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1917 ANNUAL REPORT 



A NEW SUGAR IN THE AVOCADO 

 Dr. W. p. Kelley, Citrus Experiment Station 



Despite the fact that various analyses have reported small amounts 

 of sugar in the avocado, it has often been claimed that this fruit contains no 

 sugar. Recently, however, some systematic studies have been made on this 

 subject with the result that a new sugar has been discovered in the avocado. 

 This investigation was made by Dr. F. B. La Forge, in the Bureau of 

 Chemistry, at Washington, who has found a new sugar, one hitherto not 

 known to exist in any of the natural fruits. 



This sugar differs from all previously known natural sugars in that it 

 contains seven carbon atoms, the first sugar of the kind ever found in nature. 

 It is also peculiar in the fact that it is apparently unfermentable, a charac- 

 teristic likewise not common among the natural sugars. The name that Dr. 

 La Forge has assigned this sugar is D-Mannoketoheptose. 



The investigations thus far have been of a very technical nature and 

 little is known regarding the practical aspects of it. Nothing, for example, 

 has been determined regarding its digestibility, nutritive value, etc., and for 

 the present little can be said regarding the practical importance of this sugar. 

 It is, however, a matter of special scientific interest and further investiga- 

 tions may reveal information of general interest. 



It is, however, interesting to avocado growers to know that this fruit 

 does contain small amounts of sugar. While this investigation is not very 

 definite, it would seem that the amount of sugar contained in the fruit, varies 

 from .5 to 1 per cent. 



CHEMICAL CONSTANTS OF AVOCADO OIL 

 F. W. Albro, University of California 



In connection with an experiment to determine the digestibility of 

 the oil of the avocado, carried out by Dr. H. A. Mattill in this laboratory, 

 it was thought to be of interest to determine the chemical constants, and 

 compare it with other common edible oils. 



A great deal of difficulty was had in extracting the oil from the fresh 

 pulp. Pressing, centrifuging, filtering and extracting with solvents met 

 with but little success. Enough was extracted from the fresh pulp with 

 petrolic ether, however, to compare it with oil from the dried pulp either by 

 pressing or extracting with solvents. The pulp was dried at 50° C in a 

 steam jacketed vacuum oven for ten hours and extracted with low-boiling 

 gasoline. The dark colored solution was filtered through animal charcoal, 

 which removed the rather unpleasant odor, bitter taste, and resinous mate- 

 rial. The solution was placed on a steam bath and the solvent entirely 

 removed with a stream of CO- bubbled through it. The oil was then 

 cooled to 5° C, and decanted from a white precipitate, which, if not re- 

 moved by cooling, will make the oil cloudy at room temperature. The oil 

 so obtained was of a light golden color, bland and pleasant tasting. 



The chemical constants found are given in the following table: 



