December, 1923
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
able effect in rapidly bringing the dough to the optimum p H for baking. Aiiother important influence of the optimum hydrogenion concentration of bread doughs is in suppressing the activities of certain bacteria other than those of the mesenteric group responsible for rope. OTHERCONSIDERATIONS There are many other aspects of panary fermentation that might be reviewed which are concerned with the effects of various agents, such as free oxygen, electrolytes, fat and other compounds, on yeast and enzyme action, as well as the interrelation of fermentation changes with the physical properties of the gluten for the retention of the gas. The study of lactic acid bacteria suitable for introduction into the dough batch for increasing the hydrogen-ion concentration is now being the subject of considerable investigation. As the tendency in baking has been to shorten the fermentation period ever since it began to adapt itself to large-scale production demands, the future probably will bring forth improvements in this direction both from the mechanical and biochemical sides. The subject in its entirety is such a broad one that many points of interest have necessarily remained unmentioned. If the impression has been created that panary fermentation offers a broad field of study for the chemist and biologist, it will have served its purpose.
1221
calories of the total 47 million million consumed. Sherman4 estimates that in the temperate zone from 40 to 75 per cent of the total calories consumed by the entire Ibopulation is furnished by cereals and breadstuffs. It is because of this. that the nutritive properties of bread should be carefully studied and efforts made to improve its nutritive qualities..
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The Role of Bread in Nutrition By Worth Hale HARVARD MEDICAL SCHOOL, BOSTON, MASS
HE importance of an adequate diet in its relation to health and growth of the laboratory animals is clearly understood. So far as animals are concerned, fairly accurate minimum requirements of fat, carbohydrate, amino acids, inorganic substances, and accessory food factors have been established. The adequacy of many individual foodstuffs has been determined and such as have been deficient have been supplemented by the diet as a whole. But among children, where the rate of growth is relatively very slow, the effects of undernourishment are less clearly defined. As a result no one attempts to establish a minimum of the individual food substances required for adequate nutrition, but rather to provide a very considerable excess as a margin for safety. Nevertheless, it is becoming more and more evident that there are many children in this country below the average in weight, height, and health, in some cases because of inherited factors, possibly more often because of faulty hygiene or because of a diet insufficient in amount or in quality. Natural foods are constantly being replaced by prepared foods, either as a matter of choice or as is necessary under conditions involving transportation, preservation, and :storage of food in immense quantity. Economic conditions limit the amount and the kind of food. “There are some children the largest item of whose diet is bread. There are numbers of children whose only breakfast is bread and coffee.”l The role of bread in nutrition is an important one. During the period 1915 to 1920 the ten-year average per capita wheat consumption for the United States rose from 5.3 to 5.8 bushels.2 This is nearly 1 pound of wheat per day per person. Some of this represents flour and cereals other than bread, but by far the larger amount is eaten as bread. I n England3 wheat and barley represent 16 million million
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1 2
8
Holt, “Food, Health and Disease,” 1922. World’s Almanac. Sarling, “The Feeding of Nations,” p 143.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Bread has been used as the sole diet of a very large series of animals, including mice, rats, and pigeons. I n the feeding tests on rodents, groups of from four to ten animals reared from the same stock, which received a diet of 40 parts rolled oats, 24 parts hominy, 16 parts meat scrap, 8 parts dried whole milk, and 1 part table salt, were fed for a period of several
Vol. 15, No. 12
The two white breads both gave some increase in weight, but later rapid declines with eleven deaths among twenty animals in spite of addition of yeast to the diet, on the seventy-ninth day. I n a later series groups of both mice and rats were fed, using, in addition to the normal laboratory diet, three white and three whole wheat breads. At the end of the experimental period of 3 months the mice on the normal diet had gained more than had any of the other groups fed on bread. However, the mice on one of the white breads (an experimental bread made with milk and an aqueous extract of wheat embryo) had made closely comparable gains in weight. I n both groups all animals were in excellent condition during the whole period. The other breads (three whole wheat and two white breads) may be grouped together as not being favorable to growth. A summary of the results appears in Table I. TABLE I-WEIGHT
CHANGES O F MICE AT 1 3 T ~WEEK OR AT DEATHOF ANIMAL IN WEIOHTDEATES BEFORE DIET GRAMS 1 3 WEEK ~ ~ Normal diet 13.0 12.4 11.6 9.9 None 10.1 9.6 None Experimental 12.2 10.3 6.5 5.0 2.9 One White 1.1 0.1 Two None 3.8 2.8 Two Whole wheat 0.8 0.4 0.3 All died Numbers in parenthesis indicate loss in weight. -GAINS
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More striking than these results on mice were those obtained using rats as the test animals. I n all cases there is a fair gain in weight during the first week or two, but after that only the control group and the group on the experimental bread continued to increase in weight. The five commercial breads were inadequate t o a surprising degree. The results may be summarized as follows:
Days
TABLE11-WEIGHT
FIG. 2-GROWTH C U R V E OF WHITE RATS:I - A ~ E R DONALDSON’S NORMAL CVRVE. I I ~ P E C I ATYPE L BREAD. 111-LABORATORY NORMAL DIET DZET. Iv-WHOLE WmAT MILK BREAD. V-BEST COMMBRCIAL Normal Experimental WHITEBREAD “WHOLEWHEAT.” VI-BEST COMMERCIAL White
months or until the death of the animal. The rate of growth and health of the animals on a bread diet were in all cases controlled by a similar group of animals on the normal laboratory breeding diet. Food and tap water, and in some cases distilled water, were given in sufficient amounts to keep the animals constantly supplied with food. Unless otherwise specified, the rats and mice were young animals, the rats approximating 50 grams, the mice 15 grams. Separate records of each individual were kept, which noted, in particular, changes in weight and in the general condition of the animal. EXPERIMENTS ON WHITEAND WHOLE WHEATBREAD I n some preliminary tests of commercial bread, two whole wheat and two white breads were selected. These were commercial breads, but one of the whole wheat and one of the white breads contained calcium as a direct addition product (as an aid to the fermentation by yeast). The other wholewheat bread was labeled to suggest the presence of vitamins. Both whole wheat breads (very probably made in 1918-of war-time flour) were far superior to the two white breads, and one of these, containing added calcium, induced a fair rate of increase in weight of 10 grams at the tenth week, which weight was maintained for 22 weeks, when the experiment was discontinued. During this period two litters of young were born though not reared. The other whole wheat bread, the trade name of which suggested the presence of vitamins, gave not quite so good initial growth, later losses in weight, four of the ten animals died, and no young were born.
CRANGES --GAINS 121 110 42
RATS AT 1 3 T ~WEEK OR AT DEATHO F ANIMAL IN WEIGHTDEATHSBEFORE GRAMS 1 3 WEEK ~ ~ 121 None 86 14 One death
OF
Whole wheat
All died
Numbers in parenthesis indicate loss in weight.
As in the case of the mice, evidences of poor nutrition, as indicated by failure t o gain in weight, are accompanied by an increase in the number of deaths. The rats, however, seemed to suffer the most,’but this may be due to the relative maturity of a mouse a t 15 grams as compared with a rat a t 50 grams, the initial weights. Younger animals always show a marked unfavorable response to an inadequate diet; older animals show a less striking response, but a t times show loss in weight or a t most a slow rate of increase. I n addition to their failure to induce growth, xerophthalmia, which is associated with a deficiency in fat-soluble vitamin A, was noted among several of the rats on the two whole wheat breads. I n the earlier series the whole wheat breads were noted t o be superior to both the white breads in the growth and health of mice, but in this series the experimental white bread was far superior while two commercial white breads (one a socalled cream bread), although much less adequate, were likewise better diets than the three whole wheat breads. Having secured so much better nutrition from the experimental bread than from the commercial breads, a third series of feeding was begun. Three experimental white breads were made with somewhat differing formula. One contained 4 per cent dried whole milk powder and an aqueous extract of wheat embryo; one, these ingredients and an increase in the protein content by adding 3 per cent peanut protein; the
INDUSTRIAL A N D ENGI NEERING CHEMISTRY
December, 1923
third was made with 6 per cent dried whole milk. Several commercial breads were fed as controls. Both rats and mice were fed, with results in general agreement with those already noted. The mice were less unfavorably affected by the less adequate bread diets than the rats. The terminal data for the rat feeding covering a 13-week period are given in Table 111.
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This bread is made with whole milk, extract from wheat embryo, and added calcium. On analysis it shows especially a higher protein content, more fat, particularly butter fat, and a higher ash content than the average white bread. The analysis shows 43.9 per cent starch, 8.9 per cent protein, 5.4 per cent fat, including 1.8 per cent butter fat. The potassium content exceeds that of the average white bread by three times, calcium by ten times, iron by two times, and phosphates by 2.5 times. Rats have made excellent gains in weight when fed on this white bread, exceeding very materially the growth already noted of those animals upon the several experimental breads. I n fact, animals on this bread diet have grown quite as rapidly as normal animals, some showing more rapid, others less rapid growth. So far as can be determined, the differences in the rate of growth are more related to the normal variation in animals from the same stock than to the diets of bread or of the mixed grains, meat, and milk of the control groups, A summary showing increases in weight of three series, each of 12 weeks' duration, is given in Table IV. TABLEIV-COMPARISONOB SPECIAL AND NORMAL DIETS ---GAIN IN WEIGHTGRAMS
DIET
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40
60
80
Days
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120
FIG. &-GROWTH CURVE O F PIGEON O N A N EXCLUSIWBREADDIET. LOWERPICTURE-POLYNEURITISO N R~~PRESENTATIVE WHITE BREAD. UPPER PICTURE-SAME ANIMAL5 HOURS LATER-AFTER BEINQ FED WHEATGERMEXTRACT
An analysis of the data in Table I11 shows, as in the second series, that the animals on a normal diet make the best gains in weight. But it is clear with this larger group of experimental and commercial breads that the three experimental breads are distinctly in a class by themselves, providing a diet on which, comparatively speaking, good growth is secured and upon which no animals died. It should be noted that one of the whole wheat breads gives distinctly better growth and maintenance than the others. (Curve V, Fig. 2) The thrce other whole wheat and the three commercial breads were very deficient from the standpoint of securing adequate nutrition from a single food substance. I n another series a whole wheat bread made with some milk gave even better growth (Curve IV, Fig. 2 ) ) indicating that milk effectively supplements wheat as an adequate food.
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The twelve rats on normal food gained 1773 grams, those on this bread 1734 grams. The weekly average gain for the rats on normal food was 12.31 grams, or those fed on bread 12.04 grams. These results are distinctly in contrast to all feeding tests made on commercial bread, either white or whole-wheat, and on experimental bread made by the addition of milk (in smaller amounts) and an aqueous extract of wheat embryo. Fig. 1 illustrates in detail the rate of growth of animals fed upon an exclusive diet of this bread (terminal data in Table IV) and on other breads (terminal data in Tables I1 and 111).
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TABLE111-ADDITIONALEXPERIMENTS ON BOTH RATS AND MICE GAININ WEIQHT7 DIET GRAMS DEATHS Normal 161 150 98 62 130 101 82 80 85 A 103 75 65 46 59 Experimental Co 84 .~ 44 58 55 56 White
I Whole wheat (1
1 16 9
1
8
10
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(5)
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(4) 10 0 (5)
Only four rats on this bread. Numbers in parenthesis indicate decrease in weight.
This comparatively good result with the one whole wheat commercial bread may be explained by the fact that it is actually made from whole wheat. The experimental white breads probably owe their better nutritive balance to the added milk and extractive from the wheat embryo. Both are essential, however, for when added to bread separately neizher gives a response equal to their combined effect. EXPERIMENTS WITH SPECIAL TYPEBREAD One commercial white bread, deserving separate consideration, has been studied to determine its adequacy as a diet.
iool
20
40
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80
100
120
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160
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FIG. 4-GROWTH. CURVE O F A WHITE RAT O N VARIOUS DIETS. VITAMIN B DEFICIENCY IN WHITE BREAD; ADEQUATE AMOUNTS IN NEW TYPE WHITEBREAD
Fig. 2 is drawn from data obtained in an experiment of longer duration with curves to show Donaldson's normal growth curve, the normal curve of the control animals, of animals fed on this special white bread, on a whole wheat bread made with some milk, and on the best of the commercial whole wheat and white breads. That this bread owes its superior growth-inducing qualities in part to an adequate amount of vitamin B is shown by feeding pigeons. On ordinary white bread, polyneuritis
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developed in about 3 weeks. The same pigeon, after having been cured by feeding vitamin B in concentrated form, remained in good health and grew normally for several months, although fed only this white bread. (Fig. 3) Similarly, of two pigeons fed on bread, the pigeon fed one of the average white breads developed polyneuritis on the eighteenth day, and subsequently died. The other has been fed this special white bread for many months with no apparent impairment of growth or health. /
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Xeropfha/mlb- D(ef Chonqed f o Specia I
20
40
60
80
Bread
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120
Days FIG. 5-GROtYTH CURVEOB A WHITE RAT. VITAMINA DEFICIENCYIN AMOUNTS I N THE NEW TYPE BREAD. ORDINARY WHITE BREAD: ADEQUATE TOP, XBROPHTHALMIA ON WHITE BREAD; BOTTOM,CURED AND NORMAL GROWTHON NSN TYPEBREAD
That vitamin B has this pronounced beneficial effect on nutrition from a diet of white bread is further shown by the fact that a diet of purified foodstuffs--starch 68, casein 18, butter fat 10, inorganic salts 4 per cent-leads to rapid loss of weight, as does also this diet mixture in which the starch is replaced by ordinary white bread. This purified diet may, however, be made sufficient for normal growth when 0.3 gram brewers’ yeas€ is added or when the starch is replaced by this new type of bread or when the whole mixed diet is changed to a diet of this bread alone. This is demonstrated in Fig. 4,which shows graphically a part of the life history of an individual rat whose diet was changed from time to time. The average commercial bread, with fat derived from vegetable sources, is necessarily deficient in vitamin A. This is shown by the development of xerophthalmia. Xot only has this not developed when feeding this new white bread, but such bread when given to animals with xerophthalmia cures the disease and induces normal growth, a contrast which is shown graphically in Fig. 5 . The increased inorganic salts may likewise play some part in the superior nutritive property of this new bread. Repeated experiments have shown that bread salts are not physiologically adequate, and that additions, particularly of calcium, to diets increase the growth response, or in the case of isolated tissues (the frog’s heart) the activity of the tissue. As a supplement to the animal tests, the cooperation of a small institution housing children was secured. The diet in
Vol. 15, No. 12
this home is rather ample and of considerable variety, so that no large changes were expected by changing the bread used. The children in the home were divided into two groups according to age and sex. To one the regular institutional diet was given, which fortunately included one of the white breads already studied on animals. The other group received the new type of bread, but in no other respect was there any change made or suggested in the diet. Of the forty-five children, thirty remained in the home several months. Measurements without clothing were made every 2 weeks. The test was discontinued a t the end of 9 months. The eight boys on the ordinary white bread gained 4.26 pounds more than the expected gain a t their age, averaging 0.53 pound more for each child. The similar group of seven boys on the special bread gained 6.33 pounds more than was t o be expected during the same period and age-an average gain over the expected rate of 0.90 pound for each child. The girls in both groups made larger gains than the boys, which suggests that the total calorie intake was low and affected the more active _. boys to a greater degree. Of the group of sevm girls on ordinary white bread each gained F.28 pounds mor; than the expected average, while of the group of eight girls on the special bread each averaged 2.46 pounds greater gain, and this in spite of the fact that one of these girls, mentally backward and losing weight, is included in the latter group. To exclude this individual the gains would be 2.28 in one case and 3.28 in the other. The numbers are too small for one to venture conclusions, but the fact remains that, in spite of small numbers and with only about 700 calories of the total diet changed, the special bread groups consistently made better weight increases. This new type of white bread clearly stands in a class by itself. Not one of the other breads begins to compare with it as a well-balanced food. Much of that which wheat had lost in the milling and refining process has been returned t o the bread in concentrated form. The proteins of the wheat have been supplemented and made adequate by the addition of a natural food product, milk. It is significant that the full nutritive value of bread, the fundamental criterion of excellence of bread, is being developed in that industry which supplies nearly one-third the calories in one’s daily food!
Symposium o n Heat Transfer As previously announced, a Symposium on Heat Transfer will be held a t the spring meeting of the AMERICANCHEMICAL SOCIETY, under the auspices of the Division of Industrial and Engineering Chemistry A number of papers are in preparation by writers well versed in various applications of heat transference. These papers may be classified as follows: 1-Heat Losses by Radiation plus Convection, through Bare and I n sulated Surfaces ( a ) From Pipes ( b ) From Furnace Walls (c) From Miscellaneous Shapes or Cooling of Noncondensable Gases 2-Heating ( a ) The Warming of Air in Hot-Blast Heaters 3-Heating or Cooling of Liquids Flowing inside Pipes ( a ) Water ( b ) Oils 4-Condensation ( a ) I n Surface Condensers and Water Heaters 5-Evaporation (a) The Analysis of Certain Comparative Tests on Evaporators (b) Heat Transfer in Enameled Apparatus 6-Miscellaneous Topics { a ) “A Heat Meter” (b) T h e Determination of Air in Steam, and the Importance of This Factor in Heat Transmission
In order that those interested may have ample time to prepare discussion of these papers, advance copies bound under one cover will probably be issued. To this end i t is necessary that the complete manuscript be in the hands of the chairman, W. H. McAdams, Massachusetts Institute of Technology, Cambridge, Mass., not later than January 15, 1924. ERLEM. BILLINGS, Secretary
