A typical tempura batter is made of a mixture of starch, low gluten flour, ice cold water, a little oil. Sometimes chefs use also baking soda or sparkling water, some spices and a cold egg. This is all barely mixed with chopsticks or a fork (not a whisk) thereby leaving lumps in the mixture. The lumps will disappear during the deep frying. The batter is made fresh in small batches and kept ice cold.
In the mid 16th century Japan was isolated from the world and Dutch and some Chinese merchant ships were the only contact with the outside world. Portuguese missionaries had brought their batter and deep fry techniques to Nagasaki, to eat deep fried seafood on fast days, the so-called tempora. In this isolation, the Japanese perfected the batter and deep fry technique for frying delicate seafood and vegetables. The Portuguese indirectly provided the name.
The art of making and using tempura batter
A batter protects many foods that contain some moist against oil penetration. The protective barrier is based on starch that gelatinizes and on proteins that denature at the higher temperatures.
As we like to obtain a closely knit protection layer, when we use flour, we like the gluten to be underdeveloped, so we should hardly mix the flour mixture and use ice cold fluids.
In the croquettes and bitter balls recipe, the protective layer is a mixture of egg and bread crumbs. The dry bread crumbs themselves contain gelatinized starch and proteins and will swell from the inside during the deep frying process.
When the foods are submerged in the hot oil, they initially will sink. The contents heat up until the contained water is close to the boiling point. Steam forms that is released in the oil and explains the vigorous bubbles. Meanwhile the protective layer forms by the starch that gelatinizes under influence of the steam and by the proteins that denature. Oil finds it more difficult to penetrate the food and replace the evaporating water. When sufficient water has evaporated and gas pockets have formed between the food and the protective layer (the batter) the foods will start to buoy and will soon be ready. Tempura batter forms such an expansive layer so quickly that most tempura battered foods almost immediately come to the surface.
1/4cupcake flour (low gluten white wheat flour)for a non-gluten version, substitute by rice flour
Ingredients for pre-coating the food items
Instructions to make the batter
Mix the cold egg with the icecold water. For this you may use a whisk.
Add the cold liquid mixture to the dry ingredients and use chopsticks to mix very gently. Some flour or starch may be visible as lumps. Add a few ice cubes to keep the mixture cold and further dilute.
Store in a larger bowl, cooled in ice water, but prepare just before deep frying starts
Instructions to coat the to-be deep fried food pieces
Dry the food items with a kitchen cloth or towel (some may have been par-boiled) and drag them through the starch powder, shake off any excess starch.
Then pull the food items through the batter, making sure it is wetten on all sides. Then lower the food item in the hot deep fry oil
If using (deveined) shrimps, make sure to make brief cuts (about 1/4 inch) perpendicular to the length of the shrimp on the belly, about every 1/2 inch. Otherwise the shrimp will very much curl and we like to keep it elongated during deep frying.
If using vegetabes, check the parboiling times in advance, usually 2-3 minutes. Thereafter cool the items down, before dusting them with starch
Method: no heat treatmentFood allergy & intolerance information: gluten, egg (using rice flour instead of cake flour will make the batter gluten free)
Tempura batter should not contain salt, according to Japanese tradition. Offer salt and tempura sauce for dipping, instead.
Would you like to have very much swollen, battered food items? Then first add drops of batter to the oil, add more and combine using the metal, slotted scoop. This all should work in seconds. Then place the battered food item in the midst of these fritters. If need be add a bit more batter on top. In Japan they will not serve like this, but just in case you are curious how other cooks do it.