POODS — HUMAN KtTTRITlON. 461 



Contribution on the chemistry and physics of jelly making, Nellie E. 

 GoLDTHWAiTE {JouT. Iiidus. aiul Engiti. Chcm., 1 (1909), AVv. 6, pp. 333-3^0). — 

 In the experiments which are reported the effect of addiuj? sugar and organic 

 acids to fruit juices in jelly making was studie<l, as well as the relation of 

 boiling point and specific gravity, and the possibility of making jelly of good 

 texture from an artificial fruit juice made of tartaric acid, sugar, and pectin 

 isolated from fruits. 



According to the author's summary, " the essential constituents of a jelly 

 making fruit juice are, first, pectin; second, acid. 



''A desirable accessory constituent is cane sugar. Too much sugar is likely 

 to be used in jelly making with a consequent deterioration of the quality of 

 the jelly. The amount of inversion preferably produced in this cane sugar is 

 yet undetermined. 



"Over-dilution of fruit juice should be avoided, since this leads to the use 

 of too much sugar; probably the extra boiling thus rendered necessary also 

 impairs the texture of the jelly. 



" The physical constants of hot juice ready to jelly on cooling are, substan- 

 tially, boiling point 103° C, and specific gravity 1.28. 



" Jelly is readily made through boiling pectin with acid, water, and sugar. 



" Jelly making seems to consist in so controlling conditions by means of acid 

 and sugar and boiling as to cause the pectin to be precipitated in a continuous 

 mass throughout the volume allotted to it." 



As regards the production of artificial jelly, the author states that jelly of 

 excellent quality was easily prepared from a 1 per cent solution of pectin 

 (isolated from fruit juices by means of alcohol) and 0.5 per cent solution of 

 tartaric acid, adding to the mixture, heated to boiling, f volume of sugar, and 

 continuing the boiling until jelly was formed on testing. " The total time of 

 boiling did not exceed 15 minutes. Jellies made as above were nearly colorless, 

 but were excellent in texture and taste. When a few cubic centimeters of grape 

 juice were added to the pectin solution the color of the jellies was very pleasing. 

 That these jellies were not made directly from fruit juice would not be sus- 

 pected from taste or texture. Jellies equally good were made in this way from 

 the pectin from sweet apples, ci-ab apples, and peaches. This last fact would 

 seem to indicate that the pectin of peaches does not differ materially, at least 

 from a practical standpoint, from that of other jelly making fruits. 



" It may be of interest to add that pectin was extracted from jelly (the jelly 

 being previously dissolved in an equal volume of water) by the method used 

 for extracting pectin from fruit juices. This pectin apparently corresponded 

 in its physical and chemical characteristics with that extracted directly from 

 fruit juices. Good fruit jelly invariably gives the alcohol test for pectin. 

 These facts would seem to indicate that pectin in the formation of jelly does 

 not undergo any deep seated change, but rather that the phenomenon of jelly 

 making is more nearly physical than chemical." 



Discoloration of canned goods, E. W. Duckwall (Caniier and Dried Fruit 

 Packer, 28 (lOU'J), No. 21, pp. 29, 30). — The examination of numerous samples 

 of canned goods led to the conclusion that discoloration is in the majority of 

 cases caused by metallic sulphids, formed by the action of hydrogen sulphid. 



" The sources of the hydrogen sulphid may be bacterial action due to insuflS- 

 cient sterilization, production of hydrogen sulphid through decomposition of 

 proteids by action of steam under pressure, as in a heavy process, or by the 

 reaction of sulphids with vegetable acids or with mineral acids which may have 

 accidentally gained entrance to the container. The heavy metals, of course, 

 with which the goods come in contact are the tin and lead of the solder and 

 the tin plate and the zinc from the flux used, though the sulphid of zinc is not 



