The signature characteristics of tempura is light and crispy. In Japan, this style of cooking is an art form and as with most foods, involves a lot of science. On an industrial scale however, there is some leeway on what is considered acceptable by the manufacturer and consumer.
There are many variables to watch out for throughout the process that can impact the final texture of tempura. The type of flour, the water temperature, mixing speed, time, and apparatus all play important roles. These all impact the final product, and those variables are before the manufacturer even gets to the frying part of the process.
Mixing the batter is a vital step to achieving the signature texture and it is a tricky part to get right. The process needs to be cold, in fact, the colder the better. A cold batter will cling better to the food item being fried. Additionally, the process needs to be quick. Overmixing will produce a thin batter and allow the gluten within the flour to develop, giving a chewy, doughy texture and poor rise. Undermixing, will give an excessively lumpy batter that will lead to a thick layer of batter on the food item and poor yields.
Some lumps in the batter are desired. Lumps help to trap air and give the fried tempura that typical irregular appearance. At restaurant scale, it is easier for a chef to make a consistently excellent batter. Traditionally, is it is recommended to mix the batter with chop sticks so that shear is kept to a minimum. On an industrial scale, it is more challenging to achieve that consistency. Many mixers used for this application either provide little shear and make the process very slow or provide too much shear, resulting in an undesirable texture and yield. Admix have developed a goldilocks solution to this application. Our solution creates an appropriately lumpy batter quickly without giving gluten a chance to activate. With the correct impellers as advised by our mixing equipment experts, tempura manufactures can make perfect batter mix quickly and consistently every batch.