10 FRUITS AND FRUIT PRODUCTS. 



fully noted. The interior of the can will often show blackening or 

 corrosion due to the attack of the metal by the fruit juices. This is 

 especially true of goods that have undergone some fermentation or 

 decomposition in the can. 



PREPARATION OF SAMPLES. 



FKESH FRUITS. 



Pulp the whole, well cleaned, edible portion of the fruit in a large 

 mortar, or by means of a food chopper, and mix thoroughly. With 

 small fruits the entire fruit is employed, no effort being made to 

 separate the seeds; with the apple, pear, and like fruits, the core is 

 first removed, while with stone fruits the pits are separated. If desired 

 the percentage of nonedible material ma}' be determined in a weighed 

 portion. Samples must be kept in well-stoppered bottles and in a cool 

 place. Owing to the fact that fermentation begins in a very short 

 time it is necessary to make the determinations of total and volatile 

 acidity and sugars and the polarizations at once. Portions for polari- 

 zations and reducing sugars may be weighed and an excess of lead sub- 

 acetate added. The samples may then be kept several days without 

 danger of undergoing fermentation. The remainder of the sample 

 may be preserved with about one-half cubic centimeter of formalin 

 without danger of affecting the other determinations. It must be 

 remembered that the sample so preserved can not be used for the 

 determination of reducing sugars. 



JUICES AND JELLIES. 



Prepare the juices by pressing in a jelly bag a portion of the pulped 

 fruit described under fresh fruits. Unless a clear liquid is obtained 

 either filter through a muslin filter or decant the clear portion after 

 allowing the liquid to settle for about an hour. Juices should be sepa- 

 rated as completely as possible from the pulp in order to obtain a fair 

 sample, as it is known that the first and the last pressings vary materially 

 in composition. Colby, "" of the California Experiment Station, finds 

 it advantageous in case of such fruits as apricots and prunes, which 

 are difiicult to press in the fresh state, to warm them sufficiently to 

 soften, but not to drive off* any water. After this treatment the juice 

 is much more easily separated. He considers the determination of the 

 relative amounts of juice and pressed pulp of value in comparing the 

 juiciness of such fruits as oranges, lemons, etc., and that the determi- 

 nation may to some extent serve as a guide for canners. By pressed 

 pulp is meant the material left after drawing off' the juice, consisting 

 largel}^ of fiber and water, some of the ash, and most of the insoluble 

 nitrogen compounds. 



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