CAROTENOID CONTENT OF CARROT VARIETIES AND STRAINS¹

Abstract

The carrot root (Daucus carota, L.) has been the source of material for much research on carotenoids and it serves as an important commercial source of carotene for experimental and nutritional purposes. Considerable discrepancy has been reported in the literature between the carotenoid content of carrots, as determined by chemical and physical methods and converted to provitamin A activities, and the actual potencies found by animal feeding experiments. This general problem has been reviewed recently by Graves (1942). It appeared possible that in some cases the analytical methods might be unreliable in that nonactive carotenoids were determined and calculated as provitamin A-active pigments. For this reason a spectroscopic study of carrot extracts and fractions was undertaken to provide a basis for more critical evaluation of methods.Very few carrot varieties and strains have bgen compared with respect to carotenoid content, and the contents of various parts of the root have not been studied quantitatively and spectroscopically to determine varietal differences. These problems are of considerable practical importance to those interested in the commercial use and value of carrots as a source of provitamin A. This paper reports results obtained in a survey of 16 commercial varieties and 18 special strains. EXPERIMENTAL PROCEDURE Extraction and FractioNation Methods:No method tried provided complete removal of the carotenoids in one acetone-hexane extraction (with Waring blender ) without preliminary blanching. The pigment remaining in the residue from unblanched carrots was not extracted by hexane or carbon disulfide but usually could be removed completely by a second acetone extraction. Samples of 10 to 15 grams fresh weight were extracted twice in a Waring blender with 125 ml. of acetone. The carotenoids thus removed were transferred to hexane by washing carefully with water three times. Carotenols2 were removed by washing the hexane solution successively with 90-per cent methanol, 20-per cent methanolic potassium hydroxide, and 90-per cent methanol (25 ml. each). The remaining methanol and alkali were removed with water and the solutions were dried with sodium sulfate, made to 100 ml., and stored at 4'C.(39.2"F.) for spectroscopic analysis. Journal Paper No. 164 of the Purdue University Agricultural Experiment Station. 'The term "carotenolJ' is used in this paper to denote the carotenoids extracted from hexane by 90-per cent methanol. The use of this term was discussed by Zscheile (1941). Such extraction should remove dihydroxy cornpounds but very little of the monohydroxy type, as shown by White and Zscheile (1942). 84

Carotenoid vitamin A precursors and analogs in foods and feeds

“…Watermelon (158) contains a-carotene, 3-carotene, /"-carotene, -carotene, and lycopene. Garden varieties of carrots average 54 mg/kg total carotene with -, ß-, -, and /"-carotene prevalent and lycopene present in some of the orange varieties (94). The oxycarotenoid fraction is usually small (21) and yellow varieties contain more oxycarotenoids and less carotenes (20).…”

Pigments in Vegetables

“…carotenes-'}'-carotene, lycopene, and r-carotene, the last being widespread-were detected (Strain, 1939;Harper and Zscheile, 1945). Subsequently, phytofluene and phytoene were also isolated (Zechmeister and Sandoval, 1945;Rabourn et aI., 1954).…”

“…(Carrots are probably the most analyzed vegetable.) In a study of 16 commercial carrot varieties and 18 strains grown in the United States, the total carotene average was 54 JA.g g-I over a range of about twice the minimum: Nantes 52 and Chantenay 108 JA.g (g fresh wt)-I (Harper and Zscheile, 1945).…”

“…The phloem has a 30% higher concentration than the xylem, which is evidenced by the different colors of the two parts. The concentration of the pigments also decreases longitudinally from the top to the tip of the root (Werner, 1941;Harper and Zscheile, 1945;Booth, 1951a).…”

Studies on the inheritance of root color and carotenoid content in red × yellow and red × white crosses of carrot, Daucus carota L.

“…xanthophylls is generally less than 10 % of the total carotenoid content (HARPER & ZSCHEILE, 1945 ;SADANA & AHMAD, 1947 ;IMAM & GABELMAN, 1968 ;UMIEL & GABEL-MAN, 1971, 1972. Other pigments that have been reported to occur in carrots in small quantities are phytoene (IMAM & GABELMAN, 1968), phytofluene (IMAM & GABELMAN, 1968;KUST, 1970;UMIEL & GABELMAN, 1971, 1972BUISHAND & GABELMAN, 1979) zeta-carotene (HARPER & ZSCHEILE, 1945 ;KUST, 1970;UMIEL & GABELMAN, 1971, 1972MOK et al, 1976;BUISHAND & GABELMAN, 1979) delta-carotene (STRAIN, 1939;BANCHER et al, 1973) and gamma-carotene (STRAIN, 1939;HARPER & ZSCHEILE, 1945;SADANA & AHMAD, 1947 ;KUST, 1970 ;UMIEL & GABELMAN, 197 1, 1972 ;BANCHER et al, 1973;MOK et al, 1976;BUISHAND & GABELMAN, 1979).…”