POODS HUMAN NUTRITION. ^3 



and lessened the action of amylolytic and proteolytic enzyms, the retarding 

 action being very great in the presence of quite minute amounts of nitrites. 



" Seeing that nitrous acid and its salts produce no known chemical action 

 on starch, their inhibiting action on its digestion by amylolytic enzyms can 

 only at present be explained by their action on the enzyni. 



" But in the case of protein there are two possibilities, action on the enzym 

 and action on the substrate (protein)." 



From further studies of this question the author concludes that " the presence 

 of nitrous acid (even in the comparatively innocuous form of a salt) hinders 

 enzym action. 



" Previous treatment with nitrous acid alters a protein in such a way as to 

 render it less readily susceptible to the solvent action of digestive juices." 



Similar results to those with starch were obtained in salivary digestion of 

 sami)les of bleached Hour. 



In studies with separated gluten the comparative indigestibility of that from 

 bleached specimens of flour was marked. The decrease in digestibility was not 

 proportional to the amoimt of nitrite-reacting material i»resent in the flour. 

 " From this one would judge that the main deleterious action is exerted by the 

 nitrous fumes while in contact with the flour, and the diminution of digesti- 

 bility does not depend on the more or less accidental quantity left behind. . . . 



" The results obtained by those who have had the opportunity of examining 

 the breads show that the lessening of digestibility of the bread is less marked 

 than it is in the flour. This appears to be partly due to the reduction of the 

 amount of nitrite-reacting material which occurs during baking, and in refer- 

 ence to the protein (gluten) one can only suggest that the process of baking 

 increases the difficulty of digestion of that substance even in unbleached speci- 

 mens, so that any difference in digestibility between a loaf made from it and 

 one made from bleached flour would not be so noticeable. It can hardly be 

 doubted that this, which after all is the most important question from the stand- 

 point of the consumer, has had considerable influence with judges in deciding 

 as they have that the objection to artificial bleaching is more or less theoretical. 

 But knowing as we do the possible practical dangers which might ensue were 

 millers allowed a free hand in the use of the vei-y strong reagent they employ, 

 it is necessary that a strict watch should be exercised to keep its use within 

 the limits of safety." 



Flour bleach.ing, its relation to bread production and nutrition, J. A. 

 Wesener and G, L. Teller {Jour. Indus, and Engin. Chem., 1 {1909), No. 10, 

 pp. 700-711). — To secure data regarding the effects of bleaching on flour an 

 experiment of 11 weeks' duration was undertaken, in which bread and biscuits 

 made from bleached and unbleached flour were fed to rats. The composition 

 of the flour before and after bleaching was determined and data regarding the 

 yield of bread, the size and quality of the loaf, and other similar information 

 were recorded for the 2 sorts of flour. 



The authors state that even in the short process of bread making followed 

 the nitrites of the bleached flour were in many instances entirely removed. 



At the end of the period a number of rats from each lot were dissected. A 

 second test with rats, covering a period of several months, was also made but 

 the data are not reported, the general findings, according to the authors, being 

 substantially the same as in the experiment referred to above. " There were 

 noticed no nutritional disturbances of any kind, and the post-mortem examina- 

 tion showed no lesions which in any way could be attributed to the bread made 

 from . . . [bleached] flour. In addition to the feeding experiments conducted 

 with the rats, we have fed the guinea pigs, which we have always on hand for 

 experimental purposes, bread from bleached flour covering a period of more 



