SUGAR-CANE SIRUP MANUFACTURE 63 
must be at a suitable temperature. The semisirup, therefore, should 
be allowed to cool to the proper temperature, which is 140° to 145° F. 
(60° to 63°C.). Semisirup which tests 20° Baumé (35.8° Brix) when 
practically at a boiling temperature, or approximately 24° Baumé 
(43.1° Brix) at ordinary temperature, will test about 23° Baumé (41.3 
Brix) at 140° to 145° F. The quantity of invertase required depends 
on the volume of semisirup. As invertase is used in relatively small 
quantities, for accuracy of measurement the required quantity should 
be measured in terms of a small unit of volume, such as the cubic 
centimeter. The proportion required varies ordinarily from 40 to 60 
cubic centimeters of the most concentrated invertase preparation now 
on the market for every 100 gallons of semisirup. Other commercial 
invertase preparations are used in different proportions. Small bot- 
tles, glass vials, or cylinders graduated in cubic centimeters, usually 
sold in drug stores, are recommended for measuring the invertase 
accurately. 
The required volume of invertase is mixed with a little water 
(about a quart) and then added to the tank of semisirup. Because 
of the small proportion of mvertase added, the sirup must be well 
stirred so as to thoroughly mix it with the invertase. Although 
about 50 cubic centimeters of the most active invertase preparation 
per 100 gallons of semisirup is usually required, it may be necessary 
to vary the quantity somewhat in certain cases, owing to differences 
in the proportion of cane sugar and invert sugar originally present 
in the juice and the proportion of cane sugar converted into invert 
sugar during evaporation. Unless a polariscope is available for 
testing the semisirup both before and after the invertase has done 
its work, the only way to determine for the first time whether too 
little or too much invertase has been added is to observe the color 
and flavor of the sirup and its tendency to crystallize after evapora- 
tion to final density. If the sirup does not differ appreciably in 
quality from sirup obtained from the same kind of cane when no 
invertase was used, and if no sugar separates from the sirup, it is 
safe to conclude that the proper quantity of invertase has been 
added. If, however, the color and oe of the finished sirup differ 
appreciably from those of sirup of the same density made without 
invertase, slightly less invertase should be used thereafter. Con- 
versely, if the finished sirup shows a tendency to deposit sugar, 
the proportion of invertase used for the next lot should be increased. 
The tendency of sirup to crystallize may be easily and quickly 
tested by permitting a small sample (about a quart) to cool until it 
is lukewarm and then adding about a teaspoonful of powdered or 
fine granulated sugar and stirring occasionally over a period of two 
or three hours. If no sugar im excess of that which has been added 
appears in the sirup after it has stood for a day or two, the quantity 
of sugar which may be deposited later will be very small, at the 
most. The smallest proportion of invertase which will prevent 
crystallization should be used. 
Since invertase does not act instantaneously, a certain period is 
required for it to convert the necessary quantity of cane sugar into 
invert sugar. It has peen found convenient to allow approximately 
12 hours (overnight) from the time the invertase is added to the 
semisirup until evaporation to final sirup is started. The invertase 
is added when quitting work at night, and final evaporation of the 
semisirup is begun when operation is resumed next morning. 
