What makes raw eggs dangerous?

May 15, 2008 10:20 AM

What is the relationship between the age of a consumed raw egg and the risk of food poisoning, and what factors influence it - in general, but also specifically to salmonella?

While I understand that the longer you wait to consume a raw egg, the higher the risk of food poisoning, I have trouble understanding some details about it - specifically:

- Are the dangerous organisms typically inside the egg, or is it contamination from other sources that introduce them?

- What is more important - the quality of the egg, or the waiting time before consumation?

- Is the risk of getting salmonella via raw eggs a stochastic one (i.e. there either are salmonella in the egg, and then you will surely get it, or there isn't, and you will not get it), or is it a risk that's getting bigger over time (i.e. if there are salmonella in the egg, the chances of you getting food poisoning depends on the time you wait before eating it).

posted by lord_yo to health (5 comments total)

Either the egg has salmonella or it doesn't, and it is typically contained in the egg white, and even more specifically closest to the shell (since it enters the egg through the shell). Ingesting salmonella does not garauntee that you will show symptoms.

Salmonella are able to reproduce when in their happy zone, so keeping eggs cold (in the fridge) and cooking all egg white thoroughly keeps them out of that happy zone. Age of egg has nothing to do with it.
posted by agentwills at 10:53 AM on May 15

Lots of detail about this can be found here.
posted by TedW at 10:58 AM on May 15

The dangerous organisms are inside the egg, but introduced much before you bought them from the outside world. The quality of the egg has a lot more to do with taste and flavor than whether you'll get salmonella or not. I mean I suppose that's one measure of quality as well but it's more important that it just didn't get contaminated in any point in its life cycle. The waiting time inside your fridge isn't likely to introduce salmonella if it wasn't there before. What it can do is spoil your egg leading to that horrible rotten egg smell when you crack it open. The other day I wasn't sure about an egg that had a funny-looking, blistered shell so I performed the rotten egg test on it: dropped it into a glass of water. It floated right to the top because of all the sulphurous gases that had been released due to spoiling. A normal egg would sink to the bottom of the glass.
posted by peacheater at 11:21 AM on May 15

There's huge amounts of Salmonella information online. Probably more than you'll ever need in the following study alone:

"Considering only S. Enteritidis bacteria that are inside the egg soon after lay, available evidence suggests that growth of the bacteria depends on an increase in the permeability of the vitelline (yolk) membrane. This increase allows the bacteria access to critical growth nutrients. However, the change in permeability of the yolk membrane is time and temperature dependent. The process may take three weeks or longer, depending on the temperature at which eggs are held. Until this process is complete, there is little or no growth of S. Enteritidis bacteria within the egg. Essentially, this period represents a lag phase for the bacteria."


posted by oneirodynia at 12:08 PM on May 15

"High quality" in eggs is often associated with "fresher", i.e.: a high quality egg is generally one that's been inside a chicken within the past two days or so when you buy it. Supermarket eggs may have been collected weeks prior. As a result, fresher eggs have stronger yolk membranes and are more resistant to salmonella growth.

Is your actual question whether buying fresh farmer's market eggs instead of supermarket eggs lowers your risk of salmonella poisoning? The answer to that is surely yes, although regardless the risk is still a probability.
posted by Caviar at 9:55 AM on May 16