By Monica Mugnier
I am spoiled when it comes to pork chops. My dad is a great cook, and he used to make pork chops for dinner a lot. When I was twelve or thirteen, my best friend, Melissa, came over for a pork chop dinner. While she loved to hear Peter Brady talk about them, pork chops were her least favorite meal. But she was polite, so she tried it. She was shocked by my dad’s dinner: “Wait, they aren’t always dry?”
So I was excited last weekend when my boyfriend and I decided to try a recipe for Pork Chops with Cider, Horseradish, and Dill from The Smitten Kitchen Cookbook, by Deb Perelman. I am a huge fan of Smitten Kitchen, pork chops, cider, and horseradish (not so much dill, but oh well), so this sounded good. I was hoping for some juicy pork chops like my dad used to make.
Our attempt at making dinner had mixed results. On the injury front, I did burn my fingers moving a hot roasting pan in the sink but (for once) didn’t end up with any blisters. While I was moderately successful in not getting injured, I was much less successful in not ruining dinner. I don’t know if it was the recipe or our technique, but the chops were chewy and dry.
But, hey, dry pork chops are almost the rule, right? Melissa is evidence that some people don’t even know they can be tender and moist, and maybe you’ve heard that pork needs to be cooked well done. This belief is based on some fun science that is especially dear to my parasitologist heart (in the lab, I study these guys).
People worry about undercooked pork because of a parasitic worm called Trichinella spiralis. T. spiralis infects most meat-eating animals, including us humans; it just happens to be more common in pigs because of the way domestic pigs are fed (you can feed them anything, including garbage). Cooking kills these worms, though, so if there’s a chance your pork is infected with T. spiralis, it makes sense to cook that pork until it’s well done.
T. spiralis infection, also called trichinosis or trichinellosis, is not very common anymore, but it can make you sick, with a range of symptoms from stomach pain to problems with coordination or breathing.
Of the infections that do occur only about 5% are fatal, and many cause no symptoms at all. This is one of those cool things about infectious diseases: pathogens have evolved to survive, and they aren’t going to survive too long if their host is dead. There’s a delicate balance between using host resources and keeping the host alive.
Whether their infection is deadly or has no symptoms, these worms do some incredible things once you’ve eaten them. When a human eats undercooked meat infected with T. spiralis, digestive enzymes in the stomach and small intestine free the worms from the cysts in which they live. These cysts are actually repurposed muscle cells that scientists call “nurse cells.” Once the worms have broken out of their nurse cells, they mature and then mate in the small intestine, producing larvae who dig their way out of the intestine and into the blood or lymphatic system. Once in the blood or lymph, they can travel around the entire body, entering cells. Invaded cells usually die, except for skeletal muscle cells, where these little guys like to settle down.
By the way, when I say T. spiralis is “little,” I mean that its larvae can fit inside cells. Relative to those cells, though, they’re pretty big. It’s no surprise they kill off most of the cells they invade. Skeletal muscle cells are some of the biggest cells in your body, but T. spiralis has to perform some major contortions (spiralis, get it?) to fit inside.
I love the sinister way they describe T. spiralis and the nurse cell on Wikipedia: “This nematode is a multi-cellular parasite that lives within a single muscle cell, which it modifies according to its own requirements.”
Turns out, they are pretty sinister. One of the ways a worm modifies a muscle cell “according to its own requirements” is by stimulating the growth of blood vessels around the cell. Not only can the worm hide out from the immune system by hanging out in your cells, but it can also
steal route a steady supply of nutrients to itself. On top of this, the larvae don’t like oxygen, so they change the metabolism of the muscle cell. A cell that was once aerobic, using mitochondria to produce energy from oxygen, turns anaerobic: the worm shuts down all the mitochondria. He curls up and gets cozy in his new home, waiting for the muscle he’s living in to be eaten by a predator or scavenger, starting the whole cycle over. It’s still a mystery to scientists how T. spiralis manages this major muscle cell renovation.
Lucky for those of us in the United States, the odds that you’re going to find any worms in your pork chop if you buy it at a supermarket in the US are extremely low. The US outlawed the feeding of uncooked garbage to pigs in 1954 (yes, really, that’s a law), and the rates of trichinosis dropped precipitously. Most pork is also frozen before it is sold, so even if a pig picks up T. spiralis while munching on some roasted garbage, freezing his meat will kill any larvae.
So the next time you cook some pork, remember that it doesn’t need to be well done; the USDA recommends cooking pork to 145F, and then letting it rest for 3 minutes. Hopefully it will turn out better than ours did, and no creepy little worms will be taking over your muscles…
Read about Monica’s series, Kitchen Science, here.
- Pork chops and applesauce, Deb Perelman, The Smitten Kitchen Cookbook
- Trichinella spiralis, http://www.medicine.mcgill.ca/tropmed/txt/
- Nurse Cell, Dr. Dickson Despommier, trichinella.org
- Pig Farm, http://ebeyfarm.blogspot.com/2010/09/pigs-eating-produce.html
About the Author
Monica Mugnier is a graduate student at Rockefeller who really likes parasites and pastries. She comes from a family of fantastic cooks and is trying to catch up. She’ll be documenting her attempts at cooking, and the science behind the recipes she tries, in Kitchen Science.