What is shio koji?
It's the secret ingredient that chefs are using more and more, but what is it, and why should you be using it too? We talk to Tomoko Onuki from Rice Culture to explain this interesting ingredient.
It's important to look at what koji is first before we know what shio koji is - koji is a culture known as aspergillus oryzae. This culture gets inoculated on to grains, often rice where it feeds off the starch, and the culture grows and expels various enzymes. It's these enzymes that then break down fats, protein or carbohydrates in the grain.
One of the most common uses for koji is to make sake, where the enzymes bring out the sweetness in the rice that that's been inoculated, which then turn the starch to sugars, and then to alcohol. Koji is also used to make soy sauce and miso as well.
To make koji rice, organic rice gets steamed, then is inoculated with koji spores. The rice is kept warm at around 30C where the culture grows. After 48 hours the culture has fully formed and the koji rice is ready to use. From here the rice can be dehydrated and the culture preserved.
If you think of shio koji like miso, it's similar, but is much more of a creamy liquid. The amount of salt added to make shio koji (shio meaning salt) is about 15%. The lower the salt, the more likely the rice liquids will turn to alcohol. The more salt you use, you'll have a saltier end product which is more stable. Koji is more stable with this amount of salt and up to 35%.
To make shio koji, for 400gm of inoculated and dehydrated koji rice (see note), add 175g salt and 600ml water (this amount allows extra liquid for hydration of the rice). Combine salt, water and koji rice in a crock or large jar with a muslin lid allowing some air to escape. Leave to ferment, stirring occasionally, over 7-9 days. It's important the rice is completely covered with water in the container. You may have some rice float to the top, and these can be removed to keep the mixture submerged. Once the mixture is fermenting and bubbling, you can transfer it to the fridge to slow down the fermentation process. From here, just blend the mixture until smooth and it will keep in the fridge for up to 6 months.
Once you have made shio koji, you can start to experiment with various vegetables and flavours. When brushed over meats and marinated overnight, shio koji will tenderise meat and add a lot of flavour. The guide is to use 10% of the koji to the quantity of the meat or vegetable you're using. It can also be used to flavour soups and as a salt substitute, too. The best result is when marinating ingredients to allow the enzymes to do their work, which breaks down the protein into amino acids, acting as a natural flavour enhancer. When used on vegetables, such as cucumber, they can be transformed into Japanese pickles, where the salt draws out the moisture and preserves the vegetable, too.
Pictured: Rice grains inoculated with koji culture are soaked in water and with salt added to balance the bacteria. Once fermented the rice can be pureed with a blender, which then becomes a creamy texture.