Washington, D.C. A May, 1926 | 
COLORING CITRUS FRUIT IN FLORIDA 
By WILLIAM R. Barcer, Assistant Physiologist, and Lon A. HAWKINS, Physiolo- 
gist, Office of Horticultural Investigations, Bureau of Plant Industry 
CONTENTS 
Page Page 
Pxperimental work__.—-----_-__..... 3 | Effect of coloring on the fruit_______ 11 
Relation of temperature to rate of The ‘coloring: plant._-=--_ 2.2 tk 14 
Coloring a2 22 Un Ls EN a AE 6 | Coloring with ethylene______________ 18 
Importance of coloring quickly_______ Sik Discussions. 0.2 i ou ere ae ae 1& 
Methods of regulating temperatures in 
coloring.” TOOM Se ee ee ee ee 
The advantages of coloring citrus fruit which has reached a stage 
of development at which it is edible and desirable for food but has 
_ not yet taken on the yellow or orange color usually associated with 
maturity in the minds of the consuming public are well recognized 
in some of the citrus-growing regions of the United States. The 
practice originated in California. It was first applied to the color- 
ing of lemons and later adapted to oranges, particularly Valencias, 
which have a tendency to become green late in the season, even 
though they have once assumed the golden-yellow color. The 
method for lemons is described by Sievers and True,‘ who show 
that the coloring of the fruit is due mainly to a gas formed by the 
incomplete combustion of kerosene, gasoline, or some similar petro- 
leum product, and not, as was commonly supposed, to heat and — 
humidity. The work of these writers put the coloring of lemons 
on a stable basis in California, and cheap and efficient methods have 
been developed for the coloring of this fruit. Nearly all packing 
houses are equipped with some facilities for coloring. At some 
seasons with certain kinds of fruit, it is a very common practice and 
considered one of the essential operations in preparing it for market. 
Recently Chace and Denny? have shown that ethylene can be used 
1A. F, Sievers and R. H. True. A preliminary study of the forced curing of lemons 
Beg eticed in California. U. S. Dept. Agr., Bur. Plant Ind. Bul. 232, 38 pp., illua 
2K. M. Chace and F. HE. Denny. Use of ethylene in the coloring of citrus fruit. I« 
Jour. of Ind. and Eng. Chem., vol. 11, pp. 339-340. 1924. 
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