Feh
1917
T II 2 J O I - R S.1L 0 F I .V D 1-5'T R I d L A S D E S G I S E E RI S G CR E M I S Z'R'E
THE CHEMIST IN THE CANNED FOOD INDUSTRY' R y W. D. BIGELOW Received D e c e m b e r 1, 1916
The canned food industry was based fundamentally on scientific research. I t would appear that this fact should have suggested to the pioneers of the industry the advantage of the cooperation of scientific men. .Apparently, it did not. The laboratory was not appealed to as frequently as might have been done advantageously. The progress in the industry has been largely haphazard and there have been many blunders and enormous losses that might have been avoided by scientific control. At the same time, the laboratory has demonstrated its usefulness to the industry in many ways. DISPOSAL O F BY-PRODUCTS
The disposal of by-products is a question to which the canning industry has not given adequate attention. Some of the byproducts may be used for the preparation of food. For instance, pulp may be prepared from the peelings and cores of tomatoes. In all such cases, every possibk precaution should be taken to see that the material is proper for the manufacture of food. Decaying matter must he excluded. This work has a very close relation to the general question of factory sanitation. Some plants have found the laboratory of great assistance in connection with such matters. ECOSOMICAL DRYING O F PRODUCTS AND WASTES
Questions often arise regarding the use of some cannery by-products in the manufacture of stock foods and fertilizers. Very little has been done in this direction except in the case of certain by-products which are fed in their natural state or preserved in stacks or silos. In order to transport offal from the cannery for a considerable distance or make it available for general market purposes, it must first be dried to prevent decomposition. Some experimental work has been done on this subject, but it has not been accompanied by proper engineering skill. Experimental work is still needed to determine what substances can be dried economically. Products of this nature contain a large amount of water and their drying would be expensive. Most canneries run for a very short season, and whether the value of the by-products is ever such as to make i t practicable to install expensive drying equipment and maintain i t for a season lasting but a few weeks is yet to be demonstrated. Certainly, in many small plants it cannot be done SUPPLIES
Questions are constantly arising in which the canner will profit by being able to consult some one of scientific training. Articles of all kinds are being offered with extravagant claims regarding their value. Often these articles are of such a nature that the manufacturer is not. in a position to form an opinion regarding them. Products are offered which are claimed to have superior merit for almost every operation of the canner, from saving fuel under the boiler or keeping the boiler tubes free from incrustation to the cleansing of the floors and factory utensils or sweetening or flavoring the food. Some of these articles are satisfactory, but are offered under coined names a t prices far in excess of their value. Others are utterly fraudulent and worse than useless. Such products sometimes contain artificial sweetening material or preservatives which packers do not desire to use. SPOILAGE PROBLEMS
I t sometimes happens that an unusual amount of spoilage is noticed during the canning season. I n extreme cases this may cause a loss of several hundred or even several thousand dollars a day and it is of the utmost. importance t o learn immediately the cause of this spoilage in order that it may be corrected. 1 P r e s e n t e d 52nd M e e t i n g C h a m p a i g n . April 19. 1916.
.Lmerican
Chemical
Society,
Urbana-
187
Spoilage is occasionally found in the store-room after the packing season is over and the canner desires information regarding its cause, in order that he may make provision to eliminate it from future packs. It is often desired t o fix the responsibility for spoilage in order that, if it is due to defective cans or other supplies, claims may be made against the party properly responsible. I t is probably in fixing the cause of spoilage that the chemist is able to render the most immediate assistance to the canner and it is in such questions that experience in the industry is most essential. Certain acid fruits, such as strawberries and red cherries, formerly corroded the can and dissolved an appreciable amount of tin and iron. For that reason, the color of the product was often unsatisfactory, especially with red fruit, as the coloring matter was bleached out. The flavor of the product was also sometimes impaired. Eventually a sufficient amount of hydrogen gas was liberated by the solution of tin and iron t o bulge the ends of the can, and, though still bacteriologically sound, the food became unmerchantable. This was overcome by the use of enameled cans, but immediately a new difficulty arose. The enameled can was found to pinhole badly, thus exposing the contents of the can to air and leading to contamination. This was probably due, as suggested by Walker, to the influence of the unsaturated groups of linseed oil present in the lacquer in depolarizing hydrogen set free by the action of the fruit acids on the For metal wherever an imperfection in the lacquer occurred. several years the losses sustained by some packers owing to this cause were greater than the entire profits of the pack. Recently, as a result of further laboratory study, this difficulty has been largely overcome. SPOTTING O F CANS AND PRODUCTS
Instances are constantly arising in which packers find some imperfections in their product which make its appearance less attractive or, a t least, unusual, and thus possibly not acceptable to consumers. The difficulty may be one of flavor or color or general appearance. It may be confined to the external appearance of the cans. Small dark spots occurring a t the surface of a light colored product may cause unfavorable comment. A trivial imperfection may make the difference between profit and loss on a season's operations. These difficulties are often unattended by any change in material or factory procedure, as far as the packer is aware. I t is the business of the chemist to find their cause and to suggest a remedy. As an illustration, we may refer to the occasional formation of black patches on the inside of corn cans. These patches consist of finely divided iron sulfide, apparently in colloidal form, intimately mixed with a mass of the starchy material of the corn. Because of its colloidal nature, the amount of iron sulfide present in these patches is very much less than it appears to be. There is no objection to it, except that its appearance is unsightly. As a result, much corn has been discarded and a great deal more sold a t a loss to the packer. On the whole, a good many thousand dollars were lost by the industry from this cause alone during the season of 1914. The cause of this formation was difficult to explain. As a result of the concerted study of several laboratories interested in the industry it has been partly explained, and many of the conditions leading to its formation have been defined. Consequently, the loss during the past season was very much less, and it is hoped that directions which have recently been published will lead to the elimination of this difficulty in the future. R E S P O X S I B I L I T I E S O F CHEMISTS T O T H E PROFESSION
In legal procedure it is understood that, in its final opinion, the Court is not governed by tentative suggestions offered or casual remarks made by it during the course of a trial. Fortunately, or unfortunately, the chemist is not permitted an obiter
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dictum. He is held responsible for every opinion he expresses, even though he may base it on an imperfect or incorrect statement of facts. When such an opinion is found t o be erroneous, not its author alone but the whole chemical profession suffers in reputation. The average food manufacturer seems to ascribe a sixth sense to the chemist. Consciously or unconsciously he attributes to him some almost miraculous knowledge. He does not fully understand that the chemist uses only ordinary faculties and that his only advantages are a knowledge of some special means of study and a training in observation. To many food manufacturers, a chemist is a chemist, and all are measured by the same rule. They do not realize that a chemist may be an authority on the analysis of steel or paint and still be utterly ignorant of the chemistry of foods. They do not know that a chemist may be well informed in the manufacture of jelly or ketchups and yet know nothing of the questions involved in the packing of canned foods. Even those packers who have had larger experience with chemists and understand better our method of arriving a t conclusions are likely to attach undue importance to a casual opinion expressed in conversation. Any opinion that we express is likely t o be understood by them t o be based on experimental work and a full knowledge of the premises. We should be very careful, therefore, in expressing an opinion regarding a subject which we have not thoroughly studied. I M P O R T A N C E O F SPECIALIZATION
I n many lines of technical work, we do not make this mistake. Those of us who have not studied explosives realize our lack of information and do not hesitate to say we do not know. We who know little of the technology of iron and steel and nothing of armament would not presume to examine a sample of steel to determine its suitability for armor plate. In food chemistry, however, and especially in the manufacture of foods, we are all experts. Almost everybody thinks he knows a great deal about food. Just why, it is difficult to understand, unless it is because we all eat food. The fact remains that there is probably no branch of chemistry regarding which there is less information among well informed chemists who have not made it a specialty than the chemistry of foods, and particularly canned foods. The readiness of chemists who have had no experience in the manufacture of foods t o give a n opinion in that field has afforded many illustrations of the truth of the old adage, “A little knowledge is a dangerous , thing.” It explains some of the misinformation that has been given canners even by reputable laboratories. This has usually been done in personal conference or by letter in reporting a sample sent to the laboratory, but not infrequently the information thus given has been made public in newspapers, trade journals, or even in scientific puhlications. I will cite a few instances to illustrate what I have in mind. MISINFORMATION AMONG C A S N E R S
There is a general belief among canners that the use of hard water in the preparation of brine or syrup added to canned foods results in a tougher product than would be obtained with soft water. It seems reasonable to suppose that this would be true. The thought a t once suggests itself that when peas are heated for the purpose of sterilization the calcium bicarbonate dissolved within the peas may be changed t o insoluble calcium carbonate, making the peas tougher or harder than they would otherwise be. It has also been suggested that calcium sulfate, being less soluble in hot water than in cold, would be thrown out of Solution t o a considerable extent when the peas were sterilized. As a result of this general, but erroneous, belief, canners frequently have submitted samples of water to chemical laboratories and asked whether the water was too hard for canning peas or beans.
Vol. 9, No. a
Laboratories have examined such water and have condemned hard water for the reason given above. I n this they appear t o have been governed by a prevalent superstition rather than by the results of experimental work. It did not occur to them that the carbon dioxide formed in processing would redissolve any calcium carbonate that might be formed by the higher temperature, or that the calcium sulfate precipitated by lowered solubility during the heat of sterilization would dissolve again after the product cooled. Again, salt manufacturers have advertised their brands as relatively free from calcium and magnesium and, for that reason, have claimed that these brands of salt could be used by canners without toughening their vegetables. This claim has often been accepted by chemists, and salt has been approved or condemned on that basis. Again, some of the objectionahle colors found occasionally in canned foods have been explained by chemical laboratories as due t o iron in the water employed and canners have been warned, as the result of chemical analysis, not t o use water from certain wells because of its high iron content. I n making this last suggestion, chemists have not taken into consideration the fact that there is more iron absorbed by canned food from the tin plate than is carried by any water which they could possibly consider using. An article has recently appeared in the trade papers alleged to have been written by a chemist employed by a lithographer. The name of the chemist was not given. His report proved t o his own satisfaction that there is no object in removing food from the cans as soon as opened. To prove this, he determined the acidity of a number of foods as soon as the cans were opened and again after a lapse of a number of hours. From the fact that the acidity did not increase materially, he argued that no tin could possibly have gone into solution and, hence, that there was no objection to storing food in the open can. The obvious method of determining tin in the food a t intervals in order to ascertain whether the amount had increased does not appear t o have occurred to him. He did not consider the influence of oxygen in promoting the solubility of metals when the food is exposed to the air, although his report quoted a letter from the Bureau of Chemistry in which this influence of oxygen was mentioned. Every food chemist knows that leaving food in an open can does not make it injurious to health, though the amount of tin and iron dissolved is somewhat increased. The article just referred t o throws no light on this subject, but is evidence that experience in the field of chemistry pertaining to the printing of labels does not qualify a man to conduct an investigation with any question relating to the contents of the can. The publication of opinions of this character is not confined to popular journals and trade papers. We find them also in scientific literature. A few months ago an article on the iron content of tomatoes appeared in THISJOURNAL The writers, after determining the amount of iron in the samples examined, procured samples of soil in the localities in which the samples were grown and commented on the relative iron content of the tomatoes and of the corresponding soils. Toward the end of the article, the writers casually referred to the fact that the samples were canned. They made no mention of the method of canning, the conditions under which the product was stored or the age of the sample. All of these factors would govern the amount of iron in canned tomatoes. Under all conditions, the amount dissolved from the can is immensely greater than the amount of iron originally contained by the tomatoes. Even that fact, however, can scarcely explain the high iron content of these particular samples.
Feb., 1917
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DIFFERENT CLASSES OF C A S S E D FOODS
Wrong conclusions have often been reached by confusing different kinds of canned foods and assuming - that a certain condition in one class of foods was due t o the same cause as an apparently similar condition in another class. For instance, acid fruits dissolve an appreciable amount of tin and iron, owing to the solvent action of the fruit acids. Errors have sometimes been made by assuming that tin dissolved in some other types of foods, such as canned pumpkin or shrimp, was also due to acidity, when, as a matter of fact, i t is apparently due to the presence of certain amino bodies. The solution of tin in foods of this class is not accompanied by the generation of hydrogen’and does not form springers Attention has already been called to the fact that springers (cans under very slight pressure) are often caused in acid fruits by the hydrogen liberated by the action of the fruit acids on the metal of the container. It sometimes happens that cans of other products (such as corn) which do not dissolve tin and iron, are found under slight pressure and are apparently springers. Erroneous conclusions have sometimes been reached by assuming that the pressure in these cans is due to the same cause as that in cans of acid fruits that appear t o be in the same condition. This is not merely an academic question. Responsibility for spoilage involving many thousands of dollars is sometimes a t stake. It is often of the utmost importance to determine whether the responsibility rests with the can manufacturer, the canner, or the conditions under which the finished product is stored. VARIATIONS I N CAUSES O F SPOILAGE
In the enforcement of municipal food laws and regulations and, to a certain extent, in the enforcement of state laws, there is sometimes a failure t o discriminate between canned foods which have spoiled by reason of improper sterilization or leaky cans, and those which have become more or less swelled by reason of the hydrogen generated by the action of the fruit acids on the metal of the container. Foods of the latter class, though neither decomposed nor injurious to health, are undoubtedly not merchantable and their sale or use should not be permitted. The condition of springers, and even of what appear to be hard swells in acid fruits, is usually due to the character of storage after the product was canned and, when the goods are criticized, responsibility should be placed where it belongs. The designation of such a product as decomposed is unscientific, because it is not true. It is unjust t o the manufacturer, for the product was merchantable when it left his hands and would have remained so with proper subsequent treatment. A chemist who makes a decision of this kind works injury to the chemical profession in the minds of business men who are conversant with the situation,
It should not be understood that chemists are more prone than others to inaccurate statements regarding the manufacture of foods. Magazine writers give vivid descriptions of processes they have not seen and even prominent authorities on dietary diseases and in the practice of medicine not infrequently make statements which show a complete lack of information of the technology of foods of a generation ago, much less the practice of the present day.
It not infrequently falls to the lot of a chemist in the canning industry to explain to b siness men, as well as he can, how it is possible that a man who makes definite and positive statements regarding a subject of which he has no knowledge is not necessarily equally erroneous in his views on other matters. S 4 T I O N A L C.4h.NBRS’ h S ~ O C I A T l O N
WASHINGTON, D. C.
SOME OBSERVATIONS O N . THE PRESENT STATUS OF THE SUBJECT OF THE AVAILABILITY OF NITROGEN IN FERTILIZERS’ BY
CHAS.B. LIPMAN
In order to gain a clear comprehension of our present-day views on soil fertility it is necessary t o divest one’s self largely of traditional theories, formulas and fancies of the vintage of 1850. If this is so of soil fertility in general, and no progressive scholar in soil science will deny that i t is, it must of necessity be true of that one phase thereof which concerns itself with the availability of some of the plant food elements. These statements are not intended as destructive criticism as the following discussion will indicate. They are meant only for the purpose of arousing from their lethargy those who are either too conservative or too indolent to keep abreast of the scouting parties in soil fertility studies. No one rises with greater alacrity than the writer to render homage to the last two generations of investigators for their splendid contributions to our knowledge of plants and soils. No one appreciates more deeply the value of the gigantic work in chemical analyses of plants, soils, and fertilizers which the investigators mentioned have achieved. We could not very well have done without these numerous analyses. They constitute the growing pains of our adolescent period and as such are presumably ineluctable and necessary accompaniments of normal development. But once we have successfully weathered them, once they have contributed their quota to the creation of our modern views, they have served their purpose and the bona fide scientist must move on t o a sounder and fact-fortified science and a saner philosophy with respect to crop production. Everything which I have to say to you to-day takes its origin on such a basis of thought and action as I have just described &nd is an attempt to make as nearly lucid as my humble powers will permit the answer to the question, “Where do we stand on the problem of the availability of fertilizer nitrogen today?” Let us first understand clearly the meaning of the term “available nitrogen.” In the case of phosphorus and potassium, availability means but one thing, and namely, that some mineral compound containing the element in question is soluble in the soil moisture. So far as we can a t present determine it makes but little difference to the welfare of the plant if the latter assimilates potassium from the sulfate, nitrate, phosphate, or any other mineral salt. Likewise, it seems to be a matter of indifference to the plant, as it were, if phosphorus is presented to it in the form of calcium, potassium, magnesium, or other phosphate. The only condition upon which availability depends, therefore, in the case of all the other essential chemical elements than nitrogen to plant growth, is that they must be in some compound which is soluble in soil moisture. This is not necessarily the case, however, with nitrogen. In fact, the situation with respect to the latter element is very complicated. Some plants appear to assimilate nitrogen with benefit in a large number of water-soluble forms whereas others may assimilate these same forms but be injured by all except the nitrate form. Still others may use nitrogen in the form of ammonia without apparent injury, but are much more wasteful of nitrogen under those circumstances and need much more of i t in the form of ammonia than in the form of nitrate to produce one pound of dry matter. Availability of nitrogen, therefore, if I may repeat again, is by no means so simple a consideration as the availability of the other essential chemical elements. Fortunately, however, we know that the nitrate form of nitrogen is the only one which can be used advantageously and economically by terrestrial plants (rice and similar semi-aquatic plants are of course excepted). Time will not permit fuller consideraP r e s e n t e d at t h e 53rd M e e t i n g of t h e American Chemical Society,
New York City, S e p t e m b e r 25 t o 30, 1916.
