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T'ol. 19. No. 8
Ammonia Content of Cold-Storage Eggs An Investigation of Cold-Storage Eggs Sold at Retail in Massachusetts1 By Hermann C. Lythgoe DEPARTMENT O F PUBLIC H E A L T H , S T A T 8 HOUSZ,
T
HE cold storage of eggs is a purely commercial proposition and benefits the producer, the dealer, and the consumer. The producer gets a market for his surplus spring eggs. The dealer is able to store this surplus and sell it later in the season, usually a t a profit, but sometimes a t a loss. The consumer is able to obtain eggs throughout the year a t less variance in price than would be possible otherwise. Only about 10 per cent of the eggs produced are placed in cold storage. Of these about 5 per cent are stored by April 1, about 40 per cent by May 1, and about 83 per cent by June 1, so that all are in storage by July 1. On August 1 about 2 per cent have been removed; on September 1, about 10 per cent; on October 1, about 22 per cent; on November 1, about 60 per cent; on December 1, about 63 per cent; on January 1, about 82 per cent; on February 1, about 95 per cent. These figures represent five-year average holdings, 1920 to 1924. I n Massachusetts 18,214,980 dozen eggs were placed in storage during 1926, and the maximum holdings were 11,103,120 dozen on August 1. The maximum holdings in the United States during 1926 were 295,350,000 dozen on August 1. The Massachusetts cold-storage egg law provides that whenever eggs that have been in cold storage are sold, a t wholesale or retail, the container shall be plainly and conspicuously marked with the words, "Cold-Storage Eggs," or there shall be attached to such container a sign having upon it the said words. The law further provides that when such eggs are sold a t retail or are offered or exposed for sale without a container, or are placed upon the counter, a sign bearing the words "Cold-Storage Eggs" shall be displayed among, upon, or immediately above the eggs. The element of time in storage is not mentioned in this law, but similar legislation in other states requires a thirty-day period of refrigeration to elapse before the eggs are considered to be cold-storage eggs. In cases involving prosecution for violation of this law, it is necessary to prove that the eggs in question have actually been in cold storage, and this proof cannot be shown by any known methods of analysis. Examinations of any sort which will indicate to some extent the probable age of the egg, and its relative decomposition, are of great value to the field man, who, when armed with the information that the eggs are somewhat old but are free from extensive decomposition, can frequently gather the necessary evidence to show that cold storage was responsible for their condition. Chemical and physical examinations that will indicate the condition of the eggs also furnish valuable circumstantial evidence to supplement such direct evidence as may be available. As an egg becomes old the contents go through the forms of decomposition usual in this class of foods, such as reduction of the dextrose and increase in acidity of the fat, as well as ammonia production. The rate of decomposition is influenced by the temperature at which the egg is kept. The ammonia production is confined practically to the yolk of the egg and, consequently, when dealing with broken-out eggs, the fat determination is essential for a correct interpretation of the analysis. 1
Received March 22, 1927.
BOSTON, MASS.
The determination of ammonia in eggs for ordinary inspectional purposes was first applied to broken-out eggs as a means of detecting any admixture of decomposed eggs. For this purpose it has been very successful. For many years the Massachusetts Department of Public Health has used the ammonia content as a means of differentiating between fresh and old edible eggs. Eggs Used The cold-storage eggs used in this study 'Fvere either sold as such properly labeled by the vendor, or were ascertained to have been such by the inspector either a t the time of sale or subsequently. They all represented retail sales obtained during the past five years as delivered to the consumer. Some of the eggs were sold practically as soon as received from the wholesaler; many had been in the retailer's possession for from three days to a week; and a few had been in the retailer's possession for two weeks. Method The ammonia was determined by the well-known aerometric method of Folin,* using Xessler solution as the reagent. The cylinders were 13/8 inches (3.5 cm.) internal diameter and 1l1/* inches (29.2 cm.) high. Twenty grams of egg were used. The air pressure was sufficient to measure 2 inches (5 cm.) of mercury in a manometer attached to the outlet pipe. Two hours' aeration was sufficient to recover all the ammonia.
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Figure 1-Variation
3 9 90
4 1
in Ammonia Content of Cold-Storage Eggs
Results The ammonia figures, segregated by months, were compiled as summation series, expressed as percentage of samples containing up to and including the quantity of ammonia indicated in Table I. Table I-Ammonia Number of samples Lowest Lower quartile Median Geometric mean Arithmetic mean Upper quartile Highest
Ocr. 82
Content of Eggs Examined Nov.
DEC.
JAN.
FEE
405 374 187 40 MzZlzgrams ammonza per 100 grams 2.2 1.4 1.8 1.9 2.1 2.80 2.52 2.85 2.69 2.46 3.28 2.97 2.86 2.99 2.65 3.24 2.86 3.05 3.00 2.68 3.29 2.90 3.08 3.03 2.73 3.66 3.20 3.29 3.24 2.92 4.3 4.3 4.2 4.3 3.8
The median of each series is lower than the arithmetic mean thereby suggesting that the series is of a logarithmic char* Z . physiol. Chem., 37, 161 (1902); J. Biol. Chem.. 11, 532 (1912).
INDUSTRIAL AND ENGIA’EERING CHEMISTRY
August, 1927
acter. These figures plotted upon logarithmic-probability scales3 are shown in Figure 1. Each series is approximately a logarithmic-probability series. There appears to be a close relationship between the October, November, and December series, but the February series has a much lower percentage of samples relatively low in ammonia. During January fewer samples were collected than in December, because most of the violations of the law had been checked before the latter part of January. The analyses of the January eggs do not represent an average 99,
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JAN
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OCT
Figure 2-Estimated
Seasonal Variance in Ammonia Content of Cold-Storage Eggs
as of January 15, but as of an earlier date. Consequently, the curve falls nearer to the December curve than it would had collections of samples followed the rule of the other months. The eggs collected in February were practically all purchased as cold-storage eggs and were’collected with a view of finding decomposed eggs rather than of ascertaining the existence of violations of the cold-storage egg law. Assuming that the difference in ammonia content between cold-storage eggs sold in September and in October would be relatively the same as exists between those sold in October and Kovember, as well as between those sold in November and December the estimated September line was drawn on the chart from which the lower quartile, the median, and the upper quartile were taken, and similiar values were taken from the other lines. These values are given in Table 11. Tahle 11-Average Ammonia Content as of Fifteenth of Month (Figures in milligrams ammonia per 100 grams)
LOWER QUARTILE
September October November December January February
2.1 2.3 2.5 2 6 2 7 2.8
MEDIAN 2.4 2.6 2.9 2 9 2 9 3 2
LrPPER QUARTILE
2.8 2.9 3.1 ? 2 .3 2 3 5
These figures have been plotted using logarithmic-probability scales, the months being plotted on the probability scale as percentages of nine months, the usual time elapsing from the maximum to the minimum holding of eggs in cold storage. With the exception of the January figures, for reasons already explained, each series plotted approximately in a straight line, and from this line was determined the figures employed in preparing Figure 2 upon arithmetic-logarithmic scales, which shows the expected seasonal variance in the ammonia content of commercial cold-storage eggs when
* For a description of this type of plotting see Whipple, J . Franklin I n s f . , 182, 37, 205 (1916) ; “Vital Statistics,” p. 392, John Wiley:& Sons, Inc
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sold at retail. The figures from September 1 to October 15, as well as those from February 15 to March 1, are extrapolated. The zone between the upper and lower quartile represents the estimated content of half the storage eggs on the market. It is to be expected that 25 per cent of commercial cold-storage eggs will be above the upper quartile, and 25 per cent will be below the lower quartile, in ammonia content. The actual market conditions indicate that cold-storage eggs of low ammonia content soon disappear, and during February they are practically all gone. This is the result of commercial conditions. During the early part of the season it is of financial advantage to the unscrupulous dealer to sell the better grade of cold-storage eggs as fresh eggs a t fresh-egg prices. The better grades of cold-storage eggs are therefore removed from storage prior to the middle of January, after which there is no particular advantage in violating the cold-storage egg law because of the usual seasonal decrease in the price of all eggs. A compilation of eleven hundred analyses of cold-storage rggs collected during the entire season for a period of five vears, and plotted upon logarithmic-probability scales, is ih0n-n in Figure 3. The points form a straight line between 2.1 and 4.3 mg. of ammonia content and represent about 95 per cent of the total samples. It is therefore reasonable to assume that it is improbable but not impossible to market cold-storage eggs with an ammonia content below 2.1 mg. per 100 grams. Although the ammonia content of some of these eggs was above 4 mg. per 100 grams and they were not perceptibly rotten as judged by the odor, this fact cannot be construed as showing that broken-out eggs containing such amounts of ammonia are not decomposed, because considerable of the excess of ammonia in such “shell eggs” is caused by evaporation, which increases the fat as well as the ammonia. Jenkins and Pennington4 in 1919 studied the commercial preservation of eggs by cold storage. They showed the changes in ammonia content of sixty lots of eggs stored at different times during the season. The geometric means of all these figures representative as of the first of each month were calculated by the writer and were found to be slightly above those of the median line in Figure 2, and for the months 4
C S Dept. Agu., Bull 715.
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covered by the chart t$e ammonia content is as follows: September, 2.50; October, 2.72; November, 2.83; December, 2.86; January, 2.94; February, 3.26; and March 3.35 mg. per 100 grams. Conclusion
It is an axiom in the egg business that with an advance in price deliveries should be delayed in anticipation of fur-
Vol. 19, No. 8
ther advances, and as prices decline the goods should be rushed to market in order to avoid losses by continued declining prices. The consumer can take advantage of this trade custom by watching the wholesale quotations published each day in the newspapers. He should purchase the best grade of cold-storage eggs in the early part of the season when the price of the non-storage eggs is high and advancing, but when the prices begin to drop he should buy the non-storage variety.
Effect of Weathering 'on the Softening and Solidification Points of Coal' By T. E. L a y n g and A. W. Coffman UNIVERSITY OF ILLINOIS, URBANA, ILL.
ANY methods have been used for the storage of coal, but none have been perfect, so that it is necessary to furnish a control test for storage which will enable the consumer to move his coal a t such a time as will conserve to the best advantage the heating and coking properties of the fuel. It was with the hope of establishing such a control test that this study of the effect of weathering on the softening and solidification points of coal was undertaken.
M
A p p a r a t u s and M e t h o d
The apparatus and manipulation used for the determination of the softening and solidification points of coal are described in detail by Layng and Hathorne2 in their work on the determination of the temperature of plasticity. I n brief, this method consists of passing nitrogen through a small mass of 20- to 6 0 - m e s h c o a l , simultaneously h e a t i n g the coal mass in a combustion tube surrounded by an electric furnace. As t h e temperature increases the coal softens and offers resistance to the flow of the nitrogen, setting up a back pressure which is measured by means of a manometer. The pressure and temperature are noted a t regular intervals. Description and P r e p a r a t i o n of Samples
The following samples of coal were used : (1) Taylor-English coal from Vermilion County, Ill. 2) Ziegler coal from Franklin County, Ill. 3) Pocahontas coal No. 3, W. Va., from the coke plant of the Inland Steel Co., Chicago, Ill. (4) Vinton Colliery coal from Mine No. 6, Vinton, Pa. ( 5 ) Elkhorn coal from the Elkhorn Seam, Latcher County, KY. (6) Two samples of Vermilion County coal which had been in storage for 6 weeks. One sample was from the outside of the storage pile and the other was taken at a point in the pile where localized heating had led to spontaneous combustion. (7) Jellico County, Ky., coal.
f
Received March 31, 1927. :THIS JOURNAL, 17, 165 (1925). 1
(8) O'Gara Coal Co., Saline County, Ill. (9) United Electric Coal Co., Mine No. 4, Vermilion County,
Ill. (10) Hickory Hill coal, Gallatin County, Ill.
All samples were obtained fresh. A11 were ground through a coffee mill and sized to pass through a 20-mesh but not
through a 60-mesh screen. Oxidations mere carried out under a stream of oxygen in a constant-temperature oven at 110" C. All preheated samples were heated in the tube of the apparatus immediately before the test was made. In determining the temperatures of plasticity a rate of heating of 2" C. per minute was used over the critical range. Interpretation of Results
Table I lists the res u l t s obtained on five different coals that had been weathered by. acc e l e r a t e d oxidation at 110" C. f o r v a r i o u s p e r i o d s of t i m e . It should be noted that such a weathering increases t h e t e m p e r a t u r e of i n i t i a l p l a s t i c i t y , decreases the m a x i m u m pressure, and decreases the temperature of solid coke formation; furthermore, that such an oxidation progressively decreases the quality of the coke formed. Figures 1 and 2 show typical sets Figure 2 of data d o t t e d graDhically. Table I aiso-shows similar data for a coal taken from storage. I n this case also the changes took place in the portion of coal which had undergone excessive weathering. This shows that the changes of a coal upon oxidation are of such a nature that i t should be possible to use the softening and solidification points as an indication of the extent of weathering. Coals that are plastic over a greater range of temperature are more difficult to oxidize and may consequently be stored with less difficulty. Table I1 shows results obtained upon preheating coals to various temperatures in both air and nitrogen and then cooling in the same atmosphere before determining their range of plasticity. A temperature of 150' C. in air s e e m to be the maximum to which a coal can be heated without being
