18 BULLETIN 656, U. S. DEPARTMENT OF AGRICULTURE. 
stored for precipitation in barrels instead of in 5-gallon containers. 
For the most part, grapes grown on the Bass Islands, in Lake Erie, to 
the north of Sandusky, Ohio, were used in the preparation of the 
juices. The fruit, which was of good quality, was immediately 
crushed and heated without being stemmed. The pulp was heated 
in aluminum kettles to about 145° F., and pressed on hydraulic 
presses in the customary manner. The juice was strained through 
several thicknesses of burlap, heated in glass-lined kettles to about 
175° F., after which it was run into 50-gallon barrels, previously 
sterilized by steam. The barrels were filled to the tops with the 
hot juice, and immediately carefully bunged. After having been 
stored for precipitation, the juice was run into the trade packages 
and sterilized in the customary manner. 
OCCURRENCE OF SMALL AMOUNTS OF ALCOHOL. 
Under usual factory conditions it is impossible to produce juices 
which are wholly free from alcohol. Grapes are carriers of yeast 
cells, and the juice itself is an ideal medium for yeasts. Moreover, 
the temperatures attained during the latter part of the pressing 
process are very favorable to conditions yielding alcoholic fermenta- 
tion. Then again, as the pressing season advances, the press beds, 
racks, press cloths, and floors of the factory become thoroughly im- 
pregnated with vigorous yeast cells. The danger from alcoholic 
fermentation is still further increased by the fact that the yeast cells 
brought in on the grapes to the air of the factory assist in starting 
fermentation wherever conditions of temperature are favorable. 
Special care was taken to discover the causes for the occurrence of 
small amounts of alcohol occasionally found in commercial grape 
juices. One possible cause is undoubtedly the fermentation in the 
fruit itself. As has been shown, however, grapes of good quality 
contain such small amounts of alcohol that this source may be dis- 
regarded. The principal cause must, therefore, be sought in the 
manufacturing process. Tables 7 and 9 show that the alcohol con- 
tent does not increase in the precipitation vessel during storage. 
Improper methods of pasteurization might, of course, cause fer- 
mentation in the trade package, but alcoholic fermentation, once 
started, would proceed very rapidly until it finally destroyed the 
package. 
A very definite development of alcohol was found to occur during 
the pressing period in one establishment. Alcohol was distinctly 
discernible by odor, and toward the end of the pressing frothing set 
in. Samples of the material were taken at the various pressing stages 
and analyzed for alcohol. Table 10 shows the results thus obtained. 
