240 THE VITAMINES 



of this vitamine by alkalis, Daniels and McClurg (654) stated that 

 they observed no destr iction of cabbage and soya beans so treated. 

 It is possible, however, that the latter investigators fed too much 

 of the active material. According to Daniels and Heisig (655), the 

 effect of the addition of soda upon vitamine C was deleterious. In 

 this connection, Hess and Unger (656) point out that soda is used in 

 the preparation of proprietary infant foods. This is true also of 

 commercial cod liver oil emulsions, which give an alkaline reaction, 

 and to which soda is added in order to obtain a better emulsion. Yet 

 we have no exact experiments to show whether the activity of the 

 above emulsions is affected by the manner of preparation. Experi- 

 ments started by us have not yielded any definite results up to the 

 present. We must say, however, that the vitamine A of cod liver 

 oil must be quite resistant in order to withstand the treatment 

 undergone during the process of manufacture. 



It has often been stated that the stability of orange juice is 

 explained by the acid reaction of the medium. Still, according to 

 the findings of Delf (I.e. 651), the neutralization of the juice did not 

 ha.ve any harmful effect. 



Summing up the subject matter of this important chapter, we may 

 say that the stability of the vitamines on heating depends not on 

 the temperature but on the duration of the heating. In this respect, 

 the view of Givens and McClugage (657) is of interest; they believed 

 that when antiscorbutics are heated at a low temperature for a long 

 time, as in gradual drying, the ferments contained in the tissues 

 destroy the vitamine. If the ferments are inactivated by rapid 

 heating at high temperatures, then vitamine C is much more resist- 

 ant. These statements naturally require further corroboration. 3 

 Aside from this, the vitamines seem to be more stable in the natural 

 condition than in the form of extracts or pressed-out juices. Oxidation 

 plays a big part in the destruction of vitamines A and C, while the 

 chemical reaction of the substrate plays a part in the destruction 

 of all the vitamines. 



3 This behavior may be brought into relationship with the stability in 

 acid solution, if it is assumed that these ferments act in alkaline solution; 

 we have in mind here the oxidases, the action of which is delayed in acid 

 medium. 



