II. CHEMISTRY AND INDUSTRIAL PREPARATION 7 



Further purification is accomplished by low temperature fractionation from 

 hydrocarbon solvents. 



b. Industrial Preparation 



The most widely distributed provitamin A carotenoid in nature is /3- 

 carotene, and a number of processes have been developed recently for the 

 large-scale isolation of this carotenoid.'""'- Certain dry vegetable leaf wastes 

 are rich sources of this carotene. For example, dry spinach, beet, carrot, 

 turnip, kale, and broccoli leaf wastes contain an average of 300 to 700 7 

 of carotene per gram. Table II show's some of the important industrial 

 sources of /3-carotene.'^ 



TABLE II 

 Important Industrial Sources of /S-Carotene 



In one'" of the recent industrial methods dry leaf wastes were ground in a 

 mill to 30-40 mesh and then extracted in a large Soxhlet apparatus of 4.5 

 kg. (10 lb.) capacity, using low-boiling saturated hydrocarbons (Skel- 

 lysolve F, b. 35 to 59°). Purification of the extracts was accomplished by 

 one of two methods. The carotene was adsorbed from the extracts directly 

 onmagnesia'^ from which it was eluted with a mixture of hexane (Skellysolve 

 B) + 5 % acetone. About 85 % of the carotene relatively free from chloro- 

 phyll and xanthophyll was obtained by this method. A second method was 

 recommended in which the hydrocarbon extracts were mixed with 95 % 

 ethanol containing 5 % potassium hydroxide and the mixture was refluxed 

 for about one-half hour. SuflRcient water was then added to make the al- 

 cohol concentration 80%, thereby causing the separation of the layers. 

 The upper layer contained all the carotene in Skellysolve. Chlorophyll and 

 xanthophyll were thus removed and found in the alcohol layer. Adsorption 



i" M. E. Wall, E. G. Kelley, and J. J. Willaman, Ind. Eng. Chem. 36, 1057 (1944). 

 " W. H. Shearon, Jr. and O. F. Gee, Ind. Eng. Chem. 41, 218 (1949). 

 " H. L. Mitchell, W. G. Schrenk, and R. E. Silker, Ind. Eng. Chem. 45, 415 (1953). 

 " H. H. Strain, J. Biol. Chem. 105, 523 (1934). 



