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.
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That video is a bizarro cultural artifact that I overall felt kinda funny about.
Regarding potato salad, from what you said, I'm still not clear what makes it a unique problem. Lots of casserole/salad type foods end up at room temperature for a long time, and involve hand preparation. I'm thinking fruit salads, pasta salads, other veggie salads. Is it really the case that potato salad is a particularly common source relative to other foods - or is potato salad simply more common to start with?
JMT: Pasta salad, veggie salad are also frequently encountered, although the latter, not if you use vinaigrette (too acid). As for casseroles, they served room temp but they have been baked in the oven after hand prep so the pathogens have been killed. Fruit salads also often too acid.
I've last had the staph from takeout leftovers. Husband had it from bad whip cream, only took an hour from fine to undead. That was the night he figured out the tub was a better target than the toilet since it was harder to miss the vast size, could hang and rest his body over the edge and turn on the water when he needed it without getting up. I just had to bleach it down the next day.
The staph food poisoning is why health codes usually won't allow restaurants and caterers to donate leftovers to shelter kitchens and it must be thrown out instead but most folks screaming about food that the homeless could eat don't know that.
Makes sense! Thanks!
Are there regional differences in the likelihood of potato salad food poisoning outbreaks?
The reason I ask is that our 'family' recipe calls for dill pickles and mustard as well as mayo. Could this extra acidity help a bit? I'm not even sure this is a regional difference, but think it might be.
My mother got food poisoning when she was a teenager and was always careful about refrigeration and contamination from raw meat.
My paternal grandmother would leave food unrefrigerated all day. Lunch was the big meal of the day, and it was simply covered with a tablecloth to keep flies off and then served for supper. Nobody died... but I'm not sure why!
Keep meaning to watch that vid. Also thanks for the tip, will remember to eat potato salad very quickly after making it (om nom nom).
A few years ago there was a tiny circus that came through our tiny village. I brought my youngest son to see it because I was curious and I also felt that it was important to support such a small enterprise.
It turns out that the "Circus" was one family that did everything. One of the acts was the young mother doing a routine very similar to the one in the video. She bent and twisted and did all sorts of incredible things, and then when her routine was finshed she threw a circus looking jacket over her costume announced the intermission and while she sold popcorn with one hand she rocked her baby in the stroller with the other.
What a performance!
So glad I said "no" to the canteen potato-salad before reading this. (But I always do after what happened last time I ate it.)
Good article Revere. I would just note that making questions like "why does the mayo does not kill the staph" although interesting are slightly misleading in the context of staph food poisining because the bug it self does not cause disease as it is extremelly rare for it to survive the stomach environment and colonize the gut (which anyway environmen is not a particularly hospitable for staph and extremelly competitive as it is crowded with other flora).
When studying a staph foodpoisining what we have to keep always in mind is the toxin.
The bug is relativelly resistant to low temperatures, low aW (water availability i.e. sal, sugar and drying) but not so much to pH alterations and high temperatures. However the range of conditions in which it produces the toxin are way more restricted (temp above 10 celsius, high water availability). Once produced, the toxin is very hard to destroy. So the correct quetion perhaps should be why does the mayo not restrict the bug's ability to produce toxin. Exactly the same answer at the end of the day.
Once again, very good article. Congrats.
Lowlander: I was trying to say what you said better and you sharpened the question by focusing it further on conditions of toxin production, not just bug growth. So thanks.
Clearly, the 1940's were stranger than we give them credit for.
I've always wondered about the personal equation in food poisoning. I have a cast iron stomach -- have done a lot of rough water sailing, and major turbulence on flights including puddle jumpers has no effect. I am fortunate. I have never for a nanosecond doubted the prevalence of food poisoning, seasickness, or air sickness -- but people vary remarkably in rate. It can't all be environment.
Info on the Ross Sisters on a blog:
" . . a little research on these fembots... The Ross Sisters were a trio of female sibling dancers
consisting of Aggie Ross, Elmira Ross, and Maggie Ross whose real names were:
Vicki (Veda Victoria Ross),
Dixie (Dixie Jewel Ross), and
Betsy (Betsy Ann Ross)
They were 15,17 & 18 years old in this clip."
"Potato Salad" is the only Ross film remaining. Yes, decidedly odd. My quick search did not find any current information other than: they worked in England for a while, two sisters appear to be alive, one died at 34 years in England - had married an OBE.
As an ex-coach, I agree on their lack of muscular development -- but much of muscle bulk is due to injury, i.e. inefficient muscle. Muscle builders use specific routines/schedules to induce injury. And there is a whole lotta steroids goin' 'round now. Mark McGuire finally admitted? Anyone have any doubts? Classic blocky steroid shape.
I was under the impression that the culprit in the starch salads was the inability to cool the potatoes/macaroni/rice quickly enough to food-safe temperature before adding dressing, and the starch-thriving bacteria was allowed to grow. Please correct my misconception, but I do recall temperature during handling/storage to be an issue.
anna: Doesn't have to do with starch but with first introducing a pathogen (staph from your hand or a sneeze or cough) while the potato salad is in preparation but not hot and then letting it sit in the "danger zone" (between 45 degrees and 120 degrees F.) for more than 3 or 4 hours. If a pathogen is in their it will grow and elaborate toxin.
Perhaps it has to do with more "opportunity" for staph. Thanks for the info on mayo, she was quite a beauty in high school! I worked for a competitor to the other hamburgers joints, Wetsons for awhile after a camp full of pinkeye, a dishwasher, and recall that the fresh potatoes there at Wetsons were put into a machine hooked to a water hose and as the potatoes descended through the machine of circulating rough discs, top to bottom, most of the skins would be rubbed off and washed away before cutting and frying, which can be used in cars (see "Greasy Rider"). Wetson was the boyfriend of Margaux Hemingway and I wonder still today, where they Long Island or Idaho potatoes?
The video doesn't exist anymore, but the stuff about potato salad really helped with a project, so thanks.
From what I remember from Food Safety, high carb foods like Pasta, rice and potatoes are a perfect fuel or food environment for bacteria to grow. They need that sugar. It's like jet fuel for their production. so it's the potatoes,rice or pasta that actually facilitates their growth, not the mayo.