Tasty science

‘Chemistry, it’s basically cooking isn’t it?’ A question I’ve heard a few times in my life, but I’d like to think that my experiments in the kitchen produce better smells than the average organic lab. With that in mind, I thought I’d investigate how chemistry can help us cook our traditional Christmas fare.

Christmas dinner for me has always involved some sort of poultry, from the old school goose to that modern usurper the turkey. So, what’s the chemistry going on with a roast turkey?

Cooking changes the flavour and texture of meat, in part because the heat denatures the muscle proteins. However, muscle enzymes naturally present also break down protein, generating flavour molecules and tenderising the meat. This is what happens when meat is aged, but also what happens if meat is cooked slowly at a temperature low enough to speed up the enzymes but not denature them. This is why chefs like Heston Blumenthal can often be found cooking meat in a water bath at such low temperatures.

If your kitchen isn’t equipped for sous vide cooking, and you don’t fancy nipping in your lab at Christmas, slow roasting the turkey in a low oven can do the same job. A final blast at a high temperature will turn the skin crispy and yummy due to Maillard reactions, the reactions of carbohydrates with amino acids to produce a range pyrroles, pyridines, thiophenes etc.

As for the trimmings (possibly my favourite bit of the meal), there are a few tricks chemistry can teach us:

Gravy can be thickened by the addition of starch, which can hold water between its polymeric strands. A roux made of the turkey dripping and cornflour, which is basically pure starch can be whisked into the gravy on the stove. If you get a spare few minutes you can then have some fun making a non-Newtonian fluid with the cornstarch, just don’t get too distracted and burn anything!

I’m a great fan of Delia Smith’s parmesan baked parsnips, the glutamic acid in the parmesan giving extra umami flavours. For both roast parsnips and roast potatoes the trick is to boil them well first and then wait for the hot oil to help do its Maillard magic.

Brussel sproutsAs for sprouts, two traditional ways to keep your greens green involve adding baking soda to the coking water or using copper pans. Making the cooking water alkali with baking soda prevents the hydrolysis of an ester on the chlorophyll, which is then water soluble and leaks into the cooking liquid. However this does have the side effect of destroying the vitamins in your sprouts and can turn them even more mushy. The copper pan trick works by replacing the central magnesium at the centre of the chlorophyll and then resisting displacement by hydrogen. These days, I tend to fry my sprouts in butter, mainly to avoid mushiness and the formation of the trisulfides that are responsible for the smell of overcooked cabbage.

Finally, I’ve been selflessly experimenting with mulled wine recipes in the spirit of science (honest). I suggest you do some experimentation of your own but to start you off, here’s my basic recipe:

1 bottle of unoaked red wine

300ml water

1 orange studded with around 5 cloves

1 or 2 cinnamon sticks

1 bay leaf

1cube of crystallised ginger and double the amount of fresh ginger, grated

Sugar or honey to taste (I use 3 tsp of honey).

Slowly warm the whole lot in a saucepan, avoiding boiling. Once it’s been warming for 15 minutes and is hot, turn off the heat, stick on the lid and leave to infuse for half an hour. Enjoy.

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