

AVAILABILITY AND FUEL VALUE OF FOOD MATERIALS. 95 

calories per gram. Since the heat of combustion of dextrin 
and sugar is not greatly different from that of starch, and the 
amount in the cereal food materials relatively small in amount, 
the heat of combustion of the carbohydrates of these materials 
may be taken at 4.2 calories per gram. 
The carbohydrates of the ripe seeds of the legumes like those 
of the cereals consist very largely of starch with more or less 
fiber, and the heat of combustion is here taken as 4.2 calories 
per gram. The food materials consisting largely of starch, 
such as corn starch, tapioca, etc., may also be assumed to have 
a similar heat of combustion per gram of carbohydrates. 
The heat of combustion of the glucoses averages not far from 
3.75 and of sucrose 3.96 calories per gram. It is here assumed 
that the heat of combustion of cane sugar, and the sugars of 
sirup, molasses, etc., may be taken as 3.95 calories per gram. 
The carbohydrates of vegetables such as potatoes, turnips, 
squash, etc., consist very largely of starch and cellulose with 
more or less sugars. The quantity of sugar in beets and pars- 
nips is considerable, that in potatoes and turnips insignificant 
in amount. ‘There is probably a larger proportion of pentosans 
in the carbohydrates of vegetables than in that of the cereals. 
The heat of combustion of the pentosans appears to be rather 
higher than that of the polyhexoses, and may perhaps offset 
the lower heat of combustion of the sugars. In lack of more 
definite data it is here assumed that the average heat of com- 
bustion of one gram of carbohydrates of vegetables is, like that 
of cereals and legumes, 4.2 calories per gram. 
When we come to consider the carbohydrates of fruits, how- 
ever, allowance must be made for the large proportion of 
sugars chiefly dextrose and levulose, the heats of combustion 
of which are considerably smaller than of the starches. ‘There 
are at the same time certain amounts of starch, pentosans and 
cellulose, which tend to increase the heats of combustion of 
the mixed carbohydrates of fruits. In the lignt of these con- 
siderations it would seem that the average heat of combustion 
of the carbohydrates occurring in fruits might be not far from 
4.0 calories per gram. 
In the following table the heats of combustion of some of the 
principal kinds of carbohydrates and the values here assumed 
for the carbohydrates of different kinds of food materials are 
