April, 1932
I \ D C S T R I 4 L A4hD E N G I S E E H I N G
from the dry-ashing procedure. The authors were not able to demonstrate a loss of added aliiiiimum in smoke evolved in ignition of various materials. An investigation was made of the removal of iron, which interferes by Of The effected very completeJ but the 'lethod was cumbersome and required an ashing procedure to remove the excess of cupferron. Iron is not removed completely by centrifuging, but, by adsorptive filtration through two filter papers, the mercaptoacetic acid test becomes uniformly negative. A study of the interference of silica in colorimetry reveals that it is sufficiently removed by dehydration so that hydrofluoric acid treatment is unnecessary. The absolute quantity of aluminum present in a given tissue, of course, cannot be determined by any method. Recourse must therefore be had to experiments on the recovery of added aluminum to prove the accuracy of a method. A well-mixed sample of ground beef liver showed, after the manipulations of grinding and mixing, 5.0 p. p.m. of aluminum. When 0.05 mg. of aluminum was added to 25 grams of the beef liver (yielding 0.125 mg. of aluminum), making a total apparent aluminum content of 0.175 mg. before asbing, 0.1785 and 0.1725 mg. were recovered. When the aluminum was added to the ash, 0.1725 and 0.1715 mg. were recovered. The reader is referred to the articles cited (2, 5 , 6, 9) for other details of technic and for the underlying principles of the method. Other articles in this series ( 3 , 4) haye been
CHE3fISTRY
105
published, and further contributions will follow. Copies may be obtained by addressing the senior author. ACKNOWLEDGMENT In the developnlent of this method W. N, Bradley, Alary L. Dodds, L4,D. filelavan, F. J , Murphy, and Ilelpn B. Jvigman have rendered technical assistance. The authors also wish to acknowledge their indebtedness to G. D. Beal, R. R. Bridges, and F. C. Frary for many helpful suggestions. . LITERATURE CITED (1) Lyons, E., J . Am. Chem. SOC.,49, 1916 (192i). (2) Myers, V. C., Mull, J. TV., and Morrison, D. B., J. H d . Chern , 78. 595 (192s).
(3) Schwartze, E. W:, Murphy, F. J., and Cox, G. J . , J N u t r i t i o n , 4, 211 (1931). (4) Schwartze, E. IT., Murphy, F. J., and Hann, R. M., Ibid,, 2, 325 (1930).
(5) Thrun, W. E., J. Phys. Chem., 33, 977 (1929). (6) Underhill, F. P., and Peterman, F.I., B m . J. Physiol., 90, 1 (1929).
(7) Winter, 0. B., J. Assoc. Oficial A g r . Chem., 13, 220 (1930). (8) Winter, 0. B., and Bird, 0. D., J. Am. Chem. Soc., 51, 2964 (1929). (9) Winter, 0. B., Thrun,
W. E., and Bird, 0. D., Ibid.. 2721 (1929).
RECEIVEDJanuary 18, 1932. Present addresses of authors are a8 f o l l o w : E. W. Schwartze, hledical Department, University of Georgia, Auguata, Ga.; R. M. Hann, National Institute of Health, Washington, 13. C.;R. B. Unangst, Aluminum Co. of America, New Kensington, Pa.; J. L. Neal. 1125 W Onondaga Si..Syracuse, N. Y
e,...
11. Aluminum Content of Foodstuffs Cooked in Glass and in Aluminum GEORGED. BEAL,RICHARD B. UNANGST,HELENB. WIGMAN,AND GERALDJ. Cox Mellon Institute of Industrial Research, Pittsburgh, Pa. XECESSARY qualificaFoods cooked in glass and in aluminum hate pected (phosphorus starvation) been analyzed for aluminum, and the average when overwhelming doses of tion of all materials that soluble aluminum salts are fed come into contact with increase has been calculated. The taking up of have also been described ( 3 ) . I n food during its production, disaluminum by neutral foods is negligible: acid the present paper a study of the tribution, cooking, or service is that they must not in any way and alkaline foods are relatively more corrosive. amounts of a l u m i n u m which depreciate the q u a l i t y of the I n no case, howecer, is suficient aluminum disenter foods by contact with alufood. Primarily, it is not persolced from utensils to interfere seriously with minum in a variety of culinary missible that any essential conphosphorusabsorption. average daily intake practices will be recorded. In every case the amount of alumiof the food be removed of aluminum in case all foods are cooked in or any harmful substance added. num added to foods by utensils Of secondary importance is the aluminum is estimated at mg.9 of which made of it has been found to be requirement that a specific un5 mg. is deriz\ed,fromthe utensils. small and far below that necesdesirable taste or odor should sary to produce p h o s p h o r u s not be imparted and that a discoloration should not be pro- -starvation and its sequelae, the only abnormal conditions which duced in foods by containers during any of the operations the authors were able to cause by administering to experimentioned. It is, of course, also of importance that the utensil mental animals excessively large doses of aluminum. be inert to corrosion by foods in order that it survive use in PREVIOUS STUDIESOF ALUMINUM CORROSION cooking. Aluminum is today the most popular of all materials for the A few quantitative and many qualitative studies of the construction of cooking utensils because of its light weight, corrosion of aluminum by foods have been made, especially in bright attractive appearance, durability, high heat conduc- European laboratories. The latter have consisted of observativity, and ease of cleaning and maintenance for constant use. tions of pitting, polishing, or staining of aluminum surfaces This wide popularity of aluminum after about thirty years exposed to foods; of precipitates in water and clear liquids; of employment is convincing evidence that it is satisfactorily of discoloration of foods; and of alleged changes in taste. resistant to food attack, and that no harm results from eating Occasionally, chemical demonstrations of the presence of foods customarily prepared in aluminum vessels. It has aluminum in the food have been mentioned. Most of these been shown elsewhere (14) that only barely (detectable reported findings, both qualitative and quantitative, are of amounts of aluminum appear in the tissues, following diets little value now, as they were obtained by the use of articles containing large amounts of aluminum; the results to be ex- constructed of various grades of early commercial aluminum
A
IXDUSTRIAL AND ENGINEERING CHEMISTRY
406
Vol. 24, No. 4
I. ALUMINJUMCOXTENT OF FOODSTUFFS COOKED IN GLASSAND IN ALUMINUM ALUMINUM ALUMINUM CONTENT Av. CONTENT AT. D U R A -Cooked Cooked INCREASE D U R A -Cooked Cooked INCREASE TION OF in in IN ALUMIrIox OF in in I N ALUMIFOODSTUFF COOKIBGElass aluminum NUM R E ML R K S FOODSTVFF COOKINQd a a s aluminum NUM Min. P . p . m. P . p . m P p m Win P . p . m P . p m P p m Fried bacon 5 0.25 0.68 Creamed onions 30 0 50 1 10 0.26 0.68 0 43 1 11 0 61 TABLE
Boiled ham
120
Beef pot roast
120
Creamed chicken
120
Beef soup stock
150
0.78 0.78
2.1 2.1
1.32
0.64 0.64
0.87 0.86
0 23
0.95 0.98
2.43 2.28
1 39
0.16 0.16
0.39 0.39
0 23
\Teat on11 and proportional part of gravy
5 minutes dripping
Creamed celery
20
1 00 1 00
1 57 1 57
0 57
Creamed cabbage
45
0 37
2 76 2 80
2 41
Creamed cabbage
45
0 34 0 34
Creamedcauliflower 20
0.64 0.64
2 10 2 12
1 47
Cranberry sauce
0 53 0 54
7 90 7 90
7 36
Bright pan uithout sugar
0.62 0 63
3.12 3 20
2 54
Bright pan sugar
5
0.097 0.097
0.38 0.38
0 28
Percolated coffee
15
0.25 0.25
1.03 1.03
0 78
Boiled potatoes, whole
30
0.26 0.25
0.25 0.27
0
Cranberry sauce
Boiled potatoes, skin removed
30
0.55 0.54
1.10 1.10
0 55
150
1.51 1.43
9.13 8.28
Stewed tomatoes
20
0.12 0.12
4.36 4.20
Stewed tomatoes
30
0.14
15.3 15.6
Sauerkraut
45
0.83 0.83
16.4 16.4
Green beans
90
0.91 0.91
2.28 2.28
1 37
Navy beans
180
1.44 1.44
3.60 3.60
2 16
0.57 0.58
0.74 0.74
Drip coffee
Oatmeal
Beets
150
time
4.16 15 3
Cranberry sauce Cranberrs sauce
7.24
Bright pan Dark pan
15 6
0 16
which, because of impurities and methods of fabrication, were more susceptible to corrosion than the high-grade metal used in modern cooking utensils. Two types of quantitative procedure have been employed in performing observations of corrosion of aluminum. One of, the methods most frequently used has been the determination of the loss of weight of strips of metal or of utensils per se after exposure to foods. The other experimentation has been based upon analysis of the foods for increase of aluminum due to contact with the metal surfaces. The work of Lunge and Schmid ( 8 ) is an example of the earlier investigations. Lunge and Schmid found that aluminum strips exposed to various food acids in concentrations from 1 to 5 per cent for a period of 6 days lost from 1.08 to 4.77 mg. per 100 sq. cm. They ascertained that coffee caused a loss of 0.5 mg., but could not detect loss of weight in the case of plates exposed to tea or beer. Smith (16) has cited similar investigations showing that corrosion of aluminum by foods is insignificant. Studies that have been described since the appearance of Smith's book, give confirmation to the findings of the older investigators. Quam (12) has shown that aluminum is very inactive to corrosion by milk. Up to 70" C. no change in weight was detectable in aluminum plates immersed in milk; above 70" C. an increase in weight of 0.12 to 0.18 mg. per 100 sq. cm. occurred. Chiaria ( 1 ) . using the same method, has verified Quam's results on the relation of temperature and extent of corrosion of aluminum by milk. Mrak and ' Cruess (10) have found small and varied degrees of corrosion of aluminum strips by various fruit juices. Colobraro ( 2 ) has analyzed various materials for aluminum after 1000 cc. were boiled in an aluminum vessel of 1400 cc. capacity for 1 hour.
REXARK~
10 10 10
0 37
0 52 0 53
90 8 90 8
28.0 28 0
90 5
3 40 3 50
Rhubarb
5
0 95 0 95
13 45 13 35
12 5
Rhubarb
5
0 94 0 94
41 8 41 8
40 9
ipricots
40
73 3 73 3
48 7
Prunes
40
4 60 4 60
7 10 7 10
2 50
ipple sauce
10
0 28 0 28
1 40 1 40
1 12
lpple butter
390
5 28 5 28
90
0 30 0 35
3 06 3 06
2 76
2
0 31 0 31
2 24 2 24
1 93
Orange marmalade Lemon-pie filling
uith
sugar
Dark pan uith sugar
0 75 0 75
118
Cooked with NaHCOI
Dark pan uithout 27 5
10
24 6 24 6
Cooked without NaHC03
2 70
113
Bright pan Dark pan
Includes time t o concentrate cider
He has reported 1.69 mg. of aluminum in milk, 5 mg. in olive oil, 2 mg. in a sugar solution, 9.54 mg. in compote, 43.6mg. in tomato preserves, 1.2 mg. in broth, and 1.83 mg. in white wine. Plagge and Lebbin (12) were the first to examine foods to show indirectly the extent of corrosion of aluminum utensils. They included whole meals and compared the analytical results thereon with those of meals cooked in iron: but their data are of little value, owing t o the inadequacies of their analytical methods. TheLancet in 1913reported in an editorial ( 6 )on the corrosion of aluminum by a variety of foods. S o t only were the utensils examined for the appearance of corrosion, but the foods were ashed and examined qualitatively for aluminum. Later The Lancet presented, also editorially ( 7 ) , an account of a similar series of experiments by Glaister and Allison. I n this latter report it was stated that the maximum amount of aluminum was observed in orange and lemon marmalade. The 1.018 grains of aluminum hydroxide that were found in 2.5 pounds of marmalade are equivalent to 20 p. p. m. of aluminum. No other quantitative data ITere given. Schwartee, Murphy, and Cox (Is),in one of the present series of investigations, have accorded attention to a fresh milk whose aluminum content was 0.07 p. p. m.; after pasteurization in aluminum for 30 minutes a t 60" C., it was 0.67 p. p. m. It is of interest, 'n studying the quantity of aluminum introduced into foods by utensils and observing the effects of dietary aluminum, to know the amounts of aluminum that occur in raw foods in common use. The analyses of the tissues of various animals by several investigators (9, 1 1 ) show how little aluminum is to be expected in fresh meats. Winter and Bird (18) have analyzed a large
....... .
April, 1932
1 N D U S ' l I< I A I.
A U 1)
E N G I N I?: Is I
