Safflower, A Potential Source of Protein for Human ... - ACS Publications

17 Safflower, A Potential Source of

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Protein for Human Food G. O. KOHLER Western Regional Research Laboratory, Western Utilization Research and Development Division, U. S. Department of Agriculture, Albany, Calif.

Safflower has been grown for centuries in the Nile Valley and in parts of Asia. It is a newly established U.S. crop and is expected to become a major one. In dry climates where adequate soil moisture is available it yields over a ton of seed per acre, rich in high quality oil and protein. Chick experiments indicate that the meal is relatively free of physiologically deleterious components and, properly supplemented, produces high growth rates. The relatively high content of sulfur amino acids and low content of lysine suggest combinations with soybean protein. Preliminary work has yielded low fiber, palatable foods. More research is needed to develop the potential of safflower as a source of human food.

T

he critical nature of the problem of feeding an expanding world population, large segments of which are already undernourished, has been documented thoroughly (2, 28, 29). Since both calorie and protein deficits present primary problems, it is logical to look to the oil seeds as major direct food sources of the future because oilseeds are rich i n both calories (as oil) and protein. During the past decade a "new" oilseed crop, safflower (Carthamus tinctorius L . ) , has been developing at a healthy rate i n the United States. Initially grown as a source of industrial oil, broader markets are developing for the oil as a food oil. Research on the protein-rich meal indicates that safflower has promise as a major source of protein for direct food use as well as a source of calories. A useful bibliography on safflower is available (17). Reviews of production, processing, and utilization of safflower have been published (11, 18) and a symposium on safflower was presented at the 1965 meeting of the American O i l Chemists' Society (1). 243

In World Protein Resources; Altschul, Aaron M.; Advances in Chemistry; American Chemical Society: Washington, DC, 1966.


244

WORLD PROTEIN RESOURCES

Although i t is a new commercial crop i n the United States, safflower is actually one of the oldest of the cultivated plants. It has been grown since ancient times i n the Nile Valley, the Middle East, and the Orient, primarily as a source of the dyestuff, carthamin—for example, some of the linen wrapping cloths of the mummies of Egypt were dyed with safflower flower extracts (9, 88). Commercial types of safflower are thistle-like annual plants which grow from V/2 to 4 feet in height and produce light yellow to deep orange flower heads (Figure 1), each of which contains 15 to 50 white seeds resembling sunflower seeds i n shape but somewhat smaller.

Figure 1. Safflowerflowers.Left. Seed head withflower.Right. Cut in half to show developing seeds. Courtesy of P. F. Knowles, University of California, Davis, Calif. The plant is adapted to dry climates such as are found in the Central Valleys of California and extensive plain areas from Arizona and New Mexico to southwestern Canada. Yields in unirrigated areas average 350 to 1500 pounds of seed per acre. On irrigated land, yields are i n the range of 1800 to 3000 pounds per acre. Experimental and commercial yields as high as 2% tons per acre have been recorded, showing that the productive capacity of the crop is extremely high (18). Although safflower was introduced to this hemisphere by early Spanish immigrants (12), no serious effort was made to develop it as an oilseed crop until the introduction of new seeds and beginning of research by the U . S . Department of Agriculture i n 1925. Outstanding i n the early research



17.

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245

Safflower

effort was the pioneering work done at the University of Nebraska under its ehemurgie project in the 1930's and early 1940's. Although several abortive attempts were made to develop commercial supplies prior to 1948, successful development of the crop started when production was begun in California where there was a good environment for the crop and strong support from a few oilseed processors. The subsequent growth i n annual production, shown in Figure 2, was based on development of improved disease-resistant, high oil varieties, on i m proved agronomic practices, on development of industrial uses for the oil through technological research (24), and on increasing export markets for the seed, largely in Japan. The large spurt in 1963 reflects the entry of safflower oil into the food market. Riding the crest of public interest i n the blood cholesterol-depressing effects of polyunsaturated oils, new producers and processors swelled production of safflower oil as the poly unsaturated oil par excellence (80% linoleic acid). The resultant over production and temporary imbalance between production and marketing were serious but are now history and, regardless of the medical significance of blood cholesterol-lowering effects, resumption of the steady growth pattern is expected, with safflower oil selling at prices competitive with corn or cottonseed oil. 300

ο

/

1950

1955

1960

Ε

1965

Year Figure 2. U. S. production of safflower seed

A t present the United States produces about one half of the world supply of safflower seed, which was roughly estimated at 640,000 tons in 1964. The second and third largest producers of safflower seed are



246


India and Mexico, which produce about 750,000 and 60,000 tons, re spectively. Successful experimental crops i n Australia and Venezuela may lead to expanded production i n these and other countries (30). E a r l y varieties of safflower seed contained 49 to 5 2 % hull (20). Typical seeds of present commercial varieties are made up of 55 to 6 5 % kernel and 35 to 4 5 % hull (16). The whole seeds contain about 35 to 4 0 % of oil and about 13 to 1 7 % of protein. Almost a l l of the o i l and protein are located i n the kernel, so that a completely dehulled or de corticated kernel contains about 6 0 % of oil. The completely decorticated, oil-extracted kernel contains about 60 to 7 0 % of protein. Figure 3 shows the products theoretically obtainable from 1 ton of seed. Safflower has wide genetic variability, and plant breeders are well along i n the development of thin-hulled gray, brown-striped, and white varieties which contain only half as much hull as present commercial types. These new types of seed contain proportionately higher levels of oil and protein and can be expected to replace the present types (18, 27). Types of safflower seeds have also been found, the oils of which are strikingly different from the safflower oil of commerce, e.g., oils containing up to 7 5 % oleic acid (H). These new types give promise of expanded broader uses of safflower oils with the accompanying increased supply of protein. Table I compares the essential amino acids of safflower kernel protein (24) with those of 5 0 % protein soybean meal and with the F AO-recom mended provisional amino acid reference pattern (7). The data on safflower and soybean meal were obtained by the method of Moore and Stern (21), using correction factors established for safflower protein for

800 lb. Hull 2000 lb. Safflower Seed

•720 lb. Oil

^1200 lb. Kernel 480 lb. Flour •containing 312 lb protein Figure 8. Theoretical yields of products from one ton of safflower seed


17.

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247

Safflower

Table I. Safflower Seed and Soybean Proteins Compared with FAO Provisional Reference Amino Acid Pattern Provisional Pattern G./16g.N

Safflower


G./16 Orig. Adjusted g. Ν Isoleucine 4.2 Leucine 4.8 Lysine 4.2 Phenylalanine 2.8 Tyrosine 2.8 Total sulfur A A 4.2 Methionine 2.2 Threonine 2.8 Tryptophan 1.4 Valine 4.2 β

3.4 1.7 3.3 1.1 2.8

4.0 6.2 3.1 4.4 3.1 3.3 1.7 3.3 1.6 5.7

Soybean

% of Pattern

G./Î6 % of Pattern g. Ν Orig. Adjusted Orig. Adjusted 95

95

4«

74«

79 78

97

7

4.8 7.3 5.8 4.8 3.0 2.9 1.4 3.8 1.7 5.0

Chemical score is per cent of pattern for first limiting amino acid.

the labile amino acids (threonine, serine, and tyrosine) and for the difficultly released amino acids (isoleucine and valine). B y applying the fluorodinitrobenzene method (26) i t was found that the apparent availability of the lysine i n safflower flour was 100%. T h e first limiting amino acid of safflower is lysine. However, methionine is limiting to about the same degree, based on the 1957 F A O reference pattern. More recent results on human requirements (10, 28) suggest that several of the figures for individual amino acids i n the original pattern are too high and, in one case, too low. The numbers under "provisional pattern" adjusted i n Table I refer to adjusted F A O pattern figures for four of the amino acids in question. Using the adjusted F A O reference value for methionine, safflower is limited only b y lysine, and isoleucine and methionine are borderline. Soybean protein shows a lower chemical score than safflower based on the 1957 pattern. Reducing the methionine i n the adjusted pattern raises the score of soybean meal since methionine is the first limiting amino acid. Another comparison of safflower, and soybean, with egg protein as a reference protein, is shown i n Table I I . This is calculated as suggested in the 1965 F A O / W H O report (10). Safflower protein is comparable to soybean protein i n ratio of essential to total amino acids (E/T value) and i n score. When lysine is added to the safflower, its "egg reference" score goes up to about 85, and methionine and isoleucine become about equally limiting. Based on the adjusted 1957 reference pattern, a com bination of }4 safflower and % rice protein would have a chemical score of 81, higher than either one alone but still limited by both lysine and me-

American Chemical Society Library

1155 16thAltschul, St., N.W. In World Protein Resources; Aaron M.; Advances in Chemistry; American Chemical Society: Washington, DC, 1966. Washinfton, D.C. 20038

248


Table Π.

Comparison of Safflower and Soybean Proteins (Egg protein as reference pattern)


Ratio g. essential amino acids per g. Ν (E/T) Chemical score based on egg protein Limiting amino acid

Egg

Safflower

Soybean

3.22

2.17

2.58

71 Lysine

70 Methionine

100 —

thionine. B y combining safflower protein with soybean on a 3 to 2 basis, a score of 93 is obtained. Thus safflower and soybean proteins show excellent mutual supplementation. Similarly, milk, fish, pulses, and other protein sources rich i n lysine will adequately supplement safflower (β).

A comparison of safflower and soybean protein from the standpoint of amino acids not included i n the provisional pattern is shown i n Table I I I . Safflower contains adequate amounts of histidine to meet the needs of children. It is a rich source of glycine and arginine, which are essentials for the chick. Since safflower shows great genetic variability i n fatty acid composition, seed shape and color, hull thickness, etc., we wondered if amino acid composition might also be controlled by breeding. I n a very preliminary study (24) of some 20 widely different seed types, we found that none of the essential amino acids varied more than about 7% from the mean. More research is needed along these lines, including tests of individual plants from widely divergent sources. Literature reports on biological evaluation of safflower protein are very sparse. According to Baliga et al. (S, 16) the biological values Table ΙΠ.

Amino Acids Not in FAO Provisional Reference Amino Acid Pattern Amino Acid, G.I 16 G. Ν Safflower

Soybean

Histidine Arginine Glycine Aspartic acid Glutamic acid Serine Proline Alanine

2.4 9.3 5.8 9.8 19.4 4.4 4.1 5.8

2.5 6.9 4.0 10.6 17.6 5.1 5.2 4.1

Total (% of protein)

61.0

56.0



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(BV) of safflower protein of two samples of safflower meal were 84.9 and 86.0%. The coefficient of true digestibility was 92.4 for a 35.7% protein sample and 76.5 for a 21.8% protein sample. The only protein efficiency ratio ( P E R ) value found i n the literature was 1.3 for hydraulic pressed safflower cake (22). Our results, adjusted to the casein standard (4), on two samples of commercial partially decorticated meal were 1.40 and 1.26, respectively. P E R values of a sample of pilot plant produced meal from brown-striped thin-hulled seed and a sample of laboratory-produced unheated safflower flour were 1.24 and 1.35, respectively. Supplementation of the laboratoryproduced 5 8 % protein safflower flour with methionine alone (Table I V ) raised the P E R only slightly. Adding lysine as well raised the P E R to 2.09. I n other experiments adding lysine without methionine had little effect on P E R . Thus the P E R assays verify the chemical score estimates based on rat requirements and show that lysine and methionine are almost equally limiting amino acids for the rat. Table IV.

Effect on PER of Supplementation of Safflower Flour with Methionine or Methionine Plus Lysine Cystine plus Methionine, G.116 G. N.

Safflower flour (58 % protein) Same plus methionine Same plus methionine and lysine

3.34 4.20 4.20

Lysine, G./16 G. Ν 3.09 3.07 5.00

ρββ 1.39 1.59 2.09

Since the amino acid balance appeared excellent when methionine and lysine were added, we set up chick experiments to determine whether methionine-supplemented safflower meal could provide the basis for a bioassay of available lysine. Quadruplicate equalized groups of seven 5-day-old broiler type chicks were fed rations devised to be complete i n all known required nutrients except lysine. Partially decorticated safflower meal (44% protein), supplemented with methionine, was used as the p r i mary source of protein with corn or glucose as the primary energy source. Graded levels of L-lysine were added. The results given i n Figure 4 show that the types of dose response curves obtained were satisfactory for assay purposes. The results show two other important points. First, even when safflower protein is fed at levels high enough to supply over 9 3 % of the chicks' protein intake—e.g., glucose safflower ration—there is no evidence of any inhibitors such as are found i n unheated soybeans and i n raw cottonseed meal. Second, at optimum levels of lysine addition, safflower consistently produces faster growth than optimally treated soybean meal. Further data substantiating this observation are shown i n Table V . I n



250


Figure 4. Dose-response curves for chicks for lysine supplementation of safflower meal-based rations

all cases safflower meal produced better rates of gain than did soybean meal. Fisher et al. (6) showed a similar growth effect of safflower during the course of net protein value ( N P V ) assays with chicks. I n this study the safflower-fed chicks grew better than soybean-fed chicks, even though the N P V for safflower supplemented with methionine and lysine was only 46.2 as compared with 68.8 for methionine-supplemented, decorticated soybean meal (6). I t does not seem likely that the effect is due to amino acid imbalance i n soybean protein since attempts to increase growth by amino acid supplements to the soybean ration have been unsuccessful. More research will be needed to determine whether this difference between safflower and soybean meals is due to the presence of inhibitors i n the soybean meal, the presence of an unidentified growth factor i n the safflower meal, or some ration imbalance i n the soybean protein not immediately apparent. The high fiber content of safflower meal makes it unacceptable as a protein source for human foods. It is generally considered that high protein products, at least for children, should contain less than 5 % fiber. H u l l has not been separated commercially from kernel to produce such products from safflower. For the past several years one company has been selling a partially decorticated safflower meal containing 4 2 % protein for use i n poultry and swine rations. This product contains about 1 5 % fiber and is thus undesirable for a human food. W e have been able to prepare products with 57 to 6 0 % protein and about 3 % fiber from thin-hulled seeds by an experimental laboratory pro cess based on air separation, roller milling, and screening operations (8).



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Safflower

Although a great deal more laboratory and development research w i l l be required to develop a commercially feasible process, the difficulties do not appear insurmountable. The products obtained by this experi mental process were very light colored but had a bitter taste. Preliminary experiments showed that practically a l l of the bitter principle could be extracted with acetone or alcohol with less than 5 % loss of nitrogen. The washed product, which contained about 7 0 % protein, had a rather characteristic mild flavor which was not deemed undesirable by an informal taste panel. Further preliminary tests showed that meat-like patties containing this 7 0 % protein safflower flour were acceptable to the panel. When the product was added to a bread at a 5 % level based on the flour, loaf volume was reduced only slightly and a detectable but not unpleasant flavor was noticeable. More extensive tests are i n progress. Other promising routes to human products lie i n preparation of protein isolates (82) and i n preparation of textured products (δ) from safflower. Here again, considerably more research will be needed to bring preliminary results to commercial usage. Table V.

Growth of Chicks Fed Safflower" as Compared with Soybean Meal 6

Protein in Ration, %

Duration of Experiment, Weeks

% Increase

22

2 2 2 2 2 3 3 4 4

6.4 6.8 6.3 12.2 10.0 3.7 4.0 17.8 6.0

20

+ + + + +

2

0

3.3 17.6 18.6

a With added methionine and lysine. With added methionine. Weight gain on safflower meal—weight gain on soybean meal 6

c

weight gain on soybean meal

χ 100.

Conclusions Safflower is a rapidly expanding commercial oilseed crop which may well become a major world crop. I t is adapted to semiarid lands of the types found i n many protein-deficient areas of the world. I t is already


252

WORLD PROTEIN RESOURCE8


a high yielding plant, but its genetic variability gives promise of still further improvements through breeding. It produces high yields of edible oil as well as protein. The protein is highly nutritious if properly supple mented with lysine. Its relatively high content of sulfur amino acids and low lysine content suggest its use i n combinations with soybean protein. Preliminary work has shown that conversion to palatable food products is possible, although much research and development work are needed. Acknowledgments Acknowledgments are made to A . R . Gramps and Κ . V . Smith for assistance i n processing; M. Heid and Elizabeth E r m a n for formulating and preparing the meatlike products and bread, respectively; D . D . K u z m i c k y for assisting i n carrying out chick assays; Rhoda Palter for carrying out amino acid analyses; A . N . Booth and Dorothy J. Robbins for running rat P E R assays; and John Kneeland, Pacific Vegetable O i l Corp., Richmond, Calif., for generously supplying substantial quantities of commercially produced partially decorticated safflower meal. Literature

Cited

(1) American Oil Chemists' Soc., J. Am. Oil Chemists' Soc., 42, 457A (1965). (2) American Society of Agronomy, Madison, Wis., "World Population and Food Supplies, 1980," Publ. 6, (1965). (3) Baliga, B . R., Rajagopalan, R., Shivaromiah, K . , Indian J. Med. Sci., 8, 704-8 (1954). (4) Derse, P . H., J. Am. Oil Chemists' Soc.,45, 418 (1962). (5) Elmquist, L . F., U. S. Patent 3,175,909 (March 30, 1965). (6) Fisher, H . , Summers, J. D . , Wessels, J. P. H . , Shapiro, R., J. Sci. Food Agr., 13, 658 (1962). (7) Food and Agriculture Organization, United Nations, "Protein Requirements," Report of FAO Committee, Rome, Italy, October 1955, FAO Nutritional Studies 16 (1957). (8) Goodban, A . E., Kohler, G. O., unpublished results, 1965. (9) Goodman, D . H . , J. Allergy 35, 38 (1964). (10) Joint F A O / W A O Expert Group, "Protein Requirements," F A O Nutrition meeting report Series 37, and WHO Tech. Report Series 301 (1965). (11) Kneeland, J. Α., "Processed Plant Protein Feedstuffs," A . Altschul, ed., Academic Press, New York, 1958. (12) Knowles, P . F., Crops and Soils, 12(4), 17 (1960). (13) Knowles, P . F., Econ. Botany 9, 273 (1955). (14) Knowles, P . F., Econ. Botany 19, 53 (1965). (15) Kohler, G . O., Guggolz, J., Herring, V., unpublished data, 1965. (16) Kuppaswanu, S., Srinivasan, M., Subrahmanyan, V . , "Proteins in Foods," Indian Council of Medical Research, New Delhi, India, 1958. (17) Larson, N. G., "Safflower 1900-1960, A List of Selected References," Library List 73, Natl. Agr. Lib., Washington, D . C., 1962.



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(18) Lorance, D . G., Proceedings of Safflower Conference, Tucson, Ariz., June 1963. (19) Lyman, C. M., Kniken, Κ. Α., Hale, F., J. Agr. Food Chem. 4, 1008 (1956). (20) Milner, R . T., Hubbard, J. E., Wiele, M. B., Oil Soap, 22, 304 (1945). (21) Moore, S., Stein, W. H., "Methods of Enzymology," Vol. VI, S. P. Colowick and N. O. Kaplan, eds., Academic Press, New York, 1963. (22) Narayana Rao, M., Swaminathan, M., Subrahmanyan, V., Bull. Central Food Technol. Res. Inst. 3, 158-9 (1954); CA 49, 535. (23) National Research Council, Washington, D . C., "Evaluation of Protein Quality," Publ. 1100, (1963). (24) Palter, R., Kohler, G. O., unpublished data, 1965). (25) Purdy, R. H . , Cummings, L. O., Claassen, C. E., Kneeland, J. H., J. Am. Oil Chemists' Soc. 36, 26, 28, 30 (1959). (26) Rao, S. R., Carter, D . F . L . , Frampton, V . L., J. Agr. Food Chem. 35, 1927 (1963). (27) Rubis, D . D., Proceedings of Safflower Conference, Tucson, Ariz., June 1963. (28) U . S. Economic Research Service, "The World Food Budget, 1962 and 1966," U . S. Dept. Agr. Foreign Agr. Econ., Rept. 4 (1961, rev. 1962). (29) U . S. Economic Research Service, "The World Food Budget 1970," U. S. Dept. Agr., Foreign Agr. Econ. Rept. 19 (1964). (30) U . S. Foreign Agriculture Service, Foreign Agr. Circ. FFO-11-64, 15, (October 1964). (31) Valadez, S., Featherstone, W. R., Pickett, R. Α., Poultry Sci. 43, 1372 (1964). (32) Van Etten, C. H., Rackis, J. J., Miller, R. W., Smith, A . K . , J. Agr. Food Chem. 11, 137 (1963). (33) Watt, G., "The Commercial Products of India," p. 276, J. Murray, London, 1908. R E C E I V E D November 8, 1965.


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