Food Processors Face Challenges In Fight Against Listeria

Aug 30, 2016

Earlier this year, the Food and Drug Administration discovered a dangerous type of Listeria in the Jeni’s Splendid Ice Creams manufacturing plant in Columbus.  

The two positive tests came nine months after Jeni's issued a nationwide recall because the same strain of Listeria was found in Jeni's ice cream for sale in Nebraska.

For more on just common Listeria is and how it is to kill, WOSU's Debbie Holmes spoke with Ahmed Yousef, a professor of Food Science Technology at Ohio State University.

Click the play button below to hear their conversation

The below text is an automatic transcription of the above conversation, please excuse all errors and typos.

Debbie Holmes: Listeria we think that it's this horrible, horrible germ bacteria, but how common is it?

Ahmed Yousef: It's interesting that although it is very common in the environment and some raw food, we can't find it in very large population anywhere we look for it. Only humans and animals are allowed to grow and reach high numbers in our intestine or if it infects the animals or humans.

Silages also is known to propagate listeria. Silages is the animal feed.

Debbie Holmes: Are there different types of listeria then, some more dangerous than others?

Ahmed Yousef: There are Listeria monocytogenes is what we really worry about, but there are varieties of Listeria monocytogenes strains.

Debbie Holmes: Was this listeria then found in the Jeni's ice cream plant on the floor?

Ahmed Yousef: Yes. FDA would only be concerned about Listeria monocytogenes.

Debbie Holmes: And was this the type that was found in the ice cream last year?

Ahmed Yousef: It is the same type found in ice cream last year. I believe in Nebraska and found in their environmental samples last year and again in their environmental samples early this year.

Let us try first to understand how listeria can persist in a processing environment. Coming to an environment is easy come. Can come with compost on somebody's shoes, can come with ingredients that happen to be contaminated.

The reality is if you don't get rid of it immediately, it may persist in the environment, in the processing environment for long time.

It may also enter the plant with raw ingredients that are not meant to be sterile. Some raw ingredients can carry Listeria monocytogenes, raw milk for example can carry Listeria monocytogenes until we pasteurize it.

Once it finds a niche in the plant. Once it finds an environment where there is enough humidity, a little bit of nutrients it may survive. There are situations where it's survived in a factory for 12 years.

Debbie Holmes: So what then can a plant do then to get rid of it when they find it?

Ahmed Yousef: Sanitation, paying attention to hiding places, crevices avoid creating aerosols or dust particles that may spread on clean surfaces. The point here is being vigilant, being capable of discovering what problematic area, if any and if in a processing factory and how to deal with these problematic areas.

Debbie Holmes: So then if it's on the floor then, wet cloths soaked with some kind of bacteria killing cleaner then should be put on the floor directly?

Ahmed Yousef: There are standard sanitization methods that all factories or processing facility use.

There are bleach for example is is very, very powerful on a microorganism on a floor. However if the micro-organism is hiding in a crevice, in cracks, if it is multiplying and forming biofilms in these hiding places and the sanitizer cannot reach it then there is no way to eliminate this.

Our detection methods have improved tremendously, and actually most of the the major improvements happen only in the past couple of years. And this is why it's easier to track a pathogen like listeria now than ever. We can reduce the risk, but we cannot eliminate pathogens totally from the picture.

Debbie Holmes: I've been talking with Ahmed Yousef of food science and technology professor at Ohio State