I know Jennifer's done a couple of posts on molecular gastronomy, the branch of culinary science wherein foam plays a large part. She's actually eaten some of this stuff (I hesitate to call it food) so she knows whereof she speaks. The closest I've come is a dessert I had in Spain (coincidentally, the home of Ferran Adria, the father of molecular gastronomy) at Barcelona's Cinq Sentits: a lemon foam that was, well, lemony and foamy, i.e., insubstantial and tasty, but kinda gimmicky and nutritionally null. Several years before, I'd had an equally toothsome dessert in New Orleans at Commander's Palace, a bread pudding souffle with whiskey sauce, that was equally insubstantial, so I wasn't that impressed by the foam thing.
I'm glad I got to try it though, since I am something of a foodie. I scored pretty respectably on the food meme that was going around for a while, I cook quite a lot myself, collect food pron, and I read a number of food blogs. Michael Ruhlman's is one of my favorites, because he's usually so level-headed about food, even while he's passionate about it. He's been discussing a new book by Harold McGee, Thomas Keller, and photographer Deborah Jones called Under Pressure, an expensive doorstop of a cookbook which is about, let me quote: "One of the most important culinary inventions of modern times. [emphasis in the original] McGee continues: What is this great advance? 'A way of heating foods precisely. At last!' Such a simple notion but an impossibility until the immersion circulator . . . arrived in the restaurant kitchen." Here I thought fire did the trick. Silly me. The beauty of sous vide cooking is that it allows seasonings to fully infuse meats and vegetables, and time enough for the long, tough protein chains that make meat tough to break down, which tenderizes the it without losing flavor. Braising also does this, but open even pots with lids lose liquid and vacuum-sealed food doesn't. So you get both tender and moist food with sous vide cooking.
Cooking is really a type of chemistry, dependent upon the reaction of molecules to the application of heat, as much as anything. Proteins, lipids, and complex carbohydrates break down and/or change their shape when they're heated. McGee, who helped write Under Pressure, is also the author of On Food and Cooking: The Science and Lore of the Kitchen, which is a history of food and cooking, a technical manual, and a chemistry text that explains what happens to various foods when you cook them using different methods and temperatures. Many foods, McGee explains, lose flavor, color, nutritional value, and texture when you cook them at high heat. This is because heat increases the action of enzymes before it stops them. Enzymes are another type of protein that increases the rate of chemical reactions, like breaking complex, long-chain proteins into digestible bits in your stomach. This is what happens in cooking, too, to a lesser extent.
The immersion circulator of sous vide cooking is this thing at the right, and has joined other expensive gadgets in the test kitchens of the world. Here's the principle of how it works and why chefs are flipping out over it. Sous vide cooking is basically slow cooking at lower than usual temperatures over an extended period of time, in a vacuum. Foods are seasoned, sealed in vacuum pouches, and slowly heated in a water bath whose temperature is well below boiling, often for around 24 hours. Sound like a recipe for botulism? I thought so too. So does the New York City Department of Health, and it initially banned sous vide cooking until there were government-approved standards for it. Even now, restaurants are likely to be shuttered for violating their "Hazard Analysis and Critical Control Point" plans. One restaurant found itself not only shuttered, but throwing away hundreds of pounds of improperly vacuum-packed raw meat.
That's because many deadly microbes love this kind of environment: warm, wet, and anaerobic. Clostridium botulinum, the bacteria that causes botulism, lives in soil and much prefers low-oxygen environments. It crops up now and then in improperly home-canned goods where the vacuum seal hasn't quite taken or the jars and food haven't been sterilized well enough. High heat destroys the bacterium, but sous vide cooking isn't warm enough to do that. So careful food handling and sterile food prep conditions become even more important in this type of cooking.
Now, I loves me some kitchen gadgets (Food processor? Check. Waring blender? Check. Kitchenaid mixer? Check. Pasta maker? Check. Juicer? Check. Slow cooker? Check. Coffeemaker? Check. You get the drift.) but this is probably one gadget I'm not going to invest in. My love of kitchen gadgets probably stems from the thing I always had for chemistry lab ware. In college, my work-study job was setting up the bio and chemistry labs and autoclaving the glassware & solutions. It was a glorified bottle washer's job, but I loved it because I got to handle beakers, Erlenmeyer flasks, titration burets and petri dishes. Hey, come on. Everybody's got a fetish.
I also was in charge of the distiller. No, not that kind of distiller, sadly. This one was strictly for water; labs go through a lot of distilled water, and it's much cheaper to make your own. (I suppose moonshiners feel the same way.) Most distillers work with heat: bring whatever's in it to a boil and let the steam condense elsewhere, leaving behind the original impurities. Or most of them, anyway. Vacuum distillers use pressure (or lack of it) do the same thing the heat does. In this case, boiling occurs when the vapor pressure of the liquid is higher than the ambient pressure in the distilling vessel. No heat involved to force evaporation.
Distilling has a long history in the kitchen, too, as anybody who's fond of beer, wine, or spirits knows. Then there's Spanish chef Joan Roca's eau de dirt. Roca is another proponent of sous vide cooking, but that's not the point here. Bear with me for a minute here: Winemakers, especially the French sort, often talk about the terroir of a particular wine, which boils down to the region the grapes are grown in, the soil, the weather and the winemaker's "style." Unless you're really a foodie or hell-bent on buying organic produce, most people don't think about how the dirt their food is grown in influences the flavor. Different soils have different mineral contents and those are absorbed by the plants growing in them. So much of our food is fertilized with commercial fertilizers that we don't notice much difference, but this is one of the things that makes San Marzano tomatoes so flavorful. They're grown in the volcanic soil of Mt. Vesuvius unlike the more familiar and common Roma plum tomatoes. Volcanic soils tend to have a high phosphate content, which plants like. The soil also seems to make San Marzanos a little sweeter than Romas and perfect for sauce.
But what if you could capture the flavor of the soil itself? This is what Roca was trying to do when he threw a shovelful of soil into a vacuum distiller and added water. Why a vacuum distiller instead of the usual kind? For one thing, it's quicker, and for another, heat distillation would have left Roca with nothing but tasteless distilled water. Vacuum distillation distills out the most volatile of the dissolved chemicals with the vapor, without changing the composition of the dissolved minerals. Not terribly sanitary, but I suppose irradiation could take care of that. I'll Let Michael Ruhlman describe Roca's experiment:
Roca presented first a video of this technique then demoed it the next day. The stylish video showed Roca trudging through the woods of his homeland with a shovel and a bucket. He dug up a few shovelfuls of dirt and returned to his kitchen. He added water to the dirt and stirred thoroughly to make a dirt batter, known here in America as mud.
He then added some of this mud to a large glass beaker, fitted the beaker into a distilling machine and turned it on. The beaker rotated and the mud heated up and gave off a vapor which went up through some glass tubes, condensed and dripped down into a smaller beaker, crystal clear liquid, a literal distillation of his terroir. And this was the technique, eau de dirt.
How did he use this dirt essence? He put a spoonful of it on an oyster as part of a small oyster dish. Surf and turf. Oyster with eau de dirt.
There are moments when I despair for the future of food the way I despair for the future of art. This was one of them. But apparently some dirt actually does taste, well, like more than dirt. Roca's Spanish dirt evidently has some more interesting minerals in it than Hyde Park, NY, dirt, where the technique was also demonstrated at the Culinary Institute of America. You can bet I'm not going to be distilling any Bronx dirt in my kitchen. Beer, maybe, but no dirt. And I'll stick to fire for the rest of the cooking, too.