I discovered a stunning Youtube video via Boingboing, so consider this post just an excuse to show it to you. But as long as its title involves potato salad, I thought I’d reiterate some points we’ve made in the past about potato salad and food poisoning.
Potato salad is a frequent vehicle for one of the nastier foodborne illnesses, staphylococcal food poisoning, although it can also do the same favor for salmonellosis, Bacillus cereus, E. coli, campylobacter, Norovirus and Shigella (there is a rundown here). Much of what we say here for staph holds true for the others although it is the classical “first you are afraid you are going to die and then you are afraid you aren’t going to die” type of food poisoning. Nausea, vomiting and cramps typically strike about 3 to 6 hours after the meal, although it is sometimes shorter and sometimes longer. Still, even 6 hours is relatively short and is indicative more of a chemical poisoning than a foodborne infection. In a sense that’s correct for staph food poisoning, since it isn’t the organism itself that’s at fault but a very heat stable toxin that some strains of S. aureus produce. Often the bug isn’t even there anymore, just the toxin it left behind. It is the toxin that produces the nasty (but usually self-limiting) symptoms although for reasons that are unclear, not everybody is equally susceptible to it.
So what is there about potato salad that makes it such a common suspect in staph food poisoning? The answer many people is: mayonnaise. Wrong. There is something about potato salad that makes it a more frequent vehicle, but it usually isn’t mayonnaise. Mayonnaise is an emulsion of oil, salt and vinegar or lemon juice, with the emulsifier being raw egg yolks. Home made mayonnaise may be the source of Salmonella food poisoning because of the raw eggs and imprecise control of acidity, but commercial mayo almost never. The reason is that there is very good control over the vinegar or lemon juice content which lowers the acidity down to the low fours in pH. That’s pretty inhospitable for pathogens and indeed commercial mayonnaise has been shown to be bactericidal. Mayo’s salt content has also been cited as a reason, and that may be true for many pathogens, but the staphylococcus bug is pretty salt tolerant, so that may be less of a factor.
This means you can leave commercial mayonnaise out at room temperature and not worry it will grow deadly bugs. That’s not true of mayo containing potato salad, though, and constitutes one of the reasons it is a common vehicle. Potato salad is prepared and served at room temperature, often outdoors at picnics where there is no refrigerator. It is not uncommon for it to be at room temp or higher for hours at a time, between transportation and time to serving. If there are any staph (or other) pathogenic organisms in it, they don’t start to multiply right away. It takes two to four hours for them to get accustomed to their surroundings and really get ready to ramp up binary fission. This initial period is called the lag phase but it is succeeded by the log phase where there is exponential growth: one bug divides to two, two to four, four to eight, etc. If the potato salad has been sitting at the right temperature to incubate pathogens for several hours and it had pathogens in it, even very few, trouble will ensue. Hence the classical church picnic scenario.
Two questions: why doesn’t the mayo kill the staph? And how do the pathogens get in the potato salad to begin with? The answer to the first question is that the potatoes (or chicken or pasta) tend to neutralize the low pH and raise it to the level where pathogens can live. And how do the pathogens get in there? Potato and chicken salad often involve hand preparation and one of the places that staph hangs out is on our skin and nose/facial area. There can also be cross contamination with uncooked meat or sneezing or coughing on the food. Once they get in there, they are just waiting for you to put them into a virtual incubator so they can go to town and you can go to the commode.
That’s a long way of introducing this spectacular video of the Ross Sisters. They were singing and dancing siblings popular in the 1940s. Dancing, though, doesn’t exactly describe it, although acrobatics and contortionism comes closer. Especially contortionism. This clip, from 1944, has been a Youtube favorite for a while, but I’d never seen it. I showed it to Mrs. R. and her first reaction was, “Nice wax jobs.” But as she watched further her eyes widened and I expect so will yours. The muscle control and flexibility here rivals any Yoga Master I know of (of course I don’t know any Yoga Masters, but so what). The spectacular stuff doesn’t start until over one minute in and begins with some tame floor-exercise like acrobatics. But then the flexibility and muscle control stuff starts and it is really something. There are places where the juxtaposition of body parts is so bizarre and disorienting I couldn’t quite figure out what was what.
Enjoy. Lots more fun than staphylococcal food poisoning.