Friday, August 03, 2007

The Science of Cooking

In the lab, we're used to following recipes and measuring out reagents with microlitre precision. Yet these skills seem to rarely transfer well to the kitchen. This is doubly odd, considering the amount of science that can be found there. Many people probably know that baking powder is used, like yeast, as a leavening agent (baking powder is a mixture of sodium bicarbonate and an acid salt which react to create carbon dioxide when mixed with water). Fewer will be familiar with the Maillard reaction, the chemical process by which many foods brown when cooking.

Recently, some scientists (and chefs) have been making a push to bring more science into the kitchen, and the result is "molecular gastronomy". Chemist Hervé This (pictured) and physicist Nicholas Kurti coined the term in the late 80s/early 90s, and This is the first (and only) person to hold a Ph.D. in that discipline. His ongoing education is spent collecting, testing and explaining what he dubs 'cooking precisions', various "rules" of the kitchen ranging from recipe instructions (eg. when making a souffle, add the eggs 2 at a time), to anectodal methodology (eg. cut the head off a roast pig immediately when removed from the oven to ensure a more crispy skin), to the absurd (eg. women having their period cannot successfully make mayonnaise). An essay by This on the history and nature of molecular gastronomy can be read here [pdf]. (For the record, the first 2 'precisions' above hold true, but the third is false). Hervé This has also done extensive work with emulsions and foams, developing a system of equations for making them by reducing them to their basic components. It's in this way that he was able to make 24 litres of mayonnaise from a single egg yolk. His equations for foams have paved the way for innumerable inventive sauces and mousses including, but not limited to his famous chocolate chantilly.

A more ovbious example of his scientific leanings is his discovery of the perfect way to cook an egg. The traditional 10-minute boil for a hard-boiled egg, leaves the egg tough and rubbery. By considering the varying temperatures at which specific egg proteins denature and coagulate, This determined that 65 degrees Celsius produces an egg with a custardy white and a soft orange yolk. Just 2 degrees higher and the yolk begins to set, becoming malleable in the hand but still not the grainy-textured yolk of a 10-minute egg. And it's not the time of cooking that matters, it's the temperature. These eggs can be cooked at 65 degrees overnight with the same result. (For those worried about salmonella, it can't survive for more than a few minutes at 60 degrees) Ovalbumin, the most abundant egg white protein, coagulates at around 84oC which is why a boiled egg becomes rubbery. While his work of this nature isn't found in your traditional scientific journal, he does maintain a lab and some of his work can be found on Pubmed (I recommend the Nature Materials commentary if you have access for a good overview of This' work).

Molecular gastronomy is taking the world by storm, combining the study of food and cooking that Hervé This pioneered with the use of advanced technologies. Some of the top restaurants in the world specialize in this style, inventing new flavour combinations (white chocolate and caviar?) and methods of preparation. Chefs of this nature don't shy away from using chemical ingredients you would only find on a candy-bar wrapper, like polysorbate-60 as an emulsifier or chemical thickeners. This allows them to create interesting new textures without compromising the taste of the food, like creating a parsley sauce by thickening parsely juice rather than mixing chopped parsley with oil. Their method, they would argue, delivers a purer dish. Chemical ingredients aren't the only innovation. Dessicators and vaccuum sealers are the norm in these types of restaurants, with the anti-griddle being one particularly cool tool (pun intended) in use. This piece of gadgetry maintains a surface temperature of -34oC, instantly freezing most foods. Why serve something on an olive oil flavoured cracker, when you can serve it on a frozen disk of pure olive oil itself? And with these innovations, the line between kitchen and laboratory becomes more obscured.