There are 3 schools of thought when it comes to food safety:
The good doobie philosophy -- cook everything according to FDA recommendations. Why take any risks when it comes to food?
The chef and foodie philosophy -- I am willing to eat anything raw: eggs, fish, beef -- bring it on!
The stats philosophy -- I realize that there is a small risk associated with eating certain dishes. I want to know what it is so that I can make a decision.
Until 4 years ago, I was in the chef and foodie camp, but then we decided to have kids. As you can imagine, not even pregnancy could turn me into a good doobie. But it sent me on a wild goose chase to learn about the risk of food-borne illness from various foods. In other words, I joined the stats camp. My rule of thumb was this: if the risk is significantly lower than the risk I take when driving, I can eat it. Turns out that driving is a lot more dangerous that mercury in fish, raw eggs, unpasteurized cheese, and raw fish combined. Each one of these things is a story on its own. The fish related topics I have covered in depth on my blog. But today I'd like to concentrate on beef, since it's burgers we are talking about.
How is a medium-rare steak different from a medium-rare burger in terms of safety? Whatever bacteria might make you sick is found on the outside of the meat muscle (assuming the meat is not completely spoiled and decomposed fairly deeply, but that would be easy to smell). When you are eating a medium-rare steak, its outside gets to very high temperature very quickly (most skillets and grills are at about 500F, and bacteria die at 160F almost instantly). So even if the inside is raw, the bacteria is dead and you can happily dig into that mooing steak without any worry. When the meat is ground, some of the outside that might be contaminated with bacteria could end up inside and won't hit the temperature high enough to kill bacteria unless you cook your burgers to the scary internal temperature of 160F. That's what FDA recommends you do. But eating a well-done burger is a worse punishment to me than not eating a burger at all.
Another little problem with beef is that it can have a very unpleasant little bacteria, known as E. Coli. That can make you way more sick than the bacteria responsible for just decomposing the dead animal. For little children and fetuses it can even be fatal. Driving can be fatal too, but I know what that risk is, and besides, it's unavoidable. What is the risk of E. Coli from eating undercooked ground beef is very hard to tell. Unlike car accident statistics, many cases go unreported, but USDA estimates around 58,784 food-borne illness cases from E. Coli 0157 per year resulting in 61 deaths. Compare that to 40,000 people killed in car accidents per year. My guess is that you are more likely to be severely injured or killed driving to the store to pick up the meat, than by eating a medium-rare burger, but that's just a guess. There are lots of unknowns here. Surely, we drive much more often than we eat burgers, and most burgers are sadly, but safely well-done. So how dangerous is it to eat a medium-rare burger? I still don't know.
But what about organic and local cows? If you know where your food comes from, isn't it safe? I wish I could tell E. Coli to only breed in intestines of factory farmed animals, but it won't listen. It can be found in any cow's intestines. The real question is how carefully was the cow butchered to make sure none of digestive tract comes in contact with its meat. Even when you go to the most upscale butcher, it's hard to tell where their meat has been. No butchers that I know of in Boston ever butcher a whole cow. They get their meat in primal cuts. There is this idea that if you grind the meat yourself, you don't have to worry. That's not completely true. If you blanch it in boiling water for 30 seconds to kill all outside bacteria and then grind it, you really don't have to worry, but if you are grinding it as is, who knows what's on its outside.
Yet, all the nice restaurants these days offer medium-rare burgers, and if many customers got bloody diarrhea from them, it wouldn't be the best form of advertisement. So I posed this question to Kenji Alt, the food writer and food science geek. How do chefs decide what they can and can't serve raw? He told me that chefs just don't worry about it. If you work with the best ingredients you can find, and avoid cross-contamination (the number one source of food-borne illness), the odds of making someone sick are very small. But then he found out that I was pregnant, and said that being pregnant changes everything -- for 9 months you can live without almost any food. That's true, but what do you do when your 3 year old wants a bite of your burger? How long should I be subjecting my children to well-done burgers? Until they are in elementary school or until they are old enough to drive?
That's when a little trick occurred to me, known as sous-vide. To understand how sous-vide makes a medium-rare burger safe, you need to know something FDA doesn't tell you about the "safe" temperature. They assume you have attention span of a 2 year old and care about food as much as I care about sports -- basically not much. The danger zone where bacteria grow and prosper is not 40 to 140, but 40 to 130. It doesn't rhyme, but not everything in nature does. Starting at 131, bacteria can be killed. The question is how long does it take? At 160F they are killed instantly. That's why FDA tells you to cook your ground beef to 160F. But bacteria will be killed just as successfully if held at 150F for 10 minutes, 140F for 30 minutes, or 131F for 1 hour. The problem is most conventional cooking methods don't let you keep food at a precise low temperature like that. But sous-vide does.
Isn't sous-vide that complicated method that fancy restaurants use? Yes, but it's not very complicated. Here is my post on how it works. Don't you need a $500 immersion circulator and a $100 vacuum sealing machine? If you are planning to cook short-ribs that take 3 days, yes, you need all that equipment. If you are going to cook something that takes 2 hours or less (fish fillets, chicken breasts, steak, burgers, eggs), all you need is a huge beer cooler, a thermometer, some zip lock bags, and ability to pay attention. I found that zip lock bags actually work better on burgers than a vacuum sealer because vacuum sealer tends to give them a funny squashed shape.
For my first experiment, I thought I'll cook them to 140F. Kenji's beer cooler trick worked like a charm. I found that most of the heat was coming out of the top of my cooler (it's the only poorly insulated side), so I put a folded bath towel on it. In 90 minutes, I only lost 3 degrees, but that was easily remedied with the addition of a little boiling water. In 2 hours, I proclaimed my burgers done and completely safe. I figured it would take them at most 1 hour to get to 140F and another 30 minutes for all bacteria to die. I added an extra 30 minutes to account for a slight drop in temperature, potential inaccuracy of my thermometer, and general guilty conscience of a pregnant woman who is about to eat a medium-rare burger and serve it to her 3 year old. 2 hours after the burgers went into my hot cooler, I removed them from the zip lock, dried off on paper towels, seasoned with salt and pepper, and seared in an extremely hot cast iron skillet with a couple teaspoons of canola oil. The result? Yum -- extremely tender and juicy. On the scale of 1 to 10, I'd give these burgers a 9.
Here are a couple of things that I'd like to improve next time.
- I know this sounds weird, but they were a bit too soft and tender. I hear that mixing salt into the ground beef and letting it sit for about an hour can make burgers tougher, so some people swear by seasoning only the outside. I seasoned only the outside and only after the burgers came out of the water bath and got dried off, but I wonder if for sous-vide burgers mixing the salt into the meat before shaping is just the thing.
- 140F was good, but I bet 135F would be even better. Next time I'll try that.
- I was worried about overcooking the burgers by popping them under the broiler to melt the cheese, so I ended up putting the cheese on the buns to melt it. I thought it would be the same thing, but it wasn't. There is some magic to the cheese dripping down the patty. I think I'll risk it next time. If I put the cheese on the patties as soon as I flip them, just 30 seconds under the broiler should do the trick. I should probably get them out of cast iron pan for the broiling part to avoid continuing to cook them from the bottom.
- I turned the toppings into bottomings for convenience sake. In other words, I prepped the bottoms of the buns with lettuce, red onions, tomatoes, and avocado and the tops of the buns with melted cheese. This way I had all the buns ready when the burgers were done. But this resulted in some lost juices. The burger juices dripped off the lettuce leaves and onto our plates, instead of being soaked up by the bottom bun. That's just not right. Part of what makes a burger a burger is that the bread gets up close and personal with the meat.
- I used 85% lean beef from John Dewar's. I am not even sure if it was 85% based on how it looked. To my surprise even this upscale butcher couldn't grind me the cuts of my choice to make it fattier? They claimed that they can only grind chuck because they don't want to contaminate their grinder. Apparently their chuck is washed with a "citrus solution" to kill E. Coli since it's intended for grinding, but other cuts aren't washed. I tried to get more info about this "citrus solution," but couldn't get anything out of them. I got their ground chuck anyway thinking that sous-vide would keep a lot more juices than a regular cooking method. That turned out not to be true (at least at 140F). A lot of juice and fat leaked out of the burgers during the water bath time. So next time, I am going to Roche Brothers and getting myself 80% ground beef. It will have a bright red sticker that will say "Cook to 160F." But now that I have my beer cooler, E. Coli can't scare me.