From the enticing aroma of the turkey in the oven to the “whoosh’” of the flames as the brandy-soaked pudding comes alight, Christmas is a wonderful time for the senses. But have you ever considered the science behind our best-loved festive traditions? Here is one of my seven food and flammable favourites: The others can be found on this website.
Most people know that cooking involves chemistry, and where better to start than the Christmas Day turkey? The turkey meat you cook is muscle tissue, about 20% of which is protein (nearly all the rest is water), with a small but important amount of carbohydrate. If you “hang” the meat and allow it to age, enzyme catalysts naturally present in the muscle start to break down the proteins so that they lose their naturally rigid structure and the meat becomes more tender.
You can speed up the tenderising process by heating the meat, but above a certain temperature the enzymes stop working. This is why many chefs cook the turkey for a long time at a low temperature – if they just stuck it in a hot oven, the protein chains would tend to bunch together, which, coupled with the loss of water, results in tough and dry meat.
Simply cooking the meat at low temperatures wouldn’t give the meat its brown colour and the wonderful smell and taste that go with roast turkey. This is down to a chemical reaction known as the Maillard reaction, which kicks in above 140°C. It’s named after the discoverer, Louis Camille Maillard (that’s Maillard, not mallard, which would be a duck, not a turkey).
Roast potatoes are cooked at a higher temperature than boiled potatoes – and traditionally in animal fat too – which allows Maillard reactions to occur, generating the smell and also the browning.