| Summary: | The problem of this investigation was to develop a satisfactory method by which insect infested corn could be treated continuously to eliminate the contamination normally found in the corn meal produced from the corn.
An extensive literature review was compiled covering the processing of corn, the description of insects infesting stored corn, the sources of insect contamination, the tests for contamination in the corn meal, and the methods now employed or proposed for the reduction of this contamination.
In connection with the fumigation of stored grain, tables were prepared showing the results of fumigations of grain insects with more than 400 chemical compounds. Those compounds which appeared to be best suited for this type of treatment of the corn, were then listed in a separate table and the properties of the compounds detailed so that a selection of the optimum compounds for experimental testing could be made.
In addition to fumigation procedures, thermal procedures employing infrared radiation and dielectric heating were possible methods for killing the insects in the corn. Another procedure recommended for this purpose was the use of the mechanical force to kill the insect by means of high speed centrifugal machines called "Entoleter" Infestation Destroyers.
By means of fragment analyses of samples of corn meal, it was found that the source of the corn and the care which it received during storage and handling were of primary importance in producing corn meal free from contamination by the present milling procedures. As a result of similar analyses it was found that precracking and aspirating of the corn on certain types of equipment prior to the normal grinding of the meal did not result in a reduction in the quantity of fragments present in the meal.
Carbon tetrachloride and trichloroethylene were selected for possible utilization in very rapid fumigation of the infested corn. Laboratory apparatus based on the operation of the solvent-vapor degreaser for metal parts was constructed. In the resulting tests, it was found that with infested corn suspended in the vapor of boiling carbon tetrachloride or trichloroethylene the mortality of all stages of the rise weevil was 100 per cent after an exposure period of only one minute. Other tests indicated that after air drying of the grain the carbon tetrachloride did not have any deleterious effect on the baking properties of the corn.
In connection with heat sterilization methods, tests were conducted which indicated that the baking properties of corn heated to temperatures below 160 °F were not impaired. Further tests were conducted which indicated that both infrared heating and dielectric heating were 100 per cent effective in killing all stages of rice weevil in infested com after an exposure period of two minutes to infrared radiation or one minute to dielectric heating. In both cases the temperature of the com did not reach 160 °F.
Tests conducted with the "Entoleter” centrifugal machine indicated that the damage to the whole grain com by the action of the machine was excessive and all of the rise weevil were not killed.
After due consideration of the experimental results it was decided that the system of rapid fumigation of the infested corn was the most reasonable solution to the problem of killing the insect infestation in the corn, The equipment necessary for the proposed system can be assembled with a few modifications of solvent-vapor, metal-degreasing equipment and with a suitable solvent recovery system. It is anticipated that the removal of the dead insects, larvae, eggs, and pupae can be accomplished on commercial milling equipment now available if the insects are killed prior to the processing and the reinfestation of the product is not an important factor during the processing. === Master of Science
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