Cooperative Research Borne From a Responsibility for Food Safety
The Listeria monocytogenes bacteria (L. monocytogenes) is a very severe bacteria that is a major cause of food poisoning, potentially leading to premature birth miscarriages and even cases of meningitis and other serious health problems. It is reported to occur mainly in unpasteurized natural cheese, meats, vegetables and fruits. In France reported cases of the L. monocytogenes found in pasteurized liquid eggs have made it essential to better understand just what the risk is. Kewpie, one of Japan’s largest food ingredient manufacturers and a major egg product producer, teamed up with the University of Tokyo’s Graduate School of Agricultural and Life Sciences Research Center for Food Safety to develop a growth model of bacteria in liquid eggs in order to increase their understanding of the risks.
From its inception, Kewpie has followed the spirit of “Good products are only made from good ingredients,” and that food safety is something that must always be strived for to the best of their abilities, as explained by Miho Okochi, who is part of Kewpie Corporation’s R&D Center Food Safety Division Microbial Laboratory. “In our laboratory we focus on technology and research of microorganisms necessary in product development, and microorganisms that may contaminate products,” he explained.
Bacteria Surviving Even After Pasteurization
Since contamination growth research for chicken eggs did not previously exist, the lab first conducted research on the L. monocytogenes contamination rate in unpasteurized liquid eggs. The results showed a lower rate of contamination and lower bacteria counts compared to other livestock meat products. This led them to believe that L. monocytogenes could be sterilized enough in the normal pasteurization process of liquid eggs. However, the French reports showed the L. monocytogenes present in liquid eggs even after the sterilization process, demonstrating there is definitely a chance of L. monocytogenes surviving and contaminating eggs, even after pasteurization.
“Because of this we decided to research the growth rate of L. monocytogenes in liquid eggs. We built a growth model based on L. monocytogenes counts in varying storage temperatures and times in liquid eggs so that we could understand under what conditions the risk of L. monocytogenes growth would increase,” explained Okochi.
“I had always wanted to create a growth model of food bacteria, but this was a bit much for one researcher to tackle. Growth modeling in the risk analysis of food microbiology is an important tool – and the research results are important for the entire industry,” he said. For help with the task, Okochi turned to Tokyo University’s Research Center for Food Safety, one of the few universities working in this field, to establish a joint research project.
Professor Katsuaki Sugiura
Graduate School of Agriculture and Life Sciences, University of Tokyo
Using @ RISK to Predict the Growth Parameters of L. Monocytogenes in Liquid Eggs
It is normal that the speed and rate of bacteria growth will vary, even when applying the same bacteria to the same food sample. The growth parameters must be well understood if researchers are to make use of data in actual food safety. The challenge is that it is difficult to produce enough bacteria to accurately find average values, standard deviations and other statistically significantly values, but by using Palisade’s @RISK software, researchers can use a Monte Carlo simulation of the growth model coefficient to estimate the growth parameters. @RISK, an add-in to Microsoft Excel, uses Monte Carlo simulation to examine thousands of different possible scenarios in any quantitative model.
Okochi explained how they learned about @RISK: “We heard about the software from a university professor who was researching food safety. It is used in the risk assessment of food microbiology and becoming more widely used in Japan.” @RISK has a number of benefits, he said. It has been adopted in many industries, it uses industry standard Microsoft Excel, and the spreadsheet files can even be opened by computers without @RISK installed. In the food safety industry there are a number of users, and the availability of training in Japanese from Palisade is a great benefit. The @RISK software is also available in Japanese.
For this research, the experimental kinetic data were fitted to the Baranyi model, and growth parameters, such as maximum specific growth rate (µ(max)), maximum population density (N(max)), and lag time (?), were estimated using a Monte Carlo simulation with @RISK. As a result of estimating these parameters, the researchers found that L. monocytogenes can grow without spoilage below 12.2°C, so they then focused on storage temperatures below 12.2°C. Predictive simulations under both constant and fluctuating temperature conditions demonstrated a high accuracy, and with this joint research model they were able to predict growth of L. monocytogenes in pasteurized liquid eggs under refrigeration. The results of this research provide crucial information to the food safety industry.
@RISK Working Across Industries
According to the researchers, the advantages of @RISK include the capability to run simulations even when the case is mathematically difficult. It is also easy to understand the simulation results, since researchers can visually verify the results using charts and graphs, making it extremely powerful and useful.
Professor Katsuaki Sugiura, professor and researcher at the Laboratory of Global Animal Resource Science at the Graduate School of Agriculture and Life Sciences, part of the University of Tokyo, praised the joint research as well as @RISK.
“Through Mr. Okochi’s research, we have been able to attain valuable results in a research field with little precedence, based on the development of a growth model of the L. monocytogenes bacteria in liquid eggs. I believe that @RISK will play a valuable role in the field of microbiology forecasting. As @RISK is used in fields besides food safety, from 2013 I have used it as one of our information processing tools with my students for risk analysis in other fields. The real benefit of @RISK is that it is an add-in for Microsoft Excel, so you do not need any complex programming language. I look forward to seeing more and more research results in various fields.”