Eggs in cold storage

Front matter

4o j i

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Preface

IN the interest of a better understanding- and dissemination of knowledge on the cold storage of eggs, the writer has communicated with quite a large number of individuals and companies, asking their ideas and requesting that they give full answers to a printed list of questions sent them. Although, at first, the replies were rather slow in coming in, the total result of these letters has been most gratifying; nearly one-half acknowledging receipt of the inquiry, and more than one-half of this number giving fairly full replies to the questions submitted. Considering the fact that the inquiries were regarded by some as being of a rather personal nature, the proportion of managers sending full replies is large. Several gentlemen were frank enough to say that personal considerations prevented them from giving any information; others gave guarded or partial repli&s,:: In the main, however, storage men have been willing to give information and exchange ideas.

The list of inquiries sent out covers the subject very thoroughly, and divides it into six different parts, with three separate questions relating to each. To the data so cheerfully furnished by others is added information from thewriter's experience and practice, with such explanation of theory and practice as may seem necessary to a clear understanding of the principles of successful egg refrigeration. It is hoped that those who are new to the business may obtain valuable information from these collected data, and that those with experience may derive some benefit in the way of a review, and possibly pick up some new ideas as well.

A large portion of the matter contained in these

4 PKKFACE.

pages appeared in Ice and Refrigeration as a series of articles entitled: "Eggs in Cold Storage." The present book is printed for the purpose of putting the matter in permanent form, believing that those who have followed the orig-inal articles would find it convenient for future reference. While the present book has many shortcomings, and there is no doubt room for the addition of much information, reliable data, and the results of extended observations and tests, there has not heretofore been anything like a complete write-up of the subject; and in consideration of this fact the reader is asked to be liberal in his criticism.

If any errors or lack of details are noted, the author would gladly acknowledge and explain the points at fault if his attention is called toany. No other object has been in mind in writing these articles than a furtherance of scientific knowledge on the subject of refrigeration as applied to the preservation of perishable products, and the great assistance rendered by those who have written painstaking replies to the list of inquiries is hereby acknowledged. The combination and comparison of information are beneficial, and if those who have further data or records of tests will only put them before others in their line of business, no loss will be sustained by the individual giving the information, while much general good will result.

Introduction

THE value of the eggs placed in cold storage for preservation is estimated at about $20,000,000 annually for the United States alone. Considering the importance the industry has already attained, its rapid growth and future outlook, the amount of accurate information available to those engaged in the business seems very meager. The difficulties to be overcome, the skill required. and the importance of a well designed structure are not usually explained by those interested in promoting new enterprises in this line, and consequently not appreciated by those making the investment. Financial disaster has overtaken many large companies who have erected costly refrigeratingwarehouses; those which have succeeded have been forced to install new systems, make expensive changes, and make a thorough study of the products handled. The experience of nearly all has been emphasized at times by heavy losses paid in claims made by customers for damage to goods while in storage, or the necessity of running a large house while doing a very small business. Those about to become interested in the business may find food for thought in the above, and the history of a dozen houses, in different localities,willbegood information for would-be investors.

The scarcity of knowledge on the subject in hand, while being partly the result of the half developed state of the art until very recently, is also very largely owing to narrow-mindedness on the part of some of the older members of the craft, who have largely obtained their skill by years of experience and study, some of them having expended large sums on experimental work. The same experiments have

6 INTRODUCTION.

perhaps been made before, and are of necessity to be made again by others, simply because the first experimenter would not give other people the benefit of his experience, It seems at this stage in the development of refrigeration, that the improvements to be made during the next twenty years will be of very much less importance than those made during the twenty years just ending; trade secrets, so jealously guarded by some, must disappear, as they have in other branches of engineering. Storage men have been obliged to work out their own salvation in storing problems, sometimes sending their most difficult points to be answered through the columns of Ice and Refrigeration, and, perhaps, comparing ideas with those of their personal friends in the same line of business. It is to be observed that the most progressive and up-to-date manufacturing concerns in the United States to-day are giving their contemporaries every opportunity of observing their methods, and are very willing and anxious to talk over matters pertaining to their work, from an unselfish standpoint. So, too, the successful cold storage of the future will be sure to make " visitors welcome."

In anything which will appear in these articles, it is not the writer's intention to convey the idea that any mere theoretical knowledge, which can be acquired by reading and study, or even by an exchange of ideas in conversation, can take the place of practical observation in actual house management; but there are applications of well known natural laws, which are not generally understood by storage men, and their progress is handicapped from lack of this theoretical knowledge. The two following illustrations, bearing on temperature and ventilation, are among the common errors made in practice, yet easily understood when studied and tested: Some storage houses have formerly held their egg rooms at 33° F., fearing any nearer approach to the freezing point of

INTRODUCTION. /

water (32° F.), thinking - the eggs would freeze. A simple experiment would settle this point, g'iving the exact freezing" temperature, as well as the effect of any low temperature on the egg" tissues. Again, others have thought to ventilate by opening" doors during warm weather. It never happens that storage rooms can be benefited by this treatment at any time during the summer months, and only occasionally during spring and fall. The dew point of outside air is rarely below 45° F. during summer, and when cooled to the temperature of an egg room, moisture will be deposited on the goods in storage, causing a vigorous growth of mildew.

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EGGS IN COLD STORAGE.

Chapter I. Temperature

TEMPERATURE is selected for first considera- Temperature . . , . 1 P ~ . . moreimportant

tion, as it is the primary element of refrigeration, than any other and more important than any other condition. Correct temperature alone, however, will not produce successful results, anymore than a good air circulation, or correct ventilation, would give good results with a wrong temperature. This applies more especially to egg refrigeration, some products requiringonly alow temperature for preservation. The common impression of cold storage is what the name implies — simply a building in which the rooms may becooled to a low degree as compared with the outside air. Even those who build, sell and erect refrigerating machinery and apparatus often show either gross carelessness or ignorance of the requirements of a house which w 7 ill produce successful results. After a careful examination of some of the recently constructed houses, supposed to be strictly modern and up to date, the writer gets the impression that the architects regard temperature as the only requisite for perfect work. Some of theunskiiifuiiy rooms in these new houses are simply insulated and egg rooms. fitted with brine or ammonia pipes, the location of the coils having no attention whatever, being placed, in most cases, in convenient proximity to the pipe main, and in one or two, instances, the top pipe of the cooling coils was fully two feet from the ceiling. The necessity of providing for air circulation seemed not worthy of consideration, to say nothing of the lack of anything like an efficient ventilating system.

Questions regarding the correct temperature of Opinions

i 1 ii n<- regarding

egg rooms have been asked repeatedly of storage correct "

men who have been in the business long enough to be

EGGS IN COLD STORAGE.

Questions relating - to temperature.

Figures received relating - to correct temperature.

looked to for advice, the same person, perhaps, giving- a different answer, from time to time, as his ideas changed. The query has also been asked and answered through the columns of Ice and Refrigeration a number of times. At present, however, there is no temperature on which a large majority of persons can agree as being- rig-ht, and as giving- superior results to any other. The claims made by the advocates of different temperatures will be considered, to determine, if possible, what degree is giving the best results in actual practice.

The three questions relating to temperature were written to draw out opinion as to the right temperature, the lowest safe temperature, and what deleterious effect, if any, the egg sustained at low temperatures, which did not actually congeal the egg meat. The three temperature queries were:

First. — At what temperature do you hold your rooms for long period egg storage?

Second. — What temperature do you regard as the lowest limit at which eggs may be safely stored?

Third. — What effect have you noticed on eggs held at a lower temperature?

All the replies received contained answers relative to temperature, and by a very small majority 32° F. is the favorite temperature for long period egg storage. Some few, 33° F. and 34° F., with a few scattering ones up to 40° F. Under the freezing point, none recommended a temperature lower than 28° F., and for a very obvious reason, this being near to the actual freezing temperature of the albumen of a fresh egg. A very respectable minority say a temperature ranging from 30° F. to 31° F. is giving them prime results; and several recommend 30° F. straight, and say they should go no lower. In recent years there has been a decided tendency among storage men to get the temperature down near the safety limit, but many houses are so poorly equipped that they are unable to maintain a uniform low temperature below 33° F., without danger of freezing eggs where they are exposed to the flow of cold air from coils. A house must be nicely equipped to maintain low temperatures with safety. More houses would use temperatures under 32° F., were they able to, ^ n a d r e d n g wer without danger to the eggs. A very successful east- ^™P^ature ern house issued a pamphlet in 1892. At that time they maintained a temperature of 32° F. to 34° F. in their rooms. In sending- out this little book during the winter of 1897-98 a postscript was added, as follows: "This pamphlet was published in 1892, when our plant was started. Since that time all first-class cold storage houses have lowered their temperatures materially." No better illustration than this can be cited to show the tendency of the times. These people now use a temperature of 30° F. for eggs.

Most of the replies received contained answers to Replies to

'-vt i i • querv No. 2.

question JNo. 2, and the greater portion state this as being about 2° F. lower than that recommended for long period storage. It is presumed that these two degrees are allowed as leeway, or margin of safety, for temperature fluctuations. Some state that eggs cannot be safely held below 32° F., but give no reason why, while two or three say a temperature of 27° F. will do no harm to eggs in cases. One reply states that eggs held in cut straw at 25° F. for three months showed no bad symptoms. It has never been made clear how the package can be any protection against temperature, when the temperature has been continuously maintained for a length of time sufficient to allow the heat to escape; and we know that eggs will positively freeze at 25° F., as proven by experiments mentioned in another paragraph.

The answers to question No. 3 were few in num- Replies to ber, but cover a wide range. The scarcity of data on queri this point indicates that few have experimented with eggs at temperatures ranging- from 25° F. to 30° F. Some say: "Dark spot, denoting germ killed"; others, "white gets thin"; others, "eggs will decay more quickly"; or, "they will not 'stand up' as long when removed from storage." It is also claimed that "yolk is hardened or 'cooked' when temperature goes below 32° F." Some answers state a liability of freezing if eggs are held in storage at a temperature below 32° F. for any length of time. theadvoctte S by As f ar as possible, we will dig out reasons for the tempCTatures.™ claims made by advocates of both high and low temperatures, both having equal consideration. Taking 29° F. or 30 c F. and 38° F. or 40° F., as representing the lowest and highest of general practice, we will see what is claimed by each; and also the faults of the other fellow's way of doing it, as they see it. Those who are holding their egg rooms at 40° F. say it is economical, that the eggs keep well, that the consistency of the egg meat is more nearly like that of a fresh egg after being in storage six months, than if held at a lower temperature. As against a low temperature they say: A temperature of 30° F. is expensive to maintain; the yolk of the egg becomes hard and the white thin, after being in store for a long hold ; and that when the eggs are taken from storage in warm weather it will require a longer time to get through the sweat than if held in storage at a somewhat higher temperature, resulting in more harm to the eggs. Some claim that the keeping qualities are impaired by holding at a temperature as low as 30 c F., and others note a dark spot, or clot, which forms in the vicinity of the germ, when eggs are held below 33° F. Against this formidable array of claims, the low temperature men have some equally strong ones, although fewer in number. They say: There is very much less mildew, or must, at 30° F. than at temperatures above 32° F.; the amount of shrinkage or evaporation from the egg is less; an egg can be held sweet and reasonably full at this temperature from six to eight months. This last claim is a broad one, and very few houses are turning- out egg's answering to this description.

The following, relating to high temperatures, is man-^oplnion quoted from a letter written by one of the best posted temperatures. men in the business, who has spent much money and time on experiments, and studied the question for years. He says: "A temperature of 40° F. is very good for three months' holding, but if they run over that, it is more than likely the eggs will commence to cover with a white film, which grows the longer they stand, and finally makes a musty egg.^ This gentleman advocates a temperature of 30° F. for long period holding. It should be noted that the high temperature men ignore entirely the effect of high temperatures on the growth of this fungus, spoken of above as a white film. The worst thing about most storage eggs is the taste caused by this growth, (usually called mildew or mold), which results in what is commonly called a musty egg. To enable us to understand the validity of these claims made by the 30 c F. people, it will be necessary for us to ascertain the conditions which are favorable, and also the conditions which are unfavorable for the propagation of this growth of fungus, which has given storage men so much trouble, ever since cold storage was first used for the preservation of eggs.

Heat and moisture are the two conditions leading- causes operat-

° ing- to produce

to its rank growth, and the opposite — dryness and cold a growth of

r r J fungus on eggs

— will retard or stop the growth entirely. In moist, in cold storage, tropical countries many species of this parasite grow, while in the cold, dry regions of the north its existence is limited to a single variety. The causes leading to a growth of the fungus on the outside of an egg are not far to seek. It feeds on the moisture and products of decomposition which are being constantly given off by an egg, from the time it is first dropped until its disintegration, unless immersed in a liquid, or otherwise sealed from contact with the air. This evaporation not only takes moisture from the egg, but carries with it the putrid elements from the egg tissue, resulting from a partial decomposition of the outer surface of the egg meat. Conditions of excessive moisture and the presence of decaying animal or vegetable matter, together with a moderate degree of heat, are essential to the formation of fungus of the species which are found growing on eggs in cold storage. As the heat and moisture are increased, the growth of fungus will be proportionate. Furthermore, we all understand that heat hastens decomposition, and the partial decomposition of an egg results in a growth of the fungus, as before explained, when conditions of temperature and humidity are favorable. If the temperature is low, this growth is slow; for instance, if eggs are held at a temperature of 30° F. in an atmosphere of given humidity, the growth of fungus is less rapid than if held at any temperature higher, with the same per cent of humidity. As our subject merges into humidity here, the reader is referred to what is said under this head in another chapter. someexperi- Returning to the objections urged against low

ments on the ... ^ , ^ • 1 • 1

freezing point temperatures, we will see what damage is claimed from the use of a temperature of 29° to 30° F. The objections are: Liability of freezing; germ is killed; white becomes thin; yolk is hardened, and eggs will not keep as long when removed from storage. Some interesting results are obtained from experiments made by the writer. Half-rotten or "sour" eggs freeze at temperatures just a trifle under 32° F. Fresh eggs freeze at 26° to 27° F. In testing eggs which had been held in storage for several months, it was noted that the freezing point had been depressed from 1° to 2° F. An egg which is leaky will freeze at 2° to 3° higher temperature than one which is sound, probably owing to the evaporation resulting in a lower temperature. The freezing- point of eggs, as above, is understood as being- the degree at which they begin to form ice crystals inside. Of the replies received touching on the freezing point of eggs, nearly all agree with above experiments. The " dead germ " theory Dead germ the writer has never been able to locate in fact, having never seen anything of the kind in eggs held as low as 28° to 29° F. for several weeks' time; nor in eggs held at 30° F., or a trifle under, through the season. As only two or three mention having noted this result, it would seem that some local conditions, and not low temperature, were responsible.

The matter of the white becoming thin when eggs {^^atures are held at low temperatures has some bearing; in oneggs - fact, any egg held at a cold storage temperature for a long carry will show this fault, to a certain extent, especially if cooled quickly when stored, or warmed suddenly when removed from storage. With reference to the above, it is the writer's opinion that a difference of 4° to 6° F. in carrying temperature will not be noticeable in its effect on the albumen of an egg; and as to the effect of a low temperature on the egg yolk, it has been demonstrated that any temperature, which will not actually congeal the albumen, will not harm the yolk of an egg. There is a slight tendency, in this case, to a similar effect to that produced by a low temperature on cheese; that is, causes it to become " short " or crumbly.

In regard to a low temperature egg not keeping as long when removed from storage, it has been the experience of the writer that no difference was noted between eggs put out from storage and the current receipts of fresh eggs, so far as any complaint or objection was concerned, the eggs being shipped in all directions, in all weathers and subject to many different conditions. A test was also made, by placing a test showing

j. v. j j- -i • -i i 1 , •-•• keeping quali-

tnree dozen of eggs, which had been carried in storage ties of eggs at a temperature of 28^ F. to 30^ F. for five months, temperature.

in a case along - with three dozen fresh eggs. After three weeks no pronounced change was noted in either, both showing considerable evaporation as a result of exposure to the dry fall atmosphere. They were exposed to the temperature of the receiving room, fluctuating from 50° F. to 80° F. The eggs from storage went through a "sweat," while the fresh were not subjected to any such trial. As most eggs are consumed inside of three weeks after being removed from storage, this would seem like a good practical test of the vitality of a low temperature egg. A mere matter of economy between holding "a room at 40° F. and 30° F., while readily appreciated and admitted, seems of very small importance, when a positive advantage can be obtained by carrying eggs at the lower temperature; and a difference of 4° F. to 5° F. would be scarcely worth considering. Low tempera- An advantage of low temperature, not vet men-

ture prevents x J

"spot" rotten tioned, is the increased stiffness, or thickness, of the

eggs.

white of the egg while in storage, holding the yolk in more perfect suspension. When eggs are held at a temperature of 36° F., or above, for any period longer than four months, the yolk has a decided tendency to rise and stick to the shell, causing rotten eggs, known as "spots." It is usually understood that the yolk settles; but, being of a fatty composition, it is lighter than the albumen, and rises instead. If the albumen is maintained in a heavy consistency, the yolk is retarded from rising, and held in a more central position. It was long a practice with storage men to turn eggs at least once during the season, to prevent the above trouble, and some recommend it even now; but the practice has been generally abandoned with the advent of low temperatures for egg storing. Putting- eg-g-s in When eggs are put in cold storasre they should not

and removing- o o r o j

from storage, be CO oled rapidly. The effect on the egg tissues is bad — they should have time to rearrange themselves to the changed temperature. This is especially true where eggs are placed in storage in extreme warm weather. Sudden warming is also detrimental to the welfare of an egg, for a similar reason to above. The most noticeable effect of either is a thinned albumen. If this process of cooling and warming could be practiced carefully (which is not always practicable commercially), a well kept storage egg would come out of storage with nearly the same vitality it had when fresh.

CHAPTER II. Data available on humidity practically nothing

Evaporation and mold can be prevented.

Questions relating 1 to humidity.

HUMIDITY.

INFORMATION on the subject of humidity, as applied to the cold storage of eggs, is very meager. Not more than a dozen of the replies received in answer to the lis t of inquiries sent out contain information on the three queries under the head of humidity. Considering the amount of talk we have all heard, with dry air as a subject, this scarcity of knowledge is rather surprising. Those who have had experience with cold storage work and the products handled are well aware that an essential for good results in egg refrigeration is a dry atmosphere in the egg room ; but just how dry, very few are able to give even an approximate estimate. Very likely if a cold storage man is asked in regard to it, he will reply that an egg room should be "neither too moist nor too dry." What this "happy medium " is, that will not shrink or evaporate the eggs badly, and yet keep down the growth of fungus to a minimum, is what all are striving for, and very few have the means of knowing when this point is reached. A few years ago a prominent commission man, in conversation with the writer, speaking of storage eggs, said : "You storage men are between the devil and the deep sea. You always shrink 'em or stink 'em"; meaning that eggs which were held long in storage would show either a considerable evaporation or a radical " musty " flavor. To some extent this is true, but with a penetrating circulation, careful ventilation and a judicious use of absorbents (all of which will be considered under their proper heads) egg can be, and are, turned out of storage without this strong, foreign flavor, and with little evaporation or shrinkage. The questions relating to humidity were written with a full understanding of the scarcity of information on the subject, and were designed to locate, if possible, those who were making- tests of air moisture, and get opinions on the correct humidity for a given temperature. The following are the queries:

First. — What tests, if any, have you made of the dryness or humidity of your egg rooms?

Second. — What per cent of air moisture do you find gives the best results at the temperature you use?

Third. — What instrument do you use for testing air moisture?

Questions 1 and 3 are practically the same, the latter being written simply to make the query more plain and indicate whether an instrument or some other test was used for determining air moisture. Four houses reporting are using the dry and wet bulb thermometers ; the others are using hygrometers of French or German make.

The answers to question 2 vary greatly ; some Replies reiat-

71 . . in S to correct

also giving the actual testing humidity of their rooms humidity, and their opinion of a correct degree as well. From 70 to 80 per cent of humidity is the test of nearly all reporting, and of the rooms tested by the writer, nearly all show a similar humidity, with one occasionally going as high as 85 per cent, and some as low as 65 per cent. Two answers recommend a humidity of 65 per cent, and one a humidity of 60 per cent, with a temperature of 30° F. to 32° F. Others hold that their testing humidity of 70 to 80 per cent is correct. The matter of correct humidity will be discussed further on.

The humidity of a room depends on the season to^^^ s a moderate extent, and the condition of the room, as humidity. regards ventilation, in some cases. In late fall or winter, especially, if air is taken directly into the room from the outside, the humidity will be low. As cool weather approaches, the tendency is for the humidity to rise, and unless kept down by ventilation or by the use of absorbents, serious consequences are sure to follow.

EGGS IN COLD STORAGE.

What relative

humidity

sisrnifies.

Quoted from "Instructions to Weather Observers."

To enable us to thoroughly understand the meaning- of relative humidity, as it is called, we will study a few extracts from " Instructions to Voluntary Observers, " issued by the Weather Bureau at Washington, D. C. Humidity is considered on a decimal scale, with 100 the saturation point of the air, at which it will hold no more water vapor, and the point at which air contains no moisture whatever. The various percentages between these points is a degree of humidity relative to these two extremes, or relative humidity- The quotations below are not contained in the recent issue of instructions, but are from the issue of 1892, which is now superseded by that of 1897.

WATER VAPOR IN AIR.

The air contains vapor of water, transparent and colorless like its other gaseous components. It only becomes visible on condensing- to fog- or cloud, which is only water in a fine state of division. The amount is very variable at different times, even in the vicinity of the ocean. The amount of moisture that can exist as vapor in the air depends on the temperature. There is a certain pressure of vapor, corresponding to every temperature, which cannot be exceeded ; beyond this there is condensation. This temperature is called the temperature of saturation for the pressure. When the temperature of the air diminishes until the saturation temperature for the vapor contained is reached, any further fall causes a condensation of moisture. The temperature at which this occurs is called the dew point temperature of the air at that time. The less the quantity of moisture the air contains, the lower will be the temperature of the dew point. For different saturation temperatures, the weight of vapor, in grains, contained in a cubic foot of air is as follows: