Journal Of Food Science 1

VITAMIN C CONTENT O F VEGETABLES. I. SPINACH” D. K. TRESSI,ER, G. L. MACK, AND C. G. HIKG

N e w York State Agricultural E x p e r i m e n t Station, Geneva, N e w Pork, alzd the Department of Chemistry, University of Pittsburgh, Pittsbwgh, PennsyEva.nia (Received for publication, October 23, 1935)

Fresh spinach has long been known t o contain relatively large amounts of vitamin C ; however, the amounts reported by the several workers differ greatIy. One difficulty in comparing the published results lies jn the fact that there is littIe uniformity in the mode of reporting the data obtained. Most analyses reported recently have indicated the amounts of ascorbic acid in milligrams per gram of spinach. If one assumes, as suggested by Bessey and King (1933), that 0.5 mg. of a.scorbic acid per day is required f o r protection of a guinea pig from scurvy, the data in recent papers may be recalculated on a uniform basis (Table I.). TABLE 1

Previous R e p o r t s

OR

Investigator

the Asambic Acid Content of Spinach Source or rariety of spinach

Ascorbic acid mg.

Eddy, Kohman, and Carlsson (1925) Hessler and Craig (1929) Hessler, Johnson, and Walsh (1931) Von liahn (1931) Wasson (1931) Kifer and Munsell (1932) Kifer and Munsell (1932) Kifer and MunseU (1932) Bessey and King (1933) Bessey and King (1933) Tauber and Kleiner (1935)

“Market” “Fresh” Bloomsdale Unknown “Fresh ” Virginia Sarog Viroflay Princess JuIiana “

Fresh

’

Market” “ Fresh” “

p e r gm.

>O.G 0.07 to 0.10 0.17 t o 0.25 0.10
0.5 <0.5 <0.5

0.50 to 0.62 0.4 to 0.5 0.43 t o 0.46

While variations in technique employed in making the vitamin C estimation may account for some of the differences in the results obtained, yet it is probable that the spinach examined by the different workers did vary widely in its ascorbic acid content. As shown in data presented above, Bessey and King (1933), have indicated that fresh * Approved by the Director of the New Pork State Agricultural Experiment Station for publication as Journal Paper No. 101, July 25, 1935. 3

FOOD RESEARCH,FOL.1, No. 1

4

D. K. TRESSLER, G . L. MACK, AND

C. G . KING

spinach is higher in ascorbic acid than “market” spinach. Wasson (1931) working in Brookings, South Dakota, states “The spinach grown in the college gardens does not seem t o have as high vitamin C value as spinach that has been tested in some other laboratories.” Moreover, she also finds that “home grown spinach had greater antiscorbutic potency than the spinach bought in the market.’ ’ Kifer and Miinsell (1932) reported slight varietal difference in vitamin C content among three varieties tested, Virginia Savoy, Viroflay, and Princess Juliana, the last being lowest in potency. Ton Hahn and Gorbing (1933) found that the vitamin C content of spinach varies depending on the type of fertilizer used. Unbalanced fertilizers (i. e, those especially high in some one component) yielded’ spinach relativeIy low in vitamin C, whereas soil treated with balanced fertilizers produced spinach high in this vitamin. The work reported in this paper was undertaken in order t o obtain some data concerning the relative importance of variety, freshness, maturity, and soil on the ascorbic acid content of this vegetable. METHODS USED

The method of determining ascorbic acid described by Bessey and King (1933) mas employed, but €or purposes of comparison biological assays were also made on two samples. The procedure employed in making them is described below : Samples of the freshly picked spinach were carefuIly packed, frozen, and kept in a container with dry-ice. The curative type of test was used as a measure of antiscorbutic value. The guinea pigs were kept on the standard Sherman and Smith (1931) diet supplemented with a generow allowance of fresh spinach for two weeks to assure their normal. growth rate, and t o permit them t o reach approximately 325 gm. in weight. They were then given the basal diet only f o r 14 days, at which time there was evident an average slight loss in weight. Test feeding mas then begun with weighed port.ions of food supplied separately t o each animal, The quantity to be fed was calculated from the indophenol titration value. T h e food was consumed rapidly so that there would not have been a significant loss from oxidative destruction before it was eaten. Control groups mere given standard portions of freshly prepared v h m i n solution, fed from graduated pipettes. I t is evident from the data (Table 2) t h a t the animal assays correspond closely with the indophenol titratiou values. EXPERIMENTAL

Relatz/ue Potency of Leaf a i d fitern Appreciating the fact that leaves and leaf petioles often differ markedly in chemical composition and therefore might contain very different quantities of ascorbic acid, the ascorbic acid content of leaves and stems of freshly harvested spinach grown on Ontario clay loam soil was determined. The ascorbic acid content of the leaves and

5

VITAMIN C CONTENT O F VEGETABLES

stems of the Prickly Winter spinach was found to be 0.78 and 0.06 mg. per gram respectively; that of the Ieaves and stems of the Hollandia variety was 0.79 and 0.04 mg. per gram respectively. These data indicate that whereas the leaves are high in ascorbic acid, the sterns are almost devoid of this vitamin. This shows that i n euamining spinach, either the entire plants should be taken o r else the TABLE P

Biological Assay of Yitamin G in S@ncbeh Basal diet supplement

Prickly Winter Spinach

No. of animals

4 4

Holitlndia Spinach

4

Ascorbic Acid Solution

4 7 6

llnsupplemented

6

Vitamin C

Initial

fed per day

weight

w.

gni .

0.5 1 .o 0.5 1.0 0.5

320

1.0 0.0

319 307 309 311

310 329

LFfiWe8

Gain in weight during 14 days

Scu rr? scare at

autopsy

gm .

38 17 35

1 0 2

43

0

41

2

63

-113

0

19

leaires and stems should be assayed separately; otherwise it would be difficult t o obtain uniformly reliable data. Since in spinach the ascorbic acid is principally in the leaves, the data presented in this paper refer t o the composition of the leaves.

Maturity and Ascorbic Acid Content Spinach is a crop which grows and matures very rapidly in the spring. Often within one week from the time that the first leaves are ready to harvest, the crop passes optimum maturity and begins to bolt (go to seed). T o determine the influence of maturity of the crop upon its ascorbic acid content, freshly cut spinach leaves from two varieties mere analyzed before the spinach became large enough €or harvesting, again four days later when i t had nearIy attained full growth, and again when it began to bolt. On these dates t h e ascorbic acid content of the Prickly Winter variety mas 0.72, 0.75, and 0.78 mg. per gram respectively ; that of the Hollandia variety was 0.78, 0.75, and 0.79 mg. per gram resp’ectively. These figures indicate that the ascorbic acid content of spring spinach leaves is nearly constant during the growth period.

Influence of Variety and Soil Twelve varieties of spinach at optimum maturity were harvested from upland soil (Ontario d a y loam a t Geneva, N. Y . ) and the same varieties harvested on the same day from muck soiI a t Holcomb, N. Y. One sample from each lot was analyzed f o r ascorbic acid. While there

6

D. K. TRESSLER, G. L. MACK, AND C. G. RING

is a varietal difference, the soil on which the crop is grown (Table 3 ) apparently has a somewhat more important influence on the ascorbic acid content of the leaves. It is noteworthy that on both soils the Princess Juliana variety is the lowest in ascorbic acid and that variety is the one found by Kifer and Munsell (1932) t o possess the least antiscorbutic acid value of the three varieties examined by them. TABLE 3

Ascorbic Acid Content of the Leaves of Smeral Varieties of Spring S@m& &own on N w &and Upland Soil aad Harvested on the Same Day Ascorbic acid in leaves harvested from

Variety of spinach Mucksoil

om. 0.62

mg. p a r

Eskimo .................................................................... Old Dominion.......................................................... Nobel.. ..................................................................... Vietoria

...................................................................

Viroflay ................................................................... Broad FIanders ...................................................... Long Standing Bloornsdale................................... Virginia 6;cvoy....................................................... Prickly Winter ....................................................... Hollandia ................................................................ King of Denmark .................................................... Prineess Juliana ..................................................... Mean..................................................................

I

Uplandsoil m g . per

gm.

0.77

0.56 0.55

0.70 0.79

0.55 0.53

0.66 0.78 0.89

0.49

0.49 0.48

0.46 0.42 0.40 0.38 0.49

0.74 0.80 0.75 0.75 0.64

0.53 0.75

On the average the amount of ascorbic acid in the spinach leaves grown on the upland soil was 50 per cent higher than that o f the spinach from the muck soil. This point will be checked by examining spinach grown on other muck and upland soils, to see if this difference is a general one. Loss of Ascorbic Acid During Xtmage Samples of spinach, cut as for market, were held at room temperature for 17 days. Duplicate samples were kept a t 1t o 3" C. (33.8 to 37.4' F.) . Leaves from each of t.he samples were analyzed for ascorbic acid (Table 4 ) a t the start of t h e experiment and at the end of 3, 7, and 17 days. The spinach on standing for three days at room temperature lost approximately one half of its ascorbic acid ; but after three days' storage a t 1 t o 3" C. (33.8 to 37.4" F.) the spinach retained practically all of its ascorbic acid. This shows the importance of refrigerating spinach soon after it has been cut. SUMMARY AND COKCLUSIONS

The ascorbic acid contents of twelve varieties of spinach grown on upland soil were compared with that of the same varieties grown on

7

VITAMIN C CONTENT OF VEGETABLES

muck soil, all samples being harvested and anaIyzed on the same day. Those grown on the upland soil averaged 50 per cent higher in vitamin C than those from the muck. While in both instances certain varieties ran somewhat higher than the average in ascorbic acid, yet the varietal differences are believed to be of secondary importance. The vitamin C content of spinach as marketed is principally in the leaves, the stems being nearly devoid of this vitamin. Spinach stored a t 1t o 3' C. (33.8 to 37.4" F.) lost its ascorbic acid very dowly, whereas that held at room temperature lost approximateIy one haLf of its ascorbic acid in three days, and practically all of it in seven days. TABLE

4

Loss of Ascorbic Acid from S p i ~ during ~ h Storage Variety of spinach

Storage

Ascorbic acid in leaves after storage for the number of days indicated below

in degrees C. 0

1

3

1

7

1

17

mg.per gm mg.pergm. m g . g c r g m . mg. p e r gm.

Prickly Winter Prickly Winter

Hollandia Hollandia

It0 3 23 t o 26 lto 3 23 t o 26

0.78 0.78

0.79 0.79

0.76 0.44 0.76 0.39

0.72

0.05 0.64 0.03

0.39 Spoiled 0.49

Spoiled

The percentage of ascorbic acid in growing spinach leaves did not change materially during the harvesting period of one week. REFERENCES BESSEP,0.A., AND EING, C. G., 1933. The distribution of vitamin C in plant and animal tissues, and its determination. 5. Biol. Chem. 103, 687 698. EDDY, W. H., KOHblAN, E. F.,A U D CAELsSON, v., 1925. Vitamins in canned foods. 111. Canned spinach. Ind. Eng. Chem. 17, 69-74. v. HLHN,F. v., AND GORBING, J., 1933. Inflnence o f fertilizers on the vitanijn c content of spinach. 2. Untersuch. Lebensm. 65, 601 16. V. HAEIN, F. V.,1931. Vitamin studies. IV. The vitamin content of vegetables of the German retail business. Z. Untersuch. Lebensm. 61, 545-610. HESSLER, M. C., AND CRAIG, G . C., 1929. Vitamin C content of spinach and Jonathan apples. Mo. Agr. Expt. Sta. Bull. 272, 67-8. HESSLER, M. C., JOEINSOH, D., ANI, WrrZISH, R. B., 1931. The vitamin content of Bloomsdale spinach. Mo. Agr. Expt. Sta. Bull. 300, 83 84. EIFER, HILDAB., AND MUNSELL,€1. E.,1932. Vitamin content of three varieties of spinach. 3. Agr. Res. 44, 767-71. SIIERNAN, H. C., AND SMITK,S. L., 1931. The Vitamins. 2nd Ed. ReinhoId Company, New Pork City. TAUBEE,H., AND KLEINER,I., 1935. A method for the quantitative determination of ascorbic acid (vitamin C). J. Biol. Chem. 108, 563-70. WASSON,G. E., 1931. Vitamin C content of fresh and canned spinaeh, Swiss chard, asparagus and carrots. 8. Dak. Agr. Expt. Sta. Bull. 261, 3-28.