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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
presented in Table I; i t may be noted t h a t there was
a greater deteriorative activity revealed in t h e former case where t h e moisture ratio was actually much lower. This would seem, upon the surface, t o contradict t h e conclusion t h a t a lowering of t h e concentration of t h e medium increases t h e deteriorative activities of molds. However, i t must be remembered t h a t t h e deteriorative activity of molds in any single medium is a resultant of a t least two variables, i. e., concentration and amount of inoculum. We have shown in another paper1 t h a n an increase in amount of inoculum is responsible for an increase in inversion in any sugar solution of definite concentration. T h a t this principle applies t o manufactured sugars is indicated here, for t h e inoculum used in Table I1 was approximately IOO times as large as t h a t employed in Table I. Consequently, this experiment shows t h a t a decrease in concentration causes increased deteriorative activity in mold-infected sugars, all other things being equal. Nevertheless, t h e effect of other variables cannot be overlooked. A similar experiment was repeated over a period of 4 mo. and t h e d a t a gave similar evidence with moisture ratios varying from 0 . 1 8 t o 0.29. Considering t h e importance of t h e moisture ratio in predicting t h e keeping quality of sugar in storage under what is known as t h e “factor of safety” rule, i t is of special interest t o note t h a t here is presented evidence of t h e deterioration of manufactured cane sugars with moisture ratios from 0.08 to 0 . 2 9 when sufficiently infected with mold spores; and, furthermore, t h a t this deterioration occurs even in films of t h e highest concentrations, namely, of blackstrap molasses. I n sugar solutions we have already arrived at t h e resultant effect of t h e combined variables of concentration and amount of inoculum. I n other words, in saturated sugar solutions upwards of 5000 spores per g. are required t o effect inversion.’ We have experiments nearing completion which should establish similar criteria for sugar coated with films of known concentration as herein described. I n this way it is our purpose t o arrive a t a satisfactory method of judging t h e keeping quality of a sugar from t h e standpoint of mold infection, which we have shown t o be capable of inducing serious economic losses i n sugar as a result of i t s deteriorative activity. We wisli t o acknowledge our indebtedness t o t h e Station staff for their kind assistance. SUMMARY
I-A decrease in concentration of molasses inoculated with molds is responsible for a progressive increase in reducing sugars and a decrease in sucrose Clerget when incubated at 30’ C. for 4 mo. 2-A decrease in t h e concentration of films in inoculated laboratory-made sugars having films of known concentration and moisture ratios of 0 . 0 8 t o 0 . 2 0 , caused a n increase in reducing sugars (and a decrease in sucrose Clerget) which gave evidence of active deterioration. These sugars were incubated a t 30’ C. for one month, and similar results followed a like incubation of 4 mo. 1
Kopeloff and Byall, Loc. cit.
257
3-Aspergillus Sydowi Bainier, followed by Aspergillus niger, and Penicillium expansztm, in t h e order named, effected t h e greatest deteriorakion in both molasses and sugar. 4-There is evidence t h a t an increase in inoculum is responsible for an increase in inversion at definite concentration. This investigation with laboratorymade sugars corroborates previous results obtained with sugar solutions. THE CAUSE OF DETERIORATION AND SPOILING OF CORN AND CORN MEAL’ By J. S. McHargue KENTUCKY AGRICULTURAL EXPERIMENT STATION, LEXINGTON, KENTUCKY
Considering t h e great economic importance of Indian corn in t h e world’s commerce, it is evident t h a t t h e proper conditions for t h e preservation of this grain should be well understood and closely adhered t o under all circumstances. T h a t such is not t h e case, however, is shown by t h e fact t h a t every year thousands of tons of sound corn are subjected to conditions under which the grain deteriorates or spoils during storage in bins or while in transportation in cars or ships. The American Cooperative Manager states t h a t t h e loss t o shippers, in €our months of one year, through the deterioration of corn arriving in t h e Chicago market, amounted t o more t h a n $4,000,000. It is also well known t h a t tremendous losses are sustained in t h e exportation of corn t o European countries. The problem of keeping meal made from t h e whole grain of corn in a fresh, sweet state and fit for human consumption has long puzzled both miller and consumer. Partly as a war measure and also on account of its economical importance in times of peace, an investigation was suggested by t h e Director of the Kentucky Agricultural Experiment Station, about a year ago, the object of which was t o determine t h e underlying causes of t h e deterioration and spoiling of corn and corn meal while in t h e channels of commerce. Thus far our experiments have been confined t o t h e laboratory and were therefore carried out on small portions of material. However, t h e conditions under which t h e results have been obtained were so planned as t o represent what may be considered a duplication of those under which much larger quantities of corn spoil. For t h e experiments in this investigation a quantity of sound and thoroughly air-dry grains of corn of t h e crop of 1917, which contained 1 2 per cent of moisture, was selected. This was divided into t,wo equal parts, one of which was ground into meal, t h e other remaining unground. The unground grains and t h e meal were further subdivided into 1000-g. lots, each of which was stored separately in glass jars, sealed t o exclude air and moisture. CORN GRAINS
bIoIsTuRE ABSORPTION-FOr a n experiment on t h e hygroscopic property of corn containing 12 per cent 1 An abstract of this paper was read before the Division of Agriculture and Food, 58th Meeting of the American Chemical Society, Philadelphia, Pa., September 2 to 6, 1919.
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Vol.
12,
No. 3
i
of moisture, 1000 g. of the grains were placed in a porcelain evaporating dish resting on an ordinary “acid dish’’ partly filled with distilled water, the whole being covered by a bell-jar on a glass plate. A small wedge, about z mm. thick, placed between t h e rim of the bell-jar and t h e glass plate, provided a small opening for partial ventilation. .The dish of corn was weighed at intervals. Table I shows t h e increase of weight due t o moisture absorbed by t h e air-dry corn from a moist atmosphere. TABLEI-ABSORPTIONOF MOISTURER Y AIR-DRYCORN GRAINS
Initial wt. Wt. after Wt. after Wt. after Wt. after
Average Observed increase weight per day G. G. of corn (12 per cent moisture). . . . . . . . . 1000 .. 1 day.. . . . , . 1008 8 2 d a y s . . ........................... 1015 7 3 d a y s . . ........................... 1020 5 4 days 1024 4
..
Wt. after 7 days ................... Wt. after 1 1 days Wt.after 16 days Wt. after 19 d a y s . . . . . . . . . . Wt. after 27 d a y s . . ........................... Wt. after 41 days Wt. after 90 d a y s . . ...........................
1034
3
1040 1047 1050
1.5 1.4 1 0.75 0.57 0.2
1056
1064 1074
The total moisture content of the grains of corn after.exposut-e t o a moist atmosphere for go days was found t o be 19.67 per cent, as determined by drying t h e ground corn in a Freas oven a t 100’ C. in air. From t h e foregoing table it will be seen t h a t there was a gradual absorption of moisture during t h e go days, but t h a t t h e rate of absorption was much more rapid during t h e first week t h a n during the remainder of the time, nearly half of t h e total increase in weight having taken place in this period. I n t h e fir@ 16 days t h e increase in weight was 4.7 per cent, while in t h e remaining 74 days i t was only 2 . 7 per cent. The absorption of water, however, seems t o have been greater t h a n t h e apparent gain in weight. By the end of t h e 16th day, molds had developed. They increased rapidly and t h e corn soon acquired a musty odor. At first the growth occurred only on t h e germs of t h e grains of corn, b u t later other molds developed on t h e starchy and glutinous part. At t h e conclusion of this experiment t h e corn was in a badly damaged or spoiled condition. ACIDITY-The following acidity determinations were made on this spoiled corn and also on sound grains of corn t o show by comparison what changes had taken place in the acidity of the grains as a whole and in some of its separate parts, during t h e experiment. OF SPOILED AND SOUND CORNGRAINS,EXPRSSSSD AS Cc. OF NORMAL NaOH PER KILO Spoiled corn Sound corn cc. cc. 57.6 18.0 Whole grains.. . . . . . . . . . . . . . . . . . . 17.6 Degermed grains.. . . . . . . . . . . . . . . . 2 0 . 8 336.0 52.0 Germs o n l y . .
TABLE 11-ACIDITY
....................
From Table I1 i t will be seen t h a t t h e acidity of t h e entire grain had increased more t h a n 3 times while, in the degermed portion of t h e grain, t h e in-
crease was slight. The acidity in t h e germs had increased more t h a n 6 times, showing t h a t the germ is t h e seat of t h e greater p a r t of the acidity of t h e grains of spoiled corn. A quantity of t h e spoiled grains of corn was dried and ground and t h e f a t removed with ether, t h e excess of ether distilled off and t h e last traces removed b y heating in an atmosphere of natural gas. The oil thus obtained had a dark red color and a musty odor. The acidity was found t o be equivalent t o 1,450cc. of normal alkali per kg. of oil. The oil obtained b y extracting meal made from t h e sound corn had a pleasant odor, a light lemon color and an acidity of 56.8 cc. of normal alkali per kg. Qualitative tests showed t h a t all of t h e sugars and, apparently, the greater part of t h e starch had disappeared from the germs, as a result of t h e spoiling. From the results obtained in this experiment i t is t o be noted t h a t air-dry corn absorbs moisture readily when exposed t o moist air and t h a t when t h e moisture content of t h e corn reaches about 1 5 per cent and t h e temperature is favorable, molds develop, flee f a t t y acids are liberated, and the sugars and starches in t h e germ disappear. It is therefore assumed t h a t t h e results obtained in this experiment indicate t h e nature of t h e changes t h a t take place when much larger quantities of corn are spoiled, coincidentally with the growth of molds. FERMENTATION-In addition t o t h e changes t h a t are brought about in coin b y the growth of molds, perhaps even greater and more rapid factors in t h e deterioration and spoiling of corn are those accompanied by heating, souring, and fermentation. To determine approximately t h e percentage of moisture necessary t o bring about fermentation processes in grains of corn, enough distilled water was added t o three 1000-g. samples of corn t o make a total moisture content of 1 5 , 20, and 2 5 per cent, respectively. The jars containing t h e corn were sealed and kept at an average room temperature of z j ’ C. They were kept under daily observation and a t t h e end of I O days each jar was opened and examined more carefully t o note any evidence of deterioration. I n t h e portions with 20 and 25 per cent of moisture, some gas pressure had developed and t h e corn evolved a slight sourish odor, indicating t h a t fermentation was under way. I n the sample containing oniy I j per cent of moisture no pressure or sour odor were detected, but after standing for another period of I O days t h e presence of molds was observed. The growth of molds continued with the prolongation of the experiment but no evidence of fermentation changes was observed a t any time during t h e experiment, which indicates t h a t molds will thrive on corn t h a t contains no more than I j per cent of moisture, whereas i t requires a greater percentage of moisture t o bring about fermentation. After 30 days t h e acidity of t h e samples containing Ij, 2 0 , and 2 5 per cent of moisture was found t o be equivalent t o 2 3 , 30, and 5 0 cc., respectively, of normal alkali per kg. After 60 days each of t h e experiments may have been described as follows:
Mar.,
1920
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
15 per cent of moisture-molds present, musty odor. per cent of moisture-badly damaged, sour odor, grains brownish. 2 5 per cent of moisture-badly damaged, sour odor, grains dark brown. 20
A duplicate of t h e experiment containing 20 per cent of moisture was arranged in a a-liter, wide-mouthed glass bottle carrying a perforated rubber stopper. The bottle was connected b y means of glass and rubber tubing with a gas wash-bottle containing a saturated solution of barium hydroxide. The experiment was allowed t o stand undisturbed for several weeks, during which time a considerable precipitate of barium carbonate was formed in t h e wash-bottle. Upon opening t h e bottle containing t h e corn, a sour odor was detected. A poltion of t h e corn was removed, ground, and subjected t o steam distillation with water slightly acidified with sulfuric acid. After 300 cc. of distillate had been collected t h e distillation was stopped. The acid distillate was neutralized with a n excess of calcium carbonate and evaporated t o dryness. The residue was taken up in hot water a n d t h e excess of carbonate filtered out. T h e filtrate and washings were evaporated t o a small volume, and alcohol and strong sulfuric acid added. The pronounced odor of ethyl acetate proved t h a t acetic acid was one of t h e products of t h e fermentation. A quantity of t h e germs was separated from t h e soured grains of corn, dried, and ground fine. The fat was removed with ether and t h e dry, fat-free, germ meal was found t o contain no sugars and little starch. Apparently the greater p a r t of t h e starch h a d undergone fermentation, indicating t h a t in t h e souring of corn t h e sugars and starches contained in t h e germ undergo acetic acid fermentation. It is assumed t h a t t h e greater p a r t of t h e odor evolved by souring corn is due t o t h e presence of this acid. From t h e foregoing experiments i t appears t h a t corn containing as much as I j per cent of moisture will mold if confined in air-tight vessels a t ordinary temperature, whereas, if it contains 2 0 per cent of moisture or more, it undergoes alcoholic and acetic acid fermentations. It is also shown t h a t sound corn containing 1 2 per cent of moisture can be kept in good condition in storage for at least 1 2 months, provided it is not exposed t o conditions in which moisture can be absorbed. The chief cause of t h e deterioration and spoiling of corn appears t o be t h a t it has never been dried t o a moisture content safe for storage in large quantity or, if i t has been so dried, moisture has been absorbed. Corn t h a t has been dried t o a-moisture content of 1 2 per cent may be exposed during slow processes of loading or unloading, or during transportation in cars which are not closed sufficiently tight t o exclude moist air, until enough moisture is absorbed t o make i t unsafe for storage. Apparently t h e reabsorption of moisture is a very important cause of t h e spoiling of large quantities of export corn while in transit t o European ports. If corn containing no more t h a n 1 2 per cent of moisture were stored. in perfectly dry holds and so protected t h a t moisture could not enter, there appears t o be no reason
259
why such corn should not keep in a sound condition during transportation on t h e ocean. CORN MEAL
What has been said in regard t o corn applies in a general way t o corn meal. There is, however, one very important deterioration t h a t takes place in corn meal which does not occur in unbroken grains of corn. I t has been stated in t h e discussion t h a t sound grains of corn containing no more t h a n 1 2 per cent of moisture could be kept without a n y appreciable alteration for long periods of time. It is well known t h a t this is not t h e case with corn meal. I n a series of experiments t o determine t h e cause of the deterioration of corn meal, eleven 1000-g.samples of fresh meal made from one of the parts into which t h e original large sample of grain corn was divided, were sealed in glass jars.
Months
At t h e first of each of the 1 2 months through which t h e experiments were carried on, 2 j g. of meal were weighed from each of t h e I I jars for acidity determinations, which were made as follows: Each 25-8. portion of meal was transferred t o a clean, dry 2 j 0 - C C . glass bottle and treated with I O O cc. of neutral, 8 0 per cent alcohol. The bottles were closed with clean rubber stoppers and allowed t o stand for 20 hrs., with occasional shaking by hand during this time. This method gave identical results with samples shaken continuously in a shaking apparatus for 6 hrs. A t t h e expiration of t h e time interval t h e contents of the bottles were filtered on dry, folded filters,
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY TABLEI III-ACIDIW
NUMBER OF EXPERIMENT
...... ............... Apg. 1, 1918. ................ Oct. 1, 1918 ................. Nov. 1, 1918 ................. Dee. 2, 1918 ................. INITIALPER CENT H z 0 . . CONDITIONS..
Jan. Feb. Mar. Apr. May June
DEVELOPEDIN MEALSO F DTFBERENT WATER-CONTENT, UPON KEEPING
1 12 .Room temp.
................. ........... . . . ................. ................. ................. ............... ................ ................ .........
18.0 38.8 41.6 44.0 44.8 44.8 48.0 51.2 56.0 62.4 67.2 73.6
2 12
15'
C.
18.0 30.4 32.0 34.0 35.2 35.2 35.2 36.8 40.0 41.6 42.0 42.5 43.2
3 12 Oxygen 18.0 39.2 39.6 45.2 46.4 46.4 46 4 48.0 54.4 59.2 64.0 67.2 73.6
2, 1919 1, 1919 '.. 1, 1919 1, 1919 1 , 1919 2, 1919.. July 1 , 1919 Aug. 1, 1919 Acidity of oil, cc. normal alkali per kg., August 1919 1377.0 864.0 1530.0 1 All at room temperature (25' C.) except 2, a t 15°C.
18.0 30.4 31.2 32.0 32.0 32.0 33.6 34.4 35.2 35.2 35.2 35.2 35.2
1290.0
386.0
a 50-cc. aliquot p a r t of each clear filtrate was transferred t o a zoo cc. Erlenmeyer flask, a n equal volume of distilled water and a few drops of phenolphthalein were added, and the solution was titrated t o a second degree of pink color with N / I O alkali. T h e results, expressed in terms of cc. of normal alkali per kilo of meal, are given in Table 111. They show the degree of acidity attained in each of the different experiments during the time of t h e investigation. From t h e d a t a contained in this table, curves have been plotted t o show the degree of acidity attained as related t o the time, with the exception of Expts. 3 and 4, which show little variation from the results obtained in Expt. I . I n the table are recorded the acidity of t h e freshly ground meal when i t was p u t into the jars a t the beginning of t h e experiments, on August I , 1918, a n d the acidity a t t h e end of each month thereafter. The last line at the bottom of t h e table shows the acidity of t h e oil extracted from t h e meal in each of t h e experiments a few days after August I , 1919. Eachnumberrepresentsthenumberof cc. of normal alkali required t o neutralize the acid contained in 1000 g. of meal or oil. From the table and plot it will be observed that the degree of acidity developed corresponds very closely with the amount of moisture present in each of the experiments. In Expts. I to 8, inclusive, it will be noted that the acidity almost doubled during the first month, and thereafter the increase was very gradual. This rapid increase in acidity apparently resulted from the absorption of oxygen which brought about a hydrolysis of the fatty glycerides contained in the oil and the liberation of free fatty acids. In Expt. I the total acidity after 12 months a t room temperature was a little more than 4 times the acidity of the freshly ground meal. The increase during the first month was approximately 30 per cent of the total. That the acidity was due to a slow hydrolysis of the fatty glycerides is indicated by the nature of the oil. A steam distillation showed that the meal contained no volatile acids of the acetic series; furthermore, the meal retained a part of its fresh nutty odor throughout the experiment and did not acquire a musty or sour odor. In Expt. z the meal was kept in a refrigerator a t 15' C. The retarding effect of the lower temperature upon the development of acidity in the corn meal is shown by comparison with Expt. I In addition to a lower acidity in the meal and also in the d, the meal retained throughout the experiment the odor which is characteristic of meal Freshly ground Erom whole grains of sound corn. In Expt. 3 , in which the meal was kept in an atmosphere
18.0 30.4 34.0 36.8 36.8 36.80 37.6 38.40 39.2 41.6 43.2 44.0 45.6 706.0
18.0 30.0 33.2 34.40 34.40 34.40 34.40 35.2 35.2 36.8 37.6 37.6 37.6 337.0
12,
No. 3
IN TIGHT VESSELS'
4 5 6 7 8 12 12 8.46 3.62 1.3 COS Over HzSOq Dried 50' C. Dried 75' C. Dried 98' C. 18.0 37.6 38.0 44.0 44.0 44.8 44.8 48.0 52.8 55.2 60.0 65.6 65.6
Vol.
18.0 28.0 29.6 30.4 30.4 30.4 30.4 31.20 32.0 32.1 33.6 33.6 33.6 180.4
9 15
..
18.0 70.0 71.2 73.6 74.4 76.8 77.6 78.40 80.0 82.4 83.2 84.8 86.4 2266.0
10 20
..
11 25
..
18.0 70.4 72.4 76.0 80.0 81.6 84.0 87.0 96.0 118.4 126.4 129.6 131.2
18.0 74.0 77.6 90.4 97.6' 99.2 99.2 137.6 152.8 160.0 206.4 208.0 219.6
664.0
556.0
of oxygen, the acidity is practically the same as found in Expt. I, although that of the oil is slightly higher. I n Expt. 4 the meal was kept in an atmosphere of carbon dioxide. The total acidity is not quite as great as in Expts. I and 3 and that of the oil is also slightly less. I n Expt. 5 the meal was kept under a bell-jar with a reservoir containing concentrated sulfuric acid. Very little change in the acidity took place in the meal after the first month. After that time the slight increase in acidity is about what would be expected as a result of the loss of moisture that took place from month to month. At the end of the sixth month a moisture determination showed that the meal contained only 3.43 per cent of moisture, so that 8.57 per cent had been absorbed by the acid. The total acidity after 12 months was only 35.2 cc. normal alkali, which was 8 cc. less than in Expt. 2. The acidity of the oil was slightly Iess than one-half of that of the oil in the same experiment, showing that in the presence of a small amount of moisture there was less hydrolysis of the fatty glycerides a t room temperatures than in meal containing 12 per cent of moisture but kept a t a considerably lower temperature. In this experiment and also in Expts. 7 and 8 it is clearly demonstrated that as the percentage of moisture in meal decreased the formation of acidity in the meal and also in the oil it contained is correspondingly retarded. I n Expt. 6, 1000g. of the meal were dried in an electric oven a t 50' C., and stirred several times to facilitate a more uniform desiccation. At the end of 72 hrs. the meal was sealed in a jar and a moisture determination showed that it still contained 8.46 per cent of moisture. This drying caused a corresponding retardation of the development of acidity in the meal and oil during the time of the experiment. It also appears that meal containing 8.46 per cent of moisture will develop about the same degree of acidity a t room temperature as meal containing 12 per cent of moisture when kept a t 15' C. I n Expt. 7 the same quantity of meal was dried in an electric oven for 7 2 hrs. at 75' C. The meal had browned somewhat as a result of the drying. A moisture determination gave a value_ of 3.62 per cent. The acidity acquired by the meal and the oil was considerably less than that in the previous experiment and about the same as that in Expt. 5 . In Expt. 8 the meal was dried in a current of dry, natural gas for 24 hrs. a t 98" C. The meal acquired a slightly brown color as a result of the drying but was not nearly as dark as the meal that was dried in air a t 75' C., indicating that the browning in the latter case was in all probability due to the absorption of oxygen. A moisture determination a t 100' C. showed that the meal which had been dried a t 98' C. contained 1.3 per cent of moisture. The oil extracted from the meal required only 180.4 cc. of normal alkali per kg. which indicates that in Expts. 5 , 6, and 7 the production of acidity intheoil was in some measure accelerated by the process of drying in an atmosphere containing
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1920
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
oxygen. The acidity of the oil extracted from freshly ground, sound grains of corn was equivalent to only 63 cc. of normal alkali per kg., which is approximately one-third of the acidity of the oil in Expt. 8, showing that some hydrolysis of the fatty glycerides had taken place as the result of the drying. In Expts. g, IO, and 1 1 enough distilled water was added to each of three 1000-g. samples of meal in porcelain dishes to give a moisture content of approximately 15, 20, and 2 5 per cent, respectively. After mixing the meal in each dish until the moisture was uniformly distributed, each sample was placed in a glass jar and sealed in the usual way. Determinations on each of the samples, after sufficient time had been allowed for the uniform distribution of moisture through the meal, showed that they contained 15.35, 19.87, and 25.60 per cent of moisture, respectively. Each of the experiments was kept at room temperature and all had undergone considerable deterioration as a result of the addition of the water. At the end of the first month the meal in Expt. g had developed molds and a musty odor. The acidity increased more than four-fold in the first month but very slowly during the remainder of the experiment. The acidity of the oil from the meal in this experiment was greater than that found in the oil of any of the other experiments. The meal acquired properties which are characteristic of deteriorations that give rise to musty odors, whereas in Expts. IO and 1 1 fermentation changes predominated. In Expt. IO sour and alcoholic odors were prominent, and in Expt. I I alcoholic odors were most prominent. It is interesting to note that the oils extracted from the meals in which alcoholic fermentation took place contained much less acid than in Expt. 9. Alcohol, aldehydes, and acetic acid were detected in the distillate from portions of the meal in Expts. IO and I T that were subjected to steam distillation. From the results contained in Table I11 it is evident that different percentages of moisture in corn meal give rise to different degrees of deterioration. It appears that if the moisture content of corn meal does not exceed approximately I Z per cent only slow hydrolysis of the fatty glycerides takes place and the increase in acidity due to the liberation of fatty acids is gradual. Meal containing this percentage of moisture has been kept in sealed glass jars for 12 months without acquiring any rancid or musty odors. In fact, the meal so kept has even retained some of the sweet odor which is characteristic of fresh meal made from sound, whole grains of corn. The most noteworthy change that took place in the meal during the experiment was the rather rapid increase of acidity which occurred during the first 30 days. At the present time this increase in acidity can only be explained by assuming the presence of a readily oxidizable substance in the germ, which has been protected from the oxygen in the air by the outer integuments surrounding the grain, previous to grinding. M E A L F R O M D E G E R M E D GRAINS O F CORN
Within recent years millers have received so much complaint about t h e spoiling of meal made from whole corn t h a t they have been induced t o invent machinery for t h e removal of t h e germ from corn grains, previous t o grinding, hoping thereby t o eliminate the chief cause of t h e spoiling of corn meal. I n Table 111 t h e experiments show t h a t meal made from t h e entire corn grain t h a t does not contain more t h a n 1 2 per cent of moisture can be kept for a period of I Z months, when air and moisture are excluded, without acquiring any musty or sour odor. The only change observed during this time was a gradual increase in the acidity, which was confined mainly t o t h e oil. How seriously this increase i n t h e acidity of t h e oil affects t h e palatableness a n d wholesome-
261
ness of bread made from such meal remains t o be determined in future experiments. Except from t h e standpoint of acidity, t h e meal is apparently in a perfectly sound condition and has even retained a n u t t y odor. From t h e Standpoint of nutrition, meal made from degermed corn is very much inferior t o meal made from whole grains of corn, because practically all of a highly nutritious oil, valuable proteins, and a large proportion of the mineral matter are contained in the germ of t h e corn grain. T h e analyses in Table I V show t h e most important constituents contained in germs and in t h e degermed grains of corn, expressed as percentages of t h e moisture-free materials. TABLEI V Crude ash.. ........................ Si02
............................... .............................. MnsOc ............................. CaO. .............................. M g O.............................. KaO ............................... NazO .............................. PzOs............................... S.................................. N ................................. Protein (N X 6.25).................. Fat. ............................... Fez08
GBRMS 7.900 0.057 0.027 0.021 0.158 1.541 2.196 0.150
4.513 0.233 2.634 16.463 28.295
DECERMED 0.968 0.004 0.003 0.003 0.031 0.180 0.156 0.160 0.452 0.137 1.697 10.606 0.196
Inasmuch a s t h e germ constitutes about one-tenth of t h e whole grain, it follows from these analyses t h a t meal made from degermed grains of corn contains about one-half of the mineral matter present in meal made from t h e whole grains. Nearly all of the f a t is also found in t h e germ. Since i t has been shown t h a t corn oil i s one of t h e most valuable vegetable oils from t h e standpoint of nutrition, its removal from a food product entails the necessity of substituting some other fat, with t h e probability t h a t this may often be inferior to the natural oil. It is also well known t h a t bread made from degermed corn meal lacks much of the pleasant n u t t y flavor imparted to bread made from meal containing t h e germ. T h e proteins are also of a much superior quality to a n equivalent amount of the proteins contained in t h e degermed grains of corn. It therefore appears t o t h e writer t h a t t h e practice of degerming corn intended for human consumption is both harmful a n d unnecessary and should be prohibited by law. MOLDS
T h e different species of molds which developed on certain samples of corn and corn meal have been isolated, grown in pure cultures, a n d identified. A dark bluish mold developed on t h e germs of grains of corn which were exposed t o a moist atmosphere for 16 days. Upon growing this species in pure cultures a n d making a microscopic study of its structure it was identified as Penicillium expansurn. This mold confined its growth t o t h e germ of t h e grains of corn a n d i t made t h e most prolific growth of a n y o€ t h e species t h a t developed on t h e corn. Aspergillus glaucus, a species bearing yellow spores, developed in isolated clusters on t h e germs. Its
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growth was quite sparce as compared to t h a t of Penicilliu m e x p a nsu m. Aspergillus alhus, a white mold, developed on t h e germs of t h e corn grains after Penicillium expansum a n d Aspergillus glaucus had been growing €or several weeks. Citromyces s p . , a beautiful whice, cottony mold, made a vigorous growth on t h e degermed, or glut’lnous and starchy part of t h e grains of corn. I t was not observed growing a t any time on t h e germ of t h e corn grain. I t is interesting t o note t h a t t h e species of t h e Petzicillium and Aspergillus appear t o attack only the oily portion of t h e grain. Perhaps this is due in part t o the fact t h a t t h e germ contains more mineral matter as well as more readily digestible proteins, fats, and carbohydrates. I t s softer structure perhaps also aids these specLes in obtaining a foothold more readily. It is quite t h e opposite in the case of Citromyces, and it therefore appears t h a t this mold exercises selective properties towards the medium upon which i t develops and grows. It is not t h e intention of t h e writer t o infer that these are t h e only species t h a t will grow on corn or corn meal b u t simply t o state t h a t these are t h e ones t h a t have developed under t h e conditions of t h e experiments described. Doubtless many other species would have developed also had their spores been present. CONCLUSIONS
I-Excessive moisture is t h e chief cause of t h e deterioration and spoiling of corn. 2-Sound grains of corn containing no more t h a n 1 2 per cent of moisture can be preserved €or a considerable length of time. g-Grains of corn containing 1 2 per cent of moisture will readily absorb more when exposed t o conditions in which free moisture is present. 4-Molds will develop on grains of corn containing as much as 1 5 per cent of moisture a t normal cemperatures and with restricted ventilation. 5-Molds cause a very rapid deterioration of the oil, sugar, and starch contained in t h e germs of corn. 6-Alcoholic and acetic acid fermentations take place when grains of corn containing more t h a n 2 0 per cent of moisture are deprived of ventilation and kept a t normal temperatures. 7-Apparently t h e cause of export corn spoiling i s because it is not thoroughly air-dry ( 1 2 per cent moisture) befcre being p u t into dry holds and 1s not kept a t t h a t state of dryness during t h e voyage. 8-The germ contained in sound grains of corn apparently contains an easily oxidizable substance and when fresh meal is made from whole grains of corn and exposed t o t h e atmosphere t h e acidity increases as a result of t h e absorption of oxygen from t h e air. 9-Meal made from whole grains of sound corn containing 1 2 per cent of moisture can be kept in a condition suitable for human consumption from 4 t o 6 months, provided moisture and air are excluded.
Vol.
12,
No. 3
I o - C o r n meal deprived oE its moisture undergoes little or no change i n acidity. I I-Lowering t h e temperature retards t h e development of acidity in corn meal. 12-Meal made from degermed grains of corn is inferior t o meal made from whole grains of corn. ACKNOWLEDGMENT
The author wishes to acknowledge his indebtedness t o Dr. A. M. Peter, head of t h e Department of Chemistry, €or helpful criticisms in the preparation of t h e manuscript THE RELATIVE AVAILABILITY OF NITRATE NITROGEN AND COMMERCIAL ORGANIC NITROGEN. FIELD AND CYLINDER EXPERIMENTS] By A. W. Blair N. J. AGRICULTURAL EXPERIMENT STATION, NEWBRUNSWICK, N. J.
The question of the availability of nitrokenous fertilizers is one of great importance t o the farmer. He desires a material t h a t will be sufficiently available t o benefit the immediate crop and at t h e same time he wishes t o guard against undue loss of plant food through leaching. I t is a matter of perhaps equal importance t o t h e fertilizer manufacturer, since he wishes t o sell t h e farmer a fertilizer t h a t will give results, a n d also to use all t h e available by-products t h a t may be worked into fertilizers. Since nitrates are readily soluble in water and a r e assimilated directly b y plants, they are considered readily or immediately available materials. Organic nitrogenous materials must undergo decomposition in order t h a t t h e nitrogen may be converted into ammonia and nitrates, a n d are therefore considered less readily available than nitrates. If, however, we allow sufficient time for their decomposition, will they n o t give as good results as t h e nitrates; t h a t is, does the greater residual effect of t h e organic matter balance t h e ready availability of t h e nitrates? I n other words, taking results covering a period of years, is a pound of nitrogen in t h e form of organic matter as effective as a pound of nitrate introgen? For more than twenty years t h e New Jersey Experiment Station has been making a scudy of t h e availahility of different nitrogenous materials and t h e results of much of this work have been published. I t seems worth while, a t this time, however, t o summarize briefly certain phases of this work, and t o include new material which has not yet been published. I n much of this work t h e comparison was confined t o a nitrate and an organic compound, a n d on this account this discussion will be confined t o results obtained with nitrates and organic materials. The work has been carried on b y means of field, cylinder, a n d pot experiments. The pot experiments constitute a minor part and need not be reported here. CYLINDER EXPERIMENTS-SERIES
A
The work t h a t has been carried on in these cylinders was originally outlined under t h e rather broad heading “Investigations Relative t o t h e Use of Nitrogenous 1 Presented before the Fertilizer Division at the 58th Meeting of the American Chemical Society, Philadelphia, Pa , September 4, 1919.
