Before joining the TAMU faculty in 2002, Dr. Castillo was a professor in the Department of Biology and Pharmacy at the University of Guadalajara, Mexico. He is also an honorary professor at the University of Buenos Aires in Argentina and has taught graduate courses in food safety at the University of Guatemala Valley, Guatemala and the University of Central America in Nicaragua.

Dr. Castillo's research interests include the development of control measures for minimizing and reducing pathogens in fresh and fresh-cut food products, the bacterial reduction on beef and pork products and fresh produce by sanitizing rinses and the use of electron beam irradiation for food safety purposes.  He has published numerous articles in peer-reviewed journals, has authored or co-authored four book chapters and has published two books as editor. He teaches the graduate course in Microbiology of Foods and co-teaches the HACCP stacked course.

Dr. Castillo is a member of the Editorial Board for the Journal of Food Protection and is the Texas A&M representative in the Board of Directors for the National Alliance for Food Safety and Security. He is an active member of the International Association for Food Protection and member of the American Society for Microbiology and the Institute of Food Technologists.