Eyebrow-Raising Recent Study on Safe Cooking Temperatures

I just came across this 2012 study, showing that a variety of pathogenic bacteria were able to survive for a shocking amount of time on the surface of chicken breasts in boiling water. The standard 6.5D Salmonella reduction table in Modernist Cuisine indicates that the pasteurization time at a temperature of 185 F (85 C) is 0.02 seconds. In this study, though, researchers report that it took about 2 minutes to obtain a 1D reduction in bacteria, even though the surface temperature of the chicken reached 85 C within 1 minute. That implies a 6.5D reduction time of 13 minutes in boiling water - 650 times longer than the 0.02 second time predicted by the pasteurization table! I am completely floored by this.

How much do we really know about pasteurization times? In doing further research, this literature review explains that bacterial death observed in experiments often does not fit predicted linear behavior, and the reasons for this are complex and sometimes unclear. It also cites extensive research on heat tolerance in pathogenic bacteria. The situation sounds far more complicated and uncertain than the standard pasteurization tables led me to believe.

This 2015 study also found that FDA recommended cooking techniques for poultry (which seem excessive when compared with the Salmonella pasteurization table) did not eliminate all Salmonella bacteria in the most contaminated samples.

Finally, a report prepared for the UK Food Standards Agency on the safety of sous vide cooking cautioned that there is insufficient data on the behavior of pathogens in the 40-60 C temperature range to create a reliable model for predicting bacterial death.

I would be very interested in hearing opinions on this. At the very least, the 2012 study calls the ChefSteps method for chicken tartare into serious question. It also leads me to wonder about how reliable the Salmonella pasteurization tables are. If they are primarily based on laboratory studies of bacterial cultures, do they really represent bacterial behavior on the surface of intact meat?

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Comments

Robert_Conn_II_123023

I don't know of any current studies but I do know what temps Ive been cooking at sous vide for the last 7 years and they are much lower than the FDA or other temps in mainstream recipes. I have cooked for countless hundreds of people this way and in all that time I have never been or gotten a report of anyone getting sick.

I have read tables years ago that described how long it takes the internal temp to reach a desired mark (usually between 15 and 30 minutes depending of what ingredient it is and it's thickness) then the rest of the table is how long it needs to stay at that temp to be considered safe.

No method kills all pathogens, that's not the point. It is to bring them down to safe levels.

Refrigeration is another consideration. It too does not kill or prevent the spread of germs, bacteria and other pathogens, it slows their growth at an acceptable rate, but eventually, even foods help at 35 degrees F will spoil and rot. I suppose it all depends or your understanding of food safety and whose "study" you choose to believe in.

There will always be conflicting reports. It is currently an even numbered year so I bet the FDA is again saying milk is bad for us again....until next year.

fisher23

Very well said and much more eloquent than I would of.

Afonso_Tito_de_Morais_164825

I too have cooked food at much lower temps and have had zero issues. Like Rob says, there'll always be contradicting studies. From my personal experience I find it to be safe to eat. It also depends where and how the food is grown, kept, etc, so there's a bunch of factors to take in account.

tshewman

See Robert Conn's response and also realize pasteurization does mean sterilization.

Matthew_Snyder_68770

Every time I read something like this, I'm reminded of the old George Carlin bit about how supercharged his immune system was because he swam in raw sewage as a child.

Marc_34938

Thanks for the responses, everyone. I should mention that I've also been cooking various proteins sous vide for 2.5 years now, and I've never been sick from it. I've read a variety of sources on the topic, including Modernist Cuisine and excerpts from Douglas Baldwin's online guide, and I've always followed the pasteurization tables they provide. Clearly, given our combined experience, those tables must generally yield safe results.

On the other hand, the multiple sources I cited left me with the sense that the science is quite a bit murkier than I ever realized. I understand that we're not trying to sterilize meat, but I like following safe food handling practice whenever possible. And it sounds like safe food handling might be more difficult to define than I thought. If the pasteurization time for surface bacteria on chicken breasts is 13 minutes in boiling water, that's dramatically different than I ever dreamed possible -- and pretty impractical if we want chicken that's not dried out to the consistency of chalk.

I wonder if pasteurizing chicken at lower temperatures is more effective than traditional high temperature cooking. Modernist Cuisine presented experimental data for ground chicken meat that was similar to the standard Salmonella table. Maybe at high temperatures, there is an unusual heat tolerance effect?