476 



NA rURE 



[October 14 1909 



but this is not a true index of strength. It is the gas 

 evolved in the later stages of panary fermentation which 

 is of importance, and the gas-retaining power ot the 

 dough which is the most important factor in strength. 

 This is apparently a function of the quality of the gluten, 

 and dependent on the proportions of various acids and 

 salts which affect the physical properties of the gluten. 



Dr. E. F. Armstrong followed with some notes on the 

 chemical properties of flour and an. account of the recent 

 work on ■ strength. Flour is composed of (i) starch ; 

 (2), several kinds of proteins; (3) mineral matters present 

 only in small quantity ; (4) a little sugar ; (5) a little fat ; 

 (6) moisture ; (7) enzymes. It has been the object of the 

 chemist to seek to correlate the chemical properties with 

 baking qualities. Most attention has always been paid to 

 the gluten of flour ; generally the strongest' flours have the 

 most gluten, but this test is not absolute. Attention has 

 further been directed to measuring the quality of the 

 gluten either by physical or chemical means, such as the 

 amount of water it will retain or the proportion of gliadin 

 in it. The total nitrogen of a flour is another rough 

 indication of quality ; latterly the distribution of nitrogen 

 in its various forms has also been studied. To make a 

 light _ loaf the flour must be one which w-iU give rise to 

 sufficient gas during fermentation ; it must contain enough 

 diastatic enzyme or have its starch in a form which "is 

 easily attacked. Whymper has found that the largest 

 starch grains are those first attacked by enzymes, and it 

 appears that different flours contain different proportions 

 of large starch grains. The mineral matters and enzymes 

 of flour are likewise of the very greatest importance in 

 affecting quality. 



Mr. W. B. Hardy, who followed, dealt with the influence 

 of the minerals of flour on its quality. Gluten owes its 

 tenacity and elasticity to the presence" of salts and acids 

 in certain proportions, pure gluten having no tenacity. 



Prof. R. Harcourt, of Guelph, directed attention to the 

 comparative milling and baking qualities of a number of 

 Canadian wheats. Though the Manitoba spring wheats 

 do not contain more gluten than the Alberta winter red 

 wheats, they give a better yield of bread and a larger 

 loaf. Blends of Alberta red with soft Ontario winter 

 wheats give a flour superior to either of the constituent 

 flours baked singly. This confirms the common practice 

 of English millers. The discussion then turned to the 

 breeding of wheats. Dr. C. Saunders gave a most valu- 

 able account of wheat-breeding e.xperiments in Canada, 

 and a highly suggestive paper on the influence of good 

 seed on wheat production was read bv Prof. C. .\. Zavitz. 

 A paper by Prof. L. S. Klink dealt' with individuality in 

 plants. A general discussion of great interest followed, 

 and it was subsequently agreed bv the general committee 

 that the discussion be printed in full in the report of the 

 meeting. 



Tuesday, August 31, was devoted to a joint meeting 

 with _ the representatives of physiology and agricultural 

 chemistry to consider the subject of "food." The views 

 developed were of the verv greatest importance, more 

 especiallv as indicating the lines on which future work in 

 this field should proceed. .Mter some introductory remarks 

 by the chairman, a paper on "Proteins: the relation 

 between composition and food value," was read by Dr. 

 E. Frankland .Armstrong. The quotient of the amount 

 of nitrogen in a food material multiplied by the factor 

 6J is commonly spoken of as protein without any refer- 

 ence to its nature, although it has long been realised that 

 proteins of different origin are not the same. The proteins 

 have been proved in the main to be built up of amino- 

 acids, belonging both to the aliphatic and aromatic series, 

 or derived from cycloids containing nitrogen, of oxvamino- 

 acids, and of diamino-acids. In different proteins these 

 structural units are present in vnrving nroDortions, and. 

 since the amino-acids are very different from one another 

 in their chemical structure, it must be supnosed that they 

 each fulfil somewhat different functions in building up the 

 tissues of the bodv. It thus becomes important to see 

 that each is suoplied in the prooer proportions required 

 by the body. Further, the analytical results point to the 

 irnpossibility of entirely replacing a diet composed of one 

 kind of protein — for example, meat — by another diet com- 

 posed, let us say, of nuts, since the two proteins, though 

 NO. 2085, VOL. 81] 



made up of the same structural units, contain these in 

 entirely different proportions. 



It remains to solve such problems as the precise func- 

 tion and significance of each amino-acid in metabolism, 

 how far they may replace one another or be absent 

 altogether ■ without injurious effects ; further, to what 

 extent each is concerned in the maintenance of a particular 

 tissue. Probably the presence of most, if not all, of 

 them is necessary in a food if health is to be maintained. 

 Tryptophane, for example, has been .shown to be essential 

 by VViUcock and Hopkins. The ideal diet should contain 

 as much variety of protein as possible in order to provide 

 sufficient of all the possible units of constructive 

 metabolism. 



Prof. Starling, F.R.S., suggested that it was possible to 

 attach too much importance to protein as a mere source 

 of nitrogen. In reality, four-fifths of the protein of food 

 is not connected with the nitrogen question. Proteins may 

 decompose in two ways ; in the one nitrogen is immedi- 

 ately eliminated, and a residue produced which contains 

 as much energy as the fats or carbohydrates, and furnishes 

 this energy on o.xidation. Only a small amount of the 

 protein is built up into the body. .A protein diet is never 

 stored as fat, neither is the above-mentioned carbonaceous * 

 residue stored as fat. h. protein meal is followed by a 

 large output of carbon dioxide and intake of oxygen, the 

 residue being more easily o.xidised than the original pro- 

 tein. The value of proteins as a food is due to this, and 

 it is important that the fate of the residue in the body 

 sh.ould be investigated. 



Proteins also undergo decomposition in another manner, 

 namely, the carboxyl group is eliminated and amines are 

 formed. These amines have a marked physiological action ; 

 for example, those from tyrosine and phenylalanine have 

 an action like tliat of .adrenalin. \ big meat-eater usually 

 has a high blood pressure, whilst the constant formation 

 of such amines causes the various disorders of middle age. 



Dr. E. J. Russell, of the Rothamsted Experiment 

 Station, next dealt with the problems of the stock feeder, 

 who asks for methods by which he can determine the 

 relative food value of various agricultural products. Ex- 

 perience has shown that animals fed on barley meal or 

 cotton cake singly do not do so well as those fed on a 

 mixed diet of both ingredients. K single food is not 

 enough, but it is not known what the ideal mixture should' 

 be. Swedes grown on chalk loam have not the same 

 feeding value as those grown on sand. There is a similar 

 difference in the value of grasses grown under substantially 

 the same conditions. Fibre is of very little value as a 

 food — it acts merelv to distend the stomach. The mineral 

 constituents are of great importance, and may account 

 for some of the facts recorded. Pigs fed on maize give 

 a low-grade bacon ; a diet of maize and minerals gives a 

 better bacon ; and the best article is obtained by feeding 

 with barley meal. The food has an effect on the character 

 of the beef and on the production of milk. Cotton cake,' 

 for instance, causes the production of milk, whereas with 

 linseed cake the cows lav on flesh instead of producing 

 milk. Prof. Cushnv, F.R.S., alluded to the influence of 

 taste and the imoortance of the mineral constituents. 



Mr. F. T. Shutt d-^scribed some experiments on pi,ff- 

 feeding. The Canadian pork was originally found 

 to be too soft for the packers owing to the quality of 

 the fat. This was got over by the addition of skim 

 milk, which, together with corn, was found to afford an 

 ideal diet. \\\ increase in the proportion of corn softens 

 the fat ; too much actually kills the pigs. The fat of the 

 animal and of the cereal Is stated to be the same. 



Dr. F. N. Alcock alluded to the changes in the habits 

 of the women of the upper middle classes during the last 

 fifty years. ■ Their diet to-day contains less protein and 

 less malted liquors, and this is probably to be associated 

 with the fact that they no longer have large families or 

 are able to nurse their offspring. Infants commonly get 

 too little protein, which necessitates that thev receive only 

 a minimum auantity of some — probably essential — residue. 



Prof. J. Wilson indicated in historical sequence the 

 views which had in turn prevailed on the feedinr? of stock. 

 In early days the cattle practically starved during the 

 winter on a large amount of straw, and had no energy 

 left in the spring. K great improvement was experienced 



