JAMS. 58 



show a hig-h percentag'e of iuvxr.sion as well a.s a high acidity. The 

 crabapple jelh' is a striking- exception. Its acidity is v^ery low, yet 

 the amount of inversion is high. 



The invert polarizations of the jams at SC)^ are peculiar in that 

 the}" are strongh' positive, with two exceptions, while the same read- 

 ings made on the fruits, juices, and jellies are either zero or negative, 

 with the exception of plum juice and mixed fruit jelly. The cause of 

 this change has not been worked out, but it is probable that some of 

 the insoluble matters of the fruit have been changed to soluble, 

 optically active bodies by the continued heating of the jams. 



Tables 16 and 17 show to very good advantage the relative amounts 

 of protein present in the jams and the jellies. The average content of 

 protein for the eight jams given is 0.468 per cent, Avhile for the corre- 

 sponding jellies the protein content is only 0.230 per cent. In no 

 case is the content of protein sufficiently high in the jelly to interfere 

 with the detection of added gelatin ])y the simple method of deter- 

 mining the nitrogen content. 



COMMERCIAL FRUIT PRODUCTS. 



The fruit products examined have been divided into jams, jellies, 

 canned fruits and miscellaneous fruit products, brandied fruits, fruit 

 butters, and marmalades. The meaning of the term "jelly" is well 

 understood, but there is considerable difference of opinion regarding 

 the definition of jams and marmalades. Undoubtedly the usage varies 

 in different parts of the countr}" and with different manufacturers. 

 Products in every respect similar with trade names and secret formulae 

 for their preparation, are often represented as entirely distinct prod- 

 ucts. But for the sake of convenience in comparison and discussion 

 in the following tables jams include marmalades and fruit products in 

 which the pulped fruit is reduced to the consistency of a jam. The 

 term ''brandied fruits" needs no explanation. Fruit butter is the 

 boiled-down fruit juice containing some of the pulp, but as a rule no 

 sugar is added. In the preparation of this product the methods may 

 vary widely in different sections of the country, depending upon the 

 kinds of fruit available. In case sour apples are employed, cane sugar 

 may be added, while if sweet apples are used an addition of cane sugar 

 will not be necessar3\ 



.TAM8. 



Discussion. — Anal3^ses of 96 samples of jams were made. Of this 

 numl)er, 86 were commercial products and 10 were prepared in the lab- 

 orator^^ Of the conunercial jams, 18 samples, less than 20 per cent, 

 contained no glucose, 58 contained glucose, but were not so labeled, 

 and the remaining 15 were purchased as compound goods. The jams 

 are arranged according to the above classification in three sets of tables 

 which follow the discussion of this subject. 



