Many restaurants deep-fry battered shrimp and call it tempura. But not just any battered, fried shrimp qualifies as tempura. Tempura is one of my all-time favorite foods and I have been on a lifelong quest to make perfect lacy tempura at home. I have prepared many a soggy tempura. Hard-as-a-rock tempura. Tempura that rolled up in a ball from the shrimp curling. Here are my findings from my tempura quest:
Furai vs. tempura
First let us clear up any confusion over culinary terms. If any food is coated in bread crumbs before frying, it falls into the category of Japanese cooking called furai or fried food. (See BellaOnline Japanese Basic Furai Fried Food Recipe.) Lightly battered food is tempura. Tempura does not use bread crumbs. It does not need any. A perfect tempura should feature the seafood or vegetables nestled in a light, lacy network of thin, crispy batter. Many Japanese restaurants do not serve perfect tempura, choosing instead to serve furai shrimp or a heavily battered shrimp and hope that their patrons do not know the difference.
Cooking oils can impart flavor which may be a desirable or undesirable quality. For frying tempura, you want an oil that does not impart flavor to preserve the delicate flavor of the seafood. Hence, I choose to use canola or vegetable oil. Peanut, coconut, soybean or olive oil is fine for furai foods or heavily seasoned foods but for tempura, I choose vegetable oil. Start with a fresh batch of pure vegetable oil.
You can strain and reuse cooking oil but you should not do that very often because each time the oil is heated, its chemical properties change. The oil breaks down after a while. It darkens and does not cook the food as efficiently, soaking into the food more than frying the outside quickly which decreases oil absorption. It also becomes rancid from oxidation. Some contend that the oil gets seasoned and it does get flavored by any seasonings from the foods fried in it. But any bits of herbs, spices, bread crumbs or batter left behind tends to burn, leaving a scorched taste.
The correct frying temperature is important, too. If the oil is not hot enough, the batter will absorb too much fat. If the oil is too hot, the outside of the food will cook before the inside. Using a deep-frying thermometer works great (about 375 degrees F.) but after some practice, you will be able to tell the correct temperature by dropping a bit of batter into the hot oil and watching how it sizzles.
Choose only fresh, large-size shrimp. Wash and peel them, leaving on the tails. Devein the backs and slice almost all the way through, being sure that the shrimp remains in one piece. Flip it over. Then, make several shallow cuts along the underside of the shrimp, perpendicular to its length. Flatten gently. This breaks the tendons in the shrimp so it will not curl during cooking. Others have tried to ice the shrimp, run skewers through it or pound it, but this is the secret: cut the tendons.
Egg vs. no egg
To add egg or not to add egg has been the culinary question. Egg adds flavor and binding. But the yolk tends to soften, resulting in a less crispy batter. Because of this, some people choose to separate out the yolk and use only a whipped egg white. My experience with this has been a somewhat crispier tempura but with a lot less flavor and an uncooked, white color. Some add extra salt and food coloring to make up for this but it is just so unnecessary. Add the egg. Natural color, natural flavor. And not too many. The more egg you add, the softer the batter will become so use it sparingly.
Is leavening necessary?
The original recipe for Japanese tempura actually has only a few ingredients: flour, egg and water. Not even salt is added. Perhaps, this recipe works if you 1. Use copious amounts of tentsuya (dipping sauce) which is seasoned and 2. You eat this immediately after it departs the fryer. It softens quickly. After testing this recipe out on several people, we concurred that it is not very impressive in crunch or flavor.
I have tried recipes that use baking powder, biscuit mixes, seltzer soda water and even beer in an attempt to increase the crunch factor. Leavening adds height and puff but not necessarily crunch, I learned. Lacy tempura is not fluffy. It is crisp. Still, I add just a touch because my recipe has a large amount of cornstarch in it which, without the leavening, can get hard.
Here is where I made some headway. Wheat flour gives a good flavor but gets soggy fast. When I experimented with replacing half of it with a cornstarch, the results improved. In fact, most packaged tempura batter mixes use a combination of wheat flour and corn or wheat starch. The results improved further when I used a combination of rice flour and cornstarch. If you choose to use wheat flour for the flavor, it is vital NOT to overmix or you will activate the gluten in the flour and make a very chewy batter.
It is true that tempura is served with a dipping sauce but the batter improves with just a little seasoning, too. Ajinomoto (do not be afraid of it, really. It is still sold as Accent seasoning and adds an important dimension of umami/savory flavor) and salt are enough. (I am embarrassed to admit this but I cannot help but add a pinch of garlic powder to mine because I am a garlic head. My dear Japanese grandmother told me that my tempura had the best flavor and I did not want to tell her it was because I ventured far from the traditional path and added a good bit of both garlic and onion powder!) The egg adds more flavor.
The only liquid in tempura batter should be ice cold water. In addition, I place my batters in a bowl filled with crushed ice to keep them cold. When the icy batter hits the hot oil, the outside of the batter will sear and insulate the inside of the batter from absorbing oil.
A tale of two batters
The secret to lacy tempura is...drum roll, please...TWO batters when frying. One should be slightly thinner than the other. Be sure when mixing the batters, that you only mix enough to combine the ingredients. There will be lumps! Too much mixing will activate the gluten in the flour (if you use wheat flour) and result in a chewy texture. Use a light hand when mixing.
Both batters should be icy cold. When the oil is sufficiently hot, dip a shrimp into the thicker batter and carefully place it into the hot oil. Then quickly, dip your fingers into the thinner batter and let it drip around the very edges of the shrimp in the oil, making drips to form a netting around the shrimp. (If the thin batter is too thin, it will scatter into bits instead of sticking together in a string-like netting.) Cook for a few minutes and then flip to cook the other side. Practice and experiment with how much of a lacy network you like on your tempura. The tempura should be cooked but not browned. Drain on a paper towel. And be sure to scoop out the little bits left behind. That is valuable stuff called Tenkasu that makes a great crunchy topping for all sorts of other dishes like ramen, chazuke and okonomiyaki.
I would like to add the recipe here but for space constraints, it appears in its own article. Be sure to read Lacy Tempura and Tentsuyu Recipes here at BellaOnline Japanese Food site.