Fermenting revolution: uncovering miso’s health benefits

It has been used in Asian cooking for centuries and is becoming a favourite on Australian menus, now researchers are looking into the health benefits of miso.

PhD student in the School of Science, Psychology and Sport, Joanne Allwood, and Senior Lecturer in Microbiology, Dr David Bean, are extending their research in fermented foods by looking at microorganisms which are found in the fermented soybean paste.

They found there was very little recent research into miso, but work on other fermented foods is giving a clearer picture of the effects and benefits of these foods on health.

“Fermentation has always been used to preserve foods and to create interesting flavours, but it also makes things easy to digest because it breaks down food, with the nutrients then becoming more bioavailable. The nutritional value is also improved when food is fermented because the microorganisms leave by-products, such as vitamins and antioxidants,” Ms Allwood said.

“So, we’re not only looking at fermented food because it tastes good, but we’re looking at how it might be good for us. Many fermented foods have been studied, but we decided to look at miso because it is relatively new to Australia and it's getting more popular. You can see miso appearing more frequently on menus, where it’s often used in marinades, but is also delicious as a spread with avocado on sourdough and miso can even be used in desserts.

“It has an umami or savoury flavour, which happens when the proteins in the food break down and provide a natural glutamate. It’s a fairly addictive type of flavour that people are enjoying using.”

Miso’s fermentation process means it contains live, active microorganisms. The researchers want to determine whether these microorganisms mean miso is a beneficial whole food. Miso also contains prebiotics, known to be good for gut health, making miso even more appealing to the health-conscious.

The research will include the production of miso in a controlled laboratory environment over six-months. Miso production can take anywhere from two weeks to two years. By contrast, the fermentation of another popular food, sauerkraut, takes three weeks and has been less challenging for researchers to study its microorganisms.

“There isn't a clear picture of what microorganisms are in miso. We’ve found some older studies – but they used older methods and didn't actually give a clear picture – and there were quite a few limitations. We couldn't find anything up-to-date on Japanese miso or any Australian made miso,” Ms Allwood said.

“We’re making our own miso and we will test it using more modern techniques including metagenomic analysis throughout the fermentation process, to see how these microorganisms change along the way.

“As far as we know, there's some lactic acid bacteria along with some yeasts, these are microorganisms that are already on the foods or appear from the environment. They’re super hardy, and it's just amazing to watch and see that they're in there, but we want to know exactly what is in there, and how they change over a long fermentation time.” Joanne Allwood

The researchers are also looking at the role of rice koji – cooked rice that is fermented with a food-safe mould, Aspergillus oryzae, and is the first step in the two-step fermentation process to make miso.

“Rice koji smells amazing and has a kind of fruity, hard-to-describe smell. Making good koji is important, as it produces enzymes. Koji is used in the second stage, where it is added to soybeans and salt to make miso. Koji is also used to make soy sauce, or when fermented with more rice it can be used to make sake,” Ms Allwood said.

Miso production is becoming more popular in Australia with a trend towards fermented foods, with health-conscious buyers behind the growth in unpasteurised foods which still contain live microorganisms. Products often found in supermarkets with a longer shelf life have been stripped of these microorganisms after being pasteurised.