FAST-FOOD, PIZZA, & BURGERS
..... Burgers, wraps, hot dogs, shawarma, pizza...all eaten in vast quantities, but how safe are they? Let's take a look at some of them and what you need to watch for...
......In general, as for street food anywhere, the safest are those cooked ONCE, cooked THOROUGHLY, and served IMMEDIATELY. Otherwise, some caution is needed.
Q: What conditions on a pizza left unrefrigerated would allow Staphylococcus to grow?
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A: Staphylococcus aureus, like most other pathogens, has certain requirements for survival and growth (and production of its enterotoxin). For example, the pH should be greater than about 4.6, and closer to 7.0 for optimal multiplication rate. This eliminates your green peppers, pineapple, tomatoes, and most tomato pastes as growth media.
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Water activity (aW) for most bacteria should be >0.95, but S. aureus can grow down to around 0.85. The post-cooking aW of a pizza will have lost much of the moisture through steam, and the remaining materials will have lower aW due to salt concentration. So we can rule out the cheese, bread base, pepperoni, ground beef, anchovies, onions.
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The only ingredient that MAY possibly allow S. aureus to grow is the ham. Even though it's salty (and contains nitrites), S. aureus can survive. HOWEVER, S. aureus bacterial cells are destroyed at 71C (160F), which is far exceeded in the pizza oven. So they are not going to be alive to start to multiply. If the ham had been retained at room (or warm) temperature for many hours or overnight BEFORE being placed on the pizza, it may already have produced its toxin, and the toxin would remain on the cooked pizza, - even after the bacterial cells were destroyed. So this becomes a question of hygiene and handling BEFORE cooking, and nothing to do with handing after cooking.
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Pizza is one of the safest foods, and is typically absent year after year in all the reports of foodborne illness investigation, despite it being one of the most popular foods, and one that is eaten by students on a regular basis without much regard for temperature-control.
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That said, of course if an open, cooled, pizza was coughed on by someone with a septic sore throat (usually Streptococcus), or handled by fecally fingers, or someone with norovirus or hepatitis A virus, it is possible that the pizza could convey these pathogens to the next person who ate a slice. We can’t rule it out, but it never forms a recurring route of infection.
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