COLORING CITRUS FRUIT IN FLORIDA 3 
of fruit which has not reached the stage of development at which 
it is desirable for food and that consequently might be considered as 
artificial coloring to conceal inferiority or immaturity is repre- 
hensible and should not be permitted. 
EXPERIMENTAL WORK 
The investigation proceeded along two lines, (1) testing the effect 
of the gas on the various types of fruit and working out methods 
for coloring these fruits experimentally, and (2) the application of 
these results to the coloring of fruit on a commercial scale. This, 
of course, entailed the testing of different methods of making the 
gas, the working out of methods of applying it, and the designing 
of suitable rooms and equipment. The effect of the coloring on 
the commercial value of the fruit was also taken into consideration. 
THE GAS FOR COLORING 
The gas commonly in use for the coloring of citrus fruit is made 
by the incomplete combustion of kerosene, gasoline, or a smiliar 
petroleum product. When kerosene is burned without sufficient oxy- 
gen for complete combustion, several gases are given off, among 
which is the gas or gases which will destroy the chlorophyll or green 
coloring matter in the skin of the orange without killing the cells 
or otherwise injuring the fruit. The yellow coloring matter present 
in the skin but masked by the green is evident when the chlorophyll 
- green has been bleached out. The fruit attains an attractive yellow 
color. From the work of Denny* it seems probable that the active 
principle of this gas may be ethylene. He has found that ethylene 
can be used for the coloring of citrus fruits and has developed a 
process for coloring on a commercial scale with this gas. 
COLORING GRAPEFRUIT WITH THE EXHAUST FROM A GASOLINE ENGINE 
The first experiments carried on in Florida in this investigation 
were in coloring grapefruit with the exhaust from a gasoline engine. 
This work was done at Homestead in a small experimental room 
built for this purpose. The room was large enough to contain 60 
standard field crates of fruit, was made practically gas tight with 
building paper and sheathing, and was provided with¢a small venti- 
lator in the ceiling which could be closed with a slide. The exhaust 
from a 214-horsepower gasoline engine was piped into the room and 
liberated in about the middle of the floor. 
Three lots of about 60 boxes each were colored in this room in 
these first experiments. The first lot consisted of fruit ranging in 
color from 5 to 30 per cent. In coloring this fruit the engine was run 
intermittently for 7 to 12 hours during the daytime, and the door and 
_ ventilator were opened at night to allow the air to circulate through 
_ the fruit. A relative humidity of 75 per cent was maintained by 
_ hanging wet sacks around in the room, and 46 hours after the engine 
had been started the fruit ranged from 90 per cent to full color. The 
engine had been run 2914 hours during this time. 
*F. BE. Denny. MHastening the coloration of lemons. In Jour. Agr. Research, vol. 27, 
pp. 757-769, illus. 1924. 
