FOODS HUMAN NUTEITIOIST. 365 



corresponds to about 30 per cent of the total nitrogen absorbed, rising to 40 

 per cent in tlie more biglily bleached samples. After the lapse of several days, 

 the proportion of nitrites present decreases considerably in the higher con- 

 centrations, but remains very nearly the same in the more slightly bleached 

 samples. 



"Approximately 60 per cent of the total nitrogen introduced as nitrogen 

 peroxid into the flour during bleaching can be recovered as ammonia a short 

 time after bleaching by reducing the aqueous extract of the flour with a copper- 

 zinc couple, and may be assumed to be present in the flour as nitric and nitrous 

 acids or as nitrates and nitrites. After keeping the bleached flour for some 

 days the amount of nitric acid extracted with cold water decreases. Experi- 

 ments with pure glulenin and gliadin indicate<l that in certain circumstances 

 nitric acid may be withdrawn from solution or 'absorbed' by these proteins. 



"In highly bleached flour a considerable increase in the amounts of soluble 

 proteins and soluble carbohydrates takes place. If 1 kg. of flour is bleached 

 with 300 cc. of nitrogen peroxid, the amount of soluble nitrogen is doubled. 

 This appears to be due almost entirely to the solubility of gliadin in nitric acid 

 of certain concentrations. The simultanoous increase of soluble carbohydrates 

 would seem to point to an intimate relationship between the gliadin and certain 

 carbohydrates in flour. 



"If highly bleached flour is allowed to stand for some time after bleaching, 

 the oil undergoes veiy considerable alteration and acquires the characteristics 

 of an oxidized oil. About 6 to 7 per cent of the nitrogen introduced as nitrogen 

 peroxid during bleaching is absorbed by the oil. 



"The absorption of nitrogen peroxid by flour does not appear to be ac- 

 companied by the production of free nitrogen, nor was any evidence obtained 

 of the formation of diazo-comi)ounds. 



"Sodium nitrite was found to exert no inhibitory action on the digestion of 

 soluble starch by saliva, but the rate of digestion was greatly retarded if the 

 starch had been previously treated with nitrogen peroxid gas. Bleaching was 

 found to exercise an inhibitory effect on the salivary digestion of flour." 



A report by Harden is appended. On Certain Experiments in Relation to 

 Bleached Flour carried out at the Lister Institute, in which samples bleached 

 by a commercial electrical process were used as well as overbleached samples 

 prepared in the laboratory. The data regarding the amount of nitrite- reacting 

 material in overbleached flours show "that the sodium nitrite content of over- 

 bleached flour varies very considerably with the time. It would appear prob- 

 able that the nitrous gases first of all dissolve in the water of the flour and 

 then gradually undergo a change which destroys their nitrite-reacting power." 



In grossly overbleached flours the amount found was considerably less than 

 that present in flours " treated with much less NO2, and indicates that some 

 difl'erent or more intense reaction occurs under the conditions of the prepara- 

 tion of this sample [of gi'ossly overbleached flour]." 



In tests for the presence of nitrogen in diazo-form no definite evolution of gas 

 could be observed. 



" It was found very difiicult to remove all the air from the flour and the 

 results were therefore not very accurate. They show, however, conclusively 

 that no considerable proportion of the nitrous gas goes to form diazo-compounds 

 capable of being decomposed with evolution of nitrogen by boiling hydrochloric 

 acid. The equivalent of sodium nitrite present in the flour at the time of the 

 experiment was 22.8 parts per million, so that the nitrogen obtainable by the 

 action of the corresponding nitrous acid on the proteins of the flour for a 

 quantity of 20 gm. would be 0.15 cc." 



