Tag Archives: food safety

Listeria in Ice Cream Causes 3 Deaths

By ThinkReliability Staff

On April 20, 2015, the Centers for Disease Control and Prevention (CDC) announced a recall of all Blue Bell Creameries products due to possible contamination by Listeria monocytogenes.  While the company has not yet determined the source of the outbreak, they are working with outside agencies to determine potential causes and implementing solutions to reduce the risk of food-borne illness in the future.  Says Paul Kruse, the CEO and president, “We’re committed to doing the 100 percent right thing, and the best way to do that is to take all of our products off the market until we can be confident that they are all safe.  At this point, we cannot say with certainty how Listeria was introduced to our facilities and so we have taken this unprecedented step.  We continue to work with our team of experts to eliminate this problem.”

Performing a root cause analysis can help clarify the goals of an investigation, determine the causes of the problem(s) related to an issue, and provide ideas for action items to reduce the risk of the issue recurring.  We can gather the information known so far about the outbreak in a Cause Map, or visual root cause analysis.

The Cause Mapping process begins by capturing the what, when and where of an incident.  Here, the “what” is the Listeria outbreak.  The “when” in this case is believed to have started in 2010 and continued to the present.  It can be helpful to capture any noted differences about the particular investigation.  For example, most outbreaks don’t last 5 years.  The use of genome sequencing (starting in 2013) allowed investigators to tie Listeria cases from 2010 on to this particular outbreak.  An additional difference is that Listeria can replicate in very cold temperatures.  This is unusual because freezing foods generally reduces the risk of propagating food-borne contamination.  The “where” is across the US – all products have been recalled and all plants have been shutdown, with several having been implicated in spreading Listeria.  Another useful piece of information can be the task being performed.  In this case, the contamination was discovered during random sampling.

The next step is identifying the impacts to the goals.  For this incident, the safety goal was impacted due to the sicknesses and deaths.  The outbreak of Listeria can be considered an impact to both the environmental and customer service goal, while the loss of production (no Blue Bell products are currently available or being produced for consumers) is an impact to the production goal.  The disposal of the estimated 8 million gallons of ice cream covered by the recall impacts the product goal, and the response and investigation impacts the labor goal.

The analysis step begins with an impacted goal.  Asking “why” questions develops the cause-and-effect relationships that led to the impacts.  In this case, the sicknesses and deaths were caused by a Listeria outbreak.  In order to have a food-borne illness outbreak, the food needs to be contaminated AND it needs to be delivered to consumers.  In this case, the contamination was not known because ice cream is not tested for Listeria.  There is no history of Listeria outbreaks in ice cream and testing is difficult on perishable products because of the time required.  Once ice cream products are again manufactured for consumers, Blue Bell has said it will implement a test and hold process (holding product until testing comes back negative).

The Listeria contamination results from the introduction of Listeria into the ice cream.  As discussed before, Listeria can replicate in cold temperatures.  The contamination source is likely surfaces in the production facilities or cross-contamination from other food products.  Because multiple plants are contaminated and cleanliness issues have been a concern in the past, it is likely that the outbreak is due to contamination of surfaces, on which Listeria can remain for a long time if not properly sanitized.

In addition to the test and hold process, Blue Bell is in the process of implementing a number of other changes to reduce the risk of future contamination.  Employees are being trained in microbiology and an expanded cleaning and sanitation program.  Prior to production resuming, equipment is being disassembled, cleaned, and tested for contamination and design changes that would make cleaning easier (reducing the risk of future contamination) are being considered.

While it is sometimes difficult to determine the success of solutions, the test and hold process to be used for future ice cream products should provide almost real-time feedback on the success of the programs and ensure that future problems are quickly identified.

To view a one-page PDF of the analysis and solutions, please click on “Download PDF” above.  To learn more about the ice cream Listeria outbreak, click here.  To read our previous blog about the 2011 fatal Listeria outbreak in cantaloupe, click here.