Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Microbiology and Preventive Medicine

First Advisor

George W. Beran


Viruses are becoming increasingly recognized as major causes of foodborne diseases. While adequate cooking is a time-tested method of inactivating viral contaminants, the numerous outbreaks of viral foodborne disease indicate that either thorough cooking does not occur or that the foods are contaminated after cooking. These studies investigated other methods of inactivating viral contaminants in ground pork and pork products;Storage conditions can be used to decrease viral numbers in pork, but the time needed makes this impractical. At refrigerator (4°C) temperatures, most viruses tested lasted long after the product would be considered spoiled. At home freezer (-20°C) temperatures, many viruses were extremely hardy. Hepatitis A virus survived for one year in the freezer with little loss in titer. Even for those that were inactivated by freezer storage, the time needed for total elimination rendered this method impractical;Viral contaminants in foods can be eliminated by irradiation. However, viruses are substantially smaller targets than bacteria, so a correspondingly larger dosage is needed for inactivation. Currently approved dosages will lower viral numbers but will not inactivate all of the viruses present in foods, unless the viral numbers are quite low;Processing has been shown to adequately inactivate even the most durable of viruses. However, if products are contaminated with viruses after processing, this study indicates that the changes that processing induce in the products will not be effective in inactivating the viruses. This becomes an important control point especially for those products which are meant to be eaten with no further cooking or processing.



Digital Repository @ Iowa State University,

Copyright Owner

Terry Allen Proescholdt



Proquest ID


File Format


File Size

120 pages