CAROTENOIDS 



number of other unidentified carotenoids noted by Brunstetter and 

 Wiseman ^ ^ " may well be artefacts, for they were dealing with potatoes 

 processed in a number of different ways (dehydrated, SO 2 treated, etc.). 



(iii) Distribution 



Commercial importance has no doubt stimulated the numerous 

 quantitative investigations on the distribution of carotene in carrots. 

 The phloem (cortex) has a 30 per cent, higher concentration than has 

 the xylem* (core) ^•''•^ 24,325 ^j^^j contains 80 per cent, of the total 

 root carotenoids. ^ 2 ^ The earlier work of Emsweller, Burrell and 

 Borthwick ^ ^ ^ which indicated that the carotene concentration decreased 

 from top to tip has been repeatedly confirmed.* Harper and Zscheile, ^ ^ '' 

 for example, found that although the centre and tip may have almost 

 the same concentration, their concentration at the top is 50 per cent, 

 greater than that at the centre or tip ; further, Werner ^ ^ 5 reported 

 that samples taken 1 in. from the root have concentrations of only 50 

 per cent, of those taken 1 in. from the stem. The concentration also 

 increases in moving from the inner to the outer layers of the cortex. ^ ° ' 

 As in the case of leaves the concentration of the carotene in the root 

 increases with growth and becomes maximal about 100 days after 

 sowing. 3 2 5-327 According to Smith and Otis ^ ^ 7 t^e difference between 

 the carotene concentration of the cortex and the core, when measured 

 on a dry weight basis, decreases during maturation ; the quotient 

 cortex/core for young and mature carrots being 1 -5 and 1 -2 respectively. 

 These investigators also claim that in contrast to the well established 

 synthesis of carotene during maturation, the xanthophyll content 

 decreases ; more supporting evidence is required before this can be 

 accepted. The possibility of a relationship between carotene content 

 and size and shape of the carrot has attracted some attention, Otis and 

 Smith 3 2 7 and Schuphan ^ ^ ^ noted that the longer the carrot [? irrespec- 

 tive of state of maturation] the higher the carotene concentration. 

 Pepkowitz, Larsen, Gardner and Owens ^ ^ * claim an inverse relation- 

 ship between size and concentration in different varieties, and state 

 that small varieties have a higher concentration than have large varieties; 

 Dark and Booth ^ ^ ^ confirmed this, but even so it does not exclude the 

 size /concentration variation within a given variety. Pepkowitz et al.^^^ 

 also found no relationship between ** shape ratio " (width : length) 

 and carotene concentration. 



Carrots lifted and stored certainly maintainors ^^d probably 

 increase 2 4, 3 3 1 their carotene content until they begin to sprout. 

 Stored sweet potatoes ** ripen " and increase their carotene content 



* Recently confirmed by Booth, V. H. (1951) X Set. Food. Agric, 8, 350. 



56 



