In the first installment of a series, Sofia Della Sala explains the science behind cooking a turkey.
Christmas: the time to gorge yourself on foods that you never eat at any other time of year, to lock chocolates away behind tiny numbered doors and wear hats made out of paper. It’s magical. Call me corny but I think the real magic is in the science.
Since at this time of year we have to feed the world and let them know it is Christmas time, we may talk about how there is a lot of science behind a perfectly cooked turkey. Let’s start with the fact that we rarely eat turkey at other points of the year and part of the reason could be due to it not being a very tasty meat (controversial but true!). As Michael McIntyre said: “There is no Kentucky Fried Turkey''. We can all agree that turkey is a bit dry but interestingly our perception of moisture in meat comes less from water itself and more from fat. Since Turkey has relatively little fat, it is intrinsically drier than other meats. Combine that with the fact that the oven sucks moisture out of anything that goes in it and we are almost at a loss. Turkeys are big birds, so they, of course, need more time in the oven than other birds or cuts of meat. Not only have we started off with dry meat but we also have dried it out further than we would most other meats. Yum.
I am not trying to convince turkey lovers out there of the downfalls of the beloved Christmas centerpiece, but there are two ways we can improve your turkey skills, scientifically. One involves a process called dry-brining. Dry-brining is achieved by covering the bird in salt (under the skin) and letting it stand for 48 hours before cooking. Through a process called diffusion, this salt travels into the turkey since diffusion involves the movement of molecules from an area of high concentration to an area of low concentration. Meat is made up of muscle fibres which in turn consist of proteins. Salt causes proteins to denature, essentially unwinding them. This allows water molecules to bind to the unwound proteins, keeping them in the meat, hence preventing water loss during the cooking process in our moisture-sucking oven. It is important you salt the bird well in advance though, because otherwise you will end up just taking water out if it, instead of locking it in - I never said food science was easy!
So that was one way to retain moisture in a turkey... the second is to sack all that effort and cook a nice environmentally friendly nut roast. Sorted.
How about the lovely crackling skin? Whether you like chemistry or not, there is a chemical reaction we have all performed countless times: the Maillard reaction. It is the reaction responsible for the brown colour of your crusty loaf of bread or the sweet nuttiness of cookies. So even if we are dreaming of a white Christmas; we crave a golden-brown turkey. The process involves the reaction between amino acids (the building block of proteins) and sugar to give you beautiful flavours and attractive golden colours. This reaction is the basis of nearly all oven-cooked dishes but there are ways in which we can accelerate it for maximum flavour and texture. The reaction occurs between 140 - 165ᵒC so having a thermometer to check the temperature of your meat is very handy. Another factor is pH. Generally speaking, the Maillard reaction takes place at higher pHs: more alkaline conditions. And because nothing is ever simple, acids (which are the devil to our angel alkaline) are actually a by-product of the Maillard reaction, causing the reaction to slow down as it progresses. We want to counteract this to ensure the reaction runs optimally. So let’s add that alkaline! And thankfully this can be found in the form of a nice cupboard stable: baking powder. Sprinkle that on the bird and you’ll have a cracker.
Whatever you choose to cook this Christmas, there will be plenty of chemistry happening in your kitchen - sadly this year it won’t be due to the mistletoe, but thanks to the wonderful reactions that bring food to our plates. So next time you kick back with a festive cookie and hot chocolate, you can revel in the fact that chemistry can actually be pretty sweet. Literally.