Using Fermentation As a Collaborator in Reducing Food Waste

Kirsten K Shockey

May 22, 2023

Last October, American food professionals visited fermented food producers to deepen their knowledge of Japanese fermentation culture during the “Hakko Tourism in Japan” tour campaign. As part of the tour, organizers held a tasting session where guests gave candid advice from the perspective of the American market to food product manufacturers looking to enter the United States market.

Our relationship with fermentation

Fermentation is preservation. It is very much coaxing which microbes will transform our foods to keep them available as nutrition for a little longer, as opposed to microbes that spoil.

Fermentation happens. Microbes have transformed organic matter on this planet since the beginning.

There is no definitive history of humans and fermentation. At what point humans discovered that some unfermented foods were toxic and could be rendered nutritious with fermentation is also murky and fascinating. We have ancient pot residues of fermented foods, yes, but likely humans were fermenting, or at least eating microbe-kissed foods way before these pots that give us tangible evidence.

Many of us wonder, what are the stories of the first people who noticed these changes and then were brave enough to take the risks of consuming, sometimes moldy foods. The important thing to understand, though, is fermentation in our ancestors’ past was survival, not only because the preservation made food available in lean times but also because fermentation techniques can insure, we get the most from our food.

Fermentation today

It is probably safe to say that fermentation as we know it today was born from necessity—a necessity from every scrap of nutrition needing to be secured and amplified. For example, some Japanese tsukemono techniques arose to find uses for the by-products of other food productions.

For instance, nuka-zuke are fermented in rice bran (nuka), a by-product of polishing rice. Interestingly, eating nuka-zuke was shown to reduce the occurrence of beriberi, a disease that comes from vitamin B1 deficiency resulting from the widespread consumption of polished rice.

kasu-zuke are pickles fermented in sake lees (kasu), the mash of rice and yeast that is a by-product of making sake. In a modern twist Ine to Agave Brewery is now redefining what is possible with the sake kasu from their brewing. They are turning it into a delicious vegan mayonnaise—Koji Mayo. This mayonnaise is rich and creamy and doesn’t disappoint the palate.

In Indonesia, okara, the soybean mash left over from making soy milk and tofu, is made into oncom: a tempeh-like bean cake that is delicious, filling, and nutrient-dense. These foods are the original protein rich meat analogs.

Preventing food waste with fermentation

“Fermentation is recognized as a cost-efficient way of … giving new value to food waste by making it nutritious again,” says William Chen, a professor in food science and technology at Nanyang Technological University in Singapore, in an article in Japan Times. Chen and his team are also working with fermenting okara “to replace high-cost fetal bovine serum, extracted from cattle fetuses’ blood and used to grow meat cells to produce (lab-grown) meat,” the professor explains.

It is ironic that now a third of all food is wasted, according to the Food and Agriculture Organization (FAO). At the same time, a 2021 study published in Nature Food reports the global food system is accountable for over a third of human-caused greenhouse gas emissions. Food waste is a huge issue that many individuals in their homes or businesses are trying to tackle, and our survival depends on it.

Enter fermentation. Fermentation plays numerous roles in tackling food waste. It is a cost-effective, natural, safe, delicious, and nourishing way to give life to food waste.

We should honestly also add the word fun. It is exciting and hopeful to see the creativity emerging. Fermentation is being tested in labs and by forward-thinking food producers worldwide.

Rediscovering fermentation

Scientists are also looking at fermented avocado seeds for flour in the Middle East and fungus-based fermentation in Colombia. With fermentation, they can turn a current edible waste product that mostly gets tossed out into something that could provide incredible nutrition.

The avocado pit is the most nutrient-dense part of an avocado; 70 percent of its antioxidants are locked up in it. In Eastern Europe, stale rye bread has been used for centuries to make a lightly alcoholic beer called Kvass.

These traditional ferments are no longer relics of the past but are being rediscovered and reimagined.

In Boulder, Colorado, Mara Jane King and the team at Dry Storage, a grain mill and bakery, are using their stale bread to make delicious Kvass to serve in their restaurant. Mara is also making enchanting sourdough gochujang and a delectable Japanese milk bread tian mian jiang.

In Chiba City, Chiba Prefecture, Japan, a bakery, Kawashimaya, and a brewery, Makuhari, are collaborating to develop bread beer and other products from unsold bread in their Chiba Upcycling Lab.

Mara Kings bread tianmianjiang
(Photo by Kirsten K. Shockey)

Upcycling with fermentation

Upcycling with fermentation is something anyone can do in their own home. So many foods we are in the habit of discarding can become delicious.

Let’s start with bread. It gets dry and stale, you’ve burned it in the toaster, and maybe you don’t like the ends or the crusts. When we think a moment about how many inputs and carbon it takes for grains to go from farm to bread and how much of this we easily send on to the landfill (where it continues to add to the carbon load), we see how easily each of can make a tiny difference.

Your bit can become your new favorite light ale—kvass and even delicious miso.

Bread Miso

One year and two year bread miso in glass jars

(Photo by Kirsten K. Shockey)

The idea for this miso is to use stale bread, ends, crusts, and even burnt toast (seriously!) and ferment it into a tasty paste. Use sourdough, rye bread, or your favorite bread.

You can also mix different varieties. Since you may not have enough bread at one time, feel free to save your ends in an airtight container in the freezer until you are ready to make it.

It takes a bit of time for the bread to soak up the liquid. I have tried making this miso by making the bread into crumbs before adding the liquid.

It takes less time to mix everything, but the resulting miso is wet and grainy in texture. However, when I wait for the water to soak in and slowly hydrate the koji and bread, the whole thing is much tastier with a smooth paste-like consistency.

The recipe below gives measurements, but it is nice to understand general guidelines because we are talking about utilizing scraps. I use two parts bread to one part koji and 12 % salt because I know it works, and I am happy with the results.

However, feel free to play around with this and make it the way you like it. These pastes can be smooth and umami-rich or a little funky and yeast or lactic. It’s all in controlling the ferment with salt, temperature, and time. (Hint: the lower the salt and the higher the moisture content will give you more lactic and funky flavors.


  • 340 grams bread bits, cut into crouton-sized pieces and toasted to a near char
  • 170 grams koji rice
  • 2 cups (473 ml) water (boiled and cooled to around 100°F/38°C)
  • 61 grams sea salt
  • Extra salt for packing in jar


1. Prepare the bread by cutting it into crouton-sized pieces and toasting. When the bread has cooled, place in a bowl and add the koji, water, and salt.
All the ingredients for bread miso in a green bowm

(Photo by Kirsten K. Shockey)

2. Massage it together and let it sit. It will take some time for the hard toasted bread to hydrate. After an hour or so, massage again. When the mixture feels moist and ingredients are well combined, it is ready to pack into a jar.

3. Using a bit of boiled water, cooled to handle, rinse the inside of your fermentation jar, making sure to coat all of the surfaces. Then sprinkle about 1 tablespoon salt into the jar, coating the vessel’s sides and bottom.

4. Spoon the chickpea mixture into your jar or crock, doing your best to remove as many air bubbles as possible.

5. Set a small piece of unbleached cotton cloth or parchment paper cut to fit the diameter of your vessel on top. Sprinkle about 1⁄2 tablespoon of salt along the edges of this cover to seal any gaps. Weight the miso as best you can with weights or a salt-filled plastic bag.

6. Cover the jar with a cloth, securing it in place with a string. Set it in a cool spot and allow it to ferment. Ferment for 6 months or more, but feel free to taste it much earlier.

Bread Miso in jar ready to ferment

(Photo by Kirsten K. Shockey)

7. When you are ready to harvest your miso, open it up. You may need to scrape off the top surface of the miso until you get to something that looks nice and rich in color. You can either strain off the tamari (the liquid pooling on the top of the miso) or you can mix it back into the miso and eat it as is. Your miso may be chunky; if you prefer a smoother paste, process it in a grinder or food processor. Store in an airtight container. The miso will keep indefinitely in the refrigerator.

Miso in glass jars
(Photo by Kirsten K. Shockey)
Author, Fermentation Expert | + posts

Kirsten K Shockey is a renowned fermentation expert, author, and co-founder of The Fermentation School. She empowers people to connect with their food through hands-on workshops and her popular books, including Fermented Vegetables and Homebrewed Vinegar. Her expertise has made her a trusted authority in the world of fermentation.