07 December 2013

Cooking to Internal Temperatures: Duration Matters



I don't remember where I found this chart [apologies, kudos, and thanks to the originator] but it illustrates a key concept in cooking that many home cooks are ignorant of: "safe" internal temperatures when cooking depend on duration.

Usually "official" recommendations for food cooking give just a temp at which most pathogens would perish instantly and at which the taste and texture of your food also perish instantly. The government doesn't care how your food tastes, they are optimizing for reduced illness. And companies don't want to get sued because you got sick. I don't want to get sick, either, but I'm honestly not that bothered. I do want my food to taste good and I don't want to go to the expense of sourcing really good meat to eat only to ruin it by cooking it too long.

The chart above is a simplification. The poultry curve is for salmonella. Certainly there are other pathogens that might be in poultry. And I've looked at the raw [heh heh] data from FSIS, and the other simplification is that the curve changes depending on factors such as %fat of the poultry in question. But the chart is perfect for illustrating the temperature and time aspect of cooking safely.

So the FDA says to cook your chicken or turkey to internal of 165F, which is horrible thing to do to a good breast. On the previous post, Joe mentioned he got much better results cooking to 160F (for 3min).  A few degrees can make a big difference. So can a few minutes.

What the chart tells me is that if, say, I'm smoking chicken at a relatively low temperature, and thus it is taking a long while to cook, and if the lowest internal temp is 62.5C at a given checkpoint, I can pull it off in 15 minutes regardless of what the internal temp is then. So if I wanted to take it off the heat at 65C, I would go with either 65C or 15 minutes elapsed, whichever comes first.

Cooking isn't always about the lowest temperature possible. For delicate items or ones that dry out easily -- poultry white meat, pork loin, good steak, most fish -- I err on the low side. For other items, I cook them to much higher temperatures not out of safety concerns but because I think they are better that way. Best examples: goose leg confit (all poultry legs, for that matter), pork shoulder (pulled pork), various braising cuts and such.

Bottom line: if you want to avoid overcooking a particular piece of meat, think of duration when it comes to internal temperatures.

There's plenty of good information on the web about food safety. Douglas Baldwin, for example, has a really nice introduction to it, written as part of a sous vide primer but of good general interest.

2 comments:

JustJoeP said...

it's all an energy equation =)

JustJoeP said...

"while spoilage bacteria begin multiplying at 23°F (-5°C)" - I did not know they could multiply that cooly. Learn something new everyday.

University of Texas at Austin are doing some fascinating studies on the "awareness" of bacteria when around other bacteria of various species. Interviewer: "so bacteria are aware?" UT scientist: "Absolutely they are aware. They know where they are, how many of their friends are around, and what they can do as a group" ... and then went on to give multiple examples, from bioluminescence to protein signaling to working with other species to increase toxicity.

I just wish I got a better analog radio signal for NPR here in Southern OC, where the hill geography occludes both LA and SD stations frequently.. I'd learn so much more while driving from point A to point B.