

 pipe when pressure is removed outside. 

 At the middle of the top of the cooker is 

 a dome fitted with a pipe connection 

 which leads to a "cross." From one side 

 of the latter connection is made to the 

 steam supply, which must be carried at 

 about 50 pounds pressure; from the other 

 side connection is made with the vacuum 

 pump, and from the top a pipe leads to 

 a blow-off valve. On top of the cooker, 

 at one end, there is a manhole through 

 which water and meal may be introduced, 

 and in the bottom, at one end, there is a 

 discharge valve which opens into a pipe 

 leading to the drop tub. The operation 

 of this cooker is as follows: 



Water in the proportion of 20 to 25 gal- 

 lons for every bushel of corn is first run 

 in and is warmed up to about 120 degrees 

 Fahrenheit. The rakes are then started 

 and the grain, which should be ground to 

 a coarse meal, is added slowly enough to 

 keep it from forming lumps. When the 

 meal is all in, the manhole is closed and 



steam is turned on through the small 

 valves in the bottom, the blow-off valve 

 being left open. When the temperature 

 of the mash has risen to 212 degrees the 

 blow-off valve is closed and pressure is 

 allowed to rise within the cooker at such 

 a rate that the thermometers and a pres- 

 sure gauge in the dome indicate a fairly 

 constant equalization of temperature in 

 the contents. The pressure is allowed to 

 rise to about 50 to 55 pounds, correspond- 

 ing to a temperature of about 300 degrees 

 Fahrenheit, but is maintained at this 

 point for a few minutes only, after which 

 the steam is shut off and the blow-off valve 

 is opened until the pressure is completely 

 relieved. The blow-off valve is then closed 

 again, and the valve between the cooker 

 and vacuum pump is opened. Application 

 of the vacuum causes renewed boiling and 

 a rapid fall of temperature in the con- 

 tents of the cooker, and when the ther- 

 mometers read from 140 degrees to 145 de- 

 grees Fahrenheit the vacuum is released 

 and the malt is added. 



The amount of malt employed is usu- 

 ally about one-tenth of the weight of corn 

 in the mash. It is ground quite fine and 

 is mixed in the small grain tub with 

 enough lukewarm water to make it flow 

 freely through the pipe which leads to the 

 cooker. The length of time allowed for 

 saccharification in the cooker will vary 

 from fifteen minutes to an hour, accord- 

 ing to the temperature — which should be 

 held between 140 degrees and 145 degrees 

 Fahrenheit — and the amount and diastatic 

 strength of the malt. It is advisable not 

 to hasten this part of the mashing process 

 unduly, and the completeness of the 

 starch conversion should always be proved 



Fig. 1. Small Laboratory Still, 

 ■t holier oi- kettle of still: B, opening for fllling 

 or chai-sinK: C. tbermometer, sometimes 

 omitted; D. connection to condenser: DO. 

 inner condenser tube, passing tbrough EF. 

 water jacket, with water inlet at E. and 

 outlet at f : O. outflow for distillate. 



