THE EFFECT OF OIL TREATMENT OF RAISINS ON NUMBERS 

 OF INSECTS INFESTING RAISIN PACKAGES 

 Albert P. Yerington— 



SUMMARY 



Raisins with and without vegetable oil coatings were packed in standard 15-ounce 

 cartons with cellophane overwraps and exposed to insects to determine whether the 

 coatings would prevent or reduce insect infestation. Both oiled and unoiled raisins 

 became infested, but after 3 months, raisins receiving the standard commercial oil 

 treatment contained one-half to two- thirds as many insects as the unoiled raisins, 

 and raisins with a double treatment of the oil contained one-tenth as many. Dermestid 

 beetles were more tolerant of the oil treatments than the other stored- product insects 

 in the test. 



INTRODUCTION 



A large percentage of seedless raisins are packaged as "natural raisins" (with 

 nothing added to them). "Nectars, " another large percentage, are treated with a 

 light coating of vegetable oil to keep them from sticking together. Personnel in the 

 raisin packaging industry received fewer complaints of insect infestation of nectar 

 raisins than of natural raisins. 



2/ 

 Hurlock— has reported that oiling raisins appears to make them more susceptible 



to attack by merchant grain beetle but impairs breeding of Indian- meal moth. An 



experiment was planned to determine whether oil treatments actually did affect insect 



infestation of raisin packages. 



PROCEDURE 



One group of packaged raisins used in the test were untreated (natural) raisins. 

 The second group (nectars) had received the standard commercial oil treatment — 

 a combination of hydrogenated soybean and cottonseed oils applied at a rate of 0.25 

 percent by weight. A third group had been treated with the same oils applied at the 

 rate of 0.5 percent by weight, which was double the amount generally used com- 

 mercially. All raisins had been dried from Thompson Seedless grapes. The packages 



— Research entomologist, Dried Fruit and Tree Nut Insects Investigations, 

 Market Quality Research Division, Agricultural Research Service, U.S. .Department 

 of Agriculture, Fresno, Calif. 



.2/ Hurlock, E. T. Some observations on the ability of bleached, oiled and un- 

 treated sultanas to support insect infestation. J. Stored Prod. Res. 4(l):88-89. 1968, 



