Koji — the Biggest Food Trend of 2017?

healthy food

Story at-a-glance

  • Optimizing your gut health with fermented and fiber-rich foods is a foundational step if you seek to achieve good health. Addressing your gut flora is also important for most health conditions, be they acute or chronic
  • Among the latest trends in fermentation are beet kvass — a fermented beet juice beverage — and koji-fermented foods. Koji is a type of fungus used for millennia in China and Japan to ferment foods
  • Koji can also be used to tenderize meats, cutting the time required to “dry age” the meat down from 45 days to as little as 48 hours. It can also be used as a savory marinade for chicken, seafood and vegetables


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

Slowly but surely, consumer behavior is changing in regard to food. Many have started embracing more traditional foods and are relearning ancient culinary methods such as fermenting.1

This may be one of the most positive food trends we've seen in many decades, as fermented foods are really important for optimal gut health. In more recent years, scientists have discovered just how crucial a role your microbiome plays in your overall health and mental wellbeing.

Indeed, some have suggested your body can best be viewed as a "super organism" composed of a diverse array of symbiotic microorganisms that need to be kept in proper balance for optimal physical and psychological functioning.

They've even realized your microbiome is one of the environmental factors that drives genetic expression, turning genes on and off depending on which microbes are present.

Research suggests many are deficient in beneficial gut bacteria, making it a really important consideration if you're not feeling well, physically or psychologically. Among the latest trends in fermentation are beet kvass — a fermented beet juice beverage — and koji-fermented foods.2,3,4,5

Koji May Become Biggest Food Trend of 2017

Chefs around the world are now embracing koji (Aspergillus oryzae6), a type of fungus used for millennia in China and Japan.

To create koji, Aspergillus culture is added to cooked rice, soybeans, potatoes or roasted, cracked wheat (depending on what it's going to be used for). The mixture is then placed in a warm, humid place for about 50 hours. The resulting koji is then added to the food being fermented, often along with a brine solution.

As Aspergillus ferments, it produces a number of enzymes known to be beneficial for animal and human health, including amylase, which aids digestion and promotes a healthy gut. As explained by Clearspring:7

"The amino acids, fatty acids and simple sugars released by the action of the koji add flavor, depth and, it has been argued, a number of health benefits to foods.

For example, the fermentation of soya beans using koji to create miso is known to increase the levels of isoflavones … compounds that are said to be effective in the prevention of cancer.

One of the amino acids released by the action of koji is glutamate, which imparts an intensely satisfying and delicious savory taste known as umami. This, combined with the simple sugars also released, ensure that foods made using koji have a uniquely rounded and deep flavor."

Sake, soy sauce, rice vinegar8 and miso soup9 are all traditional Asian foods and beverages made with koji. Historically, koji has also been used to obtain protein substitutes from soy or grains like wheat and rye.

In the West, chefs are experimenting and coming up with all sorts of new koji-fermented products. As noted by David Zilber, a fermentation sous chef at Noma in Copenhagen, Denmark:10

"At Noma, we use koji for flavor. But the great thing about it is that's it's both an ingredient and an instrument. It's delicious, but you can also use it as a tool — the enzymes [the fungus produces] break down proteins, so for example you can use it to tenderize meat."

Simple, Inexpensive Meat Tenderizing Hack

An article in Bon Appétit11 explains how koji is used to tenderize meats, cutting the time required to "dry age" the meat down from 45 days to as little as 48 hours.

You can easily do this at home, using koji purchased online or from your local Asian market. It's sometimes sold under the names kome-koji (rice koji) or shio-koji (salt koji).

You can also make your own koji from scratch. Fermup.com's recipe12 calls for white rice and koji starter, and the whole process takes about 60 hours from start to finish.

Koji looks a bit like rice pudding, or little rice grains covered in powder. To use it as a meat tenderizer, simply blend it smooth in a blender and rub it onto your steak. Leave uncovered on a wire rack in your refrigerator.

Over the course of 24 to 72 hours, the enzymes in the koji break down the connective tissue in the steak and rid the meat of its moisture.

In other words, the meat is beginning to decompose — that's what makes it so tender. Just don't let it sit too long. After about three days, it begins to cure, which makes it tough. Before you cook the meat, rinse it thoroughly in cold water to remove all of the koji rub. Pat dry, then season and cook as usual. According to Bon Appétit:

"You will notice that the steak will caramelize and pick up color much faster than a normal steak. The meat has a very distinct flavor and picks up a slight miso sweetness.

That sweetness is the biggest difference between the real dry-aged meat versus the koji hack, and that's likely what causes the meat to brown or caramelize faster. The koji steak is also a little less tender than the 45-day one…"

Koji Can Be Used in Many Different Ways

You can also use koji as a marinade for fish, chicken and vegetables. In this case, as little as 30 to 60 minutes may be enough. Also keep in mind that the food may burn faster than normal, so keep a close eye on it as it cooks.

Avoid adding extra salt when using koji, as it's already salty enough. In fact, koji is often used as a salt substitute.

Besides that, koji can be added to any number of dishes as a seasoning, imparting a savory "umami" flavor cherished by chefs and food connoisseurs everywhere. Or simply add it to your vinaigrette or berry preserves to bring out the other flavors.

You can find a lot of different recipes using koji online. For example, Superfoods for Super Health has a recipe for homemade miso soup using garbanzo beans in lieu of soy.13

Why Ferment Foods?

When foods are fermented using either bacteria, yeast or, in this case, a fungus, it boosts the nutritional content of the food. It also preserves the food, allowing it to be stored for several weeks without the addition of preservatives. The fermentation process also produces:

  • Beneficial healthy bacteria that promote gut health. Fermented milk products also contain non-digestible carbohydrate galacto-oligosaccharide, which acts as a prebiotic,14 and essential amino acids15
  • Beneficial enzymes
  • Certain nutrients, including B vitamins, biotin and folic acid.16 Fermented milk products also contain higher amounts of conjugated linoleic acid (CLA)17
  • Increased bioavailability of minerals18
  • Short-chain fatty acids, which help improve your immune system function

While you can do wild fermentation (allowing whatever is naturally on the vegetable to take hold), this method is more time consuming, and the end product less certain. Inoculating the food with a starter culture speeds up the fermentation process and helps to ensure you'll end up with a consistent, high-quality end product.

Most Stand to Benefit From Fermented Foods

In my view, optimizing your gut health is a foundational step if you seek to achieve good health. Addressing your gut flora is also important for most health conditions, be they acute or chronic.

Considering current disease statistics, it seems clear that most people have poor gut health and would benefit from eating more fermented foods.19 Since different fermented foods will contain disparate bacteria, your best bet is to eat a variety of fermented foods to optimize microbial diversity.

Fiber serves as a prebiotic and is another important component, and may even take precedence if you're already healthy, as fiber-rich foods provide nourishment for the beneficial microbes already residing in your gut. By strengthening their numbers, these beneficial microbes help keep disease-causing microbes in check.

I recommend eating fermented and fiber-rich foods every day, as research shows your microbiome can be very rapidly altered based on factors such as diet, lifestyle and chemical exposures. This is a double-edged sword, no doubt, considering how many of our modern conveniences (such as processed foods, antibiotics and pesticides) turn out to be extremely detrimental to our gut flora.

On the other hand, your diet is one of the easiest, fastest and most effective ways to improve and optimize your microbiome, so the good news is that you have a great degree of control over your health destiny.

How Probiotic Foods Influence Your Health and Well-Being

Research shows fermented or cultured foods have a wide range of beneficial effects, including but not limited to the following:

Enhanced nutritional content of the food

Restoration of normal gut flora when taking antibiotics

Immune system enhancement

Improvement of symptoms of lactose intolerance

Reduced risk of infection from pathogenic microorganisms

Weight loss aid. Certain fermented foods, such as kimchi, have been shown to have anti-obesity effects in animals

Reduced constipation or diarrhea and improvement of inflammatory bowel conditions such as Crohn's disease, ulcerative colitis, irritable bowel syndrome (IBS) and necrotizing enterocolitis

Can help prevent allergies in children, including the alleviation of peanut allergy if used in conjunction with oral immunotherapy20

Antioxidant21 and detoxifying effects (kimchi).

Kombucha also has antioxidant properties, thanks to a compound called D-saccharic acid-1,4-lactone (DSL)22

Reduced risk for Helicobacter pylori (H. pylori) bacterial infection, which causes ulcers and chronic stomach inflammation

Improvement of leaky gut and associated health problems, including chronic fatigue

Reduced urinary and female genital tract infections

Improvement of premenstrual syndrome

Improvement of and reduced risk for atopic dermatitis (eczema) and acne

Reduced risk for type 1 diabetes and type 2 diabetes23

Improved mental health, mood control and behavior

Improvement of autistic symptoms24,25

Reduced risk of brain diseases, including Alzheimer's

Fermenting Your Own Veggies Is Easy and Inexpensive

I recommend inoculating the food you're about to ferment using a starter culture to speed up the fermentation process. In the video above, Julie and I demonstrate how to make fermented vegetables at home.

You can find more advice on fermentation in my previous interview with Caroline Barringer, a nutritional therapy practitioner (NTP) and an expert in the preparation of the foods prescribed in Dr. Natasha Campbell-McBride's Gut and Psychology Syndrome (GAPS) Nutritional Program. Here's a simple recipe to get you started:

Shred and cut your chosen veggies. I strongly recommend using fresh organic vegetables to avoid pesticide exposure. Also, when adding herbs, only use fresh organic herbs, in small amounts. Tasty additions include basil, sage, rosemary, thyme and oregano.

Juice some celery. This is used as the brine, as it contains natural sodium and keeps the vegetables anaerobic. This eliminates the need for sea salt, which prevents growth of pathogenic bacteria.

Pack the veggies and celery juice along with the inoculants into a 32-ounce wide-mouthed canning jar. Starter culture, such as kefir grains, whey or commercial starter powder can all be used for vegetables. Use two packets of starter culture for a 12- to 14-jar batch during summer season. In the winter, you'll need three packets for a batch of this size. A kraut pounder tool can be helpful to pack the jar and eliminate any air pockets.

Top with a cabbage leaf, tucking it down the sides. Make sure the veggies are completely covered with celery juice and that the juice is all the way to the top of the jar to eliminate trapped air.

Seal the jar and store in a warm, slightly moist place for 24 to 96 hours, depending on the food being cultured. Ideal temperature range is 68 to 75 degrees Fahrenheit; 85 degrees max. Remember, heat kills the microbes!

When done, store in the refrigerator to slow down the fermentation process.

While some fermented foods contain vitamin K2, most notably natto, a fermented soy product typically sold in Asian grocery stores, you can create therapeutic levels of this vitamin in fermented vegetables by using a special starter culture like Kinetic Culture made with vitamin K2-producing bacteria.

(Please note that not every strain of bacteria makes K2, so not all fermented foods will contain it. For example, most yogurts have almost no vitamin K2. Certain types of cheeses, such as Gouda, Brie and Edam are high in vitamin K2, while other cheeses are not.)

Our Kinetic Culture Jar Lids Help Cut Offensive Fermenting Odors

Besides a starter culture, other helpful tools include a shredding disc, a kraut pounder/vegetable tamper tool, weights and kinetic culture jar lids. Some people find the odor emitted by fermenting vegetables objectionable, and the kinetic culture jar lids can help eliminate these smells.

The lid has a one-way valve that allows the gases to be released while preventing oxygen from entering the jar, which would stop the fermentation process. A charcoal filter cuts the odors. Again, they're by no means necessary, but can be useful if you or one of your family members isn't thrilled with the smell of fermenting vegetables.

Optimizing Your Microbiome Is a Potent Disease Prevention Strategy

I believe optimizing your gut flora may be one of the most important things you can do for your health, and here you can wield your personal power to the fullest by making healthy food and medical choices. The good news is that supporting your microbiome isn't very complicated. One of the best ways to improve your gut health is through your diet.

Fermented foods are ideal, but dietary fiber is also important. Some microbes ferment fiber and the byproducts nourish your colon. You'd also be wise to take other proactive steps to support your gut health and prevent damage to your microbiome. To optimize your microbiome, consider the following recommendations:

Do: Avoid:

Do: Eat plenty of fermented foods. Healthy choices include lassi, fermented grass-fed organic milk such as kefir, natto (fermented soy) and fermented vegetables.

If you ferment your own, consider using a special starter culture that has been optimized with bacterial strains that produce high levels of vitamin K2.

This is an inexpensive way to optimize your vitamin K2, which is particularly important if you're taking a vitamin D3 supplement.

Avoid: Antibiotics, unless absolutely necessary (and when you do, make sure to reseed your gut with fermented foods).

While researchers are looking into methods that might help ameliorate the destruction of beneficial bacteria by antibiotics,26,27 your best bet is likely always going to be reseeding your gut with probiotics from fermented and cultured foods.

Do: Although I'm not a major proponent of taking many supplements (as I believe the majority of your nutrients need to come from food), probiotics are an exception if you don't eat fermented foods on a regular basis

Avoid: Conventionally raised meats and other animal products, as animals raised in concentrated animal feeding operations (CAFOs) are routinely fed low-dose antibiotics, plus genetically engineered grains loaded with glyphosate, which is widely known to kill many bacteria.

Do: Boost your soluble and insoluble fiber intake, focusing on vegetables, nuts and seeds, including sprouted seeds.

Avoid: Chlorinated and/or fluoridated water, especially in your bathing such as showers, which is worse than drinking it.

Do: Get your hands dirty in the garden. Germ-free living may not be in your best interest, as the loss of healthy bacteria can have wide-ranging influence on your mental, emotional and physical health.

Exposure to bacteria and viruses can help strengthen your immune system and provide long-lasting immunity against disease.

Getting your hands dirty in the garden can help reacquaint your immune system with beneficial microorganisms on the plants and in the soil.

According to a recent report,28 lack of exposure to the outdoors can in and of itself cause your microbiome to become "deficient."

Avoid: Processed foods. Excessive sugars, along with otherwise "dead" nutrients, feed pathogenic bacteria.

Food emulsifiers such as polysorbate 80, lecithin, carrageenan, polyglycerols and xanthan gum also appear to have an adverse effect on your gut flora.29

Unless 100 percent organic, they may also contain genetically engineered (GE) ingredients that tend to be heavily contaminated with pesticides such as glyphosate, a possibly carcinogenic pesticide.

Do: Open your windows. For the vast majority of human history the outside was always part of the inside, and at no moment during our day were we ever really separated from nature. Today, we spend 90 percent of our lives indoors.

And, although keeping the outside out does have its advantages, it has also changed the microbiome of your home.

Research30 shows that opening a window and increasing natural airflow can improve the diversity and health of the microbes in your home, which in turn benefits you.

Avoid: Agricultural chemicals. Glyphosate (Roundup) in particular is a known antibiotic and will actively kill many of your beneficial gut microbes if you eat foods contaminated with this broad-spectrum herbicide.

Do: Wash your dishes by hand instead of in the dishwasher. Research has shown that washing your dishes by hand leaves more bacteria on the dishes than dishwashers do, and that eating off these less-than-sterile dishes may actually decrease your risk of allergies by stimulating your immune system.

Avoid: Antibacterial soap, as they too kill off both good and bad bacteria, and contribute to the development of antibiotic resistance.


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