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DEEP-fried foods coated in crispy batter are enjoyed all over the world, but perhaps nowhere are they more revered than in Japan, where tempura chefs spend years mastering their craft. However, cooking battered food at home isn’t as challenging as it sounds, and a bit of science can help you get beautifully crisp results.

Let’s start with what goes in the batter. Gluten, which forms when proteins in flour are exposed to water, helps to give the batter structure, but too much can make it tough. For a light tempura batter, it is important to keep gluten to a minimum. Replacing some of the wheat flour with a low-protein alternative, such as rice flour or cornflour, is one way to do this. Another, rather left-field method is to replace some of the water in the batter with alcohol.

Using carbonated water in the batter also helps to create a light, open texture, since the bubbles of gas expand when they are heated. This is one reason why beer is commonly used in the batter for traditional fish and chips. A bit of baking powder, which produces carbon dioxide when added to water, can help, too.

and her colleagues at the University of Zaragoza in Spain concluded that “the partial substitution of water and wheat flour with ethanol, cornflour and baking powder resulted in a crispier and rougher crust that remained more stable over time”.

Make sure the liquid ingredients are cold – both to limit gluten development and so more gas remains in solution until they reach the hot oil. Finally, mix the batter just before you fry, and don’t over-mix it.

Any refined oils, which have impurities removed so they can be heated to a high temperature without smoking and developing off flavours, can be used – try sunflower, vegetable or peanut oil.

The ideal temperature for frying is 160 to 180°C (320 to 360°F). One way to check is to put a chopstick in the oil and watch the bubbles –faster bubbling means it is hotter – but this isn’t very precise. A recent study found that when you dip moist paper in oil, the sound of an exploding bubble can reveal the temperature, but you need to know what to listen for. I would just buy a good kitchen thermometer.

I use a wok for deep-frying – its wide top makes it easier to move things around and there is less chance of it spilling over. To avoid lowering the temperature too much, use plenty of oil and don’t fry too many things at once. A straining tool, called a skimmer or spider, is helpful for fishing things out – or you can use a pair of extra-long cooking chopsticks.

Cook until the batter is crisp and pale blond. That is 1 to 2 minutes, depending on what you are frying. Make a traditional dipping sauce by mixing dashi, mirin and soy sauce – or use any other sauce you like.

Sam Wong is assistant news editor and self-appointed chief gourmand at 91av. Follow him @samwong1

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