CHEMICAL COMPOSITION OF GRAPES 429 



The data illustrate the difficulty of selecting five-pound lots of the 

 same variety that will represent average samples. 



5. Effect of Location of Berries on the Bunch. All of the bunches 

 of the first crop were taken from two Muscat vines. The bunches 

 were cut into top and bottom halves. These lots were crushed sep- 

 arately, pressed, and the juices analyzed. 



TABLE 5 EFFECT OF LOCATION OF BERRIES ON BUNCH 



Sample Balling Acid 



Vine no. 1, stem end of bunch 23.6 .76 



Vine no. 1, apical end of bunch 22.7 .87 



Vine no. 2, stem end of bunch 21.3 .92 



Vine no. 2, apical end of bunch 21.3 .93 



The results show that considerable variation in composition of the 

 berries may exist within the same bunch. 



6. Effect of Thoroughness of Pressing. About ten pounds of Mus- 

 cat grapes were crushed and lightly pressed. The pulp and skins left 

 from this pressing were then thoroughly crushed and pressed a second 

 time. The juices from the two lots were analyzed separately. 



TABLE 6 EFFECT OF THOROUGHNESS OF PRESSING 



Sample Balling Acid 



First pressing 22.8 .78 



Second pressing 22.8 .79 



There was practically no difference between the juices from lightly 

 and thoroughly pressed grapes of the same lot. 



The data from the above six tests indicate that it is a very difficult 

 matter to select grapes that will represent a fair average sample of 

 the grapes to be studied. The size and age of the vine, the side of 

 the vines, the location of the bunch on the cane, and individual vines, 

 all affect the composition of the juice from the grapes very materially, 

 and these factors should be taken into account when samples are 

 taken. 



Preservation of Samples and Preparation for Analysis. In 1914 

 the samples of juice were preserved with HgCl 2 , 1 :1000. In 1915 and 

 1916 the samples were sterilized at 100 C. Before analysis the bottles 

 were heated to 100 C for an hour to dissolve any cream of tartar which 

 might have separated. The juices were filtered before analysis. Con- 

 siderable coagulation of dissolved solids took place during sterilization. 



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