1494
INDUSTRIAL AND ENGINEERIKG CHEMISTRY
of a few experiments using varying sugar and malt sprout concentrations are shown in Table 11. Over 90 per cent of the sugar was recovered as lactic acid when 3 , 5 , or 10 per cent of sugar was used. All the fermentations were completed in 8 days. Since these fermentations were conducted a t 37”, a higher t,emperature-e. g., 45 O C.-would undoubtedly result in a more rapid fermentation. The higher concentration of malt sprouts increased the yield of acid slightly, probably because of the fermentable material present in the malt sprouts which was converted to lactic acid. After fermentation the medium could be worked u p as is now done commercially, b y acidification with sulfuric acid, filtration, and vacuum concentration. Such treatments will not affect the form of lactic acid. The raw materials used by the authors (cerelose and malt sprouts) are relatively inexpensive, so that the cost of producing the active acid should be low. Moreover, any of the materials (malted grain, molasses, etc.) from which lactic
VOL. 27, NO. 12
acid is now made commercially undoubtedly could be used equally well for the production of dextrorotatory lactic acid. The organism producing the dextro form is just as vigorous and efficient as organisms producing the inactive form. Except for care in the exclusion of foreign organisms, the commercial production of d-lactic acid should be no more difficult than that of the inactive form.
Literature Cited (1) Cori, C. F., and Cori, G . T., J. Bid. Chem., 81, 389 (1929). (2) Friedemann, T. E., and Graeser, J. B., Ibid., 100, 291 (1933). (3) Gabriel, C. L., and Crawford, F. M., IND.EXQ.CHEM.,22, 1163 (1930).
(4) Pedersoh, C. S., Peterson, W. H., and Fred, E. B., J.Bid. Chsrn., 68, 160 (1926). ( 5 ) Stephenson, M., “Bacterial Metabolism,” p. 149, London, Longmans Green and Co., 1930. (6) Tatum, E. L., Peterson, W. H., and Fred, E. B., Biochtm. J.,26. 846 (1932). RECEIVED July 13,1935
Changes in Stored Corn Meal CHARLES 0. WILLITS AND FRANK J. KOKOSKI New York State -4gricultural Experiment Station, Geneva, N. Y.
S T H E work Corn meal may be stored for a long period I n most of the previous work, of the New of time without change in the crude fat e m p h a s i s was placed upon a correlation of the deterioration York S t a t e content: (a) When the moisture content Feed Control Laboratories, it of corn with its gain in acidity, is 14 per cent or higher, the storage teniBlack and Alsberg (4) stated in was noted that some feeds had perature must be maintained at 18’ C. 1910 that the degree of acidity is apparently undergone a loss in crude fat content during the inan index of the work of microoror lower; ( b ) with a moisture content less Of terval b e t w e e n t h e manufacthan 8 per cent, the storage temperature ganisms and that the highest acid content also had t h e turer’s analysis and the check may be as high as 37’ C. highest content of fat and nitroanalysis made at the laboraThe “degrees of acidity” of corn meal do gen, This was due to a loss in tories. These apparent losses not indicate changes in crude fat and theresome constituent, supposedly ranged from a f e w t e n t h s t o more than 1 per cent. Informafore may not be used as an index of crude carbohydrate, to which they attributed the gained acidity. tion c o n c e r n i n g the cause of fat losses. Duvel (7) in 1909 compared these conditions would not only the relative keeping q u a l i t i e s be hebful to the feed manuof dried shelled corn with the undried product and found that fwburir and dealer, but also to the various control laborathe dried corn kept 14 days longer without spoilage. tories. The manufacturer would be able to guarantee the The keeping qualities of ton lots of ground stored corn meal crude fat content with a margin of safety, and the dealer and were studied in 1915 by Winton, Burnet, and Bornmann ( 1 2 ) . control laboratory would be able to store feed or feed samples They found that corn meal of less than 15 per cent moisture under conditions which would cause only a minimum of underwent almost no change in taste or appearance. This change. work was checked by Davies (6) in 1928. The purpose of this investigation was to determine changes hlcHargue (8) found in 1920 that in the presence of air and in fat and acidity in white corn meal during storage, believing excessive moisture, deterioration in the qualities of corn that such a study might indicate changes in other fat-containoccurred a t low temperatures and that corn meal, deprived ing animal feeds. Corn meal was chosen since it is more or of its moisture, underwent little or no change in acidity. less uniform, and because a n adequate supply was available. A continuation of the studies, begun by Winton and others, Previous Investigations was made by Bailey and Thom (3)in 1920. Samples of corn meal were stored for 5 months in a cool room. All the samples The changes in stored whole corn and corn meal have been underwent a gradual decrease in moisture, while the acidity studied by several investigators. But since these changes increased more or less regularly. Samples stored in the labowere observed in large commerical quantities, the temperature ratory for the same period of time showed that those with a conditions of storage were not controlled ; they were either higher moisture content had a corresponding increase in the seasonal changes in temperature which the corn in the acidity and mold development. storage bins underwent, or the temperature changes to which it was subjected during shipping. Studies of acid production Storage Conditions in stored corn meal have been made but a t relatively few The following investigations were undertaken to deterstorage temperatures (6). No work has been done on changes mine some of the effects of moisture and temperature on the in the crude fat content which occurs in corn meal during crude fat (ether extract) and acidity of stored corn meal: long periods of storage.
INDUSTRIAL AND ENGINEERING CHEMISTRY
DECEMBER, 1935
1495
a t other temperatures, but are to be considered as individual cases. The term "seasonal temperature" found in the 37.0' C. tables applies to samples which were stored in the attic of the building and were therefore exposed to 13.74 the natural fluctuations in temperature. Since the 0.90 first period of storage for these samples was during the summer months, the changes in crude fat and acidity paralleled most closely t h e c h a n g e s ob22.5 25.8 served in the corn stored a t the constant tempera25.1 tures of 30.0" and 37.0" C., respectively. 46.0 59.7 The sample stored a t - 17.8" C. underwent prac75.8 98.5 tically no change in either fat content or degrees 129.7 of acidity, nor was there any appreciable change lii):5 in any of the corn meal stored a t temperatures below 23.0" C. T h a t s t o r e d a t 23.0", 30.0°, 4.64 4.64 37.0" C., and in the attic, and therefore subject 4.32 to seasonal fluctuations in temperature, showed a ... 4.24 decided loss in fat content until a value of about 4.30 4.33 2.5 per cent of fat was reached. 4.16 The ultimate changes in the degrees of acidity 3.23 ... are somewhat comparable with loss in fat content except at 18.0" C. where there traa a large increase in acidity but only a slight - loss of fat. In all cases, the rate of increase of acidity greatly exceeds the rate of decrease in fat content. The percentage of moisture in all the samples remained practically the Same throughout the time of storage and so thc: changes shown in fat and acidity were neither caused by nor accompanied by changes in moisture content.
TO TABLEI. RESULTSOF AXALYSISOF LOT A (CALCCLATED DRYBASIS)
Gtorage temp.:
"/oO-r$~;et;~, at
-17.8' C. Oo C. 18.0' C. 23.0' C.30.0'C. time
13.42 M a r . gain in % moisture: 0.45 Time of Storage Days 0
7 13 20 34 59 111 174 237 391
26.0 3i:5 26.0 34:7 35.7 39.9 34:4
0
4.58
7 13 20 34
4:42 4.58
59 111
4:i5 4.50 4.5;
174 237 391
4:60
13.18
13.74
13.71
13.74
Seasonal temp.
13.63
0.32 0.20 0.29 0.49 0.67 Degreea of Acidity Following Storage 22.3 21.8 26.9 22.0
22.5 19.8 18.0 18.5 23.8 16.8 31.0 29.5 49.6 34.7 34'0 41.0 ... 43.4 62.2 78.9 96.3 89.5 53.9 93.8 l24:4 53:l 85.7 Percentage of Crude F a t 4.93 4.64 4.61 4.75 4.68 4.58 4.58 4.50 4.45 4.54 4.64 4.71 4.67 4.36 4.90 4.56 4:03 4.51 4.24 4.63 4.06 4.51 4.54 4.26 ... 2.94 4.38 4:59
22.5 22.5 21.8 23.5 25.9 28.5 41.5 36.7 49.0 67.0 62.3 74.5 100.4 89.1 99.7 116.2 95.7 96.3 97.8 after Storage 4.64 4.64 4.64 4.62 4.51 4.70 4.39 4.64 4.75 4.48 4.38 4.48 3.66 4.49 :! .93 3.97 2.52 ... 2.24 2.51
...
Samples of different moisture contents were stored at temperatures ranging from - 1 7 , 8 ~ to 3 7 . 0 ~C. but without humidity control. The samples in lot A were of 100 pounds each and were taken directly from the mill storage bins. These were stored at -17.8", OD, 18.0" C., and attic temperature, respectively, just as they were received from the large storage bins of the milling company. The bags containing the samples w'ere placed in large metal cans and covered, but were not air-tight, Those stored at 23.0", 30.0", and 37.0" C. were subsampled from the same 100-pound lot and placed in small metal cans, which were corked and made air-tight - by" sealing with O F -4NALYSES O F L O T B (C.4LCULATED TO TABLE11. RESULTS paraffin. DRYBASIS) At the time of storage, each sample was analyzed for moisture, fat, and degrees of acidity. For com- Storage temp.: -17.8' C. 0" C. 18.0' C. 23.0' C. 30.0°C. Seasonal 37.0"c. temp. parative purposes, the moisture was determined by moisture a t drying in a circulating air oven for 1 hour at 130' C. %timeofstorage: 14.33 14.33 14.33 14.33 14.33 14.33 14.33 ( 1 , 6 ) . The crude fat was obtained by continuous exMax. gain in moisture: 0.09 0.12 0.25 0.05 0.50 0.19 0.09 traction with anhydrous ethyl ether for 18 hours on samples previously dried for 5 hours at 100" C. The Degrees of Acidity after Storage Time of Storage "degrees of acidity" (5)are equal to the number of Days milliliters of normal sodium hydroxide required to 12.7 12.7 12.7 12.7 12.7 12.7 12.7 0 neutralize the acid in an alcoholic solution of 1000 28.6 29.2 20.4 26.6 22.1 17.3 17.7 14 34.9 35.7 29.2 36.6 19.7 26.0 16.9 39 grams of corn. 37.2 47.2 43.3 58.1 24.2 37.I 19.3 Some difficulty in obtaining check results for acidity 43.1 54.3 51.4 52.6 23.0 32.0 1:: 56.3 on duplicate samples was encountered when the 72:3 51.7 217 58.8 53.9 68:6 3i:8 48.6 19:6 371 method of adding the alcohol to the sample, mixing thoroughly, and allowing to stand overPercentage of Crude F a t a f t e r Storage night, was used. To overcome this difficulty, 2.05 2.05 2.05 2.05 2.05 2.19 2.19 2.56 2.11 2.42 a mechanical shaker was employed and complete 2.17 2.09 2.09 2.40 2.00 extraction of the acid by the alcohol was obtained in 2.05 1.95 1.29 1.84 1.05 90 minutes. 1.91 1.80 1.81 1.25 1.35 1.87 1.78 .. 1.62 Because of the alcohol-soluble protein, n-hich was 1.92 1:SS 0.73 .. 0.57 thrown out of solution as water was added, the endpoint color of the titration, as shown by phenolphthalein, vias so masked that checks closer than O F ANALYSESOF LOT c (C.4LCULATED TO TABLE 111. RESULTS 0.5 ml. could not be expected when 0.01 N alkali was DRYBASIS) used. Employing this procedure and shaking for 90 minutes in all of the following experiments checks Storage temp.: -17.8O C. O o C. 18.0"C. 23.0°C. 30.0' C. Seasonal 37.0' c. temp. for the degrees of acidity were obtained on duplicate 3'% moisture a t samples. 7.68 7.68 7.68 7.68 7.68 7.68 time of storage: 7.68 I
Changes in Lot A The results of the analysis of the samples of corn meal, lot A, st'ored a t seven different temperatures for 391 days are given in Table I. This table shows changes in moisture, crude fat, and degrees of acidity, as recorded at the various t'ime intervals indicated. The samples were not aliquots of a large, gross sample, and therefore changes in fat, acidity, or moisture in a sample stored a t one temperature Rere not strictly comparable to the samples stored
Max.,gain in % moisture: Time of Storage Dall8 0
0.11
154 217 371
11.6 13.7 15.8 17.9 14:s
0 14 91 154 217 371
2.07 2.01 2.11 2.01 2:io
14 91
0.00
0.60 0.80 1.29 Degrees of Acidity after Storage
0.50
11.6 11.6 11.6 11.6 22.2 16.3 16.3 14.5 26.7 27.2 19.7 24.0 19.8 27.2 32.6 38.8 31.5 27.3 ,. 42.1 17:s 29.6 52.7 .. Percentage of Crude F a t after Storage 2.07 2.07 2.07 2.07 2.07 2.66 2.19 2.33 2.18 2.08 1.96 1.96 2.04 2.00 1.97 2.01 2.00 1.96 2.08 1.91 1.92 1.75 .. 1197 1.76 ,. 1.76 11.6 13.7 15.6
..
..
..
..
1.00
11.8 19.4 36.0
44.9 43.5 56.9 2.07 2.44 1.84 1.84 1.69 1.74
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INDUSTRIAL rlND EKGINEERING CHEMISTRY
Changes in Lot B A large sample of more than 100 pounds of corn meal was reduced to 60 mesh on a hammer mill to avoid heating. This sample, after thorough mixing, was divided into two portions, designated in Tables I1 and I11 as lots B and C. Lot B was subdivided by the cone-and-quarter method into seven smaller samples which were stored in air-tight containers at the temperatures shown in Table 11. At the indicated intervals, analyses were made. The change in the crude fat content of the samples stored a t - 17.8" and 0" C., respectively, was practically negligible, nor was any appreciable change shown in any of the samples stored a t temperatures lower than 30.0" C. At 30.0" and above, the change was much more rapid and reached a maximum a t 37.0" C. The losses in crude fat content of these samples were much more uniform than were shown in the case of lot A, owing to the fact that they were identical aliquots. The increases in the degree of acidity of the samples in lot B were much less and more uniform than those in lot A. This may be partially due to the fact that the initial crude fat content of the corn meal in lot A was twice that of the corn meal in lot B. The greater t'otal increases, as in lot -4,occurred a t the higher temperatures. The initial moisture content of the Eaniples in lot B wab 14.33 per cent, which \vas approximately the same as that of lot -4.No pronounced changes in moisture during the period of storage were noted, the greatest variation being 0.5 per cent. Therefore, changes in the crude fat content and degrees of acidity were neither caused by nor accompanied with a corresponding change in moisture.
account for the observed increase in crude fat. After 90 days the rate of loss of crude fat was greatly diminished. The samples of lot C showed slight total loss in crude fat even a t the higher storage temperatures. The only factor of lot C which is different from A and B, is the moisture content:
Changes in Corn Meal Stored at High Temperatures Four identical 60-mesh samples of corn meal mere adjusted to different moisture contents and then stored at 55.0" C. for one week. The moisture, crude fat, and degrees of acidity, before and after storage, are as follows: Percentage Percentage Degrees of Moisture Fatn Aciditya Original corn meal After 1 week of storage a t 55.0' C.
a
13.47 12.7 17.7 23 3 37.9
6.1 61.3 56.6 43.4 94.4
4.0 4 1 4.1 4 1 4.1
Calculated t o the d r y basis.
It is apparent that the greatest change, as indicated by change in degrees of acidity, occurred in the samples of highest moisture content. (The temperature 55.0" C. was chosen, since i t is about the optimum for lipase action.) The oil was then extracted from about 1500 grams of the sample, which showed the greatest change, as well as from a sample of fresh corn meal. The extracted oils were compared as to fat aldehyde value (Q), acidity as per cent oleic acid, saponification number, and iodine number. The results are as follows:
Changes in Lot C The corn meal in lot C was dried a t 95.0" C. in a steamheated compartment until the moisture content was 7.68 per cent, which was approximately that in lot B. It was then thoroughly mixed and subdivided into seven samples uhich were placed in air-tight containers arid stored a t t'he same temperatures and for the same period of time as those of lot B. Again, determinations of fat, moisture, and degrees of acidity were made a t the time of storage and a t varioiis time intervals as shown in Table 111. While lot C was stored simultaneously with and a t the same temperatures as lot B, the losses in crude fat were slight during the entire period of storage, even a t the highest temperature. However, the degrees of acidity of the various samples did increase in the same manner as was shown in lot B, but in all cases the total increase was less than that in the other two lots. The degrees of acidity of all the samples of lots h,B, and C increased during the first 160 days of storage. This increase was more or less proportional to the temperature. After 160 days of storage the acidity showed little change. With increase of temperature from -17.8" to 18.0" C., there was an increase in the rate of acid formation. Above 18.0" C. the rate was nearly constant. Comparison of the changes in the crude fat content of lots B and C of stored corn meal showed an apparent increase during the first 40 days, the increase in general (lot C more than lot B) being proportional to the temperature. This same apparent increase in crude fat was also observed by Sullivan and Kear (10) in 1933 in their studies of wheat flour. They found that one of the fatt'y acids present, if pure, was soluble in ethyl ether, but in wheat it was held with proteins and carbohydrates as a complex n-hich \vas not completely soluble in ether. This fatty acid, split off by enzymatic action, was soluble in ether, thus increasing the fat in the ether extract. A similar complex may also exist in corn and so
VOL. 27. NO. 12
70 moisture of corn meal from which oil was extd.:
Unheated Corn Meal
Oil from
Oil from Heated Corn I l e a l
12.86 10.04 6.16 189.8 108.3
37.91 1.37 20.65 234,5 89.9
The various conptants, determined on the oil from unheated corn meal and compared with those determined on the oil from heated corn meal, indicated that the oil from the heated corn meal had undergone oxidation. The iodine number decreased and the saponification number as well as the acid number increased. The decrease in the fat aldehyde value was unusual.
Acknowledgment The authors are indebted to The Patent Cereals Company of Geneva, S . Y., for all of the samples of corn meal used in this investigation I
Literature Cited A. 0. A. C., Methods of Analysis, 3rd ed., p. 279 (1930). Bailey, L. H , and Thorn, C., Operative Miller, 25, 368 (1920). Besley, H. J., and Baston, G. H., U. S.Dept. Agr., Dept. Bull. 102 (1914). Black, 0. F., and Alsberg, C. L., U. S.Dept. 4gr., Bur. Plant Ind., BUZZ. 199, 36 (1910). Coleman, D. A., Cereal Chem., 8 , 315 (1931). Davies, W.L., Fertilizer, Feeding Stu.fs F a r m Supplies J., 13, 784-5 (1928). Duvel, J. W. T . , U. 8. Dept. Agr., Bur. Plant Ind., Circ. 43 (1909). McHargue, J. S., ISD.ESG. CHEM.,12, 257 (1920). Schibsted, H., IND. ENG.CHEM.,Anal. Ed., 4, 204 (1932). ENG.CHmr., 25, 100-3 (1933). Sullivan, B., and Near, Cleo, IND. Winton, -4.L., Burnet, TI'. C., and Bornmann, J. H., U. S. Dept. -%gr.,B u l l . 215, 31 (1915). RECEIVED March 1, 1935. Approved by the Director of the
4 e w York State Agricultural Experiment Station for publication as .Journal Paper Xo. 8 5 , February 26, 1935.
