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mediately protested, and further investigations were ordered. The results of these investigations were never published but, so far as the authors know, no harmful effects from the eating of sulfured dried fruits were found. At any rate, a later decision of the food and drug authorities (1908) withdrew objection to the use of sulfur dioxide in the ordinary amounts if its presence is stated upon the label, and if abnormal quantities are not used for the purpose of marketing products of excessive moisture content. Since no definition was made of what constituted an ordinary amount of sulfur dioxide, nor an excessive moisture content for fruits other than apples, the United States Government has not enforced any limit on sulfur dioxide content in dried fruits. ARBITRARY RESTRICTIONS OK SULFURDIOXIDE The amount of sulfur dioxide in the sulfured dried fruits of California varies between a few hundred parts per million for apples and some types of sulfured raisins, and 3000 p. p. m. or more for apricots, peaches, and pears. Kumerous observations show that for the latter fruits about 2000 to 2500 p. p. m. are required to secure in the product the best commercial color and a t least reasonably good keeping quality. Except for improved keeping quality, nothing appears to be gained by a sulfur dioxide content of over about 2500 p. p. m. Recent observations by Popp and Popp (6) and others in Germany have shown the sulfur dioxide content of dried apricots imported into that country to range from 490 to 2260 p. p. m. The sulfur dioxide content is gradually lost by volatilization or oxidation during storage, according to observations in this laboratory, the loss in some cases amounting to one-third and one-half the original amount in 6 months of storage a t or around 20" C. Similar losses of sulfur dioxide take place during the soaking and cooking of the fruit for consumption. I n view of these facts its seems certain that the several foreign countries and the states of this country now permitting little or no sulfur dioxide in dried fruits could without the slightest danger to the health of their citizens increase the allowable limits to 2500 p. p. m. or more, or even remove the restrictions
Vol. 24, No. 6
entirely. Such changes in the restrictions would not only widen the outlet for California dried fruits, but would also facilitate the addition of these nutritious and economical foods to the dietaries of the people in question. A movement in this direction has recently been made in Germany where the restrictions against sulfur dioxide appear to have originated. I n addition to the fact that objections to the ordinary uses and amounts of sulfur dioxide in dried fruits can apparently not be supported convincingly by experimental evidence, a new and hitherto unsuspected useful function of sulfur dioxide in dried fruits has been revealed by the recent investigations of Morgan, Field, and Xichols (4). These workers have shown that the use of sulfur dioxide, .preparatory to drying, preserves almost completely the vitamins A and C of which several of the common dried fruits are good sources, and drying without previous sulfuring results in virtually complete loss of these vitamins. While the amounts of sulfur dioxide necessary to preserve the vitamins has not been established exactly, it appears that a t least 500 p. p. m. are required, and retention has not been complete in some products with a considerably higher sulfur dioxide content. In the light of these experiments and the apparent harmlessness of the preservative in dried fruits, it would seem that statutory minimum requirements rather than maximum limitations of sulfur dioxide in these foods would find justification in the demonstrable facts. LITERATURE CITED
(5) (6)
(7) (8)
Reythien, A , 2. Sahr. Genussm., 8 , 36 (1904). Flury, Deut. h'ahr. Rundschau, No. 9 (May 2, 1929). Kerp, W., Arh. kais. Gesundh., 21, 141, 146 (1904). Morgan, A . F., Field, A,, and Nichols, P. F., J. Agr. Research, 42, 35 (1931). Pfeiffer, L., "Die schweflige Snure," Chem. Zenlr., 19, 1414-15 (1888). Popp, G . , and Popp, H., Dcut. Sahr. Rundachau, Y o . 24 (Nov. 22, 1928). Rost, E., and Frana, Fr., Arb. kais.Gesundh., 21, 312 (1904). Wiley, H. IT,,et al., Bur. Chem., U. S. Dept. S g r . . Bull. 84 P t . 111, 761 (1907).
RECEIVEDApril 7, 1932
Stabilizing Nutrients by Canning E. F. KOHYAN,Research Laboratories, National Canners Association, Washington, D. C.
A
S INDUSTRY is said to justify its existence only in so far as it serves the public. While such attributes as convenience and economy are ascribed to canned
foods, probably the major service of the canning industry to the public in this country is in the stabilizing of nutiients. There are a number of implications in this statement. It is implied that nutrients are in part, if not all, unstable; furthermore, that the public is in need of having them stabilized. It is planned to discuss these two implications. To be assured that all are thinking on the same basis, a clear definition of the intended meaning of nutrients is necessary. Broadly speaking, any food commodity is a nutrient. In modern times it has become customary, however, to analyze and dissect each food into the various nutrient elements it may supply, such as proteins, carbohydrates, fats, mineral elements, vitamins, etc. This is necessary in the evaluation of any dietary, and it is only through such an analysis that we can arrive a t the real value of any given food in a dietary. It is not sufficient therefore to consider whether a given food product is stable or, perishable, but one must make sure that
none of the nutrient elements supplied by it undergoea deterioration. When modern industrialism was applied to our food supply, the chemical composition of our food intake was radically changed from that upon which animal life upon earth developed through the ages. In evidence of this, our annual per capita consumption of approximately 108 pounds or about 530 calories daily of what may almost be designated "pure" sucrose may be cited. At the close of the Civil War, this was a t the low figure of 8 pounds. Our wheat flour and corn meal consumption totals 900 calories per day. If to these we add the other milled cereals and refined oils, we have considerably more than half of our caloric intake consisting of foods that supply us with scarcely any of the mineral elements and vitamins and a rather poor representation of the protein material contained in the raw products from which these foods are derived. These new food products (very new in terms of the ages through which various forms of animal life have acquired food habits) have so convincingly demonstrated their advantages
from the standpoint of palirtability, culinary adaptability, economy, convenience, esthetic appeal, etc., tliat the nutritionist has been forced to seek other means of supplying ttrtx dietary elements they lack, rather than take a step backward in atteinpting to make available the raw products from which they canie. In brief, the solntion has 1,een found in tlie consumption of a grcxtrr ~rroinirtionof dairy produck, vegetables, and fruits. The wliolesnme influeiice on general health of this solution wherever ~~~
Aithoug1, dairyi&is almost uniformly productive througbolit t'he year, it is to a certaincItcritsectioiia1. Canning makes iiossilile a much more general dist.ribntioii of its major p r o d u c t , milk, The production of vegetalilcs and fruits is distinctly a. seasonal matter in any given region. Because (JF their perialrable nature, their storage and their transportation from regions
a n d a n i m a l feeding." Neither the iodine nor t i l e vitamiii I> of s a l m o n bv itself is particularly perishable, however. Tlie protein, fat, and vitamiii A ( t h e o t h e r major nutrient coinp o n e n t s of t h e salmon) in beingstabilized become the vehicle by which the iodine and vitamin D inay be distributed. One of t h e m o s t valuable types of nutrient elements contributed t o the dietary by v e g e t a b l e s and, probably t o a
1
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1 I
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saniewhat lesscr exteut, by fruits are various nrinerri salts. It cannot be nlainred bhat these arc nnstahle or perishable, though some may argue that they are niost valunble in organic combinations. Hence, the prescrvat,ion of vegetables and fruits in a stable form becomes important because they act as vehicles for stsble nutrients as well as for their perishable eornlioncnts. Howt!w-, it is the least stable nutrients that arc of greatest c o i w r i i . \'egctables and fruits possess essential nutrient el em e n t s , 11 apparently associatcd with the ~~
1
This I s rrzcessary on uccourit of the clulriging dietary dernands i$ the present day and the i perishability and seasord rinturc of m n y foods desirable lo npw demands, A lurge number of tests hme shown that the CCUVli!Lg industry has succeeded very cOmpktely in retaining inhrrmt ,food values. A number of illustrutioris ape cited. There still remains much to be done ill the and fLLuor of ,foods Ihrotqh the canning process.
tion, tlie iitarnins are mainly in milid.
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H l G H VIT.4XlN CONTEXT
CehnACTEnlsTr~ OF GREEN
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-
IX3PECTI"N
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VEGET.4BLES
I t has long Iireu recognived t h a t succnlerit f o o d s a r e desirable in tile diet. only since bhe d i s c o v e r y of the bas there been any clearly u n d e r s t o o d r e a s o n
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d aontinuuus Row makes i t possillo to handle e m i r n o u ~q u ~ n t i t i e n 80 , neoessary f o r expeditious handling ui ueriahablea.
f o o d i n t h e water, vitamin C is agaie developed. Green shoots of peas, grown in sand from which t h e y probably obtain no food m a t e r i a l , also acquire vitamin A. There is thus a close relationship between sueculency and vitamins A and C in the pea. In this illustration, peas are intended to typify certain fundamental principles regarding the value of sneculency, or, more strictly speaking, the properties of tlie
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actively metabolizing plant ccll in tlie dict. Since rrictabolic activity is most in evidcnee in green growing vegetation, it is logical that we should find green vegetables, partieuiarly leafy products, our most potent source of the least stable vitamins. Moreover, they are likewise outstanding in their mineral content vhich makes them particularly valuable to supplomerit the foods from which manufactriririg proccsscs have largely eliminated the mineral salts. There is thus ample eT4dence of the desirability of a & A i&g process for such commodities if it i n fact reiidcrs their valuable assets available during all seasons in cvcrg region. That tliis is accomplished in the commercial canning process has been put to sufticient test with a considerable number of products and the d a t a recorded (1). R a t h e r t h a n summarize o r review such evidence here, i t seems more pertinent to discuss cert.airi f u n d a m e n t a l principles embodied in the commercial canning process that make this possible.
Vol 24, No 6
I t is to he noted, however, tliat in practically all cases where kettle-cooked produets, as generally prepared in the kitchen, were compared with the canned commodity, the vitamin C content was superior in tlie canned products. It should be clearly understood that the canned products and tlie kitclien-cooked products did not represent t.he same raw material. The canned product in eaeli instance represented one lot of raw niaterial canned in seasoil in t.he regular manner in a commercial cannery. The kitchen-cooked product represented raw food purchased daily on tlie Rew York market. There m s one exception to this-namely. tomatoes-in which case tlie same lot of tomatoes was fed raw a n d in t h e c a n n e d state. This wasdone by canning tomatoes periodically as often as it becanie necessary to secure a new supply of ripe tomatoes for f e e d i n g i n tlie r a w state. To do tliis, it was necess a r y t o s e c u r e tom a t o e s from a distance out of season, and bencc they were picked green as i s done in s u p p l y i n g them to the city CANNINGS T A n m m s markets. I n this one VITAMINS instance it was definitely demonstrated Based on the evithat the canned todence available from CAPPINGMACHINEPOR SEALING SswewrY TO NINETY CANSPER MINUTE matoes were the full studies cooperatively equivalcnt of the same conducted be tween Autornatio iiitriate msahinery rnskes possible edorrnsooes that asanot otherwise be duplieateg tomatoes in the raw this laboratory and state. W . H. E d d y of Teachers College, Columbia University, New York, it h CANNIKCIllmnous SPARE VITAUINB apparent that certain foods may be canned with no 10s of vitamins, whereas with others the loss may be considerable. It is of iiiterest to consider the reason for the destruction It is apparent also that each vitamin must be considered of vitainin C in different foods in the canning process and separately. in the home cooking process. I n an experiment with apples Vitamin A is relatively stalie to the canning proccss in all it wasdefiiiitely demonstrated that, if the apples are permitted products, as no loss has been demonstrated to occur in any through tlie respiratory process to consume all the oxygen in product. Certain foods have been subjected to much higher their tissues, they can then be canned with no loss of temperatures and for longer times than are ever employed in vitamin C, whereas, without doing this, the canning process canning, with no lessening of vitamin A potency. is just as destructive of the vibmin C as the home cooking The evidence with vitamin B is somewhat difficult of process used in making apple sauce or in baking apples. This interpretation, particularly now that different fractions have respiratory process is given an unusual opportunity in apples been recognized, whercas, in most of the work reported with in commercial canning to deplete the tissue of any oxygen. canned foods, the various fractions of vitamin B as well as This is accomplished by submerging them in a salt solution vitamin G have been considered as a group. It appears, previous t o putting them into cans. The question arises, how generally is this principle applied however, that vitamin B, tested as a single factor, experiences some destructive action in leafy vegetables such as spinach in the canning of other fruits? It is not applied to the same and cabbage, whereas in certain other products, like peas, degree as with apples. This, however, is not necessary since it is more stable. That this destruction is of no serious apples are far more porous khan any other fruit, as evidenced nature is discussed helow. by the fact that approximately one-fourth their volume is gas The results with vitamin C are more specific. It is a p and that this gas approximates air in composition. Moreparent that with some products, such as tomatoes and straw- over, this gas in apples is intimately enclosed in the tissue its berries, there is little or no destruction during the canning intercellular gRs. The tissue of most other fruits contains process. With other products, such as peas, the destruction very little intercellular gas in comparison wit.li apples. The may be relatively small. With still others, such as leafy caps of strawberries and raspberries may entrap air, but this vegetables (spinach, turnip greens, and cabbage), there is easily remorable mechanically. may be a relatively high percentage of destruction alIn fruit canning, the cold fruit is first placed in the can and though the final content of vitamin C may still he as then covered with hot sirup or water. I n most instances the high as any other edible product because of the high original sirup or water may be hot enough to destroy the enzymes in the outer portions of the fruit, hut it is soon cooled by the potency.
June, 1932
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fruit to a sufiicient degree to prevent any niarked destruction siderable evidence that vegetables and fruits deteriorate of enaymes. The inner portion of the fruit, on the other hand, immediately upon being trarvested, from tlie standpoint of is warmed by this sirup and the respiratory process greatly their vitamin C content. With some this deterioration is speeded up. As the can then passes through the exhaust box, relatively rapid. the temperature is gradually raised, and up to a temperature Canned vegetables are all canned within a very short time destructive to tlre enzymes the accelerated respiratory after harvesting. Tho time necessary for distribution in the process rapidly consumes oxygen within the tissues. It may raw state to city markets is many times that elapsing between be said, therefore, that in the canning of all fruits the respira- harvesting aiid canning. 111t,lie case of those vegetables and tory process is employed in a manner that makes for the fruits that are stored, this time is greatly extended. No prescrvation of vitamin C. doubt t.his promptness in canning of vegetables and fruits In the canning of vegetables, a different process operates. a.fter harvesting is one reason for the relatively high vitamin C c o n t e n t of t h e F r o m the work rep o r t e d with tomato canned foods. p r o d u c t s , it is eviSOMERAW AND dent that,when afood CANNED Foons such as the cyclone COMPARED juice of tomatoes is rapidly heated to boilT h i s discussion i n g , e v e n though it would be incomplete has an abundance of if it omitted reference e n t r a p p e d oxygen, to some practical ret h i s oxygen is so sults a they affect the quickly driven off by public or general contlie boiling process sumer. Among tlie t h a t its destructive c a n n e d f r u i t s , the effect is minimized two largest items are a n d t h a t thereafter p e a c h e s a n d pinethe continued boiling apples. Evenwith the results in no further aid of modern transrneusurahlc destrucportation and storage tion of vitamin C even facilities, raw peaches if continued to cona r e seldom on the centrate to about market in any region two-fifths the original for over two or three volume. WASlllNG TOXATOES months per year. This process ouwDuring a considerable The edonomy of mass produotion haa made cannod foods a// everyday item of food and portion of this t i e ates in-the can&g available t o ai?. of vegetables. Most they must be transvegetables are blanched before baing canned. This hlancliiiig ported from afar where they are in season^; this necessitates is a continuous process in which the vegetables pass in a con- harvesting in an immature state. Pineapples are much less tinuous stream through Piater which is maintained a t a available in the raw state. Yet in the canned form, both relatively high temperature (in most cases near the boiling peaches and pineapples are a t least equivalent, if not superior, point). Although this water is seldom a t the boiling point in vitamin C to raw apples (the fruit most generally available (at which temperat.iire, owing to ebullition, tlie oxygen would in the raw form) and are approximately comparable to raw be driven off), it is constantly under agitation as t.1ir: vege- bananas. Oranges are admittedly richer in vitamin C, but tables are carried through it, and this agitation expeditcs the canned jieaclies outstrip oranges in vitamin A content t,o the escape of the oxygen just as ebullition docs in the boiling of name extent that oranges surpass in vitamin C. water. This blanch water, because it is only renewed by a Uot,anically speaking, tomatoes belong in the category of relatively small stream of fresh water, is constantly ixiain- fruits. Canned tomatoes have been demonstrated to be taincd relatively free of oxygen. As the vegetables come in equal to the raw in vitamin content, and superior to tomatoes contact rvitli the hot water, therefore, tlie oxygen in them is picked when immature for shipment out of season. I n driven off by the heat of tlie blanch water and the mealianical vitamin C they are similar to oranges but surpass not only agitation incident to their transfer througli the blancher. oranges but most other fruits several times in vitamin A These principles of commercial canning were developed and content. I n vitamin U content all of the above are apemployed even before tlre term "vitamins" was coined. In parently on a comparable basis. some instances they were specifically designed to rid the If we conipare the above canned commodities with head product of oxygen, since oxygcm in the can is rery detrimental lettuce and celery stalks (the two vegetables probably eaten from various angles. It is an interesting coincidciice now to in greatest quantity in the raw condition), the contrast is even note that these principles are effective in the preservation of more marked. Sherman (5) states that the vitamin A convitamins. tent of bleached celery stalks is too little to be measured by Tliere is another principle which operates a.rid is, no doubt, present methods. Whereas Dye, Medlock, and Crist ( 2 ) responsible for relatively high vitamin potency in canned report the yellow portion of head lettuce to be a good source of foods as compared with similar foods purchased on the market vitamin A, Munsell (4)found the inner portion of head lettuce and cooked in the kitchen. It has been found that cabbage, to have only one-fortieth the vitamin A content of the outer stored until tlie middle of tlie winter, is materially lower in green leaves, and that 15 to 18 grams of head lettuce were vitamin C tiran in the fall at harvesting time. Cold storage necessary to afford protection against scurvy in a guinea pig. apples uvere found to lose a material proportion of their These amounts correspond to those reported elsewhere (1) BS vitamin C within a normal storage period. There is con- the antiscorbutic dosages for botli celery and head lettuce.
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u s 'T It I .\ I.
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N ti 1 N E ts It 1 N G
This line of wiuparisous woiild be i w m p l e t c witiiuut calling attention to tlie high vitamin C potency oi green vegetables, particularly the leafy kind. Tliey are outstanding in this respcxt as well as in tlicir vita,nrin A content. They are generally eaten only in a cooked fomi. .4lthough kettle cooking and mnnirig cnusc ~ o n i rI w s of vitainiii C , these vegeta.bles are still oue of our most valiia1,lr sources of both vitamins A and 1', mid csrmiiig n f f d s i i continual supply.
Spwific r r w ~ n i a n dii:tary l eoriiimients I ~ v 1iei.u e dixii. aboye. Is it pos,siblo that there may he unknown o r 1111rtxognized riiitrients and that canning may fail tu prmwvc these? This has hem put to what seems should bc a w r y tdequate test. 'L'lic Xational Canners ,hsociatiiiii i n (xi-
operation with Teiiclicrs College, Coliinibia Universiiy, Srw York, represented by IV. W. Eddy, has carried on a feeding esperirneiit, i n d i i & rats and guinea pigs hare been fed 011 a diet made up exclusively (IS canned foods dmiiized by heat,. The former I i a \ ~reaelied tlie seventh arid the latter, the fift,li seneration on socii a diet,, and both have tlirired throughout not oiily in an average nia.nner but in an optimum condit.ion. Growth has been exceptionally good, and reproduction and lactat,ion norrrd in every nay. In carrying out this exprrirnmt, tlie one in charge of the animals vas instructed to purchase at retail stores tlie cariricd Soods as needed to prc:11are a balanced diet Sroin day to day. Ultra-violet irradiation of animals or food, or administration of cod-liver oil was hever employed. The a.ninials were uever cxposed to tlie dirert rays of the sun, atid the room in wliieh they were kcpt had o d y nonnal wiridov spwc. S o raw vegetable or h i i t juice as antiseorixtic, iior vitamin 13 concentrate, nor any pmprietary preparation was ewr adiiiinisterrd. It, is cliflirmlt to tiarmoiiiae the results of s i i r l i a11 experiiiiciil with the stat,
