50 FRUITS AND FRUIT PRODUCTS. 



of these substances. Starch, if present, will be thrown down here, as 

 well as acid potassium tartrate and the calcium salts of organic acids. 

 The acid potassium tartrate may be estimated by titrating- the alkalin- 

 ity of the water-soluble ash of the alcohol precipitate after ignition. 

 The appearance of the solution as the alcohol is added in making the 

 alcohol precipitate is a valuable indication as to the presence or absence 

 of glucose or starch. In pure fruit products there is no turbidity, but 

 the pectin bodies are thrown down in a flocculent mass, while if glu- 

 cose is present there is a white turbidit}' and the precipitate is gummy. 



The test for starch was made upon all the fruits given in Table 12, 

 and in no case was there sufficient present to give an appreciable iodin 

 reaction. This point is of particular importance in its bearing upon 

 the examination of jellies, Avhere apple is so frequentlv used as the 

 basis. If it is safe to assume that starch is never present in appreciable 

 amounts in these fruits — and the work done in this laborator}^ seems 

 to warrant the assumption — then the presence of appreciable amounts 

 of starch in the fruit jelly must be due either to apple or to added 

 starch. 



Attention is called to the composition of No. 22370, which is a sam- 

 ple of wild strawberr3\ In total solids, soluble solids, ash, cane sugar, 

 proteids, and acidit}^ it runs much higher than the four samples of 

 cultivated strawberries, and in these respects, with exception of pro- 

 teids, is higher than the average of the 20 analyses reported by Stone. 

 Reducing sugars alone are lower than in the cultivated varieties. 



JAMS AND JELLIES PREPARED IN THE LABORATORY. 



Preliminary to the examination of the commercial fruit products it 

 was thought desirable to have the analyses of a number of jams and 

 jellies of known origin. Accordingly several different kinds of each 

 product were prepared and were analyzed together with the pulped fruit 

 and the juices from which they were made. The results of this investi- 

 gation are given in Tables 14, 15, 16, and 17. The fruits were prepared 

 by heating with sufficient water to prevent scorching until thoroughly 

 softened and then well pulped. The juices were obtained by draining 

 the pulped fruit, as above prepared, in a jelly bag. Neither the fruit 

 nor the juice, therefore, is normal in its content of water, but is rather 

 the material used as the basis for the jams and the jellies. The jams 

 were prepared by adding approximately^ one part of sugar to two parts 

 of crushed fruit, heating to boiling, and maintaining at this tempera- 

 ture for about twent}^ minutes. In the preparation of the jellies approx- 

 imately equal parts of cane sugar and the strained juice were used and 

 were heated to the point of boiling, which required about twenty min- 

 utes. In all cases the cane sugar, the fruit or juice, and the finished 

 product were weighed, and from these weights the amount of added 

 cane sugar in the finished product was calculated. 



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