Creating a stir through kitchen chemistry

Over the past two centuries science has progressed by leaps and bounds. Yet, with all this expertise at our disposal, there has been little probing of the scientific basis of cooking. Fortunately, this oversight came to the attention of a French physical chemist 20 years ago. Hervé This and his colleagues created a new discipline called ‘Molecular Gastronomy’ and set out to find answers to the many questions we have long ignored.

Even today, cookery books include references to old wives tales that have since been explained by molecular gastronomy. A common example is the claim that raspberries should not be a put in copper or tin coated vessels – yet if you add metallic tin or copper to raspberries nothing happens. It is known from chemistry textbooks that anthocyanidins (pigments in many red, blue or purple fruits) can bind to metal ions. If a small amount of the ionic form of tin is added to raspberries rather than the metallic form, it causes them to turn dark purple and so look spoiled or toxic. Therefore it’s not the copper vessel itself, but the residual metallic ions in a dirty container that cause the colour change.

Through the use of molecular gastronomy, we have also learnt how to make a perfectly soft boiled egg – heat it at 65oC for an hour. Why is that? Egg is mostly protein, but it turns out none of the yolk proteins are denatured – destroyed by heating – below 70 oC and thus the yolk does not solidify even with prolonged cooking. The egg white, on the other hand, is made up of proteins that denature at a lower temperature, and so it does solidify.

The discipline also strives to understand culinary processes and recipes, especially ‘culinary precisions’. These are pieces of technical information added to recipes which are not absolutely necessary to make the dish successfully. For example, in making cheese soufflés, it is often advised that the egg white must be whisked thoroughly with the cheese in order to introduce as much as air as possible to the mixture. It is said that this air is subsequently released on heating, causing the soufflé to rise. But according to ideal gas law calculations this trapped air should only cause the soufflé to rise by 20% and yet, it is observed that it swells to almost double its size. The main rising effect in fact comes not from trapped air but from the vaporisation of the water contained in milk.

Molecular gastronomy creates new products, new tools and new methods for use in a kitchen. Cooks are taught how to skilfully use herbs and spices to create the right taste and smell. But what if we know what chemical or combination of chemicals produce a certain taste or smell? If you can’t afford a very good whisky, try adding some drops of vanillin solution to make it ‘round’. This can be used as a substitute for the years that it takes for ethanol to react with lignin extracts from wooden vats to produce various aldehydes that give it the ‘roundedness’.

It’s not just chemicals but also well-designed laboratory hardware than can be put to effective use in cooking. For example, a Büchner funnel (a cylinder with a perforated plate which can be connected to a vacuum pump for efficient filtration) will give a clearer stock than a culinary sieve and ultrasound (high frequency) boxes can be used to make an emulsion in seconds which could traditionally take many minutes of vigorous mixing by hand. Furthermore, to retain flavours, a reflux condenser can be used instead of the traditional lids over a pan.

With a looming food crisis, food of the future is often portrayed as being heavily dependent on pills and protein shakes, akin to the porridge–like gruel Keanu Reaves eats in The Matrix. But actually, with every passing day chemists are understanding more and more about the taste-giving and smell-producing properties of compounds. Why then should we think that the future of food will be bland rather than delectable? At TEDx Warwick, an independently organised TED conference, Hervé This has already exhibited a prototype for a machine that synthesises tasty food. May be the fantasy of having a food machine, like in the Jetsons, that makes fresh Irish stew on the press of a button is not too far.

This, H. (2009). Molecular Gastronomy, a Scientific Look at Cooking Accounts of Chemical Research, 42 (5), 575-583 DOI: 10.1021/ar8002078

Barham, P., Skibsted, L., Bredie, W., Bom Frøst, M., Møller, P., Risbo, J., Snitkjær, P., & Mortensen, L. (2010). Molecular Gastronomy: A New Emerging Scientific Discipline Chemical Reviews, 110 (4), 2313-2365 DOI: 10.1021/cr900105w

As published in the Oxford University’s graphically enhanced Bang! Science Magazine Trinity 2010 Issue.

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