542 SCIENCE PROGRESS 



reality it is applied to the granular products obtained when 

 the endosperm is first broken. The breaks are separated into 

 coarse semolina and coarse middhngs and the semolinas further 

 separated by wind or gravity purifiers and subsequently reduced 

 to flour which is included in the straight grade flour. All flour 

 therefore includes the semolina : this is not a special character- 

 istic of the 8o-per-cent. flour. 



The crusade has been abandoned in favour of the cry for a 

 flour containing 80 per cent, of the grain, including the semolina 

 and the germ. Such flour, it is claimed, is richer in protein, oil 

 and phosphates and is said to make a more wholesome, cream- 

 coloured loaf. From motives of patriotism and popularity, the 

 cry has also been for the exclusive use of English-grown wheat 

 to make such bread. It is true that the 80-per-cent. flour will 

 contain slightly more protein and proportionately a good deal 

 more mineral matter and oil than 70-per-cent. flour milled from 

 the same wheat but as the subsequent examination will show, 

 the percentage of chemical composition is not a criterion of the 

 nutritive value. 



From the point of view of common sense a food must be 

 judged on (i) the nutritive values of its constituents and on (2) 

 the proportion of these which are digested. Moreover, although 

 it is customary to deduce the nutritive value directly from the 

 proximate chemical analysis, it must not be forgotten that this 

 is a very uncertain way of arriving at the truth. The proteins, 

 for example, are built up of a number of separate units which 

 the chemist describes as amino-acids, etc. ; there is much 

 evidence to show that the presence of each of these units in 

 minimum quantity is necessary for the proper maintenance of 

 health. Deficiency in one unit cannot be compensated by an 

 excess of another. Proteins in foodstuff's are measured at 

 present merely by an estimation of nitrogen, which gives no 

 information whatever as to the quality of the protein. It is 

 therefore possible that in any particular food there is an excess 

 of a particular unit and a deficiency of another essential unit 

 and it is not correct to maintain that an increase in the amount 

 of protein in a particular food, as for example bread, necessarily 

 means that the body derives full benefit from it. It will be 

 obvious that the scientific valuation of food is far from being 

 a simple matter and the subject urgently requires fuller 

 investigation. 



