When Lutz Tietze hung up his lab coat, his students presented him with a collection of recipes from the world's top organic chemists. Karen Gold found the work far from formulaic.
A Buchner funnel, laboratory chemists will tell you, filters a much clearer meat stock than a kitchen sieve. Peeled potatoes oxidise unless kept covered in cold water. Souffles heated from beneath will rise higher than those in circulatory ovens, because evaporation at the base forces the mixture upwards.
And if all this sounds more like chemistry than cooking, that is because it is. For it draws on the collective wisdom of the world's leading organic research chemists, who have combined to produce not a new formula, nor a rare molecular reaction, but a recipe book.
What's Cooking in Chemistry? How Leading Scientists Succeed in the Kitchen was the idea of a group of postgraduates working for Lutz Tietze, a respected professor at the University of Gottingen in Germany who perfected molecular reactions that knock each other onwards like dominoes. For his retirement last year, his students could have organised the usual Festschrift of academic papers. Instead, building on their hunch that inside almost every chemist is a chef waiting to get out, they wrote to 100 of the world's leading organic chemists and asked them to contribute to a cookbook in Tietze's honour.
Sixty recipes arrived on their desks: everything from Green Eel a la Marie to Lemon Kiwi Pie. The quantity and quality should not have surprised them, says Steven Ley, professor of organic chemistry at Cambridge University.
"There's a high correlation between good chemistry and good cooking. A lot of chemists are particularly good cooks," he says.
What is it that gives chemists their culinary flair? Partly, says Kyriacos Nicolaou, molecular architect, professor of organic chemistry at San Diego State University and one-time part-owner of a fish-and-chip shop in London, it is an understanding of how things work, of how ingredients make a whole.
"I can go to a restaurant, have a meal and then I can reproduce the recipe," he explains. "I don't have to ask how it was done: I can make good guesses. Synthetic chemistry is the art of constructing from ingredients, and so is cooking. Chemists have a feel for what's in things."
The instinctive, freewheeling style that many organic chemists demonstrate in the lab is similar to the éclat that Jamie Oliver flourishes in the kitchen, according to Peter Vollhardt, dean of chemistry at the University of California, Berkeley. He cooks the family meal every day for himself, his wife and two children, and his favourite activity is to make a fondue with 20 different sauces.
"Cooking is like a prep in the lab," Vollhardt says. "Once you have started, you don't think in terms of theory that much. You have the ingredients, you get the set-up right, you see if the colour changes are right. You have to observe what the stuff does as you add things to it. If you are familiar with the principles then you know: oops, this is going the wrong way, this is going too fast or too slow."
He notes that graduate students who are particularly good in the lab - "you might call it manual skills but really it's intuition" - are much sought after by chemists even if their academic grades are poor.
Cooking and chemistry have an appeal that is fundamentally about patterns and symmetry, Vollhardt argues. That is why so many chemists are also Escher fans: "There is a whole branch of chemistry dedicated to making beautiful structures. We like harmony of colour, shape and taste."
In fact, professional cuisine is starting to be influenced by chemistry and vice versa, he says. In France, in particular, it is not unheard of for PhDs to be written on the chemistry of particular dishes. Cookbooks are being published based on scientific principles. Chefs collaborate with scientists on creating new flavours and textures.
The journal Angewandte Chemie recently solicited an article by Hervé This, the French molecular gastronomist. It looked at how an understanding of chemistry sheds light on cooking traditions, for example the way Escoffier insisted that putting raspberries in a metal pan would spoil the fruit.
(This concluded that dirt in 19th-century pans, in the form of anthocyanidins, used to bind itself to the metal ions and therefore blackened the berries. In today's kitchens, the fruit would be unharmed.) Good cooks and good chemists share some common attributes. One is patience.
It is no use knowing the laws of thermodynamics if you cannot restrain yourself from opening the oven door before the souffle is fully risen.
Another is dexterity: "Chemists like doing things with their hands," says Ley, whose home boasts a state-of-the-art kitchen profiled in glossy magazines for its double-size range and two preparation areas where he and his wife Rosemary (also a chemist) can cook simultaneously.
Ley enjoys making Thai and Moroccan dishes, with plenty of herbs and spices but built spontaneously on available produce: "Chemists don't like just to follow a recipe. They like to make something, to be inventive. They like a bit of freedom and flexibility in what they produce."
So what kind of recipes do Tietze's donors have to offer? Perhaps because of the book's international background - with recipes from colleagues, former students and rivals of Tietze across Europe, Asia and America - many dishes are national and/or traditional. There is barbecued kangaroo from Martin Banwell, chemistry professor at Canberra University; goma-yogoshi (cooked vegetables) with black sesame, from the Japanese chemist Ei-ichi Negishi; macaroni with hare sauce, recalled from a rural Mantua childhood by Alessandro Dondoni, gold medallist of the Italian Chemical Society; Carolina Dirt Cake from Marye Anne Fox, chancellor of North Carolina State University.
A few recipes are for industrial quantities of chilli or lasagne to feed students; there is an occasional admission that a recipe originates from a restaurant or a wife. A handful are set out with method and materials as if, rather leadenly, for experimental purposes.
But, overall, there is an overwhelming flavour of people who cook often, with ambition and for pleasure. And that is precisely because the contributors are chemists, Ley says. Ask a group of physicists and you would have quite a different book: "Physicists would have theory recipes or in silico recipes rather than dirty their hands in making something. Or they would get a chemist to make it for them."
Ley imagines physicists weighing each ingredient to the nanogram and following each instruction to the letter. But with chemists, it's "a dash of this and a shake of that".
"What we do is new, it's never been done before on the planet," Ley says.
"So it is like inventing Yorkshire pudding and working out the ingredients and defining the product you are going to make. Except it's more than that, because one day this Yorkshire pudding is going to cure cancer."
What's Cooking in Chemistry?, by Hubertus Bell, Tim Feuerstein, Carlos Güntner, Sören Hölsken and Jan Klaas Lohmann, is published by Wiley-VCH (£19.99).
KITCHEN ALCHEMY: WITHIN EVERY CHEMIST LURKS A COOK
Cinghiale in dolce e forte
This is a favourite recipe of Herbert Waldmann, professor of chemistry at Dortmund University and director of the Max Planck Institute - although it is not his invention.
1kg wild boar haunch (without bones)
1 clove of garlic
2 stalks of celery
1 bunch of flat-leaved parsley
a small sprig of rosemary
3 tbsp oil
1 tbsp flour
salt, pepper (freshly ground)
2 bay leaves
nutmeg (freshly rubbed)
100ml red wine
1 tsp cocoa powder
1 tsp sugar
1 tbsp candied lemon peel
1 tbsp raisins (soaked in 10ml grappa)
2 tbsp pine kernels
3 tbsp balsamic vinegar
Cut the meat into not-too-small cubes.
Peel the onion and garlic and cut them into cubes.
Clean the carrot and celery and cut them into cubes.
Chop the parsley and rosemary.
Heat the oil in a roasting pan. Dust the meat with the flour, then place in the pan and roast at a high temperature. Add the vegetables and herbs and steam briefly.
Season with salt and pepper, add bay leaves, a pinch of nutmeg and the red wine.
Cover and braise for 30 minutes at a low temperature.
Add the hot consomme and braise for another 30 minutes.
Remove the meat and keep it warm. Mash the roasting juice/vegetable mix before adding the meat again.
Roast the cocoa, sugar, candied lemon peel, raisins and pine kernels in a small saucepan, quench with the vinegar, and stir into the meat.
Heat gently before serving.
Dulce de leche
Peter Vollhardt, dean of chemistry at University of California, Berkeley, devised this risky-sounding dish as a postdoc because he missed the real thing.
1 can sweetened condensed milk
Remove the label from the can of condensed milk. Do not under any circumstances open the can yet.
Place the can in a pot and cover it with water. Put the pot on a stove and turn up the heat. Let the pot and can simmer gently for about two hours for runny dulce de leche, or about four hours for solid dulce de leche.
When it's done, open the can and eat directly (for the solid variety) or use as a dessert spread (for the liquid variety).
You need to keep a close eye on the can. If it shows any signs of expansion, immediately remove it from the heat and let it cool.
If you are concerned at all about the high-pressure nature of the recipe, you may poke a small hole in the top of the can and lower the water level so that the can is not completely covered. This will allow the internal pressure of the can to be released.
Fish souffle Clausius-Clapeyron
Martin Suhm is a professor of chemistry at the University of Gottingen who specialises in molecular interactions.
1 small onion
250g fish fillets (cod or angler fish, for example)
100ml white wine
1 bunch of dill
grated lemon peel
4 egg yolks
5 egg whites
Heat the chopped onion in a pan with half of the butter.
Add the white wine and the fish fillets. Braise with the lid on the pan for ten minutes.
Take out the fillets, chop them and season with salt, pepper and plenty of dill. Concentrate the liquid (preferably in a rotary evaporator) to one-tenth of its original volume.
In another pan, melt the rest of the butter, add the flour and stir for a short while.
Add the milk and concentrated fish brew and heat to boiling point while stirring constantly.
Season with salt and pepper and some grated lemon peel and keep simmering until a thick protein-glycolipid mass is obtained.
After cooling down to 40C, add the egg yolks and chopped fish.
Whip the egg whites and a pinch of salt with five millimoles of air until stiff.
Carefully mix the fish-bechamel mass with the egg whites and then pour into a greased oven-proof dish whose base has been covered with a thin layer of bread crumbs.
Initiate the domino Maillard reaction at the surface by putting the dish into an oven preheated to 200C.
After five minutes, reduce the temperature to 180C for 40 minutes.
According to Gay-Lussac's law for the air and the Clausius-Clapeyron equation for the steam, the bubble size will increase and the souffle expand to double or triple its original volume. It should become more stable.
Nevertheless, the souffle should be served immediately because Gay-Lussac's law and the Clausius-Clapeyron equation are still valid during cooling.
Serve with a salad.