20 BULLETIN 1370, U. S. DEPARTMENT OF AGRICULTURE 
The actual yield, or 85 per cent of the theoretical (p. 18), is therefore | 
19.41 gallons. With 15° Brix juice and 67 per cent extraction, the — 
theoretical yield (Table 6) is 25.5 gallons of sirup per ton of cane; 
the actual yield is 0.85 25.5, or 21.67 gallons. The increase in 
gallons of sirup per ton of cane resulting from 7 per cent increase 
in extraction is 21.67—19.41, or 2.26 gallons. 
The 5-roller mill is usually of heavier construction than the small 
3-roller mill, so that it gives less trouble from breakage. The 
crusher prepares the cane for the mill, thereby making it possible for 
a thicker and more even blanket of cane to pass through the mill. 
The tendency is to underfeed rather than to overfeed small 3-roller 
mills, owing to the fear of ‘‘“choking”’ the engine or breaking a shaft 
of the mill. This decreases the extraction because of insufficient 
pressure on the cane. | 
In the foregoing calculations the small cost of evaporating the 
extra juice obtained by higher extraction has not been considered. 
Tt has also been assumed that the quality of sirup resulting from 67 
er cent juice extraction is so nearly equal to that of sirup obtained 
froth 60 per cent extraction that the two lots of sirup have the same 
market value. Under certain conditions, for example with poor 
quality cane, this may not be strictly true. In most cases, however, 
it is believed that the small-scale boilmg and skimming method 
will yield sirup of satisfactory quality, without recourse to chemical 
clarification, provided the extraction does not greatly exceed 65 
per cent. 
COMPARISON OF METHODS OF MANUFACTURE 
Although the quality of sirup copends to a large extent upon the 
variety of cane and the type of soil on which the cane is grown, it 
may also be greatly influenced by the equipment and process used 
in manufacture and by the skill of the sirup maker.® 
Jn making sirup from sugar-cane juice, 1 gallon of sirup is obtained 
from 6 to 7 gallons of juice, 5 to 6 gallons of water being evaporated. 
Cane juice, however, contains many substances besides sugar and ~ 
water. As first obtained at the mill, the juice contains some sus- | 
pended soil, which has adhered to the cane, particles of finely ground — 
cane stalk or fiber in suspension, and certain dissolved substances. 
Among the dissolved nonsugar substances, commonly classed as 
impurities because they represent material other than sugar but 
which are just as much a part of the juice as is the dissolved cane 
sugar itself, are organic and inorganic salts, proteins, pigments, 
gums, and cane wax. These so-called impurities affect the quality 
of the sirup, but not all of them are objectionable. ‘Aunoue it is 
never necessary or feasible to remove all of them, some must be 
eliminated to get a sirup of satisfactory flavor, color, and clarity. 
In practice, therefore, the manufacture of sirup consists.in the 
evaporation of excess water and the removal of certain impurities 
by clarification. 
The methods of clarification used by sirup makers differ somewhat, 
depending on whether the operation is on a large or a small scale and 
® The methods of manufacture herein described apply primarily to the large-stalk, disease-susceptible | 
varieties of cane, which are at present most extensively cultivated. From the experience thus far avail- | 
able in making sirup from the slender-stalk, disease-resistant varieties, it is believed that the methods of 
manufacture in the future will nved to be altered but little, if at all. 
