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.