May 31,1924 
Borax Treatment of Citrus Fruits 
967 
added effectiveness in preventing such germination or subsequent invasion by 
the fungus mycelium. After the brushing the deposit of borax crystals re¬ 
mained, or was even increased in depressions, but was removed from the high 
places. 
Practical packing-house tests will be required to determine the most effective 
and economical way of applying the borax treatment. From these preliminary 
laboratory tests it seems that the treatment would be about equally effective in 
any one of the several methods of application discussed. 
Tests were made on the effectiveness of borax treatments at various intervals 
after artificial inoculation. The best results were obtained when the treatments 
followed immediately. With the lapse of two and one-half hours the treated fruit 
was no better than the untreated control. On the other hand, the tests with 
“commercially sound” fruit taken from packing houses, frequently one or two 
days after picking, indicate a material reduction in blue-mold rot and in stem-end 
rot, as is shown in figure 3. It is important to avoid delay in treating the fruit, 
and the borax treatment must not be relied upon to make up for careless handling. 
All the tests with severely wounded fruit indicate that the borax treatment will by 
no means prevent all of the rot. In general the laboratory tests had the advan¬ 
tage over carelessly handled commercial fruit of receiving the treatment promptly 
after wounding and had the disadvantage of being subjected to exceedingly severe 
wounding and holding conditions. The borax treatment should be regarded as a 
supplement to and not as a substitute for careful handling. It gives promise of 
having a place in protecting the fruit against a considerable proportion of the 
blue-mold rot that is likely to occur even with very careful handling, especially 
that incident during and after the packing process. 
Borax has the advantage of being cheap and readily obtainable. It does not 
actively corrode metal and is not a poison. It is an article of common household 
use. The coating, even when freshly made with 10 per cent solution, is not very 
conspicuous on oranges and lemons; on grapefruit it shows at first somewhat more 
prominently as a grayish coating. After the fruit has been wrapped and packed 
and held for a week or more, one must look very closely to detect any difference in 
appearance between the treated and untreated fruit. It does not seem probable 
that the borax coating, even if all is left on the fruit, will detract materially from 
its appearance or affect its marketability. 
As is well known, regulations of the United States Department of Agriculture, 
made under the pure foods act, prohibit the use of borax or certain other preserva¬ 
tives in food products and restrict their use on the surface of such products. In 
the case of citrus fruits the application of borax is made to the outside of the 
peel, a portion of the fruit that is not regarded as edible and that is discarded in 
the ordinary consumption of the fruit. If the fruit is washed before using, the 
adhering borax is readily removed. In commercial establishments for extracting 
juice and for manufacture of citrus by-products the general practice is to wash 
the fruit before using. In the making of citrus drinks the fruit is doubtless used 
sometimes without washing and the peel put in the drink. In this case there is 
considerable dilution with liquid. Our tests show that an orange of medium 
size, on an average, will remove 1 cc. of 5 per cent borax solution when dipped. 
Perhaps half of this drains off. On this basis a single orange might carry 0.025 
gram (0.4 grain) dried borax on its surface. The therapeutic dose is given as 
0.750 gram (12 grains), and is the equivalent of what might be carried on 
about 30 oranges. 
Chemical analyses are being made by the Office of Soil Fertility Investigations 
of this bureau to determine the amount of borax present on and in the peel and 
in the edible pulp portion of oranges and of lemons that had been held 15 days 
