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AlL J. -. UNITED STATES DEPART --ITT OF AGRICULTURE
S' Bureau of Entomology and Plant Quarantine
Washington, D. C.
B. E. P. Q. 506. January 4, 1940.
SUGGESTIONS ON T,-LZA2IWG CITRUS FRUITS
BY vETHODS PRESCRIBED I1 CIRCULAR B. E. P. Q,. 505
Circular B. E. P. Q. 505, which provides for the shipment of oranges
and grapefruit from Puerto Rico to the mainland on the basis of het or cold
treatments, makes no specifications as to methods or equipment required.
1. Heat treatment
Available information with respect to the high-temperature treatment
clearly indicates that by the application of dry heat the required tempera-
tures cannot be reached without injury to the fruit. Experience has also
shown that temperatures much above 110 F. may have injurious effect on the
fruit. It is important therefore that the temperature be held very close to
1100 F. and that it at no time exceeds 1120 F.
In successful treatments live steam as the source of heat was applied
in such a manner as to secure a uniform distribution of steam-heated air
introduced into the treating chamber so that it did not discharge directly
on the fruit. Uniform and gradual heating of the fruit to the required
temperatures was found necessary for the best results. A good method is to
increase the air temperature with the fruit temperature, gradually raising
it to llO F. as the fruit temperature rises. In treating rooms properly
equipped and operated commercial quantities of fruit can be heated to the
prescribed temperature of 1100 F, in not more than 8 hours, and this fruit
temperature maintained for the required period by using air at a temperature
not exceeding 1100 F. and 7t a relative humidity of 100 percent.
After tretitment the fruit should be well cooled before beii-r packed.
If fruit is to be colored by the use of gas, this should be done prior to
treatment. Wax or paraffin should not be use' on fruit either before or
2. Cold treatment.
In successful treatments employing low temperature, experience has
shown that satisfactory cooling can be accomplished in cold-storage chambers
only when the chLmb.,rs are provided with -adequate refrigeration and positive,
uniform circulation of the refrigerated air. In cold-storage rooms properly
equipped and operated it is possible to cool the fruit to the required tem-
perature and maintain this temperature with variations of 2 F. or less.
Attention is called to the fact th&.t Puero Rican fruits certified for
shi_-Lient to the mainland under the provisions of circular B. E. P. Q. 505 are
treated under supervision of a pl?.nt qu-'rantine inspector of the Departi.ent of
Agriculture in plants approved for the purpose by the Bureau of Entomology
and Plant Quarantine.
LZ: A. STRONG,
Chief, Bureau of Entomology and Plant Qua.rantine.
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