Food Safety Talk 67: John Bassett

Food Safety Talk, a bi-weekly podcast for food safety nerds, by food safety nerds. The podcast is hosted by Ben Chapman and barfblog contributor Don Schaffner, Extension Specialist in Food Science and Professor at Rutgers University. Every two weeks or so, Ben and Don get together virtually and talk for about an hour.  They talk about what’s on their minds or in the news regarding food safety, and popular culture. They strive to be relevant, funny and informative — sometimes they succeed. You can download the audio recordings right from the website, or subscribe using iTunes.1411999879196

In episode 67, Ben is on hiatus and Don talks with John Bassett. The scene opens with a vivid description of a picturesque English village with pigeons pooping on the eaves and birds chirping in the background.

John starts by telling the listeners a bit about his background. He is a veterinarian by training, having earned his degree in New Zealand.  He spent seven years as a veterinary practitioner; a bit like that depicted inAll Creatures Great and Small in Epsom (that’s in England). John returned to New Zealand and began a small animal practice but quickly transitioned to work for a government biosecurity laboratory inWellington (that’s in New Zealand) where he solved problems during extended coffee breaks taken in trendy cafes. John got his start in risk assessment using the OIE approach.  John’s next career move was to industry as a risk assessor with Unilever; this took him back to England (that’s in the United Kingdom).  The guys got sidetracked and discussed the sole-crushing bureaucracy that can be found in big industry (not that there’s anything wrong with that).  John’s latest career change finds him in a new mode as food safety consultant.

The guys discussed the recent Chobani mold incident.  From here the conversation jumped into tea.  Iced tea with added sugar was discussed as a possible growth medium for generic E. coli (special concern was expressed for sun-brewed tea) and the potential for herbal (pronounced ‘erbal’ by some) tea as a source of bacteria and maybe pathogens.

John talked about some of his current risk assessment work, and the difficulty of making risk management decisions for low-frequency events.  John explains his recent interest in Gael Risk assessment techniques. This approach can be used for semi-quantitative risk assessment, and may have value in preventing problems like the recent horse-meat food scandal.  The value of audits in science-based food safety was questioned and discussed, and Don and John disagreed about the value of semi-quantitative risk assessments.

Bandwidth on John’s end starts to suffer (perhaps due to John’s kids arrival home from school) so the conversation is paused briefly, while John (the poopy-head) sorts it out.

The show resumes with a discussion on whether HACCP is risk based or not.  John notes that one key to “selling” a risk assessment might be based on saving money in the long run, perhaps from a reduced need for testing and auditing.  A discussion of the Elliott Review takes place before the guys re-iterate the need for using computerized systems for effective traceback in the food supply chain; especially ones that do not need to be linked via paper documents.

John mentions that he will not be at IAFP 2014 due to lack of a wealthy sponsor; but he does plan to attend the IAFP European Symposium in Cardiff in 2015. Don reveals his IAFP presidential party plans (Beer, Bourbon, and BBQ), while John contemplates pork ribs somewhere closer to home.

John mentioned the use of the sear and shave technique to produce safer raw burgers in the UK.  Don didn’t seem convinced, and will continue using his iGrill and tip sensitive digital thermometer, as suggested for use in previous Food Safety Talk episodes, “because everyone’s gotta have a hobby”.  Both guys reminisced over outbreaks of Campylobacter jejuni from seared chicken livers that occurred in the UK and USA.

In the After Dark portion, Don transitioned into talking about Doctor Who, and John explained he was late for the podcast meeting because of a meeting with McDonald’s own Bizhan Pourkomailian.

Quantitative risk assessment of hemolytic and uremic syndrome linked to O157:H7 and non-O157:H7 shiga-toxin producing Escherichia coli strains in raw milk soft cheeses

Shiga-toxin producing Escherichia coli (STEC) strains may cause human infections ranging from simple diarrhea to Haemolytic Uremic Syndrome (HUS). The five main pathogenic serotypes of STEC (MPS-STEC) identified thus far in Europe are O157:H7, O26:H11, O103:H2, O111:H8, and O145:H28.

raw.milk.cheeseBecause STEC strains can survive or grow during cheese making, particularly in soft cheeses, a stochastic quantitative microbial risk assessment model was developed to assess the risk of HUS associated with the five MPS-STEC in raw milk soft cheeses. A baseline scenario represents a theoretical worst-case scenario where no intervention was considered throughout the farm-to-fork continuum. The risk level assessed with this baseline scenario is the risk-based level. The impact of seven preharvest scenarios (vaccines, probiotic, milk farm sorting) on the risk-based level was expressed in terms of risk reduction. Impact of the preharvest intervention ranges from 76% to 98% of risk reduction with highest values predicted with scenarios combining a decrease of the number of cow shedding STEC and of the STEC concentration in feces. The impact of postharvest interventions on the risk-based level was also tested by applying five microbiological criteria (MC) at the end of ripening.

The five MCs differ in terms of sample size, the number of samples that may yield a value larger than the microbiological limit, and the analysis methods. The risk reduction predicted varies from 25% to 96% by applying MCs without preharvest interventions and from 1% to 96% with combination of pre- and postharvest interventions.

Risk Analysis
Frédérique Perrin, Fanny Tenenhaus-Aziza, Valérie Michel, Stéphane Miszczycha, Nadège Bel, and Moez Sanaa;jsessionid=74BD9124E68BA3CAA0FCD6112D55BB0C.f02t01

Risk assessment of Escherichia coli O157 illness from consumption of hamburgers in the United States made from Australian manufacturing beef

We analyze the risk of contracting illness due to the consumption in the United States of hamburgers contaminated with enterohemorrhagic Escherichia coli (EHEC) of serogroup O157 produced from manufacturing beef imported from Australia.

BeefAustralia2012We have used a novel approach for estimating risk by using the prevalence and concentration estimates of E. coli O157 in lots of beef that were withdrawn from the export chain following detection of the pathogen.

For the purpose of the present assessment an assumption was that no product is removed from the supply chain following testing. This, together with a number of additional conservative assumptions, leads to an overestimation of E. coli O157-associated illness attributable to the consumption of ground beef patties manufactured only from Australian beef. We predict 49.6 illnesses (95%: 0.0–148.6) from the 2.46 billion hamburgers made from 155,000 t of Australian manufacturing beef exported to the United States in 2012. All these illness were due to undercooking in the home and less than one illness is predicted from consumption of hamburgers cooked to a temperature of 68 °C in quick-service restaurants.

Risk Analysis

Andreas Kiermeier, Ian Jenson, and John Sumner;jsessionid=43180662EA5BDBE4A8B9078767641769.f03t02

Don Schaffner: modeling listeria growth on melons: in science (and other things), faster isn’t always better

Friend of the Don Schaffner of Rutgers University writes in this guest post:

It’s every scientist’s nightmare to get scooped.  You have an idea, find the funding, do the research and write it up, scan the current literature hoping that no one else has that same idea and beats you to publication.  I don’t worry about this too much, as there aren’t many people that do what I do, and even fewer that do it rock.melon.may.12the way I do. It’s like Jerry Garcia said: “You do not merely want to be considered just the best of the best of the best, you want to be considered the only ones that do what you do.”

But getting scooped on this particular project was on my mind.  Jensen farms had just made a bunch of people sick with listeriosis from cantaloupe, so when Larry Goodridge sent the word out to a bunch of us that we should all submit interlocking proposals to our respective state Departments of Agriculture through state administered Special Crops Research Initiative (SCRI) money for research on Listeria in cantaloupe, I was in.  Larry’s been a good friend, and his nose for grant dollars is second to none.  Alas, this time is was not to be, and only a few of the states funded the interlocking proposals; New Jersey was not one of them. The good news was that Michelle Danyluk at the University of Florida was one who did get funding, and I’m Michelle’s go-to collaborator for all things mathematical.

Prior to the Jensen Farms outbreak, Listeria in cantaloupe was a theoretical risk, but the outbreak underscored the point that L. monocytogenes was a real risk in these foods. Michelle proposed that her lab would collect data on L. monocytogenes growth in cut melons, and that my lab would build the models.  As we suspected from research with Salmonella in cut melons, the organism would multiply rapidly at elevated temperatures but leave the visual appearance of the melons largely unchanged. Listeria’s ability to grow in the fridge made the potential risk even greater.

At this point, I know it’s a race against time, because some other modeler somewhere is thinking the same thing.  Uber-technician Lorrie Friedrich got to work collecting data, and I sharpened my MelonTrucksspreadsheets (or what ever it is that modelers do when waiting for data).  Lorrie soon had the data, and I began making the models, and Michelle started the hard work of writing the manuscript first draft.  All three of us work fast in general. In this particular case, we worked even faster.  We had a rough draft together when I saw the bad news.  My modeling colleagues at the U.S. Department of Agriculture, Agricultural Research Service, in Wyndmoor, PA, near Philadelphia, led by Dr. Lihan Huang published a paper entitled “Growth kinetics of Listeria monocytogenes and spoilage microorganisms in fresh-cut cantaloupe” in Food Microbiology.  A quick read of the paper didn’t leave much doubt; we’d been scooped.

Undaunted, we pressed on.  The first step was to check their model against ours.  It was then that I notice something weird.  Their growth curves showed extraordinarily high bacterial concentrations.  A quick check showed they were reporting bacterial counts in some cases as ln CFU/g instead of log CFU/g.  This explained the high counts in their figures, but even after correcting for this, their model was still giving strange predictions.  I couldn’t even get their model to match their data.  It was then that I noticed that one parameter in their model was about an order of magnitude different from the same parameter in our model.  It might be that slightly different datasets will give model parameters that vary by 25% in some case, but an order of magnitude difference means an error.  Once I corrected their parameter (multiplied by 10), their model and our model fell almost on top of one another (See Figure 2 in Danyluk et al.)

In the end, the reviewers were kind to us, and since we not only corrected, then corroborated Fang et al, (2013), we also validated both models against original data for L. monocytogenes growth in watermelon, and honeydew as well as predictions from ComBase jerry.garciaPredictor for various assumed water activities and pH values.  A contour plot of the model (Figure 3 in the paper) also shows that extended storage of contaminated cut melon slices at even slightly elevated temperatures (in home refrigerators for example) would result in significant risk amplification.

Modeling the growth of Listeria monocytogenes on cut cantaloupe, honeydew and watermelon

Food Microbiology Volume 38, April 2014, Pages 52–55


A recent outbreak linked to whole cantaloupes underscores the importance of understanding growth kinetics of Listeria monocytogenes in cut melons at different temperatures. Whole cantaloupe, watermelon, and honeydew purchased from a local supermarket were cut into 10, 1 g cubes. A four-strain cocktail of L. monocytogenes from food related outbreaks was used to inoculate fruit, resulting in ~10^3 CFU/10 g. Samples were stored at 4, 10, 15, 20, or 25 °C and L. monocytogenes were enumerated at appropriate time intervals. The square root model was used to describe L. monocytogenes growth rate as a function of temperature. The model was compared to prior models for Salmonella and Escherichia coli O157:H7 growth on cut melon, as well as models for L. monocytogenes on cantaloupe and L. monocytogenes ComBase models. The current model predicts faster growth of L. monocytogenes vs. Salmonella and E. coli O157:H7 at temperatures below 20 °C, and agrees with estimates from ComBase Predictor, and a corrected published model for L. monocytogenes on cut cantaloupe. The model predicts ~4 log CFU increase following 15 days at 5 °C, and ~1 log CFU increase following 6 days at 4 °C. The model can also be used in subsequent quantitative microbial risk assessments. 

Development and validation of a mathematical model for growth of pathogens in cut melons

Everywhere I go in Brisbane, I see cut cantaloupe.

cantaloupe.half.sep.12Rock melon as the locals call it.

From the biggest retail megalomarts to the local fruit and veg., aging cantaloupes are cut in half, wrapped in cellophane, stored at room temperature and sold at a slight discount.

This is a Salmonella growth factory.

The practice is shameful, and for every corporate food safety thingy out there who says with a straight face, food safety is our top priority, you’re full of it.

I’m looking at you, Coles and Woolworths (which control the retail grocery market in Australia).

I’m told the melon-in-half practice is prevalent in California, Florida, and pretty much everywhere.

The thing with produce – especially the ones in repeated outbreaks like cantaloupe, leafy greens and tomatoes – is that once it is cut in any way, the cut provides a growth medium for any existing microorganisms. Storing at room temperature sets fire to the flame, which is why the cold-chain is so important for cut produce.

Friend of barfblog Schaffner just can’t stop writing papers, which is good, because food safety needs more evidence and less faith.

Abstract below.

Development and validation of a mathematical model for growth of pathogens in cut melons.

Journal of Food Protection, Number 6, June 2013, pp. 928-1108 , pp. 953-958(6)

Li, Di; Friedrich, Loretta M.; Danyluk, Michelle D.; Harris, Linda J.; Schaffner, Donald W.

Many outbreaks of foodborne illness associated with the consumption of fresh-cut melons have been reported. The objective of our research was to develop a mathematical model that predicts the growth rate of Salmonella on cantaloupe.salmonellafresh-cut cantaloupe over a range of storage temperatures and to validate that model by using Salmonella and Escherichia coli O157:H7 on cantaloupe, honeydew, and watermelon, using both new data and data from the published studies. The growth of Salmonella on honeydew and watermelon and E. coli O157:H7 on cantaloupe, honeydew, and watermelon was monitored at temperatures of 4 to 25°C. The Ratkowsky (or square-root model) was used to describe Salmonella growth on cantaloupe as a function of storage temperature. Our results show that the levels of Salmonella on fresh-cut cantaloupe with an initial load of 3 log CFU/g can reach over 7 log CFU/g at 25°C within 24 h. No growth was observed at 4°C. A linear correlation was observed between the square root of Salmonella growth rate and temperature, such that √growth rate = 0.026 × (T – 5.613), R2 = 0.9779. The model was generally suitable for predicting the growth of both Salmonella and E. coli O157:H7 on cantaloupe, honeydew, and watermelon, for both new data and data from the published literature. When compared with existing models for growth of Salmonella, the new model predicts a theoretic minimum growth temperature similar to the ComBase Predictive Models and Pathogen Modeling Program models but lower than other food-specific models. The ComBase Prediction Models results are very similar to the model developed in this study. Our research confirms that Salmonella can grow quickly and reach high concentrations when cut cantaloupe is stored at ambient temperatures, without visual signs of spoilage. Our model provides a fast and cost-effective method to estimate the effects of storage temperature on fresh-cut melon safety and could also be used in subsequent quantitative microbial risk assessments.

Listeria risk from raw milk cheese 50-180X greater than pasteurized; FDA, Health Canada publish draft risk assessment

The U.S. Food and Drug Administration has announced a draft quantitative assessment of the risk of listeriosis from soft-ripened cheese consumption in the United States and Canada. The risk assessment is a joint effort between FDA and Health Canada.

The new FDA/Health Canada draft risk assessment found that the risk of listeriosis from soft-ripened cheeses made with raw milk is estimated to amy.pregnant.listeriabe 50 to 160 times higher than that from soft-ripened cheese made with pasteurized milk. This finding is consistent with the fact that consuming raw milk and raw milk products generally poses a higher risk from pathogens than do pasteurized milk and its products.

While raw milk and raw milk products put all consumers at risk, the bacteria they may contain can be especially dangerous to people with weakened immune systems, older adults, pregnant women and children.

FDA invites comments that can help FDA and Health Canada improve:

the approach used;

the assumptions made;

the modeling techniques;

the data used; and

the clarity and transparency of the draft quantitative risk assessment documentation.

To submit comments electronically, go to docket FDA-2012-N-1182 on The comment period opens February 11, 2013 for 75 days.

Why people ignore risk: EFSA@10 Conference opens with call to further strengthen risk assessment ‘community’

Monty Python says Americans like to talk.

Europeans sure like to talk. Amy is faux European, being a French professor, and she talks all the time.

And who uses dick fingers around the word community?

But talk doesn’t help people who are barfing: like the 53 who were killed and 4,400 who were sickened by raw sprouts last year.

Hundreds of the world’s leading food safety experts are gathering in Parma this week to take part in a high-level scientific conference organized by the European Food Safety Authority (EFSA) to mark its tenth anniversary.

Does high-level mean they are all stoned?

The two-day event, “Challenging boundaries in risk assessment – sharing experiences”, which kicked off this morning (7 November), brings together global specialists from a wide range of scientific disciplines who will be debating the frontiers in risk assessment and considering future key issues and opportunities.

Hubert Deluyker, EFSA’s Director of Science Strategy and Coordination, outlined the Authority’s critical role in developing risk assessment in Europe, emphasized the necessity for a continued commitment to scientific cooperation and re-affirmed the need for a regulatory environment that evolves with scientific developments yet remains predictable.

“EFSA functions thanks to the EU risk assessment community,” said Dr Deluyker. “And we are central to its progress, for instance through the development of guidance that has harmonised and modernised methodologies relating to risk assessment for food and feed over the past decade.”


Fail: sprout information from Germany

From the files of the entirely unimaginative, German risk assessors have produced a leaflet for consumers with tips to avoid EHEC.

The leaflet, “Consumer Tips: Protection against Infections with Enterohaemorrhagic E. coli (EHEC)” was produced by Germany’s Federal Institute for Risk Assessment, BfR.

“In view of the major EHEC outbreak in early summer 2011, the BfR once again draws attention to hygiene measures which must be observed in the cultivation and preparation of sprouts, since contaminated sprouts were in all likelihood the cause of the numerous infections at the time. Independently of the past EHEC outbreak, the BfR had already earlier drawn attention to the risk of contracting disease resulting from the consumption of raw sprouts.

“When handling seeds and raw sprouts, consumers should be particularly meticulous in taking hygiene measures in order to minimise the risk of an infection. If possible, sprouts should also be sufficiently heated by boiling or frying or at least thoroughly washed before they are eaten. Pathogens cannot be removed completely by light heating or washing of the sprouts. For this reason, persons with a weak immune system, i.e. infants, pregnant women, the elderly and persons suffering from illness should, to be on the safe side, only eat sprouts after they have been adequately heated.”

With 53 dead and some 4,400 sickened, mostly in Germany, it was a, uh, major outbreak. And it was most likely contaminated fenugreek seed imported from Egypt that was the underlying cause. Washing isn’t going to do much and cross-contamination is always a risk. Also not much help for those who buy sandwiches or salads in Europe (and Australia) where sprouts are ubiquitous.

Take a brochure for lunch next time and be better educated.

Reminder from German scientists: seasoned minced meat and raw minced pork are not for little children

A recent study by the Robert Koch Institute found that even small children in Germany eat raw meat more often than expected, so the Federal Institute for Risk Assessment (BfR) decided to remind Germans that raw meat for children is a bad idea.

"Raw animal foods are often contaminated with pathogens", explains Professor Dr. Dr. Andreas Hensel, president of BfR. "For this reason, especially vulnerable sections of the population, such as small children, pregnant women, the elderly and people with a weakened immune system, should as a rule not eat these foods raw."

Raw meat can transmit, among other things, salmonella, Campylo¬bacter, E. coli including EHEC, Yersinia, Listeria and also viruses and parasites.

A recent study by the Robert Koch Institute published in the Epidemiological Bulletin has shown that raw minced pork is the most important risk factor for contracting yersiniosis. Yesiniosis is a gastro-intestinal disease which is notably caused by the bacterium Yersinia enterocolitica. Yersinia are predominantly spread through food, especially raw pork. Pork, for example minced pork and seasoned minced meat, is often eaten raw in Germany. One of the surprising findings of the published study was the high number of children who had eaten raw minced pork. Even of children who were one-year-old or younger it was reported that almost 30% of those who had fallen ill (and 4 % of the control persons) had eaten raw minced pork.

In Germany and other European countries, Campylobacter is now the most prevalent bacterial pathogen for enteric infections in humans. In the year 2011, more than 70,000 human campylobacteriosis cases were reported.

Campylobacter bacteria are notably found in raw or insufficiently heated poultry meat, but also in raw meat of other animals as well as raw milk and hen’s eggs.
The number of reported salmonellosis cases in humans, especially from Salmonella Enteritidis, has fallen significantly in the last three years.

In contrast, human infections with Salmonella Typhimurium have decreased to a lesser extent. SalmonellaTyphimurium are especially common in turkey meat and pork. As part of zoonosis monitoring, salmonella, most frequently Salmonella Typhimurium, were detected in 5 % of minced meat samples in 2009. This finding confirms that raw minced meat can be a source of infection for humans.

To protect themselves against often severe cases of foodborne infections, especially vulnerable sections of the population such as children under five, pregnant women, elderly and persons with a weakened immune system should as a matter of principle refrain from eating raw foods. They should therefore avoid consuming raw mince or seasoned minced meat, raw sausage, raw milk and raw-milk cheese, raw fish (e.g. sushi) and certain fishery products (e.g. smoked and gravad salmon) as well as raw seafood (e.g. raw oysters).

All that and no mention of raw sprouts? In Germany? The risk assessors did say consumers can “protect themselves by cooking meat and poultry sufficiently and evenly” and that “such meat must be cooked until the juices run clear and the meat has a whitish (poultry), gray-pink (pork) or gray-brown (beef) color. The inside temperature of the meat should be at least 70 °C for two minutes. If in doubt, consumers can measure this temperature by means of a meat thermometer.”

Some risk assessors. Color is a lousy indicator and consumers should be using a tip-sensitive digital thermometer to erase doubt. And stop making little kids barf.

Don’t add poop: how to prevent norovirus in oysters

 The most effective public health measures to protect consumers from exposure to norovirus in oysters are to produce oysters in areas which are not contaminated or to prevent contamination of mollusc production areas.

And current methods used to remove norovirus in shellfish are not an effective means of reducing contamination.

So says the European Food Safety Authority (EFSA) Panel on Biological Hazards (BIOHAZ Panel) in a new risk assessment.

The Panel recommends establishing acceptable limits for the presence of virus in oysters that are harvested and placed on the market in the European Union. In addition, an EU-wide baseline survey on norovirus in oysters should be carried out to provide information on overall consumer exposure as well as the public health impact of control measures.

Norovirus is transmitted through the consumption of food or water contaminated with fecal matter or through person-to-person contact or contact with infected surfaces. Oysters contaminated with norovirus pose a particular risk to human health as they are often consumed raw.

EFSA’s BIOHAZ Panel concludes that norovirus is highly infectious and that the amount of the virus detected in oysters linked to human cases can vary greatly.

Scientists highlight that norovirus is frequently detected in oysters in Europe which comply with existing EU control standards for bivalve molluscs.