1048 
From the data in the foregoing table 
it appears that fruits are comparatively 
expensive sources of protein as compared 
with flour or dried legumes, the fruit 
juices being the most expensive and the 
dried fruits the cheapest of the fruit prod- 
ucts Ten cents on an average will pur- 
chase fully as much energy when spent 
for fresh fruits and more when spent for 
dried fruits than for lean meats, but much 
less than when expended for wheat flour. 
From the data as a whole it is apparent 
that fruits are reasonably cheap sources of 
energy in the diet and are well suited on 
grounds of economy for combination in 
reasonable quantity with cheap proteid 
foods to furnish a well-balanced ration. 
Cooking and Its Effects on Fruit— 
Jelly Making 
As is the case with all vegetable foods, 
the heat of cooking breaks down the car- 
bohydrate walls of the cells which make 
up the fruit flesh, either because the moist- 
ure or other cell contents expands and 
ruptures the walls or because the cell wall 
is itself softened or dissolved. Texture, 
appearance, and flavor of fruit are mater- 
ially modified by cooking, and if thorough 
it insures sterilization, as in the case of 
all other foods. The change in texture of- 
ten has a practical advantage, since it 
implies the softening of the fruit flesh so 
that it is more palatable and may be more 
readily acted upon by the digestive juices. 
This is obviously of more importance with 
the fruits like the quince, which is so 
hard that it is unpalatable raw, than it 
is with soft fruits like strawberries. 
When fruits are cooked without the ad- 
dition of water or other material, as is 
often the case in baking apples, there is 
a loss of weight, owing to the evapora- 
tion of water, and the juice as it runs 
out carries some carbohydrates and 
other soluble constituents with it, but 
under ordinary household conditions this 
does not imply waste, as the juice which 
cooks out from fruit is usually eaten 
as well as the pulp Cooking in water 
extracts some of the nutritive material 
present. Thus, a German investigator 
found that after boiling, apples and pears 
contained four or five per cent and 
*Landw. Jahrb. Schweiz, 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
peaches about seven per cent less carbo- 
hydrates than the uncooked fruit. In 
this case also such removal of nutritive 
material is of no practical importance 
The idea is quite generally held that 
cooking fruit changes its acid content, 
acid being sometimes increased and 
sometimes decreased by the cooking pro- 
cess. Kelhofer* showed that when goose- 
berries were cooked with sugar the acid 
content was not materially changed, 
these results being in accord with his 
conclusions reached in earlier studies 
with other fruits. The sweeter taste of 
the cooked product he believed to be sim- 
ply due to the fact that sugar masks the 
flavor of the acid. 
It is often noted that cooked fruits, 
such as plums, seem much sourer than 
the raw fruit, and it has been suggested 
that either the acid was increased or the 
sugar was decreased by the cooking pro- 
cess. This problem was studied by 
Sutherst,t and in his opinion the in- 
creased acid flavor is due to the fact 
that cooked fruit (gooseberries, cur- 
rants, plums, etc) usually contains the 
skin, which is commonly rejected if the 
fruit is eaten raw. The skin is more 
acid than the pulp, as was shown by 
analyses of gooseberries, in which the 
skin was found to contain 2.7 per cent 
acid and the pulp 1.8 per cent To de- 
termine whether acid is formed when 
fruit is cooked, Sutherst boiled a mix- 
ture of nearly ripe gooseberries in water 
for about thirty minutes and then meas- 
ured the amount of acid by trituration 
with sodium hydroxid solution. The 
boiled portion was found to contain less 
acid than the raw, probably because some 
of the acid was volatile and passed off 
with the steam. 
As regards the effect of cooking on the 
kind and amount of sugar present, un- 
cooked gooseberries were found to con- 
tain 1.2 per cent cane sugar and 5.8 
per cent invert sugar. After boiling, no 
cane sugar was found, while the invert 
Sugar amounted to 6.9 per cent. This 
19 (1905), pp 
601, 602 
184 Chemistry News, 92 (1905), No 2393, p 
