Koji and natto making in Wales

We had been lured to a remote valley in mid-Wales in search of the secret to Japanese cuisine:  koji. Arriving on a sunny Saturday afternoon in April, it felt as though we had stepped out of the Welsh countryside and into Edo period Japan. Reiko, our host, is a really remarkable woman as well as being a highly talented chef.

Cwm Mawr

Our reasons for seeking out Reiko stemmed from our growing understanding of and appreciation for koji. We wanted to learn more about this miracle foodstuff from someone steeped in Japanese culture and culinary tradition. Reiko was a very welcoming host, and straight away we felt very comfortable sharing food and stories in her spacious and gracefully decorated barn conversion. Despite the fact that she is approaching the age of 70, Reiko could easily pass for a woman at least 20 years younger. This seems to be at least partly due to her upbringing in the countryside of post-war Japan, where junk food was non-existent and sugar, meat and even fish were very rare indeed.

Reiko and Georgina

Reiko explained over some of her extraordinary dishes how she had begun to learn to cook at the age of ten. This was macrobiotics without the classes, books or teachers which came along in later years. It’s an authentic, artisanal form of macrobiotics and we were learning at the feet of a master.

That evening we helped her start a batch of koji made from organic short grain rice. The process takes about three days, (including pre-soaking the rice) so the plan was that the koji would be ready just before our return to the Peak District on Monday afternoon. We also began work on a large batch of organic natto for one of her customers.

Koya tofu

Reiko has spent many years perfecting her recipes and methods for the koji, miso, natto, tamari and amazake she makes herself, and it was difficult to keep up with her as she buzzed around her comfortable kitchen.  Like an artist in the kitchen,  she wasn’t one to carefully measure out ingredients or amounts, but she took the time with us to try and come up with approximate measurements. Fermentation is a type of cooking better suited to the artist than the scientist, as outcomes depend so much on a symphony of time, temperature, environment and ingredients.

The wonderful Reiko with her wonderful koji
Fresh koji
Natto preparation
Fresh natto!

But fermentation is more about waiting than it is about rushing around the kitchen, so once the koji and natto were bedded down for the night, we were able to learn more about the central part that fermentation (especially in the form of products based on koji) plays in traditional Japanese food. Koji (which can be either made with rice or barley) is a key ingredient in many important foods, most notably miso, amazake and tamari. It seems that there is hardly a single Japanese foodstuff that does not involve at least some basic type of fermentation, whether it be natto, miso, tofu, pickles or soy sauce. It feels as though the health benefits (not to mention the taste benefits!) of fermented foods are now only beginning to be better understood here in Western countries, even though many, if not most, traditional food cultures have long treasured and understood their life-giving benefits.

Our first batch of home made miso, day 1

Perhaps our modern aversion to ‘germs’ has a lot to do with this shyness for fermented foods in the Western diet. Or perhaps it’s simply down to the fact that fermented foods are rebellious and don’t take kindly to mass production and homogenization. In any case, there is something of a rebellion taking place, and Cwm Mawr is at the heart of it.

Serving lunch

On Sunday the more traditional Welsh rain had returned, so we cancelled our plans for a short hike in the surrounding hills to focus more closely on the making of other macrobiotic mainstays, namely miso and barley and rice amazake. Reiko guided us in our endeavours as we made a start on a large batch of organic miso and began fermenting the amazake with some koji we had prepared earlier. By now the natto was ready, so we were also able to watch Reiko whiz together a very tasty natto condiment which was a great accompaniment to the afternoon’s late lunch.

Natto condiment

We rose fairly early on Monday for the final day of our trip. By now the koji would be ready, allowing us to finalise our first batch of miso. The koji smelled quite extraordinary, a smell that is too elusive for words. An unusual but also pleasant smell, quite unlike the dried koji we were more familiar with.

Miso soup with mochi and noodles

And so later that day we set off north, the car packed with an array of exciting foods awaiting further fermentation and experimentation. We were both buzzing from this brief but deeply interesting culinary journey. Check back in four months when the miso will be approaching maturity! And we will soon be returning to Cwm Mawr to learn even more in our next lesson.

How to make amazake with our koji

Amazake is cooked rice mixed with koji yielding, after a period of fermentation, a naturally sweet aromatic thick beverage. Amazake is great as a wholesome sweetener for cakes, muffins or other desserts. Add a touch of unrefined sea salt and a small piece of any sea vegetable, to boost nutrients, minerals, vitamins, and to enhance Amazake’s flavour. Spirulina, blue green algae, wheat grass, nut- and seed butters, flax, vanilla, cinnamon, coriander, coconut, are just some of the foods you can add to enrich or flavour amazake.

Koji is steamed rice that has been inoculated with a variety of the Aspergillus oryzae mold that is then used to make amazake, miso, sake, vinegar, mirin, and more.

Tools needed:

  • Medium pot with lid
  • Double boiler or large pot with lid
  • Probe thermometer
  • Flame diffusers
  • Blender (optional)
  • 5 Mason jars with lids

(Note: do not use aluminium pots or tools)


  • 5 cups organic brown rice or any other whole grain
  • 7 cups water
  • Pinch of sea salt
  • 1 cup Rhapsody amazake koji (double or triple for increased sweetness)

Soak grain overnight to reduce phytic acid content (skip when using white rice). Discard soaking water (skip when using rolled oats). Bring water, grain, and salt to a boil. Simmer covered for 50 minutes.

Let grain cool down to 135⁰F. Add koji and stir well. Cover. Insert this pot into the large pot with water (double boiler style) that’s between 135⁰F and 140⁰F. Use a thermometer to be able to control the fermentation process closely. Above 140⁰F the koji will get killed, so that’s a critical temperature to stay below. Slip several flame diffusers under the double boiler, to maintain the water bath at the right temperature on a low flame. This is the trickiest part of it all, but once you have figured out what the right number of diffusers is and the setting of your stove, not much can go wrong. We use a cast iron skillet with two diffusers on the smallest burner turned down to its lowest setting.
When doing this for the first time, start in the morning so you can keep an eye on the temperature. Once you know how to keep the temperature constant (within the range of 125⁰F to 139⁰F), make it in the evening and have a tasty pot of amazake ready for you the next morning.

Check temperature of water bath regularly in the beginning to get the temperature right. You can adjust the temperature by the number of flame diffusers.

Let the mixture sit overnight (8-12 hours). Stir occasionally. Speed up the fermentation to only 2 or 3 hours by running the mixture through a blender first.

Fermentation is done when the slurry smells nice and tastes sweet. Cool it down quickly and consume within a few days or bring to a boil to stop the fermentation process to prevent souring; stir continuously to prevent burning or bring the water in your double boiler up to boiling and give the slurry a few hours to rise to above 200⁰F.

Blend until smooth if desired and pour in a mason jar while boiling hot. (Rinse jar with hot water to prevent the glass from cracking.) Or pour into sturdy plastic containers and freeze.

To make rice milk, blend 2 parts amazake with 1 to 2 parts water depending on desired sweetness and consistency. Strain through cheese cloth for smoothness. Bring to a boil and also bottle hot. Refrigerate when cool.

Unopened amazake/rice milk lasts for at least 4 months when refrigerated.

Course report: Plant-Based Macrobiotics Cooking Class, September 2nd

Last Saturday we hosted our first  Plant-Based Macrobiotics Cooking Class at our new venue in in Edale, Derbyshire. We’d hosted several classes before on a slightly smaller scale, but we’d decided to get a little more professional about it, and The Old Winery was the perfect setting on a perfect September day.

Cooking in a new kitchen is always a little daunting, especially when you are planning a 16-course meal for 10 people! So there were several late nights in the days leading up to the course while we tried to work out how many pans, knives, chopping boards and mixing spoons we would need. Thankfully The Old Winery was also quite well equipped, so even though we forgot one or two things on the the day, the clean and spacious kitchen had pretty much everything we needed.

The day started off with tea and home-made lemon verbena crisp breads in the warm autumn sunshine, while the students introduced themselves and I then talked about how the day would be structured and started explaining a little about some of the ingredients we would be using. I also talked about the benefits of the ingredients and the importance of preparing balanced meals using a range of tastes and cooking techniques, ideas that are really important in macrobiotics.

The students were all remarkably knowledgeable in different areas, and we had a nice mixture of ages, backgrounds and genders, a really interesting and lovely group to work with!

After the warm-up, I demoed an amazake dessert and a quick miso soup before the cooking really began in earnest. Each student was assigned two dishes to prepare, one relatively quick and simple one, and another slower to prepare and more difficult one to make. The idea was that everything would be finished at about the same time, which nearly worked out.

Cooking demo

While we were waiting for one of the bean dishes to finish cooking, The Fermentation Master did a quick kombucha demo, fascinating the class with the eerie mothers he had floating on a maté tea sweetened with apple syrup. We also tried a few of his other fermented concoctions, but no students were brave enough to try the sour kimchi juice.



Lunch was finally served, an amazing array of tastes, colours and textures. Again, I was really impressed at how well everything had been cooked by the students, all of whom showed a flair for cooking and a passion for what they were about to eat.



After lunch The Fermentation Master concluded the day’s teaching with a fully hands-on session in raw kimchi making. First a  basic kimchi paste was prepared and then each student worked on their own to produce their unique batch to take home.



Before setting off for at the end of the day, we finished off with tea and the chilled amazake pudding. It was great to meet so many amazing and like-minded people, and I am hoping to stay in touch with everyone.

The next course will be held on October 14th in Edale.

Some comments from the students:

“I had a lovely day. Lots to think about, new people to meet, great food and your expertise. What more could I ask for? The venue was superb and I look forward to another class in the future. The whole day was so well planned and executed.”

Great day, gorgeous food. Really enjoyed the cooking and delicious meal.

Really enjoyable & knowledge-filled day. Really impressed by the variety of dishes & flavours we cooked together. I’m inspired to continue the journey. Thanks all!


Macrobiotic Shop featured in The Sheffield Star

Last Friday The Sheffield Star published an article entitled ‘Macrobiotic cookery class bids to improve Yorkshire’s health‘. The article reports on the health crises facing much of today’s population and how a wholefoods, plant-based diet can combat many of these issues. Here is an excerpt:

“Japan underwent rapid change at the start of the 20th century when the country’s diet changed because of western influences. This brought with it many illnesses and social problems,” said Georgina.

“George Ohsawa observed the rapid decline in health and set about creating a popular movement for health.” It was based on whole grains, such as millet, brown rice, buckwheat, quinoa and pearled barley, and fermented products such as miso, tempeh, sauerkraut and pickles. He called it the macrobiotic diet.

Read more at: http://www.thestar.co.uk/news/health/macrobiotic-cookery-class-bids-to-improve-yorkshire-s-health-1-8662455




Koji is a fungus, which interestingly is only found in Japan. Koji has been extremely important in Japanese cuisine for centuries. The Japanese can now do wonders with it. Without koji, there would be no miso, no amazake, shoyu, tamari or sake! It starts fermentation processes and ensures at the same time that the often long fermentation processes can be controlled. Koji creates the unique umami flavour. It enriches, makes the flavour more powerful and creates an end product that is easy to digest.

Hatcho miso ferments in large 100-year-old cedar wood barrels. About 600 river stones are manually stacked on top in a pyramid shape.

Koji works best with warm temperatures and a high humidity. During the active fermentation, koji needs two to three days to develop explosively in the ingredients that come into contact with the koji (e.g. soy, rice or wheat). One gram of koji contains no fewer than 10 billion koji spores. This fast growth is necessary, as this way other moulds and bacteria have no chance to develop.