68 BULLETIN 1370, U. S. DEPARTMENT OF AGRICULTURE 
may contain a great deal of crystallized sugar. Most of this is 
pumped, with the sirup, into the mixing tank; the barrels are thor- 
oughly steamed while on the dumping skid to recover the rest. 
When the mixing tank has been filled to the desired depth with — 
sirup, the stirrer is started and heat is supplied through the steam 
coils to dissolve the crystallized sugar in the sirup and to raise the 
temperature of the entire mass to 140° F. (60° C.). The density 
of the sirup when ready for the invertase treatment corresponds to 
approximately 66° Brix (about 36° Baumé), measured at 140° FP. 
The addition of the dilute sirup resulting from steaming the barrels 
usually reduces the density of the sirup to approximately 66° Brix. 
The large mixing tanks are suitably imsulated to retain heat and 
are also provided with wooden covers. The steam is turned off as 
soon as the desired temperature is reached, and the required quan- 
tity of invertase is then added. The stirring is continued until the 
invertase is thoroughly mixed into the sirup (one to two hours for a 
5,000-galion tank). 
As the action of invertase proceeds most efficiently at approxi- 
mately 140° F., it is desirable to insulate the tanks so that the sirup 
will cool as slowly as possible during the inverting period. With 
suitable insulation, so that the temperature of the sirup does not 
decrease much more than 10° to 15° F. during the first 12 hours, the 
cost for invertase can be restricted to about one-half cent per gallon 
of final sirup by allowing the sirup to remain in the tank for 36 hours. 
Approximately 1 pound of invertase * per 350 gallons of sirup is 
required. Through the action of the mvertase, a sufficient propor- 
tion of the cane sugar in the sirup is converted into invert sugar to 
prevent subsequent crystallization when the sirup is canned at the 
desired density. The “apparent purity’? (ratio of direct polariza- 
tion to degrees Brix) is reduced to 50 to 55. 
The three mixing tanks operate in sequence. While one is full 
of sirup, another is being emptied, and the third is being cleaned and 
filled. At the end of the 36-hour period the sirup, ready for canning, 
is pumped from the large mixing tank to a small receiving tank at 
the rate desired, and from here it flows by gravity into the evaporator. 
Concentration of the sirup to the desired density requires only three or 
four minutes; the extent of evaporation depends on the quantity of 
dilute sugar solution which resulted from steaming the barrels and 
on the quantity of water added to the sirup. The Louisiana-type 
evaporator (p. 53), usually preferred for this purpose, serves both as 
an evaporator and as a processing kettle. 
From the evaporator the sirup flows by gravity through a cooler 
or to one of the cooling tanks shown in Figure 19, where the tempera- 
ture is permitted to drop to that required for canning. Cooling tanks 
are preierably made of copper and should be comparatively shallow, 
so that the sirup will cool rapidly. From the cooling tanks the sirup 
flows by gravity to the canning department on the floor below. 
18 The most active invertase preparation of standardized strength on the market at the present time. 
An up-to-date list of manufacturers of invertase may be obtained upon request from the Bureau of Chem- 
istry, U.S. Department of Agriculture, Washington, D. C 
