Finding a home in the world of microbial food safety

Alejandro Castillo, Ph.D., associate professor in the Department of Food Science and Technology in the College of Agriculture and Life Sciences, grew up in Guadalajara, Mexico, with a desire to be a scientist. He didn’t know his path would lead him into food safety or Texas A&M University, but 21 years later, the life-long learner feels like he is where he is supposed to be.

Alejandro Castillo, Ph.D., didn’t know his path would lead him to food safety but has found his research home at Texas A&M in the Department of Food Science and Technology. (Texas A&M AgriLife photo)

Today he teaches food microbiology at the graduate level and food safety at the undergraduate level, as well as maintains an active research program.

“My research focuses almost entirely on microbial food safety,” he said. “I have conducted projects on preventing food spoilage, but 90% of my work has been about preventing the presence of bacterial pathogens in different food commodities, including fresh and fresh-cut fruits and vegetables, fresh and processed meats, milk and milk products and water.”

Castillo discusses his focus on the microbial safety of fresh and fresh-cut produce, and his goal to contribute to the reduction in the risk of foodborne illness.

What are foodborne pathogens and why is controlling them important?

Foodborne pathogens are those microorganisms that can cause illness when transmitted by contaminated foods. There are various ways these pathogens can contaminated foods, and although infrequent, some contamination is expected to occur naturally in raw foods.

In my research, we first study the characteristics of different foodborne pathogens, how they manage to thrive in the environment and how other non-pathogenic microorganisms interact with the pathogens while living in the environment. This knowledge helps us to develop methods and processes to prevent the pathogens from contaminating foods as well as how to develop methods to eliminate them.

Since some foods such as fresh fruit, vegetables, honey, etc. are eaten without cooking, we also study ways of reducing as much as possible the number of pathogens present.

It is important to remember that the first line of defense against foodborne illness is to observe adequate hygiene, not only in production and processing plants, but also in the home. This is why our research also serves to teach people and train them in safe food handling and preparation.

What research projects are you currently focusing on?

Currently, I have three major projects.

Alejandro Castillo, Ph.D., often collaborates with fellow researchers on projects, both within The Texas A&M University System and internationally. (Texas A&M AgriLife photo by Laura McKenzie)

The first is being conducted internationally in collaboration with the University of Guadalajara in Mexico. It focuses on tracing sources of a specific pathogen, namely Listeria monocytogenes, in the environment where avocados are packed in Mexico. This project will allow us to develop strategies for ensuring that the avocados are protected against potential contamination before being shipped to the U.S. The research team is composed of four top-notch investigators: three from Texas A&M, Sapna Chitlapilly Dass, Ph.D., assistant professor in the Department of Animal Science; Rosana Moreira, Ph.D., professor in the Department of Biological and Agricultural Engineering and myself. Another team member, Ofelia Rodr?guez, Ph.D, senior research professor, is located in Mexico. I am the project director.

The second project is on the prevention of salmonella in onions, led by Vijay Joshi, Ph.D., associate professor, Texas A&M AgriLife Research and Extension Center at Uvalde. In this project, I am charged with studying the realities about the perceived antimicrobial effects of onions. This includes testing the resistance of various strains of salmonella to onion extracts, onion juice and onion tissues as well as determining the distribution of salmonella in the environment of onion packing plants.

My third project is led by Luis Cisneros-Zevallos, Ph.D., in the Department of Horticultural Sciences. I am part of a research team studying surface dynamics and food safety. We are collaborating to determine the effectiveness of superhydrophobic compounds used as coatings in various materials to prevent attachment of various pathogens. The goal of this project is to provide the fresh produce industry with a special compound that can be applied to surfaces of equipment and utensils. This compound would allow for the total removal of microorganisms during cleaning and sanitizing procedures in food processing plants.

I have seven graduate students who work under my direction, all conducting components of the various projects I am researching. Of the students, three are pursuing their doctorates and four are master’s-level students.

Why did you initially decide to pursue a career in the field of food safety?

My upbringing had an impact in me desiring to be a scientist, but not necessarily a food scientist. My father was an OB-GYN in charge of the uterine cancer task force in my state. I would go to his talks and enjoyed watching him present research data and talking to him about it at home.

I wanted to grow up to find out how to cure cancer, and when going to college in Mexico, I wanted to attend pharmacy school. However, the pharmacy program was not as well developed as I expected, so I chose biology.

I had little contact with food science while at the University of Guadalajara, other than some courses where we would do food analysis as part of other laboratories. The subject of my highest interest was microbiology, but during that time, only medical microbiology was being taught there. It was not until after graduating that I learned about food microbiology.

After I graduated, a food and water microbiology graduate program opened at the University of Guadalajara. That was the primary reason I decided I would remain in the area of food science. However, other than learning basic concepts of food science, most of my work was restricted to food microbiology.

I really came to learn food science during my second graduate program, which despite still being in food microbiology, incorporated several courses in food science. It was not until then that I saw myself as a food scientist rather than a microbiologist specialized in food microbiology.

What is your educational background?

I obtained my bachelor’s in biology, chemistry and pharmacy, focusing on biology. I then obtained a specialty degree, which is the equivalent to a master’s degree of agriculture in sanitary microbiology and a master’s degree in food microbiology and hygiene, all from the University of Guadalajara. I then enrolled in the doctoral program there to study biomedical sciences but left after two years. That’s when I found myself at Texas A&M pursuing my doctorate in food science and technology.

Why did you choose Texas A&M? And the Department of Food Science and Technology?

The people were the reason I chose to study and ultimately work at Texas A&M.

I set my goal of earning a doctorate in the U.S. while in high school. I never focused on a particular school, but I had a strong interest in studying under the direction of an outstanding researcher. I eventually met Carl Vanderzant, Ph.D., and Gunnar Finne, Ph.D., both from Texas A&M.

Alejandro Castillo, Ph.D., who first came to Texas A&M as a graduate student, has gone full circle and now mentors multiple graduate students himself. (Texas A&M AgriLife photo by Laura McKenzie)

Vanderzant had everything a prospective scientist would want for a guide: wisdom, knowledge and a drive to help people that I had not seen before. I immediately chose Texas A&M because I thought I was going to study with Vanderzant. I found out later that he was retiring, but he and Dr. Finne mentored me along with Gary Acuff, Ph.D., Emeritus Professor and Texas A&M AgriLife Research Faculty Fellow. Acuff was initially reluctant to admit me, but after being finally admitted, we formed a friendship that grew to be a close camaraderie.

When I first started my teaching and research career with the university, the Department of Food Science and Technology did not exist. I was hired by the Department of Animal Science with a focus in food microbiology. When the department was formed in 2020, I made the transition to food science and technology because I knew that was where I belonged.

What do you wish people knew about food safety?

To quote the Food and Agriculture Organization of the United Nations, “food safety is everyone’s responsibility.”

Through our program, we contribute information about food safety that is beneficial to the industry, but also information that can be applied in other settings, such as grocery stores, restaurants and homes.

What do you like the best about what you do?

That I get to help people from various countries around the world. Since a large proportion of the fresh produce consumed in the U.S is imported, my research helps protect the health of people in the country, while also helping other countries keep a healthy economy via exports. This, in turn, helps the economy in the U.S. by ensuring high-quality and low-cost foods.

What has been the biggest surprise about your research during your career?

If your research findings do not surprise you, the research may not be relevant enough, therefore I have been surprised many times.

Perhaps one of the best surprises was to learn that my research had been used as an example in meetings where government decisions were being made. This made me realize research really has the power to induce change.



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