18 BULLETIN 656, U. S. DEPARTMENT OP 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 rim 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. 



