October 15, 1920] 



SCIENCE 



351 



we worry out for ourselves is seldom for- 

 gotten. C. G. MacArthur 

 Stanfoed Universitt 



LEVULOSE SIRUP 



The present — and, we are told, very likely 

 the permanent — shortage of crystallized sugar 

 is stimulating very markedly the interest in 

 other sugars. The consumption of glucose or 

 corn sirup is increasing steadily; the making 

 of sorghum sirup bids fair to return to the 

 prominent place it once held; our friends the 

 hees are being exploited more and more; 

 and a great many breweries, instead of retir- 

 ing as requested, are now malting grain as 

 usual, but instead of fermenting it are con- 

 verting it into maltose sirup. Of the above 

 four sugar products, sorghum and honey are 

 the only ones which compete with cane sugar 

 in sweetness; maltose is much less sweet, and 

 glucose is very much less sweet, than sucrose. 

 Now, it is sweetness that we demand; we do 

 not eat sugars and sirups primarily for their 

 calories, 'but because they sweeten other, less 

 palatable, and cheaper, food products. There- 

 fore, glucose and maltose have very natural 

 limitations on their extensive utilization, if 

 sweeter materials can be found. Of the two 

 sweeter products, honey will probably of neces- 

 sity always remain a luxury; and sorghum 

 sirup has a flavor that precludes its unlimited 

 use for all purposes, although it should be 

 said that this flavor can be almost entirely re- 

 moved, with practically only the sweetness re- 

 maining, and that there is a possibility of an 

 enormously increased utilization of sorghum 

 in this way. Is there not, however, a sugar 

 which is sweeter than any of the aboVe, which 

 is not now of commercial importance, but 

 which possibly could be obtained in large 

 enough quantities and at a low enough cost to 

 become important? 



Levulose, fructose, or fruit sugar, is the 

 sweetest known sugar. Exact data as to the 

 relative sweetness of the various sugars are 

 not available, but it is often stated that levu- 

 lose is 30 to 50 per cent, sweeter than sucrose. 

 A levulose sirup, then, would be a distinct 



asset in the present commerce in sweet prod- 

 ucts. Levulose occurs in practically all fruits, 

 is abundant in honey, and is found in appreci- 

 able amounts in sorghum sirup. Its most con- 

 spicuous occurrence in plants, however, is in 

 the form of inulin in the tubers of the Jeru- 

 salem artichoke and in the bulbs of the dahlia. 

 Inulin is a polysaccharide somewhat resemb- 

 ling starch, but whereas starch yields glucose 

 on hydrolysis with acid, as in the manufacture 

 of corn sirup, inulin yields levulose. 



The inulin is present to the extent of 12 to 

 14 per cent, of the fresh tuber. As is well 

 known, the artichoke gives very large yields, 

 from 700 to 1,000 bushels per acre being nor- 

 mal. If one assume 40,000 pounds per acre, 

 and a 10 per cent, recovery of inulin from the 

 tubers, there would thus be 4,000 pounds of 

 sugar per acre. A 50-bushel crop of corn yields 

 about 2,000 pounds of starch; an acre of good 

 sorghum yields about 1,600 pounds of sugar; 

 an acre of sugar beets, 3,000 pounds; an acre 

 of sugar cane 3,000 to 4,500 pounds. 



Thus it is seen that the possible yield of 

 sugar from artichokes compares veo-y favor- 

 ably with that of our other sugar crops; and 

 the writer believes, on the basis of the above 

 facts, that levulose sirup from artichoke tubers 

 is one of the most promising sugar possibili- 

 ties that we have. The levulose would prob- 

 ably have to be in sirup form, since it crystal- 

 lizes with difficulty. The above figures are 

 estimates based on known yields and analyses 

 of artichokes. The unknown factor in the 

 proposition at present is the technology of 

 manufacture. Practically nothing is known 

 about the isolation of the inulin and its hydro- 

 lysis to levulose on a commercial scale. But 

 what is known concerning the chemistry of 

 these substances gives us every reason to be- 

 lieve that the problem connected with the 

 manufacture of levulose sirup could be solved, 

 as were those in the manufacture of the other 

 sugar products. Likewise the question of the 

 cost of production is unknown. Since, how- 

 ever, the resultant product would be so much 

 sweeter than any of the present sugars, it 

 would be worth considerably more, and a 

 greater cost of manufacture, if such should 



