Shio Koji: Why you want this mold on your food

Japan’s latest ingredient du jour is a fungus that smells like old socks, but that hasn’t stopped professional and home cooks alike going crazy for it, and it’s popularity is spreading.

Shio koji is a fermented mixture of koji (rice inoculated with the mould Aspergillus oryzae), shio (sea salt) and water.

The mixture is used as a seasoning in place of salt and is prized for it powerful, concentrated umami taste.

Despite having the appearance of beige sludge and an odour reminiscent of slightly sweet sweaty socks, Japan’s growing obsession with shio koji has seen entire blogs, websites, cooking videos and even a cartoon character devoted to the condiment that has been hailed as “the new MSG”.

Following the path of other quirky cult ingredients, brands have been quick to try and cash in on the current craze for Shio koji.  It’s being included in everything from salad dressings to pickles, while popular Japanese burger chain Mos Burger introduced a limited edition shio koji burger this summer.

Famed Tokyo ramen chef Ivan Orkin gave the burger a shout-out on Twitter, calling it an “umami bomb extraordinaire”.

But whilst the current wave of shio koji fever is getting the ingredient noticed by Western chefs, A. oryzae has been used in traditional Japanese foods for thousands of years.  The Brewing Society of Japan has even dubbed it the “national fungus” due to its importance in brewing sake.

The key is in the mould’s ability to convert proteins into enzymes, including glutamic acid, the enzyme responsible for umami.  Umami is recognized as the fifth taste – in addition to sweet, salty, sour and bitter – and the word itself is Japanese in origin, meaning “pleasant salty taste”.  The Japanese, it seems, have been onto this for a while.

A recent profile of shio koji in the LA Times revealed some of the food world’s biggest names, such as David Chang, are harbouring an affair with the ingredient and predict it won’t be long before chefs and home cooks in the West discover it for themselves.