Microbiology and food safety in a nutshell
After a Twitter exchange with saracen77 about chocolate mousse this morning, I got to thinking about how we think about food contamination generally versus the science involved. In general, we've internalized (or ignore!) a lot of the warnings without knowing why the warnings are really there. So cobbling together what I learned when I got my foodhandler's license several years ago and what I learned in microbiology a couple of years ago, here are some thoughts about common misconceptions in food safety wiith the caveat that my foodhandler's license has expired so some of the standards (in CT specifically and the US generally) may have changed and I wouldn't know it.
Two key facts that will get referred to throughout: while there are bacteria that can thrive in Antarctica and lava flows, the ones that are dangerous to humans are the ones that thrive between the temps of 40F-140F, roughly 4C-60C. Therefore, fact 2, any high risk food (mostly meat, eggs, and dairy, some veg) that spends four or more hours in that temperature range is considered unsafe. That's four total hours in its existence, from the time it was either killed or removed from its living source until it enters your mouth, not necessarily consecutive time. Also, this includes when it cools down after being cooked. Not all bacteria are killed in cooking, some leave spores that can start breeding once temps get back into the danger zone.
Raw Eggs
Yes, they are definitely a huge salmonella risk. Washing the shells before cracking them reduces this only a little, though it substantially reduces the risk of contamination from whatever unwashed hands touched them before you. To be absolutely, 100% safe, always cook eggs thoroughly or else use pasteurized eggs.
Adding vinegar to egg whites does not "cook" them. It denatures the albumin, which makes them look cooked. It does nothing to kill bacteria. (All right, some may not like the acidity, but it's not a very strong acid, so don't rely on it.)
That said, people make egg nog and chocolate mouse and other things using raw eggs (whole or just whites) or eat undercooked eggs (I prefer mine over easy or "dippy") and don't get sick. Why? The two rules above. If the eggs have been kept cooler than 40F for the most part (4 hr rule) and weren't insanely contaminated to begin with (depends on the hens and farming conditions), the bacteria levels are probably low enough to be safe. In the case of nog and mousse particularly, they're generally meant to be kept pretty cool while making them and definitely kept chilled until right before serving, so despite the addition of sugar (bacteria's favorite food), they're probably safer than my over-easy eggs.
Though I will reiterate, since there are factors you can never be sure of in terms of how much bacteria is in them to start with, undercooked or raw eggs are generally considered unsafe unless pasteurized. I'm still getting over-easy eggs when I go out for breakfast though.
Meat
This is also why undercooked meat is a risk, though generally that appears to have more to do with how it was handled between the slaughterhouse and your plate than anything to do with the animal itself. I still order my burgers rare anyplace that'll let me. A lot of restaurants won't take the risk anymore, at least around here.
The main control you have at home, though, is when you're thawing it. The safest way to thaw meat, due to the 4 hour rule (and you have no clue how long it took to get it cold once it was slaughtered, so again, this is not 4 hours in your kitchen!) is either in the refrigerator (which should be below 40F/4C anyway) or in cold water (which should be continuously below 40F/4C). Failing that, a rapid thaw in the microwave.
Sometimes people think their meat is safe thawing on the counter for hours and hours because the inside is still frozen. No. The surface temperature gets into the danger zone long before it's thawed through, and so bacteria are happily breeding and churning out toxins while the inner layers thaw. If you've been doing this for years and nobody's gotten sick, count yourself lucky. You had meat that didn't have a very high bacteria population living in it to start with.
This is also why crock pots always used to come with instructions to cook on high for the first hour or two even if you then planned to let the rest of the cooking take place over several hours. I don't like the new ones that you just program for 10 hours. I want that temp up above 140F/60C fast, and I'm not positive they accomplish that.
With all that said, one of the most fascinating things I learned at the foodhandler licensing class was that pork in the US is way safer these days than people usually think. It's now (or was in 2003) considered safe to serve it cooked medium. Most cases of trichinosis in the US are from game meats, not pork. Yeah, I still cook it thoroughly too.
Those are the ones that come to mind at the moment. Thoughts? Anecdotes? Horror stories?
Two key facts that will get referred to throughout: while there are bacteria that can thrive in Antarctica and lava flows, the ones that are dangerous to humans are the ones that thrive between the temps of 40F-140F, roughly 4C-60C. Therefore, fact 2, any high risk food (mostly meat, eggs, and dairy, some veg) that spends four or more hours in that temperature range is considered unsafe. That's four total hours in its existence, from the time it was either killed or removed from its living source until it enters your mouth, not necessarily consecutive time. Also, this includes when it cools down after being cooked. Not all bacteria are killed in cooking, some leave spores that can start breeding once temps get back into the danger zone.
Raw Eggs
Yes, they are definitely a huge salmonella risk. Washing the shells before cracking them reduces this only a little, though it substantially reduces the risk of contamination from whatever unwashed hands touched them before you. To be absolutely, 100% safe, always cook eggs thoroughly or else use pasteurized eggs.
Adding vinegar to egg whites does not "cook" them. It denatures the albumin, which makes them look cooked. It does nothing to kill bacteria. (All right, some may not like the acidity, but it's not a very strong acid, so don't rely on it.)
That said, people make egg nog and chocolate mouse and other things using raw eggs (whole or just whites) or eat undercooked eggs (I prefer mine over easy or "dippy") and don't get sick. Why? The two rules above. If the eggs have been kept cooler than 40F for the most part (4 hr rule) and weren't insanely contaminated to begin with (depends on the hens and farming conditions), the bacteria levels are probably low enough to be safe. In the case of nog and mousse particularly, they're generally meant to be kept pretty cool while making them and definitely kept chilled until right before serving, so despite the addition of sugar (bacteria's favorite food), they're probably safer than my over-easy eggs.
Though I will reiterate, since there are factors you can never be sure of in terms of how much bacteria is in them to start with, undercooked or raw eggs are generally considered unsafe unless pasteurized. I'm still getting over-easy eggs when I go out for breakfast though.
Meat
This is also why undercooked meat is a risk, though generally that appears to have more to do with how it was handled between the slaughterhouse and your plate than anything to do with the animal itself. I still order my burgers rare anyplace that'll let me. A lot of restaurants won't take the risk anymore, at least around here.
The main control you have at home, though, is when you're thawing it. The safest way to thaw meat, due to the 4 hour rule (and you have no clue how long it took to get it cold once it was slaughtered, so again, this is not 4 hours in your kitchen!) is either in the refrigerator (which should be below 40F/4C anyway) or in cold water (which should be continuously below 40F/4C). Failing that, a rapid thaw in the microwave.
Sometimes people think their meat is safe thawing on the counter for hours and hours because the inside is still frozen. No. The surface temperature gets into the danger zone long before it's thawed through, and so bacteria are happily breeding and churning out toxins while the inner layers thaw. If you've been doing this for years and nobody's gotten sick, count yourself lucky. You had meat that didn't have a very high bacteria population living in it to start with.
This is also why crock pots always used to come with instructions to cook on high for the first hour or two even if you then planned to let the rest of the cooking take place over several hours. I don't like the new ones that you just program for 10 hours. I want that temp up above 140F/60C fast, and I'm not positive they accomplish that.
With all that said, one of the most fascinating things I learned at the foodhandler licensing class was that pork in the US is way safer these days than people usually think. It's now (or was in 2003) considered safe to serve it cooked medium. Most cases of trichinosis in the US are from game meats, not pork. Yeah, I still cook it thoroughly too.
Those are the ones that come to mind at the moment. Thoughts? Anecdotes? Horror stories?