As I warned, thought this isn't a food blog per se, I do enjoy cooking and will occasionally post about it. Some friends of mine are getting into sous vide (French for "under a vacuum", and pronounced sue VEED) and asked for some tips, so I thought I'd generalize it. You can find many more exhaustive, scientific discussions elsewhere via a web search. These are just some handy things I've learned.
The first sous vide cooking was done with a piece of lab equipment called a Thermal Immersion Circulator. They were crazy expensive devices that could maintain the water temperature to within tenths of a degree. Cooking doesn't need that kind of precision, and now equipment is getting downright affordable, opening up what used to be a secret weapon in gourmet restaurants to the home chef.
How it works
Food is sealed in a plastic bag and held in a water bath at a very precise and consistent temperature. This has three major ramifications. The first is that this is what's known in the food science business as ROP, or Reduced Oxygen Packaging. The rules of pasteurization change in the absence of plentiful oxygen, and it happens on a curve. Beef, for example, can be pasteurized at only 125º F in ROP, but it takes 4-5 hours. That's why it's safe to cook it to a perfect medium rare (132º F) sous vide in spite of what you've always been told about the "danger zone" below 140º F. The second big deal is that many proteins respond to specific temperatures in very specific ways. In short: magic happens. The third is that recipe timing becomes much more flexible. When you cook a steak on a stovetop the difference between perfect and ruined can be measured in seconds. Sous vide, your window of perfection is at least hours and often days.
First thing to try
Fire up your water bath to 147º F. Gently place some eggs in it and set a timer for 1 hour. Then enjoy the most amazing soft-cooked eggs of your life. The whites will be perfect, and the yolk turns into what I call yolk pudding. Later you can try hard-cooking eggs using the same technique, but at 170 (some like 160 – experiment!). Just do it.
Bag it
New sous vide cooks, who can't afford a vacuum chamber sealer, eventually become frustrated with both the price of the fancy, food-safe bags and the inability to include liquid in the bag with the food. You can try the trick of freezing the liquids in an ice cube tray and dumping those in before hitting the vacuum button, but that can add a lot of hassle.
One of the best tips I ever got was to stop using the vacuum sealer. If you aren't working from a Thomas Keller cookbook you probably aren't making dishes that benefit from the hard vacuum anyway. Get yourself some 1 quart and 1 gallon ZipLoc freezer bags. I'm being brand-specific here because the manufacturer has stated that the plastic they use is food safe up to around 170º F, well above where you'll normally be.
So how do you seal them? The Archimedes Method involves simply dunking the filled bag under some water (which, of course, you'll have a big pot of anyway) until just the top of the bag is above the surface. Seal, remove from the water, and you're good to go. I do this pretty much all the time now and only bust out the vacuum sealer when I know I'm going to...
Freeze it
Here's another awesome side-effect of cooking in ROP: Say you've prepared four steaks and then two of your guests cancel. No problem! Prepare a large bowl of ice water. Chill the cooked steaks in it (in the fridge) for an hour or two, then toss them in the freezer. Later, when you want to enjoy them, just thaw them in a 132 ºF bath for about half an hour. They will be every bit as perfect as the ones you had tonight.
Fish
You'll find that fish is just magic prepared sous vide. While it's impossible to overcook anything sous vide, eventually delicate things like fish will turn mushy. But that takes hours. If you get the cooking time "pretty close" you're golden.
Here's my "lazy man" weeknight salmon recipe: Un-bag some frozen Costco salmon filets and drop them in some 1-qt ZipLocs with a couple of tablespoons of soy sauce. Seal them Archimedes style. When your water is up to 140º F, cook them for 30 minutes. They will thaw and cook to perfection. Dump contents of bags onto plate. Done.
Buy cheap beef
Know why you pay such a premium for cuts like Filet Mignon and Porterhouse? It's not for the flavor. It's because it's tender. Tougher cuts actually have more flavor, they just need to be cooked "low and slow". A note about doneness: It is entirely a function of temperature. When beef hits medium, or 140º F, it's as cooked as it's ever going to get. All that happens between there and well-done (170º) is that the proteins contract and squeeze out the juices. Maybe you order medium just to be on the "safe side". Well, forget that. Medium rare is where it tastes best, and now you know that it'll be medium rare all the way through.
My favorite steak is now 2-day Chuck. Sometimes I buy it as a chuck roast and cut it into two 1 1/4-ish pound pieces to cook. One gets the freezer treatment, the other gets cut into two steaks before browning. (More on that later.) At 132º the proteins never contract, but the collagens do melt. So during those 48 hours in the bath the steak gets more and more tender, more and more flavorful. Try 3-day beef ribs some time, just be sure to truss them with string first because the meat will be falling off the bone.
3-day Beef Rib
Since beef has such an incredibly wide window of perfection you can see why restaurants love this method. Say it's the weekend and you know you want steaks for dinner, but you don't know what time. Now you don't care what time. Bag 'em up and start them cooking some time in the morning. Whenever you feel like dinner they're ready.
Brown it
A critical thing sous vide doesn't do is trigger the Maillard Reaction. That's what's going on when you brown food. Literally hundreds of flavor compounds are produced, which is why toast is so much more flavorful than plain bread. You can brown things like steaks either on a grill (I have a gas one that makes this easy) or in a very hot skillet. (Use a heavy one, like cast iron or stainless steel.) Before you do either, make sure the food is dry. I just use a kitchen side towel, wrapping it around the steaks and patting them dry. If you don't, you'll get steaming instead of browning. It only takes about a minute per side.
Enjoy
Soon after you impress yourself you'll be impressing your friends. Do read the safety instructions that came with your sous vide equipment. But it's actually quite easy. Beef, poultry, fish, and eggs benefit greatly from sous vide. (Just don't push fish more than half an hour extra, or poultry beyond a few hours, or texture suffers.) There are also vegetable and dessert recipes out there. I hope these quick tips make your food-in-a-bag cooking easier and more enjoyable.