1917] FOODS — HUMAN NUTRITION. 861 



class of wheat, the averages for each class show considerable differences be- 

 tween the various classes when considered as a whole. Given in order from 

 weakest to strongest, the classes are soft white, soft red winter, durum, hard 

 red winter, and hard red spring wheat. 



"The average loaf volume in cubic centimeters for each of these classes is 

 soft white wheat, 1,909 ; soft red winter, 1,965 ; durum, 2,070 ; hard red winter, 

 2,219; and hard red spring, 2,421. In the matter of texture the several classes 

 stand in the same order, except that soft red winter has a slight advantage over 

 durum wheat. 



" Of the four more important classes of wheat under consideration, durum is 

 the highest in crude-protein content; hard red spring, second; hard red winter, 

 third ; and soft red winter, fourth. High crude-protein content as a rule is 

 accompanied by high strength, but the relation between these two factors 

 varies with the different classes of wheat and extremely high crude-protein con- 

 tent is sometimes accompanied by a decrease in baking strength. 



" The average water absorption of the flour from durum and from hard red 

 spring wheat is about the same, and that of hard red winter is only slightly 

 lower. The water absorption of the soft wheats averages from 3 to 4 per cent 

 lower than for the hard wheats. The range of water absorption of each class 

 varies within wide limits. There is a direct relation between the water 

 absorption of the flour and the bread yield of a unit quantity of the same. As 

 a rule, the higher the absorption the greater the weight of the loaf." 



Wheat and flour investigations, V, G. A. Olson {Washmgton Sta. Bui. llflf 

 {1911), pp. 12-86, figs, i^).— Cintinuing previous work (E. S. R., 26, p. 7.S8), 

 two of the three studies reported had to do with the baking quality of flour 

 and the third with the milling value of water-soaked wheat. 



In the first study a comparison of the results of the chemical and baking 

 tests of flours from 12 States included offer evidence for the belief that there 

 is no relation between the quality of flour and the total nitrogen, alcohol- 

 soluble protein components, gluten content, water-soluble solids, and acidity. 

 " Neither were relations between the gluten content and the water-retaining 

 qualities of flour observed." 



"Although no conclusions could be drawn, the volumes of the loaves appeared 

 to be inversely proportional to the gluten content. A loaf of bread having an 

 apparent specific gravity 0.25 or less may be regarded as a satisfactorily baked 

 loaf." 



With respect to the influence upon the baking quality of the removal from 

 flour of water-soluble, alcohol-soluble, and salt-free extracts, and of the addi- 

 tion to flour of electrolytes, the following conclusions from the data are reported : 



"The irregularities noted in the nitrogen-free and ash-free extract content of 

 flours giving the same and different volume capacities indicate that the nitrogen- 

 free and ash-free extracts do not bear the relation to volume that would be 

 expected according to theory. 



" There is strong evidence supporting Wood's theory that the ratio of soluble 

 ash to total nitrogen determines the shape of the loaf. Our experiments indi- 

 cate that the nature of the electrolytes contained in the soluble ash may have 

 something to do with the property of shape, and this may account for the 

 irregularities noted. 



" The baking quality of flour was not perceptibly affected by the addition of 

 lactic acid at the rate of 0.54 gm. per 100 gm. of flour ; the addition of the men- 

 tioned amount of acid, however, did affect the amount of gluten that could be 

 separated from the flour. The significance of modifying the quality of the 

 gluten and its unnoticeable effect upon baking quality should not be overlooked. 



