Koji is a fermented food that originated in China. It's cultured by adding a type of mold known as Asperigillus oryzae to grains such as rice, barley or soy beans. Koji is an indispensable part of Japan’s traditional food culture. In addition to being a key ingredient in alcoholic drinks like sake, shochu, and awamori, it was also used in Japanese homes to make amazake and cooking ingredients such as miso and soy sauce.

In recent years, koji's efficacy has been reappraised, and shio koji (koji prepared with salt) has experienced a sudden boom in Japan as a seasoning that can be used in many different dishes.

Shio koji contains many enzymes that act on foods in a variety of ways. If you pickle foods in shio koji, its enzymes will break down the starches, proteins and fats to produce amino acids, making the food more delicious. It also helps to soften meat and fish, and aids in digestion and nutrient absorption.

Koji also produces vitamins involved in the metabolism of the skin, in addition to containing lactic acid bacteria. It can provide nutrients even when used just as it is, as a sauce. It has a mellow, salty flavor that can be used not only with Japanese cuisine, but also in many other kinds of cuisines.

One of the appeals of shio koji is that it can be made easily at home. All you need is salt, rice koji and water. First, mix the salt and rice koji evenly. Then, add enough water to cover the entire mixture. Leave this in a lidded container at room temperature out of direct sunlight, stirring it once a day. The koji will soften after about two weeks and is ready to use once it has a sweet, banana-like smell.

Amazake, or sweet sake, is also made using koji. Since it contains lots of nutrients from the koji, it's also sometimes called an “intravenous drip that you drink.” Amazake tastes delicious both hot and cold and has been much loved in Japan for more than 1,000 years. It can even be consumed by children!

Amazake's plentiful nutrients offer a range of benefits. Drink it each day to make your hair and skin more beautiful. It will also boost your immune system and help with recovery from fatigue. Amazake can also be made from sake lees, but this method includes a little alcohol, so you might want to be a bit careful about drinking this type. Also, because amazake is quite nutritious, drinking too much of it can lead to obesity. About a cup a day is what to aim for.

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