158 VINEGAR, CIDER, AND FRUIT-WINES. 



the theoretical part in mashing will be briefly discussed. Malt 

 contains starch and diastase. By bringing the comminuted malt 

 in contact with water of about 131 to 133 F. the starch is 

 formed into paste and the diastase passes into solution. By the 

 action of the diastase upon the starch the latter is converted into 

 maltose and dextrin, the finished mash containing 80.9 per cent, 

 of maltose and 19.1 of dextrin. For reasons given later on the 

 finished mash is heated for a short time to 140 to 140.8 F., 

 without, however, exceeding this temperature, and then cooled off 

 to the degree required for the induction of alcoholic fermenta- 

 tion. 



Mash prepared in this manner contains, besides the stated quan- 

 tities of maltose and dextrin, effective diastase, i. e., such as 

 possesses the power of liquefying starch. (By heating to 1 above 

 158 F. the diastase entirely loses this property.) By compound- 

 ing a mash of this nature with yeast, the diastase with the simul- 

 taneous action of the yeast is able to convert all the dextrin pres- 

 ent in the fluid into maltose, and, consequently, the total quantity 

 of starch originally present is converted into alcohol by this pecu- 

 liar process to which the term after-effect of the diastase has been 

 applied. 



The yield of acetic acid which can be obtained from a given 

 quantity of malt can be calculated in a simple manner. Air- 

 dried malt contains in round numbers about 68 per cent, of 

 starch and dextrin. Theoretically 1 kilogramme of starch yields 

 71.612 liter per cent, of alcohol ; in practice, however, only about 

 55 liter per cent., and, after deducting a loss of 15 per cent, 

 during the conversion of alcohol into vinegar, the quantity of 

 acetic acid which can be actually obtained from a given quantity 

 of malt can be determined. 



Example: What is the yield of 10 per cent, vinegar in working 

 500 kilogrammes of barley malt? 



Five hundred kilogrammes of malt with 68 per cent, of starch 

 (and dextrin) contain 340 kilogrammes of starch (and dextrin). 



Three hundred and forty kilogrammes of starch (and dextrin) 

 give (with a yield of 55 per cent.) 18.700 liters per cent, of alcohol. 



One hundred and eighty seven liters of alcohol (specific gravity 

 at 59 F. mm 0.795) are equal to 148.665 kilogrammes of alcohol. 



