Christmas dinner is a joyful occasion, but if you’re doing the cooking, the pressure to deliver a perfect meal can be a headache.
Fortunately, a little bit of science can go a long way, and if you want to nail those perfectly crisp, buttery roast potatoes, win over even the most hardened Brussels sprout hater and light up the room with a spectacular flambéed Christmas pud, then look no further.
In this week’s Science with Sam, we take a look at what gives Brussels Sprouts their unique flavour, explore why crispiness is so desirable in food, and how a little bit of chemistry knowledge will wow your guests when it comes to pudding time.
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Video Transcript
Christmas dinner is a joyful occasion, but if you’re doing the cooking, the pressure to deliver a perfect meal can be a bit of a stress. To help you out, we’ve got a few science-based tips to help you nail some of the most important parts of the meal: crispy roast potatoes, Brussels sprouts to win over even the most ardent detractor and a spectacular flaming Christmas pudding.
Brussels Sprouts
Brussels Sprouts are members of the brassica family, which have evolved to produce bitter compounds as a defence against herbivores. They do this by storing precursor molecules in their cells. When the plant is damaged, the precursor molecules are released from their packaging and they come into contact with enzymes that convert them into the aversive chemicals we love to hate.
It’s no wonder then that around the Christmas dinner table nothing divides opinion more than sprouts. I think they’re great if they’re cooked well, but if you’re a hater, there are a few science-based tips that might win you over.
1. Eat your sprouts with red wine.
Now, I need little encouragement to have a glass of red wine with Christmas dinner, but a study found that drinking red wine reduced the perception of bitterness in the sprouts. The idea is that the tannins in red wine make proteins in saliva clump together, and this may interfere with the distribution of bitter chemicals in the mouth. Either that or you are too drunk to care.
2. Exposure therapy
We can learn to like foods that we dislike by pairing them with foods that we do like. In one study, children aged 3 to 5 were given Brussels sprouts as a snack for 14 days. One group got sprouts on their own, and the other with cream cheese. At the end, all the children were given sprouts on their own and asked if they liked them. Among the children who’d eaten sprouts on their own, less than a quarter said they liked the taste. But among the group that had them with cream cheese, 72 per cent said they liked them. So, if you don’t like sprouts, dip them in cream cheese, or wrap them in bacon, whatever works for you.
3. Cook them right.
For me, the best ways to cook sprouts are frying and roasting. Here, I’ve sliced them up thin and I’m going to fry them in a little oil.
The key is to get them nice and brown. High heat facilitates the Maillard reaction in which sugars and amino acids react and produce a wide range of delicious compounds. When you get them nice and brown using these methods, cruciferous vegetables develop wonderful nutty and savoury flavours that you don’t get from boiling them in water.
4. Flavour enhancers
You can also offset the bitterness by exciting your other tastes. I like to add shallots for sweetness, a squeeze of lemon juice for acidity, and bacon or parmesan for salt and umami. To be honest, these magic ingredients will perk up any vegetable side dish.
Crispy roasts
Crispiness is one of the qualities we most prize in food, but why do we find it so appealing? It could be because it often arises when raw ingredients become delicious and nutritious cooked food. Or maybe we associate it with high-fat foods, which we find particularly rewarding.
Whatever the reason, a crispy roast potato is one of the ultimate delicious and rewarding foods. Here are some tips to guide you to crunchy perfection.
1.Choose the right potato
There are two broad types of potato: waxy and floury. Waxy ones have thinner skins, have a smoother texture and stay firmer when they are cooked, so there are good in salads, but for roasting you really want the floury type, which have a higher starch content. King Edwards like these, Maris Piper or Russet potatoes are good varieties for roasting.
2. Boiling
Potato cells are packed with starch granules, which swell and burst during cooking, forming a gel. It’s this gelatinised starch that forms the crispy crust on a roast potato.
The cells of the potato are held together by a type of sugar molecule called pectin. Boiling also breaks down the pectin allowing fat to get into the potato when you roast it, helping create a nice thick crust.
You can help that even more by adding bicarbonate of soda to the water, to make it alkaline, this weakens the pectin so the potatoes soften more quickly. Half a teaspoon is enough for 2 litres of water.
3. Choose your fat and flavourings carefully
We’re going to be roasting these potatoes at about 200C. That’s quite hot and close to the smoke point of some types of oil, such as extra virgin olive oil. That means the flavour will be affected and may start to taste bitter. I prefer to roast potatoes in a neutral-tasting oil like sunflower or vegetable oil. You could also go for goose fat or duck fat for extra flavour.
I’d also avoid adding garlic or herbs at this stage as they will probably burn in the hot oven. If you want to, add them towards the end of cooking.
Preheat the roasting tray with the fat, and toss the potatoes well.
After 20 or 30 minutes, give them a turn. Keep watching them closely. They should take about an hour to get properly brown, but the exact cooking time depends on your oven and your potatoes.
Christmas pudding
A flaming pudding is the perfect finale to the Christmas meal. Follow these rules to make sure you get a fire as bright as Rudolph’s nose.
1. Get it hot
Because alcohol is easily vaporised, it mixes well with the air. It’s important that both the pudding and the alcohol are hot, so that more alcohol is vaporised. If you try and light cold spirits, it’s going to be disappointing.
2. Get the strong stuff
You need a spirit that’s at least 40 per cent alcohol, but if you’ve got anything stronger that’s going to give you a bigger and longer-lasting flame. Here we’ve got some 63% overproof rum. Nice.
3. Add a bit of colour.
Pure alcohol burns with a blue flame, which is nice but a bit muted. If you choose a spirit containing sugar or add sugar as we have here, you get a more luminous yellow flame.
The yellow flame happens when some of the carbon doesn’t get oxidised, and gives off fine particles of soot. When the soot particles ignite, they make a bright yellow flame.
Happy holidays from all of us at New Scientist. As a present, we’re giving you a 20 per cent discount on a subscription to our magazine – click the link in the description to sign up. We’ll be back with more videos in the New Year, so subscribe to your channel so you don’t miss out. Merry Christmas!
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